ABSTRACTS
The following is a list of the abstracts for papers which will be presented in the FOURTH INTERNATIONAL SYMPOSIUM ON POLYMER SURFACE MODIFICATION The listing is alphabetical by presenting author. This list is updated continually to add abstracts as they become available and make appropriate corrections. This list may be conveniently searched by using the editor provided with most popular browsers (e.g. Microsoft Explorer, Netscape, ... etc.)
Evolution and Control of Roughness During Plasma Etching of Polymer Waveguides
(Abstract not yet available)
Laser - Treatment of Polymers
(Abstract not yet available)
Failure Analysis of Adhesive Joint of DC Glow Discharge Exposed PP to Steel
The present investigation aims to analyze the failure mechanism of adhesive joint of DC glow discharge exposed PP to mild steel for attaining best adhesive joint of PP to mild steel. The as received and DC glow discharge exposed PP surfaces have been characterised by Energy Dispersive Spectra (EDS). Lap shear tensile tests have been carried out for the unexposed polymer and those exposed under DC glow discharge (i) at different power levels and (ii) for different duration of exposure. It is observed that with increasing power level lap shear tensile strength of adhesive (Araldite AY 105) joint of PP to mild steel increases till 13 W of power level, beyond which the joint strength decreases. Further, at this power level the joint strength increases with increasing exposure time upto 120 s and then joint strength decreases. At the optimized condition for the surface modification the effect of using another adhesive (Araldite 2011) on the strength of the joint has also been determined. The fractured surfaces of the specimens tested under lap shear tensile test have been examined in order to analyse the failure mechanism of the polymer to mild steel adhesive joints so that the best adhesive joint can be made. In addition, the polymer to polymer and mild steel to mild steel joints using these adhesives have also been examined. The fracture surface has been analyzed by optical microscopy and Energy Dispersive Spectra (EDS). The fracture surfaces of these joints studied under optical microscopy and Energy Dispersive Spectra (EDS), show that when unexposed polymer is joined with mild steel, the failure is confined to polymer to adhesive interface. However, when the polymer, has been modified by exposure under glow discharge the failure mode is changed. The failure is observed throughout subsurface layer of the PP. From the strength analysis of adhesive joint of either glow discharge exposed PP to mild steel, or glow discharge exposed PP to PP, it is observed that joint strength does not change with the change of adhesive and this could be possible as failure takes place throughout the subsurface layer of the PP.
§Correspondence author
Email: tapan@rtc.iitkgp.ernet.in
Wetting and Adhesion Characteristics of DC and RF Glow Discharge Exposed PP
The present investigation aims to optimise the process parameters of DC and RF glow discharge treatment through air in terms of discharge power and time of exposure for the surface modification of PP sheet, for attaining best adhesive joint of the polymer to mild steel. In order to estimate the extent of surface modification, the surface energies of the polymer surfaces exposed to glow discharge have been determined by measuring contact angles using two standard test liquids of known surface energies. It is observed that at a given power level of DC glow discharge, surface energy and its polar component increases with increasing exposure time which attains maximum and then decreases. In the case of RF glow discharge, surface energy and its polar component increases with increasing exposure time and then saturate before reaching to maximum level. Surface modification by DC glow discharge increases the surface energy of PP relatively more at a lower power compared to that observed for RF glow discharge. The dispersion component of surface energy remains almost unaffected. The surfaces have also been studied by Electron Spectroscopy for Chemical Analysis (ESCA) and Energy Dispersive Spectra (EDS). Significant oxygen peak is observed for surface modified polymer as detected by ESCA and EDS. Lap shear tensile test of adhesive (Araldite AY 105) joint of PP with mild steel has been carried out in optimising the parameters of DC and RF glow discharge for maximum joint strength. When PP is exposed to DC glow discharge, improvement of adhesive joint strength of PP to mild steel is found to be by a factor nearer to 6. On the otherhand, when PP is exposed to RF glow discharge, results in improvement of adhesive joint strength of PP to mild steel by a factor lower than 5 is found. Thus, DC glow discharge is more capable for increasing wetting and adhesion characteristics of the polymer.
*Correspondence author
Email: tapan@rtc.iitkgp.ernet.in
Modification of Tissue and Implantable Device Surfaces with Hydrogels to Control Biological Responses
Implantable hydrogels display a range of properties that can be used to modulate biological responses when in contact with tissue. They can resist or promote cell attachment depending on their chemical structure and hydrophilicity. They can promote cell migration and support mitosis when in contact with natural or synthetic cell adhesive substrates. They generally induce very mild inflammatory responses in their stable state, but can promote tissue augmentation by producing cellular responses during biodegradation.
This combination of properties of implantable hydrogels makes them useful in the medical device field as coatings for devices and tissues which modify their surfaces, creating physical and biological effects to produce favorable therapeutic outcomes.
Laser Carbonized All-Polymer Sensor Arrays for Chemical and Biological Agent Detection
The Photonics Research Center is currently investigating the concepts for all polymeric chemical and biological agent sensors. In previous studies we have demonstrated a humidity sensor based on a laser carbonized polymeric substrate, Kapton. Now, we are extending those concepts using other sensing polymers for the initial purpose of detecting DMMP, a simulated G-type nerve agent. The eventual goal is to develop a matrix of Kapton based all polymer sensors that can be integrated into a soldier's uniform.
Exposure to ultra-violet through blue-green laser light photothermally carbonizes the Kapton at the surface leaving a conducting network. There is a fine correlation between the morphology of the carbonized surface and the conductivity through the carbonized network. Working with DMMP, we have developed a one-dimensional array by drop coating solvated polyethylene oxide lithium perchlorate (PEO-LiClO4) onto the laser carbonized circuit of the Kapton. A DE 2000 Digital Laser Scanner draws the circuit onto the surface of the Kapton. The width of the carbonized filaments is entirely a function the incident laser light. The overall matrix design consists of arrays of carbonized filaments at controllable lengths and distances apart. Extensions of this array to a simple matrix and towards molecularly imprinted polymers for biological detection are also being investigated.
Wettability and Surface Free Energies of Polymeric Materials Exposed to Excimer Ultraviolet Light and Particle Adhesion to their Surfaces
Ultraviolet (UV) irradiation was applied to alter physicochemical surface properties of polymers. Excimer UV light at a wavelength of 172 nm was shined on polyethylene (PE), polypropylene (PP), poly(ethylene terephthalate) (PET), nylon 6 (Ny6), and polyimide (PI) films in ambient air. The advancing contact angles of water on the unexposed and UV exposed films were determined by the sessile drop technique as a measure of the wettability. The Lifshitz-van der Waals and acid-base components of the surface free energy of the polymer films were determined from the contact angles of three probe liquids. The considerable increase in the wettability and the acid-base component of the surface free energy were induced by the UV radiation in exposure times on the order of 1 minute. XPS data showed that the increases were due to the increased atomic oxygen concentration at the film surfaces. When the UV-exposed polymer films were stored in ambient air, the decrease in the wettability, i.e. the hydrophobic recovery, was much smaller than that of the unexposed specimens. The adhesion of polyethylene and nylon particles to the unexposed and UV-exposed PP and PET surfaces was investigated in water/ethanol mixtures. the number of particles adhering to the polymer surface was found to decrease after the UV irradiation. The adhesion behavior will be discussed in terms of the surface free energies of the polymer, particle and liquid.
A Novel Process for Formation of Release Surfaces
A large variety of chemistries and techniques exist presently to provide release properties (properties that are opposite of adhesion) from a pressure-sensitive adhesive or tacky materials. Silicone-based release coatings dominate the market because they have a reliably low release force as compared to other coatings.
To get release properties it is necessary to cross-link the silicone material. Traditionally these reactions are thermally initiated and occur by either an addition or a condensation mechanism. Radiation curing of silicone is another method used to get the required cross-linking. High intensity ultraviolet light or an electron beam (EB) can be used [1].
When one looks at the broader silicone process industry (beyond release coatings), the most common curing method is room temperature vulcanization (RTV) curing. This does not apply to silicone based release coatings where RTV curing is only at the development stage [2].
