Transient effects in dynamic modulus measurement of silicone elastomers 1. Zero mean strain measurements

The strain‐dependent dynamic storage modulus of a poly(dimethyl‐siloxane‐co‐methylvinyl‐siloxane‐co‐methylphenyl‐siloxane) based silicone elastomer, which is reinforced with fumed silica and crosslinked with peroxide, is investigated. The dependence of the resulting dynamic storage modulus on the duration of cycling at a particular test condition is investigated and compared to static stress relaxation measurements in the same strain range. The dynamic modulus results are shown to depend on the time of cycling at the current test conditions as well as the time of cycling at prior conditions of lower strains. The relaxation is shown to be related to the time of cycling rather than the number of cycles performed. The pattern of behavior of the relaxation of the dynamic modulus with respect to peak strain amplitude is different than that observed in a static stress relaxation test, both of which show significant nonlinear effects in strain. The observed phenomena are interpreted in terms of the role of the polymer phase on the dynamic behavior of the elastomer material. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1001–1009, 2005     

A novel alkoxysilane‐modified high solids hydroxyl acrylic polyurethane: Preparation and surface properties

Alkoxysilane‐modified high solids hydroxyl acrylic polyurethane was prepared by solution polymerization. Its structure, surface, and thermal properties were investigated by ¹H NMR, device of contact angle, thermo gravimetric analysis (TGA), atomic force microscopy (AFM), and X‐ray photoelectron spectroscopy (XPS). Research showed that alkoxysilane modified high solids hydroxyl acrylic polyurethane has superior properties that can be used for automotive paints. The contents of silicone in the alkoxysilane‐modified high solids hydroxyl acrylic polyurethane were 1.25, 1.5, 2, and 2.5 wt %. In this study, γ‐methacryloxypropyltrimethoxysilane (MPTS) was chosen as the modifier. Results showed that the contact angles of water and surface roughness on the film of MPTS modified high solids hydroxyl acrylic polyurethane increased, and thermal stability of the film at high temperatures improved with the increasing of the silicone content in the resins. MPTS modified high solids hydroxyl acrylic polyurethane with 2.5 wt % silicone content had better water resistance, better acid resistance, higher hardness, and excellent weatherability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1866–1871, 2006     

Effect of peroxide crosslinking on the dynamic modulus of silicone rubber

The effect of peroxide crosslinking on the dynamic modulus of a silica‐reinforced silicone [poly(dimethylsiloxane)] elastomer was investigated. Three different peroxides (t‐butyl peroxide, t‐butyl perbenzoate, and benzoyl peroxide) were employed at various practical loadings and differences in the nonlinear behavior of the dynamic modulus were found. Results are discussed with respect to changes in crosslinking density and the identity of the peroxide. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1504–1512, 2005     

Synthesis and characterization of nonionic 1‐vinyl‐2‐pyrrolidinone/methacryloxy silicone copolymers: Effects of molecular weight of silicone and crosslinking density

Nonionic 1‐vinyl‐2‐pyrrolidinone/methacryloxy silicone copolymers (VP/VS copolymers) were prepared and characterized as functions of molecular weight of silicone and crosslinking density. Fourier transform infrared spectroscopy, ¹³C‐NMR, and pyrolysis gas chromatography–mass spectrometry study showed that those copolymers were successfully synthesized. Also, the gel‐permeation chromatography spectrum exhibited a fairly narrow distribution of the molecular weight of the polymer. It was found that the turbidity in ethanol (EtOH) and the glass‐transition temperature of crosslinked VP/VS copolymers are influenced by the amount of crosslinking agent. However, in the case of branched VP/VS copolymers, a transparent solution was obtained, regardless of the molecular weight of silicone. SEM/EDS study revealed that silicone is more abundant on the coating surface than on the interface of coating/glass. This is probably because Si‐containing chains have lower surface energy than that of vinylpyrrolidinone‐containing chains. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2244–2253, 2002     

有机硅微乳液的研究进展

对近年来有机硅微乳液的研究进展进行了综述，包括有机硅微乳液的制备方法（乳液聚合法和硅油乳化法等），及其在纺织印染，化妆品及医药，表面涂覆等领域的应用。     

Preparation of polydimethylsiloxane nanolatices by emulsion polymerization in a water–aminoethanol system

