Preparation and characteristics of a waterborne preventive stain coating material with organic-inorganic composites

With the goal of developing a waterborne coating material that prevents staining, organic-inorganic composites prepared from colloidal silica and two types of acrylic resin emulsions were investigated as exterior coatings. conventional acrylic resin emulsion and organic silane hybridized acrylic resin emulsion prepared by emulsion polymerization were mixed with colloidal silica to form organic-inorganic comiposite films. The addition of colloidal silica to emulsions yielded films with higher hydrophilicities, as indicated by lower water contact angles for these films in comparison to films without colloidal silica. The water contact angles of organic silane hybridized acrylic resin emulsion/colloidal silica films were lower than those of acrylic resin emulsion/colloidal silica films. Composite films containing colloidal silica particles smaller than 100 nm in diameter showed high hydrophilicities. Observations of the dispersed state of colloidal silicaparticles in organic-inorganic composite films by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) demonstrated that colloidal silica particles were densely aggregated on the film surface. Outdoor exposure tests of the coating materials prepared from organic silane hybridized acrylic resin and colloidal silica particles with diameters of 7.5 nm showed excellent stain resistance.     

Effect of crosslinking on the conductivity of conductive silicone rubber

We investigated the effect of polyvinylsilicone oil (C gum) as a crosslinker and 2,5‐bis(tert‐butyl peroxy)‐2,5‐dimethyl hexane (DBPMH) as a curing agent on the conductivity of conductive silicone rubber with two different kinds of conducting mechanisms. The experimental results show that the volume resistivity of conductive silicone rubber changed with its degree of crosslinking. When the carbon black loading was 25 parts per hundred rubber (phr) and a completely continuous conducting network had not formed, the volume resistivity of the vulcanizates decreased with increasing crosslink density. The volume resistivity of the vulcanizate with a suitable amount of C gum decreased to 53%, and the tensile strength increased by 0.8 MPa compared to the vulcanizate without C gum. When the carbon black loading was 40 phr and a completely continuous conducting network had formed, the crosslink density of vulcanizates changed as the amount of DBPMH changed. The volume resistivity of vulcanizates first decreased and then increased with increasing crosslink density. There was a valley value in the resistivity–crosslink density curve. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3471–3475, 2003     

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     

有机硅微乳液的制备技术

综述了有机硅微乳液的形成原理、制备方法及制备过程中的影响因素.在有机硅微乳液的形成原理里,详细介绍了增溶理论和界面张力理论;在有机硅微乳液的制备方法中,介绍了转相乳化法、相转变温度乳化法、乳液聚合法;并着重讨论了表面活性剂、助表面活性剂、pH等对有机硅微乳液形成的影响.     

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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冷缩型电力电缆附件的技术与应用

简述了电力电缆附件的概况,阐述了冷缩型电缆附件的发展简史、产品的特性及应用范围,系统介绍了冷缩型电缆附件的制备工艺,重点叙述了产品原料的筛选及模具的设计。     

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