A new process for producing release surfaces with significant processing advantages over current approaches will be presented. According to the process, a silylation agent is reacted on the surface of an activated substrate simultaneously modifying a sub-surface layer of the substrate and forming an RTV cured coating on the surface. The surface modification process comprises the following two steps: (a) surface activation of the solid substrate and (b) treatment of the activated surface with a silylation solution. This treatment includes silylation of at least a portion of the reactive hydrogen groups in the surface region of the substrate with a silylating agent. The silicon-containing groups of the silylating agent become incorporated in the surface region of the substrate. In the presence of atmospheric water (relative humidity higher than 25%) a concurrent condensation reaction takes place producing moisture cured, RTV, coating.
1. M.A. Brook, "Silicon in organic, organometalic, and polymer chemistry", John Wiley and Sons, 2000.
2. D.J. Huettner, "Moisture Curing Silicone Release Coating Technology: A Coating Process is the Missing Component", Pressure Sensitive Tape Council Technical Seminar, 1988.
Multifunctional Polymeric Surfaces
The control of chemical functionality, surface distribution and spatial geometry of specific surface grafted connector molecules within the interphase facilitates the control of desired level of adhesion between surface engineered polymeric substrates and various polymeric, metallic or bio-active materials.
It is shown in this paper that surface grafted connector molecules effectively improve the adhesion and fracture performance of interfaces between polymeric substrates and adjacent materials such as adhesives or surface coatings through either or combination of two principal mechanisms: (i) interpenetration into, and/or (ii) chemical reaction with the adhering material.
It is also demonstrated that specific types of similar graft chemicals provide the possibility of tailoring the surface for controlled bio-compatibility, eg. for the cell growth of protein repellence.
The Essence of Creating a Core / Thin Shell Structure for Plating Nickel on Rubbery Microspheres
Deposition of a uniform metallic layer onto microspheres made of a rubbery polymer network is expected to have prospective applications in the energy damping / reflection coatings. The necessity of using the rubbery polymer network is linked to the fact that its loss modulus E" and the loss tangent exhibit maximum values around its Tg . As a result, the polymer substrate (microspheres) possesses a low energy surface and a too soft matrix at plating temperature besides having a diameter of micro-meter range. These three structural particulars, especially the former two, make the formation of a metallic layer on the substrate by electroless plating means become rather difficult. In the present work, the microsphers of the acrylate elastomer synthesized in house by the suspension polymerization is used as the model system to conduct the study. Two approaches aiming at introduction of a hard polymer thin shell to the microspheres prior to the electroless plating are attempted. The first approach is through anchoring acrylonitrile segments to the microspheres directly in the suspension polymerization system, and the second one is through polymerization of aniline within the surface matrix of the microspheres. Both approaches could improve the electroless nickel deposition on the microspheres. In addition to the synthesis and surface modifications, the characterizations are primarily based on SEM and DSC.
3-5-1 Johoku, Hamamatsu, 432-8561 JAPAN
Modification of Polymer Surfaces by Remote Plasmas
(abstract not yet available)
1) Integrity Testing Laboratory Inc., Toronto, CANADA
2) UTIAS, Toronto, CANADA
Surface Modification of Polymer-based Materials to Enhance Resistance to Highly Aggressive Oxidative Environments
A surface modification and testing program was conducted at ITL Inc. to evaluate the recently developed and patented surface modification technology, known as Photosil™ [1,2], on a variety of polymer-based paints and on advanced thin polymer film materials for oxidation and erosion resistance enhancement in highly aggressive oxidative environments. The program included mostly space-related polymer-based paints and films, and assessed the impact on the coatings' functional properties and resistance to fast atomic oxygen (FAO) fluxes, with energy E~ few eV, and oxygen plasmas.
Significant enhancement of FAO erosion resistance was achieved on organic-based space materials - paints, treated by various versions of the developed technology. Currently, upgraded Photosil™ technology and facilities are employed to protect and to enhance the space durability of painted sophisticated external space components of NASA's Mobile Servicing System (MSS), that is a new generation of the Canadarm, on the International Space Station. This example, as well as some other examples of the applications are presented. They include conductive and/or non-conductive white, black, gray, silver and red space paints, as well as polyimide, polyethylene terephtalate, polycarbonate, and other high-performance thin polymer films. Pristine (untreated) and Photosil™-modified samples have been tested under highly aggressive FAO beams and in oxygen plasmas, and evaluated by changes in mass loss, thermo-optical properties, surface morphology, and surface chemistry changes. Complementary surface analysis methods, such as X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Miscroscopy (SEM), and Optical Profilometry, have been used to confirm the degree and the mechanism of durability improvement by the applied surface modification treatment.
1. Y. Gudimenko, J. Kleiman, Z. Iskanderova, G.Cool, R.C. Tennyson, US Patent 5,948,484, September 7, 1999.
2. J.Kleiman, Z. Iskanderova, Y. Gudimenko, W.D. Morison, R.C. Tennyson, Canadian Aeronautics and Space Journal, 45, 2 (1999), 148-160.
Characterization of Transparent Thin Films Deposited on PET Substrates by Reactive Sputtering
Transparent ceramic thin films deposited on polyethylene terephthalate (PET) substrates are increasingly used as transparent electrodes for electronic devices, gas barrier films for food and medical device packaging. Silicon Oxide (SiOx) compounds and aluminum oxide (AlOx) compounds are the most popular materials for the transparent gas barrier application and many researchers have investigated how to produce these films. Various methods have been used to deposit these films on polymer substrates including: sol-gel methods, physical vapor deposition, electron beam vapor deposition, plasma enhanced chemical vapor deposition and magnetron sputtering. Roll to roll coaters used to deposit gas barrier films such as SiOx and AlOx on PET substrates have also been reported.
In this paper, the gas barrier properties of these transparent films are investigated. In addition, the gas barrier properties of the SiOx and silicon oxynitride thin films deposited on PET substrates prepared by reactive sputtering are characterized.
Plasma Surface Modification of Fabrics
Recently, the plasma technology has been evaluated in an EU-(European Union)-sponsored project entitled "Development of high-performance fabrics based on industrial cold plasma technology (PLASMAFAB)".
Different types of plasma modifications of mainly polyester (PES) and polyamide (PA) fabrics have been evaluated in the project in order to improve various surface properties of the fabrics. These include adhesion to various coatings, soil and stain release, antistatics, flame retardancy, wettability, water repellency, etc.
The work in the project has shown that most of the properties mentioned above can be improved. A few examples will be presented, e.g.:
Surface Modification of Fibers and Implants Using R. F. Plasma
R. F. Plasma is a powerful technique for modification of polymeric surfaces. The technique has many advantages, including: low temperature, limited penetration, capability for induced changes in the physics, chemistry and morphology of surfaces, and the application of homogeneous, stable coatings with pinhole-free coverage. This paper will review various examples that describe the potential of this technique with specific emphasis on fibrous materials and implants. Surface modifications will be shown to enhance fiber interfacial adhesion in composites and the performance and safety of biological implants. The design of chemical functionality using this technique and its application in nano-scale devices and in tissue engineering will also be addressed.
Surface Grafting of Well-Defined and Functional Polymers on Hydrogen-Terminated Silicon Substrates
The oriented single crystal silicon-polymer interface is of great importance to the microelectronics industry. Functionalization of the hydrogen-terminated Si(100) surface (the Si-H surface), via UV-induced cleavage of the Si-H bond and coupling of an w-unsaturated alkyl ester, was first carried out. Reduction of the ester groups by LiAlH4 yielded the surface-tethered hydroxyl groups, which were allowed to further react with 2-bromoisobutyrate bromide. The tethered a-bromoester was then used as the surface immobilized initiator for atom transfer radical polymerization (ATRP). Homopolymer brushes of methyl methacrylate (MMA), (2-dimethylamonio)ethyl methacrylate (DMAEMA), and poly(ethylene glycol) monomethacrylate (PEGMA) were prepared by ATRP from the a-bromoester functionalized silicon surface. Diblock copolymer brushes consisting of PMMA and PDMAEMA blocks were obtained by using the homopolymer brushes as the macroinitiators for the ATRP of the second monomer, providing further evidence to the existence of "living" chain ends. The Si-H surface was also functionalized by subjecting it to the UV-induced reactive coupling of 4-vinylaniline(4-VAn) to produce the 4-VAn monolayer-modified silicon surface (Si-VAn surface). The Si-VAn surface was further functionalized by oxidative graft polymerization of the aniline moiety of the coupled 4-VAn molecules with aniline (Si-PAn-VAn surface). Electroless plating of copper could be carried out on the 4-VAn- or PAn-modified silicon surface via a Sn-free process. Not only did the 4-VAn monolayers provided chemisorption sites for the palladium complexes without the need for prior sensitization by SnCl2 during the electroless plating process, it also served as the adhesion promotion layer for the electrolessly deposited copper.