Stable and translucent polydimethylsiloxane nanolatices in a water–aminoethanol (AE) system were prepared by the emulsion polymerization of octamethylcyclotetrasiloxane (D₄) with nonionic polyoxyethylene alcohol ethers and polyoxyethylene aryl ether as surfactants and with KOH as an initiator. The effects of the AE concentration on the emulsion polymerization rate (R_p) of D₄ and the physical properties of the resultant nanolatices were investigated. Increasing the AE concentration in the reaction mixture dramatically increased the emulsion R_p value of D₄, and the kinetics of the D₄ emulsion polymerization in this system were consistent with the Morgan–Kaler theory of microemulsion polymerization. When the AE concentration in the emulsion increased, the transparency value of the resultant emulsion increased, and the size of the droplets in the resultant nanolatices decreased. In addition, the molecular weight of the polysiloxane in the resultant emulsion also increased with the increase in the AE concentration in the reaction mixture. A nanolatex prepared by the emulsion polymerization of 0.98M D₄ with 185 g/L AE had a transparency value of 80.9% and a mean diameter of 59.5 nm. The morphology of polysiloxane nanolatices cured with (N,N‐diethylaminomethyl)‐triethoxysilane was observed with transmission electron microscopy, and the size of the globular particles was consistent with that obtained by dynamic light scattering. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 347–352, 2005     

二氧化钛与硅氧烷类物质制备高效化妆品用防晒剂(英)

探讨了利用二氧化钛与硅氧烷类物质复配,制备硅包水型或水包硅型防晒乳剂,以达到较好的防晒效果及良好的肤感和抗水性的方法,以及硅氧烷类物质的加入对防晒乳剂防晒因子值的影响.     

Oil bleed from elastomeric thermal silicone conductive pads

Oil bleed is a serious problem in elastomeric thermal silicone conductive pads. The components of the oil bleed and the effect of the silicone chemical parameters on the amount of oil bleed have been determined. The main components of oil bleeds are the uncrosslinked silicones in the cured resins, which include the unreacted silicone materials and the macromolecular substances produced by the hydrosilylation reaction. Cured resins with a high crosslinking density and a high molecular weight of vinyl silicone residues had a lower amount of oil bleed. In addition, a low Si-H content also reduced the amount of oil bleed.

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Studies on the silicone resins cured with polymethylsilazanes at ambient temperature

Polymethylsilazanes (PMS) were synthesized and used to cure silicone resins at ambient temperature. The curing degree of the silicone resins depends on the structure of PMS and its concentration in the resin. Silicone resins of different structure and different silanol content can be cured to a satisfactory degree, if the concentration of the PMS is high enough. Silicone resins cured with PMS showed improved thermal stability in nitrogen, compared with that of the heat‐cured counterparts. The mechanism of thermal decomposition of the silicone resins is discussed. The improvement of heat resistance using PMS as the curing agent is accounted for by diminished thermal rearrangement and degradation of the polysiloxane network initiated by silanol groups in the resins. © 2003 Wiley Periodicals, J Appl Polym Sci 89: 1702–1707, 2003     

Effect of metallic flask closure and investment materials on the stability of the denture base resin

This study evaluated the dimensional stability of the poly‐methylmethacrylate (PMMA) denture bases under the effect of different metallic flask closure techniques (FCT) and investment materials (IM). Sixty stone cast maxillary‐wax base plate sets were randomly assigned to six groups (n = 10) for the following treatments: 1 and 4—stone or silicone investments and flask closure with clamp; 2 and 5—stone or silicone investments and flask closure with RS system; 3 and 6—stone or silicone investments and flask closure with screws. PMMA denture bases were polymerized in a water bath at 74°C for 9 h. PMMA base‐stone cast sets were sectioned at regions (R) of the canines, first molars, and posterior palatal zone. Gap discrepancies were measured at five points: right and left ridge crests, palatal midline, and right and left marginal limits of the flanges. An optical micrometer with accuracy of 0.0005 mm was used for measurement purposes. Data were submitted to ANOVA and Tukey's test (α = 0.05). Silicone showed an adaptation mean (0.177 mm) significantly different when compared with stone (0.207 mm). The RS system presented a statistically different adaptation mean (0.166 mm) in relation to the traditional clamp (0.200 mm) and flask with screws (0.211 mm). Adaptation values for the regions of the canines (0.141 mm), first molars (0.185 mm), and posterior palatal (0.250 mm) were statistically different. For all flask closure techniques, better adaptation was shown with the RS system and silicone investment. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010