Curing rate siloxane

On the other hand, the alkoxide system presented several problems in formulation. The system first chosen as a model consisted of a trimethoxymethyl silane crosslinker, 8000 centistoke HEB siloxane, and a catalyst. A number of catalysts were used and each exhibited different cure rates and electrical properties. DuPont tetraalkoxytitante-Tyzor appears to he one of the better catalysts used in this type of curing system. Fillers are usually incorporated into the silicone formulation to improve mechanical properties, promote adhesion, and to serve as light screening and pigment agents. Cab-o-sil, a form of fumed silica, carbon-black, titanium dioxide and calcium carbonate are then used as RTV fillers. 

Figure 1. Effects of the Crosslinkers on the Surface Cure Rate of the Polyol or Siloxane Polyol/Epoxide Coatings.

Figure 3. Surface and Thorough Cure Rate of the Di-TEOS Functionalized Polyol Modified UV Coatings as a Funtction of the Ratio of Siloxane Polyol to the Parent Polyol.

Amongst catalyst modifications that achieve purely rate effects, two reports are noteworthy. One is the hydrosilation rate enhancement in the presence of j -cyclodextrins, for Karstedt s catalyst Pt2(s ym-tetramethyldivinyldisiloxane)3] and Lamoreaux s catalyst. Lamoreaux s catalyst (prepared from H2PtCl6 and 1-octanol), showed the most dramatic rate accelerations. The second instance of rate moderation is reported by Endo and collaborators. They report the use of isocyanides in just 2 1 molar ratio with Pt, to dramatically suppress hydrosilation of vinylsilane (with EtsSiH) or vinyl-terminated siloxane with methylhydrogensiloxane copolymer until 60-70 °C. Above this temperature, rapid hydrosilation occurs. This is in contrast with traditional cure inhibitors where a large excess of inhibitor (relative to Pt), typically alkynols or maleates, is needed to prevent premature cure. 

The effect of BAPPO in enhancing the flame retardancy was more in the case of phosphorous and siloxane skeletal modified tetrafunctional epoxy systems than that of sulphone-modilied and neat epoxy systems. The improved flame retardancy of siloxane skeletal modified epoxy systems cured with BAPPO maybe due to the synergism between the silox-cuie moiety of epoxy systems cuid phosphorous backbone of BAPPO, leading to VO rating from UL94 test. 

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