Plasma Process for Wide Fabric, Non-Wovens and Film
To many people plasma is a laboratory curiosity or is limited in scale. Few know that plasma is a commercial process used daily in the treatment of fabric, non-woven webs and film. This paper will review applications and processes used to modify materials up to 60" width in a roll to roll plasma reactor. The applications are quite varied. Advanced reinforcing fibers in fabric form, such as KevlarR, SpectraR and VectranR, are treated to enhance penetration and adhesion to resins used in the manufacture of composite structures. KaptonR, HalarR and other engineering films are treated to enhance metallization as well as adhesion.
Sometimes the process is simply to change the surface energy, while at other times far more sophisticated PECVD processes are employed to provide chemical barrier or alter the tribological properties. As will be seen in this presentation plasma is extremely versatile and applicable to high volume web applications.
1) PlasmaTreat North America Inc., 1-2283 Argentia Road, Mississauga, ON L5N 5Z2, CANADA
2) PlasmaTreat GmbH, Bisamweg 10, 38003 Steinhagen, GERMANY
Applications of the First Fully Industrial Atmospheric Pressure Plasma
FLUMEtm plasma systems create atmospheric pressure plasma based on Openairtm plasma technology. They are unique in that they clean surfaces to molecular levels, and strongly activate polymer based surfaces by creating a high amount of polar groups, mainly ketonic and hydroxile, when using air as carrier gas. As a result, pristine and strongly activated surfaces fully wet out with water, even low surface energy materials, like polypropylene (PP), thermoplastic olefins (TPO), thermoplastic elastomers (TPE), and ethylene/propylene/diene rubber (EPDM). This makes possible the use of simple, water based, environmentally friendly, and cost effective adhesives, coatings and inks without compromising the performance of the bond. Several case studies of actual industrial applications show how this leading edge technology has lead to a break-through in product and process development.
Surface Modification of Natural Fibers by Photografting and Photo Curing
(Abstract not yet available)
State-of-the-art Overview: Surface Modification of Polymers by Ion Assisted Reaction
Research on surface modification of polymers using ion assisted reaction (IAR) is reviewed with outstanding results regarding the hydrophilicity and adhesion of polymers. The IAR is an emerging technology in the field of surface modification of polymers which gives stable functional groups on surfaces and accomplishes permanent hydrophilicity and strong adhesion of polymers. The low contact angles below 30° and high surface energies 60-70 mJ/m2 are achieved on the IAR treated thermoplastic and thermosetting polymers such as polyethylene (PE), poly(propylene) (PP), poly(vinylidenefluoride) (PVDF), poly(tetrafluoroethylene) (PTFE), poly(carbonate) (PC), poly(ethersulfone) (PES), poly(imide) (PI), etc. In this paper, the experimental results of IAR treated polymers are presented in detail and the changes in physical and chemical properties on the IAR treated polymer surfaces are investigated by XPS, SEM, AFM, etc. On the bases of these results, the interaction mechanisms among energetic ions, reactive gas molecules, and polymer molecules involved in the IAR treatment are discussed. The review shows breakthroughs of IAR treatment in various industrial fields which include PVDF thin film speaker, conductive silicon rubber tape for plasma display panel (PDP), PTFE adhesive tapes, cell culture dishes, ITO film on plastics. This paper also describes the pilot production systems for IAR the treatment which are batch type for sheets and roll-to-roll type for web. Finally, the future applications of the IAR technique are to be suggested in the high tech area such as opto-electronic devices, semiconductors, biomaterials, etc.
Adhesion Characteristics of the Plasma Surface Treated Carbon Fiber Epoxy Composite with Respect to Release Films
The load transmission capabilities of carbon fiber epoxy composite adhesive joints are affected by surface characteristics of the adherends such as surface free energy and chemical composition, which can be changed by plasma surface treatments and release films for demolding carbon fiber epoxy composites from metal molds. In this paper, suitable plasma surface treatment conditions for carbon fiber epoxy composite adherends were investigated to enhance the strength of carbon fiber epoxy composite adhesive joints using dielectric barrier discharges of atmospheric pressure plasmas. Effects of plasma surface treatment parameters on the surface free energy and adhesion strength of carbon fiber epoxy composites were experimentally investigated with respect to flow rate of gas, ratio of flow rates of O2 to Ar, power intensity, distance between power electrode and surface of specimen, and surface treatment time. Also the surface and adhesion characteristics of carbon fiber epoxy composites were investigated with respect to release films such as PTFE, PE and nylon. Quantitative chemical bonding analysis determined with XPS (X-ray Photoelectron Spectroscopy) was also performed to understand the load transmission capabilities of composite adhesive joints with respect to the flow rate of O2 and release films.
A Study on Tissue and Blood Compatibility of DLC and CNx Coatings
Despite promising studies of diamond-like carbon (DLC) supporting their biomedical applications, few data on its blood compatibility are reported. Carbon nitride (CNx) has similar structural characterization to DLC. Its excellent mechanical and tribological properties are comparable to that of DLC. However, itt is difficult to find the reports on the investigations of the biocompatibility of CNx so far. In this work, CNx and DLC coatings were prepared using dc magnetron sputtering at room temperature. The effects of CNx and DLC coatings on cultures of mouse fibroblasts and human endothelial cells were determined by scanning electron microscopy. The results showed that the coatings caused no adverse effects on the cells. CNx coating provided a comparable or better surface for the normal cellular attachment, growth, and morphology as compared to DLC. At the same time, both coatings exhibited lower platelet adhesion and longer blood-clotting time compared with the control silicon wafer. Relatively, CNx coating provided a better surface for the inhibition of the platelet coagulation and adhesion. The coatings alsoexhibited strong corrosion resistance. These results support the tissue and blood compatibility of CNx and DLC and should initiate an interest in the biomedical applications of CNx coating.
SPM*-based Nanolithography in Polyethylene-Terephthalate Polymer Films
We report an electrostatic resistless lithography technique perfected in 50-nm Polyethylene-Terephthalate polymer films. Raised nano-dots are created using highly conductive AFM tip negatively biased with respect to the conductive layer beneath the film. This novel lithography technique allows patterning of raised structures (50-100 nm wide, and 0.2-100 nm high) without external heating of the polymer film. The nanostructures are formed within a 10-6- 10-3 second time scale suggesting a clear alternative to the recently reported method of electrostatically induced nanostructure formation using external electrodes (Nature 403, 874, 2000). Our technique is conceptually different from all lithography techniques (including thermomechanical writing - MILLIPEDE, AFM-assisted chemical modification in polymer resists, e-beam, ion-beam etc.) in polymer materials reported so far. It is based on heating of a small fraction of the polymer film above its glass transition point. Thus, the polymer film softens locally and goes into dielectric liquid state via localized Joule heating. It is then attracted, electrostatically, towards the AFM tip in strong (108-109 V/m) non-uniform electric field. This electrostatic attraction results in a mass transport of the polymer liquid in non-uniform electric field with a strong gradient, resulting in nanostructures formation.
* SPM: Scanning probe microscopy
** sfl@physics.uakron.edu: Author to whom correspondence should be addressed.
High Rate, Uniform Treatment of Polymer Films Using New Plasma Source
APT has invented a high density plasma source for uniform, high rate plasma treatment, plasma enhanced chemical vapor deposition (PECVD) and reactive ion etching (RIE) on large area, flexible substrates. The new source implements a novel magnetic field/electrode configuration that confines the electron Hall current in an endless loop adjacent to the substrate. By confining the Hall current, a dense, uniform plasma is created and sustained over wide substrates. The new source enables surface treatment of flexible substrates at metalizer web speeds. PECVD applications requiring low temperature, high rate, uniform deposition are also benefited. Data on plasma treatment tests are presented. A silicon Oxi-carbide coating is deposited by PECVD on PET film at over 100nm-m/min from a single source (measuring 20cm in the film travel direction). The source plasma physics and characterization information is presented along with the surface treatment and PECVD data.
