Silane diisocyanates

Figure 7.6 Schematic representation of hard clusters in (a) a polyurethane network composed of a long diol, a triol, and a diisocyanate (polyaddition reactions, Chapter 2). (b) a hybrid inorganic-organic network composed of a silane end-capped long diol (polycondensation reactions, Chapter 2).

Furthermore, it is conceivable to use standard chain elongation techniques, e.g., with diisocyanates known from polyurethane chemistry, to adjust the viscosity of the HO-P-OH polymers prior to the derivatization with the isocyanatomethyl-dimethylmonomethoxy silane This of course also influences the mechanical properties of the vulcanizates. 

We used a new silane which readily permits quantitative conversion of silanol-terminated fluids into aminopropyl-terminated fluids. The reaction between aminopropyl-terminated fluids and diisocyanates proceeds smoothly within a few minutes, either in solution or in the melt. The preparation of siloxane-urea block copolymers is performed in either a two- or a three-component process. By carefully choosing the inorganic segment defined by the corresponding silicone fluid, it is possible to obtain silicone mbbers with different material characteristics. The mechanical properties can be tuned from very soft to very hard. Those materials display tensile strengths up to 14 MPa without requiring additional fillers and can be used for diverse applications. 

The preparation of copolymers of aminopropyl endcapped dimethylsiloxane oligomers and isophorone diisocyanate with 1,4-benzenedimethanol as the chain extender outlined in Scheme 1 is similar to the method used by Pascault and co-workers to prepare alkoxy-silane terminated macromers.(27) This "hard segment first method allowed the separate isolation and characterization of the hard block. Thus, GPC analysis for the intermediate IPDI-BDM-IPDI-BDM-IPDI (desired 3 2" composition), also revealed peaks for IPDI-BDM-IPDI, and BDM-IPDI-BDM. The intensity ratio of the curves indicate that more than 85% of the molecules in the mixture were of the target "3 2" composition. 

Another type of sealant uses a combination of chemistry to yield a product useful as a sealant. This chemistry is a marriage of silicone and organic chemistry known as a polyether silicone. The basic polymer for this type of sealant is the reaction product of a polyether diol with a diisocyanate followed by further reaction with an amino-functional alkoxy silane. Thus, the central portion of this polymer is a polyether that is terminated with a urethane linkage that leads to the terminal group which is an alkoxy silane. This polymer can cure by the methods described above for a standard silicone but it contains the properties of a polyether. As with the normal silicones described above, these materials also have to be reinforced in order to obtain the tensile properties desired for a sealant. The same list of fillers as described above can be used in polyether silicones. Adhesion promoters such as silane coupling agents, diluents of various sorts, plasticizers, and catalysts are also added to these materials. 

Hard Segment Characterization The preparation of copolymers of aminopropyl endcapped dimethylsiloxane oligomers and isophorone diisocyanate with 1,4-benzenedimethanol as the chain extender outlined in Scheme 1 is similar to the method used by Pascault and co-workers to prepare alkoxy-silane terminated... 

---