Isopropyl myristate modified silicone as a potential new encapsulating material for implantable devices

A new modified silicone was obtained by the physical entrapment of a hydrophobic lipid, isopropyl myristate (IPM), to improve the encapsulation properties and corrosion resistance of medical electronic implants. Differences between the water transport for films in contact with water vapor versus those in contact with liquid water were identified; they showed increased permeability to water vapor, which was possibly the result of differences in the water organization at the hydrophobic film interface. Improvements, including enhanced scratch resistance and adhesion, in the mechanical properties of the modified material was also achieved. The incorporation of IPM further resulted in a significant improvement in the cell biocompatibility compared with the unmodified polymer; this suggested that the IPM combination could be a viable basis for implant device packaging. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Influence of clay modification on the reinforcement of vinyl‐terminated polydimethylsiloxane networks

A novel method was attempted to reinforce a vinyl‐terminated polydimethylsiloxane (PDMS) with two commercially available clays, sodium montmorillonite and Cloisite^® 25A. The two clays were functionalized with bis(3‐triethoxysilylpropyl)tetrasulfide (TESPT) to prepare Na⁺MMTS₄ and C25AS₄, respectively. Incorporation of the tetrasulfide group‐containing clays, especially Na⁺MMTS₄, was found to be effective for the enhancement of the interfacial interaction between PDMS and the clays by way of a plausible chemical reaction between the tetrasulfide groups (TSS) and the vinyl‐terminated PDMS. Compounding of PDMS with the TESPT‐modified clays improved the mechanical properties significantly. In particular, the elongation at break of PDMS/Na⁺MMTS₄ composite was almost twice as high as that of neat PDMS, even if the silicate layers were not fully exfoliated in the PDMS matrix. The tear strength of PDMS was also improved greatly as a result of the incorporation of Na⁺MMTS₄. According to toluene swelling test results, the crosslinking density of the composites was lower than that of neat PDMS, indicating that the improved mechanical properties of the composites arise from enhanced compatibility between the constituents and not from increased crosslinking density. Copyright © 2009 Society of Chemical Industry     

Investigating the surface properties of polyurethane based anti‐graffiti coatings against UV exposure

A permanent anti‐graffiti coating based on a polyurethane resin was prepared by incorporating different levels of an OH‐functional silicone modified polyacrylate additive. Static contact angle measurements and dynamic mechanical thermal analysis (DMTA) were employed to evaluate surface free energy and mechanical properties of the coating specimens, respectively. Effect of ageing condition on the graffiti properties of the coating samples was evaluated utilizing an accelerated weathering test. Color changes, surface morphology, and variations in the mechanical properties were also examined prior to and after being exposed to UV irradiation for 864 h in a QUV chamber. Results showed that surface free energy of the samples decreased with replacement of polyol with additive up to 5 mol %. A Scanning electron microscope equipped with energy dispersive X‐ray detector revealed that for the samples containing more than 5 mol % additive, there was an enrichment of silicone at the interface of films and air. At long exposure times and higher concentrations of additive, depreciation of graffiti properties was seen. DMTA and attenuated total reflectance‐fourier transform infra‐red studies before and after ageing showed that the silicone additive tended to degrade while it could cause an increase in crosslinking density. Water contact angles and atomic force microscopy images after ageing revealed that the cause of the depletion in anti‐graffiti properties was attributed to the deterioration of the silicone additive. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

An investigation of scratch testing of silicone elastomer coatings with a thickness gradient

Silicone elastomer coatings are currently being investigated as foul release coatings on ships hulls. Previous tests on silicone duplex elastomer coatings used a progressive load scratch test. It has been shown that the durability of uniform silicone duplex elastomer coatings is a function of thickness, indentation modulus, and stylus and that the failure mechanism depended on coating thickness and stylus. When applying silicone coatings to a ship's hull, there are regions on the ship where the coating is not uniform. This article investigates the effect of a thickness gradient on the durability of a single layer silicone elastomer coating. In these tests, a constant normal load was used as the stylus moved transversely to the surface. It was found that when the scratch test started in the silicone coating and proceeded in the direction of decreasing coating thickness (“Elastomer to Metal”), there was first a scratch tract followed by the initiation of detachment of the coating, then by gross detachment of the coating. When the scratch started on the exposed aluminum surface and proceeded into the silicone in the direction of increasing coating thickness (“Metal to Elastomer”), there was first gross detachment of the coating, followed by recovery (i.e., silicone coating is intact) and a scratch tract into the silicone. It was also found that the coefficient of friction was much higher in the silicone when the scratch test was going in the direction of decreasing coating thickness as opposed to the scratch test going in the opposite direction. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Comparison of performances of macro,micro and nano silicone softeners

A lightweight plain-woven scoured and bleached cotton fabric was treated with macro, micro and nano silicone softeners each at three levels of concentration separately. The treated fabric samples were tested for hydrophilicity and various physical properties to evaluate the performance of the softeners. By using ANOVA it is established that there were significant changes in the degree of hydrophilicity, crease recovery, stiffness, bending modulus, drape as well as tearing strength. The macro softener made the fabric less flexible and less hydrophilic in nature than the same with the micro. The micro softener imparted maximum flexibility and the nano softener the best hydrophilicity. The softness, evaluated subjectively by the judges, confirmed that the nano-finished sample produced maximum softness and maximum durability followed by micro- and macro-finished samples. The scanning electron microscope photographs confirm that the macro softener mostly deposits on the fibre surface, while the nano softener penetrates inside the fibre and the micro softener takes up an intermediate status.     

