A. Ansarifar; Materials Department, Loughborough University, Leicestershire LE11 3TU, UK

How a Sulfur-bearing Bifunctional Organosilane Changed the Shape of Rubber Formulation

Rubber compounds contain up to eight classes of rubber chemicals. The cure system consists of primary and secondary accelerators, primary and secondary activators and elemental sulfur. Excessive use of the curing chemicals is harmful to health, safety and the environment and their use is restricted by the new European chemicals policy, Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH). Reduction in the use of these chemicals is now a priority.

Some unsaturated hydrocarbon rubbers were cured and reinforced with different amounts of a precipitated silica the surfaces of which were pre-treated with bis(3-triethoxysilylpropyl) tetrasulfide (TESPT). TESPT is a sulfur-bearing bifunctional organosilane which chemically bonds silica to the rubber. The chemical bonding between the filler and rubber was optimized via the tetrasulfane groups of TESPT. The crosslink density changes were measured as a function of the loading of the chemical curatives.

It emerged that the requirement for the curatives depended on the composition of the rubber and the loading of the filler. This reduced the curatives and simplified the cure system. Major benefits were also gained for health, safety and the environment.

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A Babik and V. Cech; Institute of Materials Chemistry, Brno University of Technology, Purkynova 118, CZ-61200 Brno, CZECH REPUBLIC

Self-assembled Monolayers of Vinyltriethoxysilane and Vinyltrichlorosilane

Although a molecular monolayer is only a few nanometers thick, it can completely change the chemical and physical properties of a surface. Molecular monolayers can be readily prepared using chemisorptions on a variety of surfaces. The self-assembled monolayers (SAMs) are highly ordered two-dimensional structures that form spontaneously by the immersion of an appropriate substrate into a solution of an active surfactant in an organic solvent. The most common adsorbate/substrate combinations are alkylsilanes on oxide surfaces. Our study is aimed at SAM deposition using vinyltriethoxysilane (VTES) or vinyltrichlorosilane (VTCS) molecules chemisorbed on silicon oxide surfaces. The kinetics of formation of VTES or VTCS monolayers on planar glass substrate or silicon wafer with native silicon dioxide layer was characterized by contact angle measurements. The surface free energy and its components were evaluated using the Owens-Wendt-Kaelble geometric mean method and the Wu harmonic mean method. Spectroscopic ellipsometry was used to determine the thickness of deposited films. Detailed information on the elemental composition of SAMs was obtained by X-ray photoelectron spectroscopy (XPS). Surface morphology of deposited films was investigated by atomic force microscopy (AFM).

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Bhanu P. S. Chauhan, Leon Prasanth K, Ramani Thekkathu, Ankita Shah, Hardika Shukla, Vanessa Comerón and Tamar Lesnoy: Engineered Nanomaterials Laboratory, Department of Chemistry, William Paterson University, 300 Pompton Road, Wayne, NJ 07470-2103

Hydrosilanes as coupling agents for “Living” Metal Nanopartcles Surfaces

Transition metal nanoparticles have become one of the very important classes of nanosized materials because of their unique properties resulting due to size and shape confinement. We have been investigating the synthesis, characterization and property profiling of transitional metal nanoparticles for quite some time now and have devised very unique ways to stabilize and utilize such nanoparticles in applications ranging from catalysis, to selective drug delivery.^1-3 This quest has pointed us to investigate the surface chemistry of transition metal nanoparticles as it relates to their catalytic activity, selectivity and recyclability properties.

In this presentation, we will present our recent work³ on the coupling chemistry of nanoparticles of Ag, Au, Pd, Pt, Rh and Ru metals with various types of silanes. In our method these particles are generated via hydrosilane induced reduction of corresponding metal salts. This strategy provides a simple, one step room temperature access to stable, analyzable and utilizable metals nanoparticles in good yields. Though, the questions such as optimum stability vs optimum activity and selectivity need more investigations but our recent results show that the interaction of residual Si-H bonds with nanoparticle surface plays a very important role in this chemistry. We will also present the aspect related to their living nature and their utility in the fields such as catalysis.

