Addition cure silicones

Fig. 15. Effect of tackifying resin on storage modulus of addition-cured silicone PSA.

Addition cure silicones can be delivered from solvent, waterborne emulsions, or 100% solids systems. The solvent free versions employ base polymers of intermediate molecular weight to achieve processable viscosity. These base polymers can have reactive moieties in terminal and/or pendant positions. These lower molecular weight, more functional systems result in a tighter crosslink network which feels rubbery to the hand. Low amounts of high molecular weight additives are included in some formulations to provide a more slippery feel [51,52]. 

Yamamoto and Minamizaki [159] disclose the use of a curable silicone based release agent blended with resin particles which swell or are soluble in organic solvent. Coatings made with such blends can be written on with solvent based inks. For example, an addition cure silicone network containing 20 wt% 0.1 p,m diameter PMMA particles exhibited both good writeability (no ink dewetting and smear free) and a low release force of 10 g/cm for a PSA tape. 

Addition-cured model systems, of silicone networks, 22 569 Addition-curing silicones, 22 35 Addition-fragmentation mechanism, of chain- transfer (CT) agents, 23 383-384... 

More recently Wong (2U, has reported the results of tests designed to characterize parameters of electronic silicones by Ther-mogravlmetrlc, Fourier Transform-Infrared, and Gas Chromatography/ Mass Spectrometry. This work has concentrated upon condensation-cure materials used within the Bell System, rather than the end-blocked free radical (addition-cure) silicones. 

The formulation ofmoisture-ujriiig silicones includes a silicone polymer, filler, a moisture-reactive cross-linker, and sometimes a catalyst. A newer class of silicone sealants are known as the silicone latex sealants. These sealants are silicone-in-water emulsions that cure by evaporation of the emulsifying water. Addition-curing silicones in general are two-part systems that cure by the platinum-catalyzed reaction of a silicone hydride with typically a vinyl group attached to silicon. Because no by-products are generated by the cure, there are few volatiles and no shrink in thick sections. 

Vulcanization Kinetics of Addition-cured Silicone Rubber... 

Storage Store in cool, dry place keep tightly closed Uses Base polymer for addition cure silicone elastomers polymerized prods, provide noncorrosive shield against moisture, dirt, and contaminants for elec, components mold-making elastomers, encapsu-lants, and sealants for elec, components ManufJftistrib. Gelest... 

Phenylmethyl/dimethylsiloxane copolymer base oil, lubricant jet engine synthetic PEG-3 dipelarqonate base oils, synthetic lubricant Diester oils Trimethylolpropane tripelargonate base polymer, addition cure silicone elastomers Polydimethylsiloxane, vinyl-terminated base polymer, two-component RTV fluids Dimethicone, vinyidimethyl-terminated base, acid resolution Dehydroabietylamine base, act. ingreds. 

Addition-cured silicones Vinyl-terminated polydimethyl siloxanes DMS-V03-V22, and-V33 (Gelest) Tri- or tetra- functional potysihcon hydride (10-15 phr) Platinum-complex catalysts (2-50 ppm), PCO 72, 73, 74, and 75 (United Chemical Tech.)... 

Information on particular types of adhesive may be found in articles cited above and in the following entries Hot melt adhesives. Selection of adhesives. Silicone adhesives addition cure. Silicone adhesives condensation cure. Toughened adhesives. 

Bodas, D. Rauch, J.-Y. Khan-Malek, C., Surface Modification and Aging Studies of Addition-Curing Silicone Rubbers by Oxygen Plasma. Eur. Polym. J. 

The chemistry of silicones is summarized by following the steps necessary to produce a two-part, platinum-cured silicone containing vinyl-stopped polydimethylsiloxane, Si-H-on-chain siloxane, platinum catalyst and catalyst inhibitor. The process begins with silicon dioxide and follows the steps of conversion to sand to elemental silicon. Silicon is reacted with MeCl to make methylchlorosilanes in the methylchlorosilane reaction (MCS). The products from the MCS reaction are separated by distillation and then hydrolyzed and condensed to make the various siloxane polymers. Polymers with methyl, vinyl or Si-H functionality are made as required for the platinum addition-cured silicone product. 

The silicones industry got its start in the late 1930 s (1,2) and became viable after Rochow s 1940 discovery of the direct process which reacts elemental silicon with MeCl to produce methylchlorosilanes (3,4). This chapter attempts to summarize some of the steps which take place in the process of converting sand into silicones. The vignette chosen for this summary is the production of a platinum-cure, so-called addition cured silicone. This brief review will make use of the M, D shorthand wherein an M group is MojSiO- and a D group is -MojSiO-. Substituents on silicon other than Me are represented with a superscript so that M stands for (H2C=CH)Me2SiO- and DH stands for -(Me)(H)SiO- (5). Figure 1 summarizes the entire process covered in this review. 

Silicone - Two part, addition cure Silicone-One part ... 

Lin SB. Addition-cured silicone adhesive technology vinyl silicone crosslinker. J Appl Polym Sci. 2003 54(13) 2135-2145. 

The effect of thermally conductive particles on the thermal properties of silicone rubber was studied. Different sized aluminum oxide was blended with addition cured silicone resin at various crosslink densities and filler loading levels. Thermal impedance of each sample was measured. Statistical analysis of the experimental data showed that hardness was not affected by filler type/size or filler amount however, the amount of crosslinker was statistically significant with respect to hardness. 

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