Modification of Electrostatic Properties of Polymer Powders Using Atmospheric Plasma Reactor
Low-pressure plasma treatment is frequently used to modify various surface properties of polymer substrates. In this study, an atmospheric plasma treatment was used to modify surface structure for reducing tribocharge surface density and for increasing surface conductivity. The tribocharging as well as charge decay characteristics of polymers have a significant impact on several industrial processes such as electrostatic powder coating and pharmaceutical powder processing. Surface modification of test polymer powders was carried out using atmospheric pressure argon plasma in a fluidized bed reactor. The charging characteristics of test polymer powder were studied before and after plasma treatment. Tribocharging data after plasma treatment showed a decrease in the net acquired charge (Q/M) for both polystyrene microspheres and acrylic powder as compared to that of unmodified powders. It was found that plasma treatment significantly altered the charge decay characteristics of acrylic polymer powder. The charge decay time constants for plasma treated powder were 50% lower than those of untreated powder were. Atomic Force Microscope (AFM) characterization of plasma treated polystyrene microspheres showed an increase in surface roughness (Ra) from 13.4 to 23.2 nm resulting in increased surface area. It appears that increased surface roughness reduces contact surface area for tribocharging thus decreasing charge-to-mass ratio. At the same time, this increased surface area increases moisture absorption, therefore increasing surface conductivity and charge decay rate. The plasma treatment can be used where charge minimization on polymer surface is needed.
Controlling and Characterizing Protein and Cell Adhesion on Surfaces
The ability to control interactions between biomolecules and surfaces influences a widely divergent number of bioengineering applications. In vivo we desire materials that prevent cellular adhesion, selectively adsorb specific proteins or mimic the structure of a cell surface. In vitro, high sensitivity proteomic and diagnostic applications require the immobilization of specific biomolecules without any loss of native function. This range of applications presents challenge in terms of both surface modification methods and the sensitivity of techniques we use to characterize these systems.
This paper will discuss the physicochemical characterization of a series of surfaces designed to control protein adsorption and prevent cell adhesion. Applications of XPS and ToF-SIMS for the detection and identification of biomolecules on these and other surfaces will be explored further. In addition we will discuss the recent developments in sample preparation that are enabling ToF-SIMS to give unique insight into orientation/conformation or proteins at interfaces.
1) DETEC - Università di Napoli "Federico II", P.le Tecchio 80, 80125 Napoli, ITALY
2) DIP - Università di Genova, Via dell'Opera Pia, 15 16145 Genova, ITALY
3) DIMP - Università di Napoli "Federico II", P.le Tecchio 80, 80125 Napoli, ITALY
Role of Polymer Surface Modifiction in Adhesively Bonded Joints: Analysis and Testing
Many products, spanning in a wide range of applications, are obtained by joining together two or more parts of materials either of the same, or different characteristics. Joining two parts of the same material, or parts of different materials, without deterioration of materials characteristics, and obtaining a material of superior characteristics is a challenge to researchers and technicians. It is of utmost importance to pay great attention during the different manufacturing phases of a bonded structure such as surface treatment to enhance adhesion, adhesive selection, curing processes. Inadequate procedure may cause formation of gas bubbles, or weak boundary layers which will lead to degradation of the product performance and reduction of life.
Indeed, a major problem in industrial application of structural adhesive is related to quality assurance of manufactured joints. However, the exposure of a bonded structure to oxidizing agents, solvents, etc., is deleterious and so, a periodic inspection with the most adequate nondestructive technique should also be performed.
At present, for lack of a suitable non-destructive technique, production standards are established on the basis of destructive representative-sample tests and statistical inference. In this study, an attempt is made to search if lock-in thermography, as a tool of non-destructive evaluation, is able to deal with industrial requirements. Adhesively-bonded joints of either alluminium alloys, or steel, which are mostly used in both aeronautical and automotive fields, are analysed. The substrate surfaces were treated at a micro-geometrical level according to conventional industry practices including polishing and sand blasting. The adopted adhesive is a modified methacrylate. A specially designed positioning device allows obtaining a constant gap between the facing surfaces of the joint. Destructive tensile tests are also carried out on the samples.
Using Infrared Thermography to Analyze the Effect of Polymer Surface Modification in Adhesive Joint Applications
The attention of the present paper is focused on the aid provided by infrared thermography in the assessment of technological procedures to improve adhesion. Infrared thermographic instruments are non-contact, non-intrusive equipments, which enable us to see thermal energy radiated from objects in the infrared band of the electromagnetic spectrum. This technique can be exploited for the achievement of two main objectives:
Basically, for non-destructive evaluation two different approaches are possible: traditional pulse thermography (PT) and modulated (or lock-in) thermography (MT). The use of the two techniques is discussed through a review of experimental tests carried out by considering different types of bonded structures, which are of industrial interest. The attention is mainly focused on adhesively bonded joints and composite materials; several specimens are considered involving different bonding modes with, or without, any surface treatment before bonding.
It is found that infrared thermography, by using the most appropriate method, is able to visualize inhomogeneities in metallic, plastic, or composite materials and to determine material modifications linked to surface treatments such as plasma.
The Modification of Interphase Layer and Adhesion: Tuning and Predictability
Fundamental understanding of molecular mechanisms responsible for macromolecular adhesion is currently a lively topic. The final goal seems to be a tuning the adhesion level which can be achieved at an interface and its predictability. One of the main conclusions in this research area is that, although interfacial interactions are necessary in an adhesion process, the high loss function of the adhesive is responsible for the high practical adhesion strength.
Polymer surface modification is one of the main approaches to enhance adhesion to other materials. The extent of modification controls the interfacial interactions and loss function on the interphase layer. While the surface modification usually increases the strength of interfacial interactions, it may have unsuitable effects on loss function of the interphase layer.
In this research work the effect of chemical surface modification on interfacial interactions is measured and evaluated based on a kinetic model. The effect of surface modification on loss function of the interphase layer is calculated based on bulk damping capability of the adherends and their shifting by enthalpic interactions at the interface. Finally, these two main controlling mechanisms are combined and maximized based on modification elapsed time in an adhesion energy formula to predict the optimum modification time. Comparable results were found from aforementioned approach and direct interface strength measurement by peeling as a function of modification time. This approach can be used for tuning and prediction of adhesion strength as a function of surface modification extent or time.
1) Departamento de Tecnología de Tensioactivos. IIQAB-CSIC. Barcelona, SPAIN.
2) Textile Engineering Department. Faculty of Technology and Metallurgy. University of Belgrade. Belgrade, YUGOSLAVIA
3) Departamento de Física Aplicada y Óptica. Universidad de Barcelona, SPAIN.
4) Departamento de Química Orgánica Biológica. IIQAB-CSIC. Barcelona, SPAIN.
Surface Characterization And Properties of Keratin Fibres Treated With Low Temperature Plasmas
Keratin fibres like wool or human hair are hydrophobic due to the presence of a fatty acid monolayer in the outermost part of the epicuticle membrane. The hydrophobity of the wool fibre surface is one of the most important factors that influence on the shrinkage of wool fabrics during aqueous washing with agitation. Low temperature plasma (LTP) treatments can be used in order to confer to keratin fibre surface hidrophility and accordingly, the shrinkage of wool fabrics is considerably reduced. Morever, by LTP the water consumption and water waste pollutants generated in some conventional chemical treatments are avoided.