1.     Auerbach, A. ; Chauhan, B. P. S.; Clarke, R.P.; Haider, I. M.; Latif, U. US Patent; 2010 (08/2010), No. US 7,745,547B-1

2.     Chauhan, B. P. S.; Rathore, J. S. J. Am. Chem. Soc. 2005, 127, 5790-5791.

3.     Chauhan, B.P.S.; Sardar, R. Macromolecules 2004, 37, 5136-5139.

4.     Chauhan, B. P. S.; Thekkathu, R.; Leon, P. K.; Mandal, M. and Lewis, k. Appl. Organometal. Chem. 2010, 24, 222-228.

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L. Hoferek, E. Palesch and V. Cech; Institute of Materials Chemistry, Brno University of Technology, Purkynova 118, CZ-61200 Brno, CZECH REPUBLIC

Plasma-polymerized Films Based on Tetravinylsilane Monomer

Plasma-polymerized organosilicones constitute a class of materials with a rich and varied scientific background. This class of materials possesses a special characteristic, which distinguishes it from other plasma polymers – the ability to vary and control the degree of its organic/inorganic character (i.e., the carbon content) and the polymer cross-linking by the appropriate choice of fabrication variables. This allows one to control many physico-chemical properties over wide ranges resulting in an extraordinary potential for useful applications, which are only now beginning to be tapped. The organosilicon plasma polymers are widely recognized for their potential in optical, mechanical, and electronic applications. Mostly hard coatings are developed as protective layers, but we aimed at soft coatings using pulsed plasma. A reduction of plasma energy (power), but operated in several orders of magnitude, enabled us to control chemical composition and structure of plasma polymer coatings resulting in a wide range of mechanical, optical, and surface properties.

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Bret Chisholm, Partha Majumdar, Shane Stafslien, and David Christianson;

Center for Nanoscale Science and Engineering, North Dakota State University

Fargo, ND, USA

An Investigation of Antimicrobial Coatings Derived from Quaternary Ammonium-Functional Alkoxysilanes Using Combinatorial/High-Throughput Methods

An extensive combinatorial/high-throughput workflow was used to construct detailed structure-property relationships for moisture-curable polysiloxane coatings derived from alkoxysilanes possessing quaternary ammonium salt (QAS) moieties. An array of QAS-functional alkoxysilanes were produced that possessed systematic variations in chemical structure. These QAS-functional alkoxysilanes were subsequently used to produce approximately 200 unique polysiloxane coatings and the antimicrobial properties characterized using high-throughput biological assays. Antimicrobial properties of the coatings were found to depend strongly the chemical structure of QAS-functional alkoxysilane. In addition to being dependent on QAS-functional alkoxysilane composition, antimicrobial properties were found to be dependent on silanol-terminated polysiloxane molecular weight. Surface characterization of the coatings indicated that relationships between antimicrobial activity and chemical structure of the QAS-functional alkoxysilane was primarily driven by the process of self-assembly of QAS groups at the coating/air interface as opposed to the inherent antimicrobial activity of the QAS-functional alkoxysilanes. From the data obtained, a relatively narrow region of the compositional space was identified that resulted in the production of coatings with broad-spectrum antimicrobial activity. These coatings may have utility for combating both device-related infection in the healthcare industry and marine biofouling in the shipping industry.

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Hari T Deo; Institute of Chemical Technology Deemed University, Mumbai, INDIA

Present Address (While in USA): 1909 Waverly CT, APT 5, COLUMBIA, MO 65201-5493.

E-mail: htdeo85@hotmail.com

@rediffmail.com

The Enhanced Inter-facial Adhesion Phenomena Using Ti-based Polymeric Surface-modifying Formulations

(Abstract not yet available)

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W. Dierkes¹, M. Tiwari¹, R. Datta¹, A. Talma¹, J. Noordermeer¹ and W. van Ooij²

1) University Twente, Faculty of Engineering Technology, Department of Elastomer Technology & Engineering, Enschede, THE NETHERLANDS

2) Department of Chemical and Materials Engineering, University of Cincinnati, Cincinnati, OH 45221-0012, USA

Improving Compatibility and Interaction of Polymers and Additives in Rubber by Surface Modification in a Plasma Polymerization Process

Blending of elastomers and additives is still a challenge in rubber compounding as the thermodynamic compatibility of polymers in a blend is rather low, and the various components differ significantly in polarity and reactivity. As the quality of rubber strongly depends on morphological properties, an improvement of the compatibility of the compound components allows improving the property profile of the material.