Ethynyl aromatic siliconhybridized resin: Synthesis,characterizations, and thermal properties

A novel silicon‐containing resin (ESA resin) was successfully synthesized by the condensation reaction of lithium arylacetylide with chlorosilane in high yields. The resin was characterized by the techniques of FTIR, ¹H‐NMR, ²⁹Si‐NMR, and gel permeation chromatography. Thermal cure process was monitored by DSC and FTIR methods. This resin could melt at around 100°C and thermally cured at 200–250°C with low exothermal enthalpy. Owing to the high aryl groups containing and the complete crosslinking of ethynyl groups, the cured ESA resin exhibited excellent thermal stability and high char yield. The decomposition temperature $T_{d_5}$ of the cured resin was at 510°C, and the residue yield at 900°C was 82.9% in N₂. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Crosslinked methyl methacrylate/ethylene glycol dimethacrylate polymer compounds with a macroazoinitiator

A silane‐containing diamine, bis(p‐aminophenoxy) diphenylsilane (BADPS), was prepared by the condensation of p‐aminophenol with dichlorodiphenyl silane in the presence of triethylamine. Then, BADPS was condensed with 4,4‐azobis(4‐cyanopentanoyl chloride) to prepare macroazoinitiators containing silane units (Si–MAIs). A series of poly(methyl methacrylate) gels containing silane were derived by the solution free‐radical crosslinking copolymerization of methyl methacrylate and ethylene glycol dimethacrylate monomers initiated by these macroazoinitiators at a total monomer concentration of 6 mol/L and 80°C. Si–MAIs were characterized with ¹H‐NMR and ¹³C‐NMR spectroscopy, and the structural characteristics of the gels were also examined. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Formation and structure of poly(methyl methacrylate) gels containing triphenyl vinyl silane

A series of Poly(methyl methacrylate) gels (PMMA) were prepared for making optical lenses by solution free radical crosslinking copolymerization of 2,2,2,‐trifluoroethyl methacrylate (TFEMA), methyl methacrylate (MMA), ethylene glycol dimethacrylate (EGDM), and triphenyl vinyl silane (TPVS) comonomer systems. They were then studied in toluene at a total monomer concentration of 5 molL^?1 and 70°C. The conversion of monomer, volume swelling ratio, weight fraction, and gel point were measured as a function of the TPVS concentration, temperature, and chain transfer agents up to the onset of macrogelation. Structural characteristics of the gels were examined by using equilibrium swelling in toluene, gel fraction, and Fourier‐transform infrared (FTIR) analysis. The morphology of the copolymers was also investigated by Scanning electron microscopy (SEM). The dilution of the monomer mixture resulted in an increase in the gel point and swelling degree and a decrease in the percentage of conversion and gel fraction. Finally, TPVS is a compatible vinyl type silicone comonomer for this system. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Eucalyptus kraft pulp fibers as an alternative reinforcement of silicone composites. II. Thermal,morphological, and mechanical properties of the composites

Silicone composites reinforced with short eucalyptus pulp fibers were obtained. The composites were prepared with untreated fibers and with fibers modified with a silane coupling agent, vinyltriethoxysilane, with tetrahydrofuran or ethanol as a solvent. The surface treatment improved the adhesion at the fiber–matrix interface, and vinyltriethoxysilane was suitable for forming a covalent and nonhydrolyzed interface in the composites. The thermal stability of the composites was lower than that of the silicone matrix, with a distinct mechanism of degradation, because of the presence of the cellulosic fibers in the composite. The tensile properties of the composites depended more on the fiber dispersion in the matrix than on the nature of the interface. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3739–3746, 2003     

Silicones on glass surfaces

X-Ray photoelectron spectroscopy can be applied to the study of the bonding of highly functionalised silicones on to E-glass fibres. The adsorption of six types of silicones (hydrido, epoxy, unsaturated imino, methacryl. ‘terminal’ amino and ‘pendant’ amino) from dilute toluene solutions were compared with that of a standard silane coupling agent. The calcium concentration was found to be an effective determinant of surface coverage by the siloxanes. as well as enabling the thicknesses of the adsorbed layers to be determined.