Studies on the characterization of keratin fibre surfaces treated with oxidative LTP by means contact angle measurements on single keratin fibres, XPS, SEM, Herbig sac formation and ESR techniques revealed the following:
Surface Modification of Ultra High Molecular Weight Polyethylene Using Excimer Laser Treatment
Effects of pulsed KrF excimer laser (248 nm) on Ultra High Molecular Weight Polyethylene (UHMWPE) fibers and fiber/epoxy resin interface were studied. SpectraTM 1000 (UHMWE) fibers were treated with pulsed excimer laser with different energy density levels and number of pulses in air and in diethylenetriamine (DETA) environments. Chemical and topographical changes of the fiber surfaces were characterized using dynamic wettability measurements, and scanning electron microscopy (SEM). Fiber/epoxy resin interfacial shear strength (IFSS) was evaluated by single fiber pull-out test. The results indicate that the fibers undergo significant photoablation when exposed to excimer laser in air and their diameter decreases. Wettability data show that fiber becomes more polar after laser treatment and also more wettable. The acid-base component of the surface energy increases significantly, particularly for the fibers treated in DETA. SEM photomicrographs reveal that the surface becomes rougher after the laser treatment. IFSS results indicate that laser treatment significantly improves the adhesion strength of UHSPE fibers with epoxy resin. Some treatments resulted in IFSS improvements of up to 6 times the control value. This enhancement in IFSS is attributed to increased roughness of the fiber surface and increased interfacial area and increased polar nature and wettability, as well as improvement of acid-base component in surface energy after the laser treatment. While the increased roughness contributes to mechanical adhesion, increased acid-base component increases the possibility of hydrogen bonding.
1) Department of Physics, Indian Institute of Technology Roorkee, Roorkee-247667, INDIA
2) Department of Metallurgy and Material Engineering, Indian Institute of Technology, Roorkee, Roorkee -247667, INDIA
Surface Modification of Polycarbonate by Air Dc- Glow Discharge Plasma
In the recent years, the surface modification of polymeric materials has undergone numerous industrial as well as engineering applications (biocompatibility, enhancement of paint adhesion, improved bonding in polymer matrix composites, contact lenses, coating etc.) due to their some unique properties such as high strength to weight ratio, resistance to corrosion, design flexibility, inertness and their relatively low cost. Surface modifications of polycarbonate (PC) were performed to improve the wettability and /or polarity of the surfaces with a short exposure to DC air-glow discharge plasma. Surface modifications of the PC surface have been carried out at different power levels such as 0.05, 0.52, 2.08 and 7.6 watts. The modification is time dependent. The surface energy of PC exposed under DC glow discharge was estimated by measuring the contact angles of polar series of test liquids i.e. De-ionized water and formamide with their known surface energy components. It was found that contact angle with the te!
st liquids generally decreases with increasing exposure time at given power levels and it reaches minimum. Beyond this time the contact angle either saturates or increases in certain cases. The increase in total surface energy depends on the polar component as compared to the dispersive component. As it has been observed for the contact angle, the polar component of surface energy also increases rapidly at short exposure time of DC-air glow discharge plasma and then it either saturates or increases at longer exposure times. The dispersive component of surface energy, although significantly lower then polar component, decreases similarly and then saturates. For low power levels of 0.05 and 0.52 watts, the same contact angle at exposed surfaces has minimum values of around 400 and 200 for water and formamide respectively, whereas for higher wattage of 2.08 watt and 7.6 watt the minimum contact angles are the same 350 and 120 for water and formamide respectively.
It was also observed, that the effect of modification of the surfaces undergoes a change with time and it depends on the environment under which the surface is stored.
*To whom correspondence should be addressed. E-mail:- skbarfph@iitr.ernet.in
Quantitative Depth Profiles from Polymer Surfaces by Angle-Resolved X-ray Photoelectron Spectroscopy
The use of reactive or inert gas plasmas has become a flexible and widespread technique for the modification of the surface properties of polymers. X-ray photoelectron spectroscopy (XPS), which is able to provide information on the chemical composition of the topmost 5-10 nm of a polymer surface, is an ideal tool for the characterization of plasma-treated materials. It is typically used in combination with argon ion etching for the acquisition of surface composition depth profiles. However, the use of ion beams on polymer surfaces can induce a variety of phenomena, including cross-linking and other chemical modifications that would distort the information obtained on chemical composition as a function of depth.
An alternative approach, not requiring the use of an ion beam, is to acquire the XPS spectra at a series of photoemission angles, as the sample is progressively tilted with respect to axis of the analyzer optics. This is the basis of angle-resolved X-ray Photoelectron Spectroscopy (ARXPS). The intent is to extract the composition depth profile from the manner in which the relative intensities of the spectral peaks corresponding to the elements of interest change with respect to the photoemission angle. This procedure is equivalent to the inversion of the Laplace transform, an "ill-conditioned" problem that limits the sophistication of the depth profiles that one is able to obtain.
In this paper we will present an overview of the ARXPS technique and discuss its strengths and limitations. We will then present experimental results obtained from polystyrene samples exposed to plasmas containing oxygen, and discuss the relationship between the oxygen depth profiles and the wettability of the treated polymer surface. We will also present experiments designed to address the question of the loss of the plasma-enhanced wettability over time, and the loss of oxygen from the polymer surface during the ARXPS measurements themselves.
Comparative Xps Study of Copper, Nickel and Aluminum Coatings on Nitrogen-containing and Oxygen-containing Polymer Surfaces
Two nitrogen-containing polymers, polyacrylonitrile and poly(styrene-co-acrylonitrile), and three oxygen-containing polymers, poly(vinyl methylether), poly(vinyl methylketone) and poly(methyl methacrylate), were coated with copper, nickel and aluminum under ultra-high vacuum and their surfaces analyzed by X-Ray photoelectron spectroscopy. It was found that the morphology of the interface is mainly controlled by the properties of the metal and, to a lesser extent, by the functionalities of the substrate and its physical state. Thus, aluminum condensed quickly on the polymer substrates and formed a uniform metal layer, while copper and nickel lead to more diffuse interfaces. The mobility of copper inside oxygen-containing polymers was clearly identified and its diffusion enhanced by the rubbery substrates, promoting the regeneration of the polymer surface previously degraded by the metal condensation. In contrast to oxygen that did not move during the metallization (except when there was degradation), nitrogen diffused to the metal layer to form nitride species. In all cases (with Cu, Ni and Al), metal oxide, metal nitride and amorphous carbon were identified at the interfaces.
Atmospheric Pressure Plasma Treatment of High Performance Fibers for Composites
Atmospheric pressure plasma treatment is advantageous over low pressure plasma treatment because it did not require high vacuum and thus can be performed on a present production line of fibrous materials. Extensive research has been carried out in our laboratory to investigate the effect of atmospheric pressure plasma treatment on fiber surfaces. Atmospheric pressure helium/air and helium/air/oxygen plasmas were used to treat high performance fibers, such as ultrahigh modulus polyethylene (UHMPE), aramid, and carbon, used as reinforcement for composites in order to enhance adhesion between the fibers and matrix. The surface of the UHMPE and carbon fibers were roughened by the etching effect of the plasmas while this effect was observed for aramid fibers. XPS analysis showed a decrease in carbon content and increase in oxygen content for the fibers treated with plasmas. The microbond test showed that the plasma treatments were able to increase interfacial shear strength significantly. In most of cases, the atmospheric pressure plasmas did not have negative effect on single fiber tensile strength.
The Effect of Excimer Laser Irradiation on the Self-adhesion Properties of Some Engineering Polymers as Evaluated by Ultrasonic Welding
Excimer laser irradiation has been introduced as a new method for polymer surface treatment and micro machining. The ablation rate and the resulting microstructure of various engineering polymers such as PET, PI, PC, ABS, PS, PP, and Nylon 6, were investigated subsequent to irradiation by KrF excimer laser. SEM (scanning electron microscopy) reveals that, after laser treatment, the polymer morphology is not only related to the laser parameters, but also to the polymer optical properties, and to the evolution of structures, which are produced during irradiation. The effect of excimer laser parameters on the depth of ablation and weight loss for different polymers were investigated. The experimental results revealed that the polymeric weight loss is nonlinearly related to the laser energy and laser frequency for most of the materials tested. The laser treatment improved ultrasonic welding strength compared with the untreated samples, and the influence of laser frequency on weld strength was shown to be larger than that of laser pulse number and laser energy. The effects of laser irradiation on the thermal properties (Tg or Tm) of the different model polymers were investigated using DSC. It was found that the Tg and Tm of these materials decreased as a result of laser treatment indicating the degradation effect of the laser irradiation procedure.