Surface treatment by a plasma polymer coating allows tailoring the surface polarity and chemistry of additives while maintaining the structure, a crucial factor in the case of fillers. A study on the effect of different monomers for the surface coating of carbon black, silica, sulphur and CBS was done in straight polymers as well as in dissimilar blends. The dispersion and distribution of the additives in the polymer matrix as well as the influence on the morphology of polymer blends were investigated, next to the influence on mechanical properties.

Silica was found to be easily coated by different types of monomers compared to carbon black and curing additives. The effect of plasma-treatment of the additives on the morphological and mechanical properties of the material was varying with the chemical structure of the surface coating, allowing tailoring the additive-polymer interaction according to the requirements.

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Tsutomu Furuta and Akira Nakajima; Department of Metallurgy & Ceramics Science, Graduate School of Science & Technology, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8552, JAPAN

Evaporation and Sliding of Water Droplets on Fluoroalkylsilane Coatings with Nanoscale Heterogeneity

Evaporation and sliding behaviors of water droplets were investigated on smooth and rough fluoroalkylsilane coatings. The rough coating possesses nanoscale roughness and chemical heterogeneity on its surface. Evaporation behaviors for these two coatings differed when nanoliter-scale droplets were used, although they were nearly identical for microliter-scale droplets. The droplets on the smooth coating exhibit greater sliding acceleration and a larger slipping velocity ratio than those on the rough coating. Both the evaporation behavior of nanoliter-scale droplets and sliding velocity of microliter-scale droplets were affected by nanoscale surface heterogeneity. They are indicators for highly homogeneous smooth silane coatings.

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M. Masudul. Hassan¹, Marco Mueller², Diana J. Tartakowska² and Manfred H. Wagner²

1) Department of Chemistry, M C College, National University, Sylhet-3100, BANGLADESH

2) Technical University of Berlin, Institute of Material Science and Technology, Chair of Polymer Engineering/Polymer Physics, D-10623 Berlin, GERMANY

Grafting of Gycidyl Methacrylate on to Isotactic Polypropylene Used as a Compatibiliser For Composite Preparation

Gycidyl methacrylate grafted isotactic polypropylene (GMA-g-PP) copolymer have been manufactured by free radical polymerization using benzoyl peroxide (BPO) initiator with twin screw extruder. FTIR, DSC and SEM result corroborated the evidenced of the modification of the PP surface. GMA-g-PP is more hydrophilic than unmodified polypropylene (PP). Thus, this method can be used to obtain physico-chemically altered PP surfaces. Moreover, the modified PP matrix i.e. GMA-g-PP can be used as a compatibiliser to prepare composites with enhanced properties.

Corresponding to: M. Masudul Hassan (e-mail: msdhasan@yahoo.com)

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N. Deb¹, M. A. Hossain¹, M. Masudul Hassan¹ and M. A. Khan²

1) Department of Chemistry, M C College, National University, Sylhet-3100, BANGLADESH

2) Radiation and Polymer Chemistry Laboratory, Institute of Nuclear Science and Technology, Bangladesh Atomic Energy Commission, P.O. Box 3787, Dhaka, Bangladesh.

Role of Radiation on the Chitosan Film Extracted from Prawn Shell: Effect of Silane

The ability of chitosan to form films may permit its extensive use in the formulation of film dosage forms or as drug delivery systems. In our present study, chitosan has been prepared from prawn shell chitin. Chitosan could be dissolved in organic acids, such as lactic acid and acetic acid, prior to being casted into films. The role of gamma and UV radiation on the chitosan film has been studied. The tensile testing provides an indication of the strength and elasticity of the film, which can be reflected by tensile strength and elongation at break. Incorporation of a minute amount (1%) of silane N-(3-methoxysilyl) propyl ethylene amine in the formulation produced significant enhancement of the mechanical performance of the chitason film. The prepared film have been characterized by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS).

