Polysiloxane, unsaturated

Thermal cure system. The thermal cure system is based on a hydrosilylation addition reaction between vinyl-functionalized and silicon-hydrido functionalized polysiloxanes [32,33,35], Unsaturated organic groups react with a Si-H functionality in the presence of a platinum-based catalyst (Scheme 10). 

The CVD method can form a polymethylsiloxane layer of 0.6-0.8 nm on the inorganic particles (Table 12.1.2). Especially, the polysiloxane-modified titanium oxide has been used for the additives to cosmetics. Moreover, residual Si-H group grafted on the particles reacted with unsaturated organic compounds in the presence of Speier catalyst (47), H2PtCl6, to be functionalized by organic pendant group [Reaction (11 ). ... 

The same authors developed a process of encapsulation of polymers swelled by halogenated solvents in which ozone is greatly soluble but not monomers to be grafted. After ozonization of polymers swelled in solvents, mixtures of mono unsaturated or di unsaturated monomers are added to the activated polymers. Then, grafting is operated by UV irradiation. Grafting is mainly located at the surface of the starting polymer what prevents the modification of its intrinsic properties. This process permits to produce hydrophilic polysiloxanes used in medical applications (contact lenses, tubes, catheters, etc.). 

GC column A capillary column of intermediate polarity can give adequate resolution of isomers as well as unsaturated compounds. Many such columns are commercially available. These include 105 m long x 0.53 mm ID, Rtx-502.2 60 m long x 0.75 mm ID, VOCOL 60 m long x 0.53 mm ID, DB-62 or equivalent. Other capillary columns include 95% dimethyl-5% diphenyl polysiloxane coated columns, such as DB-5, SPB-5, Rtx-5, AT-5, or equivalent. These columns are also suitable for separation of a number of nonhalogenated organic compounds of intermediate polarity. 

Hydrosilylation is by far the most important route for obtaining monomers and other precursors to fluorinated polysiloxanes. Hydrosylilation80 is the addition of silicon hydride moiety across an unsaturated linkage using transition metal complexes of platinum or rhodium such as Speier s catalyst, hexachloroplatinic acid in isopro-... 

Alkylbenzene Linear alkylb (saturated) Branched alkylb (saturated) Linear alkylb (unsaturated) Alkylphenyl (branched) Polyoxypropylene Polysiloxane Linear dodecyl-benzene n-dodecyl 2-ethyl hexyl Oleyl Nonylphenyl CH3(CH2)5CH(C6H4)(CH2)4CH3a CH3(CH2)10CH2-CH3(CH2)3CH—ch2—(CH2CH3) (c/s-)CH3(CH2)7=CH(CH2)CH2-C9H 9(br inclied isomers)C6H4 — [OCH2CH(CH3)l — (CH3)3Si[OSi(CH3)l OSi(CH3)3 I... 

Hybrid versions of silicone-thermoplastic semi-IPNs have been developed (19). A hybrid interpenetrating network is one in which the cross-linked network is formed by the reaction of two polymers with structurally distinct backbones. Hydride-functionalized siloxanes can be reacted with organic polymers with pendant unsaturated groups such as polybutadienes (5) in the presence of platinum catalysts. Compared with the polysiloxane semi-IPNs discussed earlier, the hydride IPNs tend to maintain mechanical and morphologically derived properties, whereas properties associated with siloxanes are diminished. The probable importance of this technology is in cost-effective ways to induce thermoset characteristics in thermoplastic elastomers. 

Fig. 13. Modeling of a water-repellent silicone resin network on quartz (arbitrary assembly), viewed from the front (a) and from the side (b). Hie three-dimensional network is built up of two-dimensional monolayers (methyl derivative) for optical reasons (this leads to seemingly unsaturated oxygen atoms, which form the oxygen bridges in the three-dimensional case). A simplified silicone resin network on quartz could be composed of covalently bound polysiloxane chains, incompletely crosslinked polysiloxane, and embedded silsesquioxanes or homosilsesquioxanes (cages and ladders), going from the bottom (quartz) to the top [28, 42, 75, 78, 79]. The network has been optimized from graphical aspects. Total height approx. SO A.

On the other hand, there is a need to use inhibitors of the platinum catalysts temporarily to reduce their catalytic activity in the presence of hydro- and vinyl-polysiloxanes in order to stop the curing process at room temperature, but to allow the platinum catalyst to be activated at elevated temperature. Among the principal types of compounds reported are alkenyl derivatives, esters of unsaturated acids, crown ethers, organic nitrogen compounds, phosphines, linear and cyclic vinyl-siloxanes, and poly(vinyl)siloxanes [2], and recently fumarate [44] and maleinate [33]. New co-activators of the catalysts (precursors) have been revealed in the 1990s to reduce to ppm the levels of platinum required to effect hydrosilylation curing [45, 46]. 

Reaction 11.4 is used to decrease the unsaturation of polyether polyols simultaneously with the functionality increase. Thus, by introducing a polyether polyol with high unsaturation (0.07-0.09 mequiv/g), a low molecular weight polysiloxane compound, having 2-3 Si-H groups/mol, together with a platinum catalyst, the polyether monol present in the polyether (in fact allyl ether based polyethers) is added to the polysiloxane compound and the monol is transformed into a diol or into a triol (reaction 11.5). 

In all cases where copolymer is formed, the product gives a single GPC peak, showing that it is not admixed with an independently formed homopolymer. The ability to form copolymers by ADMET reactions of unsaturated homopolymers with a diene monomer is not confined to system 1 and is probably quite general. For an example of insertion of hydrocarbon units into an unsaturated polysiloxane, see Smith, D.W. (1993a). 

The efficiency of this process is usually less than one cross-link per peroxide molecule decomposed. To increase the cross-linking efficiency, small amounts of unsaturation are introduced into the polymer structure. We have already discussed EPDM polymers, which are essentially diene monomers copolymerized with ethylene-propylene (EPR) polymers. For polysiloxanes, copolymerization of small amounts of vinyl-methylsilanol greatly enhances cross-linkability (Equation 5.7). The unsaturation introduced into an otherwise saturated structure provides additional sites for cross-linking through chain reaction. 

Silicone-based endodontic sealers have to be mixed immediately prior to use [62,63], and this is done using a mechanical delivery system that ensures complete mixing of both pastes without the incorporation of air. Also present in one of the pastes is a trace of platinum to act as catalyst for the setting reaction. Setting involves pendant unsaturated groups on one of the polymer chains reacting with a hydrogen atom attached directly to a silicon atom (Fig. 10.4). The reaction results in cross-links between the polysiloxane chains, and these cause the material to set to a resilient rubbery solid [13]. 

See Phenylmethyl polysiloxane Siloxanes and silicones, dimethyl, [(12-hydroxy-1-oxooctadecyl) oxy]-terminated. See Dimethiconol hydroxystearate Siloxanes and silicones, dimethyl, 3-hydroxypropyl methyl-, ethers with PEG dihydrogen phosphate, compds. with N,N -bis [3-(di methyl ami no) propyl]-C18-unsaturated amide dimers. See Dilinoleamidopropyl dimethylamine dimethicone copolyol phosphate,... 

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