Hydroxyl Graft Modified Polypropylene as an Adhesion Promoting Agent
Polypropylene (PP) grafted with 0.5 and 1.0 wt% Maleic Anhydride (abbr:PPgMA) was modified, in the melt, with an excess of amine alcohol producing a hydroxyl group graft modified polypropylene (abbr:PPgOH). The modified polymer was characterized by FTIR, and contact angle. FTIR results demonstrated that PP was modified with hydroxyl groups. From contact angle and wetting tension measurements it was observed changes in the films surface polarity. Two-layered films were prepared using PPgOH film and polycarbonate (PC) film. Adhesion strengths were measured using a T-peel test. Increasing the bonding temperature, bonding time resulted in an improved adhesion to PC layers. The peeled films surface was analyzed by SEM and AFM. The Moalu test was positive indicating that a chemical reaction between hydroxyl functionality and carbonate group was taken place.
1) Plasma Physics Research Center, I.A.University, P.O.Box 14665-678, Tehran, IRAN
2) Faculty of Electr.Engineering, University of Applied Science, Deggendorf,
GERMANY
3) Dept.Theoretical Physics, University of New South Wales, Sydney 2052,
AUSTRALIA
Investigating of Glow Discharge on Polymers' Surface Properties Using Optical Spectroscopy, SEM and AFM
The effects of low pressure glow discharge (LPGD) on three kind of polymers, BOPP, Polyethylene and Nylon, have been investigated. In this paper, morphological changes and optical properties on these three polymers, have been carried out using Scanning Electron Microscope (SEM), Atomic Force Microscopy (AFM) and optical spectroscopy respectively. Glow discharge plasma, affects on the top layer of surface and do not cause any changes in the bulk properties of polymers[1-6].
Also in this study we investigate the effect of operation time on surface properties of polymers. The experiments show that, the decreasing of transmitance of the samples is strongly proportional with operation time, and topographical figures from SEM and AFM confirm this result. There is a simple model to explain the result of spectrophotometry measurements, which will be discuss in full paper.
References
[1].H.R.Yousefi, Amir H. Sari, et. al., International Symposium on GDOES for Surface Analysis, Keio university,Yokohama, Japan, November 19-21 , 2002
[2] S. Kobayashi, T. Wakida, S. Niu, S. Hazama, T. Ito and Y. Sasaki, JSDC, 111, 1995, p. 72-76.
[3]U. Vohrer, Asian Textile Journal, Vol., No.8, 1998, p. 93-96.
[4] T.L. Ward, R. R. Benerito, Textile Research J., 1982, Appril, p. 256-262.
[5] Inagaki, N., Plasma surface modification and plasma polymerization, technomic
[6] J. Ryu, J. Dai, K. Koo, T. W., JSDC, 108, 1992, p. 278-282.
Modern Finishing Processes for Surface Modification
The increasing market for functional and specialised textiles as high-performance products for technical and industrial application as well as requests for environmentally friendly processes create an immense need for simple, but efficient methods for surface treatments.
Increasingly, physical surface modifications have been dealt with in the literature. Especially gas discharge based processes and photo-induced surface modifications seem to have promising potential. Here, photon based processes appear to have certain advantages, if one makes use of well-defined absorption properties by means of monochromatic light sources. Additionally, the technical effort can be expected to be lower than for low-pressure plasmas.
Making use of the high absorption most polymers show in the uv, treatments based on photo-induced activation of the polymer offer the advantage of a well-defined penetration depth of the treatment allowing pure surface modification. Typical absorption coefficients of aromatic polymers at around 250 nm are in the order of 105 cm-1, equivalent to a penetration depth of markedly less than one micron.
A characteristic modification of the surface topography of films and fibres made of highly absorbing polymers such can be effected by excimer UV laser irradiation. Basically a micro-roughness is created on the fibre surface which depends on the wavelength of the laser and the according absorption of the photons.
Besides a number of potential applications the UV laser treatment shows a certain potential to increase the selectivity, i.e. separation of specific particle sizes as compared to others, of the textile filter. An example in blood filtration is the selective separation of the smaller thrombocytes, which are separated to more than 90 %. Similar effects can be achieved for sub-micron dust filtration or high-performance wiping cloths.
With regard to photochemical surface modification, a new approach is given by monochromatic, so-called excimer lamps which emit in the UV, but combine the simple handling of a lamp with the favourable interaction of a monochromatic light source. Far reaching surface modifications using excimer lamps can be expected from a treatment in reactive atmospheres. Fundamental studies have shown that it is possible to initialise grafting of reactive substances or even cross-linking of functional thin layers on the substrate surface. The general condition to achieve reactions like that is a marked difference of the absorbances of a low or non absorbing atmosphere and a strong absorbing substrate. The actual reaction takes place at the boundary between atmosphere and the activated substrate, where radical processes are initialized. Unlike in plasma processes, the 'atmosphere' might be gaseous, liquid or even a melt.
A final remark shall be made on interesting new applications that may be possible from combining these two methods. The fluid repellence of a textile may serve as an example here. Similar to the micro-rough leafs of the Lotus plant, the change in surface topography due to the irradiation of the textile with a pulsed UV laser in combination with a photochemical hydrophobic finish has a clear potential to create super-repellent properties.
Eckhard Schollmeyer, Dierk Knittel and Hans-Jürgen Buschmann; Deutsches Textilforschungszentrum Nord-West e.V., Adlerstrasse 1, D-47798 Krefeld, GERMANY
Applications of Textiles with Permanently Fixed Cyclodextrins
Cyclodextrins are polysaccharides built from six to eight (=6, ß=7, =8) D-glucose units and are formed during the enzymatic degradation of starch. The molecules are torus shaped with hydrophobic cavities. The cavity radii of this relative rigid molecules vary between 0.50 and 0.85 nm. Cyclodextrins are non-toxic and not skin sensitising. Cyclodextrin derivatives with reactive groups e.g. the monochlorotriazinyl group are able to react with the hydroxyl groups of cellulosic fibers like reactive dyes. Permanent fixation on fibers made from polyester is only possible with cyclodextrin derivatives with long alkyl chains or other hydrophobic groups. On polamid fibers cyclodextrin derivates with sulfonic acid groups are fixed by ionic interactions with amino groups on the polymer surface.
Textiles with permanently fixed cyclodextrins have several advantages compared with "normal" textiles:
The fixed cyclodextrin molecules are still able to complex substances into the empty cavities e.g. organic molecules from sweat. Therefore the possible formation of malodor by microbiological decomposition of the organic substances is prevented.
The complexation of organic substances from sweat results in a preconcentration and their analytical treatment becomes easier. Thus, the identification of the organic compounds from the sweat of patients enables new ways in medical diagnostics.
On the other hand the cavities of the cyclodextrins can be filled with perfumes, cosmetic compounds or even pharmaceutical active substances. All these substances are set free by wearing of the textiles. Perfumes evaporate due to their high vapor pressure. Other substances remain on the surface of the skin or will even penetrate into the skin. In this way the treatment of extensive skin diseases is simplified.
Modification of Textile Mats with Calixarenes Separation of Uranium From Mine and Seepage Waters
In 1990 the last uranium mine in Germany was closed, ending more than 40 years of uranium production in the area of Saxony and Thuringia. As a result of the mining operation, several mining plants, milling sites, about 50 big dumps and some tailings are left. The abandoned equipment and mine wastes have to be disposed of to avoid the release of radionuclides, metals and organic contaminants into the biosphere.
The separation of uranium(VI) from aqueous solution by calixarenes by means of solvent extraction has been described in literature. Calixarenes are macrocyclic ligands formed by the base inducted condensation reaction of para-substituted phenols and formaldehyde. Different ring sizes containing 4 to 8 phenolic units are known. The substitution of the hydroxyl groups by hydroxam or carboxy groups increases the selectivity of the ligand for the complexation of uranium(VI) ions.
The present work describes the development of a textile filter material for the separation of uranium(VI) from mine and seepage water using uranophile calixarenes. Textile substrates such as polyester are used for the construction of filter materials combining chemical resistance with good permeability, high specific surface area, low weight and resistance against pressure and abrasion. The ligands are permanently fixed on a polyester fabric by a process comparable to a disperse dying procedure. For this purpose the calixarenes are statistically functionalized by spacer groups.
Textile filter materials for the remediation of uranium contaminated waters are applicable for lower concentration levels because of the high selectivity of the macrocyclic ligands. Filter mats modified by uranophile calixarenes are especially suitable for smaller reclamation objects. The application of this separation technique to further actinides is expected.