Corresponding to: M. Masudul Hassan (e-mail: msdhasan@yahoo.com)

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Guo Liang Li, K. G. Neoh and E. T. Kang; Department of Chemical & Biomolecular Engineering, National University of Singapore, Kent Ridge, Singapore 119260

Silane-Promoted Synthesis of Functional Hollow Polymeric and Hybrid Micro- and Nanostructures

Combination of sol-gel reaction with distillation-precipitation polymerization, controlled radical polymerization (atom transfer radical polymerization or ATRP) and/or ‘click’ reactions (alkyne-azide and thiol-ene ‘click’ chemistry) allows the design and synthesis of a wide-range of functional hollow polymeric, inorganic and polymer-inorganic hybrid micro- and nanostructures. These micro- and nanostructures include stimuli-responsive and functional (i) hollow polymeric microspheres and concentric hollow silica microspheres, (ii) double-walled concentric hollow polymeric microspheres, (iii) concentric hollow nanospheres of mesoporous silica shell-titania core, (iv) core-double shell microspheres, (v) hybrid nanorattles of catalytic metal core and polymer shell, (vi) hairy hollow microspheres of fluorescent shell and polymer brushes, (vii) binary polymer brushes on silica@polymer hybrid nanospheres and hollow polymer nanospheres, and (viii) hairy hybrid microrattles of metal nanocore with functional polymer shell and brushes.

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Yun mi Kim*, Janis Matisons, Barry Arkles; Gelest Inc., 11 East Steel Road, Morrisville, PA 19067, USA

*presenting author, ykim@gelest.com

Evaluating the Hydrolytic Stability of Silane, Titanate and Phosphate Coupling Agents on Metallic and Silicious Substrates

Much has been written about silanes, titanates and phosphates as surface modifying agents. These materials are used to provide hydrophobic properties on various substrates. Data on the comparative performance of hydrocarbon substituted analogs of all three classes of these surface modifying agents on various substrates is generally not available. We examined three commonly used octadecyl (C18) substituted materials, octadecyltrimethoxysilane, (Catalogue No. SIO6645.0), titanium triisostearoylisopropoxide (Catalogue No. AKT887.5), and octadecylphosphonic acid (Catalogue No. OMPH062) and evaluated their hydrolytic stability on three metallic substrates (zirconium, titanium, and carbon steel) as well as two siliceous substrates, (borosilicate and quartz glasses). Each substrate was exposed to four different aqueous solutions: deionized. water at room temperature; deionized water at 80C; 1N acetic acid solution, and 1N NH₄OH solution for set time periods. The hydrolytic durability of the applied coupling agents was monitored by the change of contact angle on the substrates (after extended exposure to deionized water. This study provides invaluable information on selecting not only the best surface modifying agent, but also provides optimum application conditions on a variety of key substrates.

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L. Wang, C. Huang, E. T. Kang and K. G. Neoh; Department of Chemical and Biomolecular Engineering, National University of Singapore, Kent Ridge, Singapore 119260

Email: chenkg@nus.edu.sg

Designing Functionalized Magnetic Nanoparticles via Silane Anchors for Biomedical Applications

There is increasing interest in recent years in using superparamagnetic iron oxide nanoparticles (SPIONs) for biomedical applications such as magnetic resonance imaging (MRI) contrast enhancement, drug delivery and hyperthermia. However, designing these nanoparticles for use in a biological environment can be rather challenging. Due to the high surface area to volume ratio of these nanoparticles, there is a tendency for aggregation. Furthermore, in tumor targeting applications, these nanoparticles have to evade the body’s immune system and selectively accumulate in the tumor. In this work, we report on two strategies to modify the SPIONs with the a hydrophilic polymer shell with a cancer targeting ligand (folic acid) to achieve targeting of tumor cells while minimizing uptake by macrophages. Both strategies rely on the use of silane as the surface anchor on the SPIONs. In the first strategy, an atom transfer radical polymerization (ATRP) initiator was synthesized via the reaction of γ-aminopropyl triethoxysilane with 2-bromoisobutyryl bromide, and immobilized on the SPIONs surface. Surface-initiated ATRP of glycidyl methacrylate on SPIONs and subsequent reaction with ethylenediamine were carried out. This polymer coating renders the nanoparticles water-soluble, and at the same time generates functional groups for conjugation with folic acid. In the second strategy, nanoparticles of Fe₃O₄ core with fluorescent SiO₂ shell were synthesized and grafted with hyperbranched polyglycerol. The numerous surface hydroxyl groups of these nanoparticles were conjugated with folic acid by a thiol ‘click’ reaction. The nanoparticles prepared by these two strategies have low cytotoxicity and favorable MR properties, and exhibit selective targeting of tumor cells while concomitantly the uptake by macrophages and normal cells is minimized.

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E.H.N. Pow¹* K.K.C. Yeung¹, J.P. Matinlinna²

1) Oral Rehabilitation, Faculty of Dentistry, The University of Hong Kong, HONG KONG

2) Dental Materials Science, Faculty of Dentistry, The University of Hong Kong, HONG KONG

*corresponding author, ehnpow@hku.hk

HEMA and Silane Blend Effects on Resin Titanium Bonding

Objectives: To evaluate the adhesive performance of two activated organofunctional silane coupling agents alone and two silane blend systems with HEMA as adhesion promoters for bonding an experimental bis-GMA to a silica-coated titanium surface, under 3 different storage conditions.

Materials and methods: 1) 3-methacryloxypropyltrimethoxysilane, 2) 3-acryloxypropyltrimethoxysilane, 3) a silane blend consisting of 3-methacryloxypropyltrimethoxysilane with 0.5% vol. HEMA, 4) a silane blend consisting of acryloxypropyltrimethoxysilane with 0.5% vol. A commercial 3-methcryloxypropyltrimethoxxysilane (EPSE Sil^TM) was used as a control. The silanes were applied onto tribochemically silica-coated titanium surfaces (Rocatec®). Experimental bis-GMA resin stubs were applied and photo-polymerized onto titanium. The specimens were stored in three different conditions: 1) dry storage for 24 hours, 2) storage in de-ionized water at 37C for six months and 3) de-ionized water at 37C with regular thermocycling interval (6000 cycles, 5-55C) for 6 months, respectively. Shear bond strengths of the resin to titanium were measured by using a universal testing machine. The surface examination, after shear bond strength test, was made with a scanning electron microscope (SEM).

Results: Highest shear bond was obtained with 3-acryloxypropyltrimethoxysilane stored in dry for 24 hours (20.2+3.2MPa), and the lowest result was obtained with 3-methcryloyoxypropyltrimethoxxysilane (EPSE Sil^TM) in de-ionized water at 37C with regular thermocycling interval (6000 cycles, 5-55C) for 6 months (1.4+0.6MPa). The type of storage condition and type of failure mode affected significantly the shear bond strength (p<0.05). The shear bond obtained from dry storage was highest, while the shear bond obtained from thermocycled storage was lowest. Adhesive failure was the main failure mode with 87.2% of all specimens. The use of HEMA did not significantly affect the shear bond strengths.

Conclusion: The use of HEMA does not improve the adhesive performance of the experimental resin to titanium.

References:

Matinlinna JP, Lassila LVJ, Vallittu PK. Experimental Novel Silane System in Adhesion Promotion between Dental Resin and Pretreated Titanium. Silicon 2009; 1(4):249-254

Puska M, Lassila L, Seppälä J, Vallittu P, Matinlinna J. Effect of pH and alcohol solvent on bonding Bis-GMA/MMA resin onto silica-coated and silanized titanium. J Adhes Sci Techn 2009; 23: 991-1006.

Matinlinna JP, Lassila LVJ, Vallittu PK. The Effect of Five Silane Coupling Agents on the Bond Strength of a Luting Cement to a Silica-coated Titanium. Dent Mater 2007; 23:1173-1180.