The Influences of the Substitution Group and Molecular Weight on the Surface Properties of Non-ionic Cellulosic Ether
The surface free energy and its components for several non-ionic cellulose ethers, e.g. methylcellulose (MC), hydroxypropylcellulose (HPC) and methylhydroxypropylcellulose (MHPC), with varied substitution groups and molecular weights were studied using the column wicking technique. The data indicate that the substitution group has greater influence on the surface free energy and its components than the molecular weight for all these cellulose ethers. Whereas a comparison of the influence from different substitution groups further indicated that the increase of the methyl group is to increase the Lewis base parameter and to decrease the Lewis acid parameter. Moreover, this influence for the hydroxypropyl group is obviously on the contrary. Meanwhile, the comparison show that HPC has the greater surface free energy than MC and HPMC, and all these cellulose ethers are large in the Lifshitz-van der Waals component.
H.Taheri O1, Amir H. Sari1 ,H. Hora2,3 , A. R. Talabi Taher1
1) Plasma Physics Research Center, I.A.University, P.O.Box 14665-678, Tehran, IRAN
2) Faculty of Electr.Engineering, University of Applied Science, Deggendorf,
GERMANY
3) Dept.Theoretical Physics, University of New South Wales, Sydney 2052,
AUSTRALIA
4) Textile Department, Polytechnic University, Tehran-IRAN
Experimental Investigation of Ar+ Ion Irradiation in Oxygen Environment on Polymer Surface
Ion beam irradiation onto polymers has been attracting interest for its improvements of crystallinity , conductivity , mechanical properties , solubility , wettability etc. The physical and chemical changes on the polymer surface have been achieved by irradiation of energetic particles onto the polymer surface with plasma , corona , arc discharge , electron beam , ion beam , etc. The energetic ions create reactive radicals , due to bond scission , which can react with other reactive atoms for the surface modification.
In this study, Ar+ Ion irradiation on a polymer surface was carried out in an Oxygen environment in order to investigate the effects of surface morphology , and surface energy on wettability of polymer. Energy of Ar+ ion irradiation have been used in range of 0.5-1.5 KeV at doses between 1015 to 1016 Ar+/cm2. Formation of functional groups such as - (C=O) , -(C=O)-O- , -(C-O)- , etc, have been studies using FTIR analysis and the morphological changes have been carried out using AFM and SEM techniques. The results show the strong dependence of surface properties to energy and dose variation of Ar+ ions. Details will be discussed in full paper.
Polymer Surface Modification for Tissue Engineering Applications
Nerve fibers (axons) find the appropriate target tissue by a series of adhesive and diffusible signals that are attractive and repulsive. We are interested in creating devices that will promote axon guidance and are investigating polymer modification strategies to achieve this goal. Building on model systems where we demonstrated that surfaces with alternating regions of cell adhesion and non-adhesion are critical for axon guidance, we are now moving toward 3-dimensional patterning techniques that will allow us to create alternating volumes of cell adhesion and non-adhesion. We are creating both physical and chemical channels to achieve this goal of axon guidance within a 3-D framework. Physical channels, created by a fiber templating strategy, are modified with cell adhesive peptides and separated by non-adhesive hydrogel. Chemical channels are created by taking advantage of photochemistry and laser writing techniques within a non-adhesive agarose gel. In both strategies, the polymer is modified with peptides derived from laminin, an extracellular matrix protein. Primary neurons have their axons guided within the adhesive regions. This research lays the foundation for in vivo studies.
Plasma Chemical Model Describing Surface Treatment of Polymers in RF-Discharge
The surface tension is an important characteristic of polymer materials and often its change is tracked by the change of the adhesion work WA or contact angle theta. The change of the angle theta is a result of the treatment of the polymer in the gas discharge plasma. It shows complicated character of development and it depends on the kind of gas, parameters of the plasma, time of treatment ... etc. Consequently the statistical processing of the experimental results is difficult and in many cases leads to incorect conclusions. This can be avoided with a kinetic model describing the chemical processes on the surface of the polymer which facilitates the analysis of the experimental results. Unfortunately, because of the complexity of the interactions it is difficult to find appropriate models. In this work a kinetic model describing only the plasma chemical kinetics of the treated polymer material is presented. The questions connected with the gas discharge and plasma are not examined. In the model two general functional groups are used. This decreases the number of possible heterogeneous chemical reactions and allows for an analytical solution of the system of kinetic equations.
1) Department of Chemistry and Center for Materials Science and Engineering, Rochester Institute of Technology, Rochester, New York, 14623
2) Department of Physics, RIT, Rochester, NY, 14623
3) Endicott Interconnect Technologies, Inc., Endicott, NY 13760
4) Xerox Corporation, Webster, NY 14580
Adhesion of Copper to Poly(tetrafluoroethylene) Surfaces Modified with Vacuum UV Radiation Downstream from He and Ar Microwave Plasma
Teflon ® poly(tetrafluoroethylene) (PTFE) is an attractive material for insulating layers between conductors, such as copper, in the packaging of high-performance electronic devices because of excellent thermal, chemical, and electrical (low dielectric constant (k)) properties. Excellent adhesion between copper and PTFE is especially a challenging task because Teflon-like materials are hydrophobic and relatively inert with low surface energies accounting for their non-stick behavior. Investigations are being conducted to study the ability of plasma generated VUV radiation to control the adhesion of Cu to
low-k materials.
Films of PTFE were modified with VUV radiation downstream from He and Ar microwave plasma. During some of the experiments, oxygen flowed over the surface of the substrate. Results will be reported on the adhesion of copper, which was deposited by sputtering, to these modified PTFE surfaces. Comparisons will be made with the previously reported results obtained using VUV radiation produced from a high pressure (400-500 Torr) DC He arc plasma source [1].
[1] S. Zheng, A. Entenberg, G. A. Takacs, F.D. Egitto, and L.J. Matienzo,
Second International Symposium on Polymers in Microelectronics, Orlando, FL, Nov. 12-15 (2002).
® Teflon is a registered trademark of E. I. duPont De Nemours & Co., Wilmington, DE.
1) Department of Electronics and Photonic Systems Engineering, Hiroshima Institute of Technology, 2-1-1, Miyake, Saiki-ku, Hiroshima 731-5193, JAPAN
2) Mitsubishi Heavy Industry, Limited, Hiroshima Research Center, 6-22, 4-Chome, Kan-On-Shin-Machi, Nishi-ku, Hiroshima 733-8553, JAPAN
Surface Modification of Pet Films by Plasma Source Ion Implantation
Application of a pulsed high negative voltage (~10 s pulse width, 300-900 pps) to a substrate is found to induce discharge and thereby increase the ion current of an inductively coupled plasma. This plasma source ion implantation (PSII) technique is investigated as a surface modification method for polyethylene terepthalate (PET) film using Ar, N2, and C2H2 gases. PSII treatment of PET with N2 and Ar in separate stages is found to change the color of the PET film, effectively increasing near-ultra violet absorption. The effects of this treatment on the chemical bonding of C, H, and O are examined by x-ray photoelectron spectroscopy (XPS). PSII treatment with C2H2 gas is confirmed to produce a thin diamond-like carbon film on the PET surface. The layer is revealed to be smooth by scanning electron microscopy, and the structure is analyzed by XPS and laser Raman spectroscopy. This second treatment effectively reduces the oxygen transmission rate by up to 100 times that of unmodified PET film at a carbon film thickness of only 70 - 300 nm.
Surface Characterisation of Organc Layers by XPS, SIMS and AFM
(Abstract not yet available)
1) Institute of Microelectronics, NCSR-"Demokritos", POB 62230, 153 10 Ag. Paraskevi, GREECE
2) Department of Electronics, Technological Educational Institute of Athens, 12210 Aegaleo, GREECE
Etching Behavior of Si-containing Polymers as Resist Materials for Bilayer Lithography
In this work, we study plasma development properties of siloxanes, model Si-containing polymers for top layer resists in bilayer lithography, in an effort to evaluate these polymers as photoresist components for 193 and 157 nm lithography. In such lithography, the image is developed in the top photosensitive polymer and transferred to the usually thick organic underlayer by means of O2 - based plasma etching. The issue of line edge roughness (LER) induced by transfer etching and its reduction by means of plasma processing optimization is addressed.