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A. N. Rider¹ and N. Brack²

1. DSTO, Melbourne, AUSTRALIA

2. La Trobe University, Melbourne, AUSTRALIA

The Influence of Surface Roughening and Plasma Treatment on the Environmental Resistance of Epoxy to Titanium Adhesive Bonds

Titanium alloy was roughened using either abrasion techniques or grit-blasting with 50 micron alumina particles. The environmental resistance of the bonds formed between a rubber toughened epoxy adhesive and the titanium alloy was significantly influenced by the degree of surface roughness. Further, the addition of a thin organosilane film and primer to the titanium, significantly increased the environmental resistance of the adhesive bond. An atmospheric plasma treatment of the titanium prior to organosilane treatment also improved uniformity of the resultant thin film as determined by AFM and XPS. Characterisation of the titanium surfaces before bonding and after testing revealed some abrasive particles can be left embedded in the titanium surface. Under mode I stress and a hygrothermal environment the particles may pull-out from the titanium surface, which leads to a bond with lowered fracture toughness. The chemical composition of the abrasive particles may be related to their adhesion to the titanium substrate.

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Tsutomu Furuta and Akira Nakajima; Department of Metallurgy & Ceramics Science, Graduate School of Science & Technology, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8552, JAPAN

Evaporation and Sliding of Water Droplets on Fluoroalkylsilane Coatings with Nanoscale Heterogeneity

Evaporation and sliding behaviors of water droplets were investigated on smooth and rough fluoroalkylsilane coatings. The rough coating possesses nanoscale roughness and chemical heterogeneity on its surface. Evaporation behaviors for these two coatings differed when nanoliter-scale droplets were used, although they were nearly identical for microliter-scale droplets. The droplets on the smooth coating exhibit greater sliding acceleration and a larger slipping velocity ratio than those on the rough coating. Both the evaporation behavior of nanoliter-scale droplets and sliding velocity of microliter-scale droplets were affected by nanoscale surface heterogeneity. They are indicators for highly homogeneous smooth silane coatings.

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Gon Seo; School of Chemical Engineering, Chonnam National University, Gwangju 500-757, Korea (South)

Improved Tensile and Dynamic Properties of SBR Compounds Reinforced with Networked Silicas Prepared Using Silanes as Connecting Materials

The dynamic property of tread rubber compounds becomes an important issue to be urgently improved for manufacturing environmentally-friendly tires with better wet traction and lower rolling resistance in order to enhance their safety and fuel efficiency. Networked silicas with three-dimensional networks among silica particles have been prepared by using various silanes as connecting materials. The networked silica considerably improves the tensile property of rubber compounds by increasing the entanglement of rubber molecules with the connecting materials rather than the chemical bonds formed between silica particles and rubber molecules as in the conventional rubber compounds reinforced with silica and coupling reagent. The rubber compounds reinforced by the networked silicas also exhibit improved dynamic properties deduced from their tan delta curves. The absence of the chemical bonds between rubber molecules and silica particles lowers the restriction on the molecular deformation of rubber, improving wet traction. The entanglement in networked silica-filled rubber compounds lowers their hysteresis, resulting in lower rolling resistance. Furthermore, no emission of ethanol due to the elimination of conventional coupling reagents guarantees cleaner working atmosphere. The structure, dispersion, and surface property of the networked silicas and the performance of SBR compounds reinforced with them in terms of viscous, cure, tensile, dynamic, and abrasive properties will be discussed in this presentation.

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Roy U. Rojas Wahl; Momentive Performance Materials, 769 Old Saw Mill River Road, Tarrytown, NY 10591

The Reaction Between Organoalkoxysilane Esters And 1,3-Diols To Form Cyclic Silane Esters

"Organoalkoxysilane esters are well known coupling agents and crosslinkers. Typically, they are converted to reactive silanols by hydrolysis, which is often accompanied by release of undesired volatile organic compounds (VOCs). Here we describe certain aspects of transesterification reactions of 1,3-diols with conventional silanes as a means to yield products that can help lower VOCs. Mechanistic insights along with suggested applications will be discussed."

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