The experimental results reveal that careful adjustment of the plasma process parameters is the determining factor in the obtained patterning quality of dry developable bilayer resists with siloxane as the imaging layer. In particular, if an F- containing but not O- containing first etching step under low selectivity and low etch rate conditions precedes the main etching in O2 plasma, LER can be significantly and controllably reduced to levels obtained with wet developable resists without sacrificing much of the PDMS thickness.
The effect of different etching chemistries and processing conditions on imaging layer roughness formation is demonstrated with the analysis of scanning electron microscopy images for quantifying line edge roughness (LER) and atomic force microscopy (AFM) for measuring surface roughness (SR). X-ray photoelectron spectroscopy analysis (XPS), in-situ ellipsometry and in-situ interferometry during etching provide valuable information on surface modification and etching characteristics in order to promote process optimization for LER minimization and understanding of the mechanisms involved.
Hydroxyl Graft Modified Polypropylene as an Adhesion Promoting Agent
Polypropylene (PP) grafted with 0.5 and 1.0 wt% Maleic Anhydride (abbr:PPgMA) was modified, in the melt, with an excess of amine alcohol producing a hydroxyl group graft modified polypropylene (abbr:PPgOH). The modified polymer was characterized by FTIR, and contact angle. FTIR results demonstrated that PP was modified with hydroxyl groups. From contact angle and wetting tension measurements it was observed changes in the films surface polarity. Two-layered films were prepared using PPgOH film and polycarbonate (PC) film. Adhesion strengths were measured using a T-peel test. Increasing the bonding temperature, bonding time resulted in an improved adhesion to PC layers. The peeled films surface was analyzed by SEM and AFM. The Moalu test was positive indicating that a chemical reaction between hydroxyl functionality and carbonate group was taken place.
1) TOYOBO Research Center Co. Ltd., Research Centre, Ohtsu City, Shiga 520-0292 JAPAN
2) Department of Engineering Materials, University of Sheffield, Sir Robert Hadfield building Mappin Street, S1 3JD UK
Functionalised Plasma Polymer Coatings for Promoting the Adhesion of High Performance Polymer Fibres
Plasma copolymerised coating of Acrylic acid and 1,7-octadiene was applied to high strength and high modulus fibre, PBO (poly-p-phenylenebenzobisoxazole) fibre in order to improve the adhesion to epoxy resin. The chemical structure of the plasma polymer on PBO was investigated by using X-ray photoelectron spectroscopy (XPS) with Trifluoroethanol derivatisation technique. This confirmed that PBO was covered completely with the plasma polymer and that the deposit contained a quantitative concentration of carboxylic acid groups. The microbond test was used to evaluate the interfacial shear strength (IFSS) and the relationship between surface functionality and adhesion. The surface retention of carboxylic acid groups could be controlled by changing the ratio of monomers at constant plasma power. IFSS was observed to increase with the increase in the retention of carboxylic acid group. The tensile strengths of single fibres with or without coating were comparable. These results show that the plasma polymerised coating can control the interfacial bond between PBO fibres and the matrix resin without any damage for physical property.
Manufacture of Fiberboard from HTMP Fibers Activated by Treatment with Fenton's Reagent
(Abstract not yet available)
A. H. Sari1, M. R. Hantehzadeh1 , H. Hora2,3
1) Plasma Physics Research Center, I.A. University, P.O.Box 14665-678, Tehran, IRAN
2) Faculty of Electr.Engineering, University of Applied Science, Deggendorf,
GERMANY
3) Dept.Theoretical Physics, University of New South Wales, Sydney 2052,
AUSTRALIA
SEM Study of the Effects of Low- Temperature Plasma with Different Gases on Polymer Surface Modification
Material and new polymers have become ubiquitous material in modern manufacturing processes and offer a wide variety of chemical and mechanical properties applicable to numerous problems. Often, the surface properties of a polymer will preclude its use in an application to which its mechanical properties may be very well suited .For changing this properties we can use of low temperature plasma . In the last paper we investigated the effect of oxygen plasma on the BOPP[1]. In this work we use of, BOPP (22.75 g/m2, thickness of 25 mm, density of 0.91 g/cm3) from Poushineh plastic Co. (Tehran-Iran) treated in plasma chamber. Two plane parallel metal electrodes are connected to an D.C. power supply with an output voltage up to 4kV. The vacuum of the 10-1Pa was achieved by a rotary pump followed by a diffusion pump, which then was increased to 10-3 Pa. By introduction of gases, the pressure was adjusted to 1-10 Pa.
We investigate the effects of different gases (Argon, Nitrogen, Helium, Hydrogen, Oxygen) on polymers surface modification and compare them together using Scanning Electron Microscope (SEM). The details will be discussed in full paper.
Refrences:
[1].H.R.Yousefi, Amir H. Sari, et. al., International Symposium on GDOES for Surface Analysis, Keio university, Yokohama, Japan, November 19-21 , 2002
[2].X.J.Dai,L.Kviz,Textile Institue81st World conference, Melborne,Australia,April 2001
[3] J. Ryu, J. Dai, K. Koo, T. W., JSDC, 108, 1992, p. 278-282.
[4] S. Kobayashi, T. Wakida, S. Niu, S. Hazama, T. Ito and Y. Sasaki, JSDC, 111, 1995, p. 72-76.
[5] T. Wakida, S. Tokino, S. Niu, M. Lee, H. Uchiyama and M. Kaneko, Textile Research J., 63(8), 1993, p. 438-442
[6] T. Okuno, T. Yasuda, H. Yasuda, Textile Research J., 62(8), 1992, p. 474-480.
[7] R. L. Shishoo, The Sixth International conference on Textile Coating & Laminating, Dusseldorf, 1996.
Lehrstuhl für Materialverbunde, Technische Fakultät der Universität Kiel, Kaiserstr. 2, D-24143 Kiel, GERMANY
Nucleation, Growth and Adhesion of Metals on Polymers after Low Energy Ion Irradiation
Various hydrocarbons, oxygenated, halogenated and nitrogen containing polymers were irradiated with low energy (~ 1keV) argon, oxygen, and nitrogen ions to understand how this treatment promotes the adhesion of polymers to metals. The initial stages of the Al, Ni, Cu, Ag, Au film growth and metal-polymer interface formation during vapor phase deposition were characterized using X-ray photoelectron spectroscopy, transmission electron microscopy, atom force microscopy and radiotracer techniques. The combination of these techniques allows one, on the one hand to determine morphological parameters and condensation coefficients, on the other hand to study the surface reactions during the initial stages of polymer metallization which are crucial in determining adhesive characteristics. The observed difference in the metal/polymer interface morphology, condensation coefficients and peel strength between the native and ion treated polymers are discussed to provide the optimum in functionalization and modification of polymer surface structure.
Lehrstuhl für Materialverbunde, Technische Fakultät der Universität Kiel, Kaiserstr. 2, D-24143 Kiel, GERMANY
Ion-beam Erosion Rate, Structural and Chemical Modification of Polymers During Low Energy Ion Irradiation
Various polymers were sputtered with low energy (0.2 - 2 keV) Ar+, O+, N+ ions in order to determine their erosion rate, structural and chemical modification under these condition. Hydrocarbons, oxygenated, halogenated and nitrogen-containing glassy polymers with a weide range of the glass transition temperature (Tg) were chosen. The erosion rate was measured using a stylus profilometer and x-ray photoelectron spectroscopy (XPS)technique. At the same time the surface chemical modification during sputtering was studied. The well known effects of polymer degradation, cross-linking and the formation of new functional groups associated with ion-polymer interaction were observed. Comparing the erosion rate to various polymer properties several conclusions could be drawn. The chemical composition of polymers plays an important but not dominant role in the erosion rate. Two different groups of polymers with significant difference in erosion rate were found. It was shown that the chemical structure of polymers plays the dominant role in the surface erosion, so the sputter rate of polymers such as PS and PMS was significantly different. The erosion rate of polymers reduced dramatically ( in order of magnitude) with ion fluence. This behavior is associated with a crosslinking effect during ion bombardment which is accompanied by a significant increasing of Tg and chemical modification of the polymer surface.