Copolymers siloxane composites

Polymers are used frequently in paints and varnishes. These materials are usually filled with opaque materials and are difficult to separate or analyze by other procedures. Pyrolysis can be used to identify the nature of the paint, to measure quantitatively residual monomers, for quality control, and to examine additives [5, 13, 14]. Paints may contain a variety of polymers and copolymers such as vinyl derivatives, polyurethanes, phthalate polyesters, etc. Varnishes may contain various copolymers, siloxanes, etc. and can have a complex composition. This composition can be successfully analyzed using analytical pyrolysis. For example, the composition of a coating material consisting of the terpolymer poly(2-hydroxyethyl methacrylate-co-butyl acrylate-co-ethyl methacrylate) crosslinked with butoxy melamine resin has been analyzed with excellent results based on various monomer ratios resulting from pyrolysis at 590° C [15]. 

This instrument has been used for the evaluation of buildings, furniture, transport, aerospace, wood and electrical materials and composites. Polymers to which this technique has been applied include PP and PP-composites [42], ethylene-vinyl acetate copolymers [43], polyamide-6,6 [27], silicate-siloxane composites [44], glass-phenolic composites [45], polyolefins [46], conveyor belt materials [47] and roofing materials [48]. 

Moreover, many siHcone-based copolymer or composite films have been manufactured by mixing siloxane with other organic polymers for improving the physical properties of the pure silicone such as selective gas permeability. Thus, polyethersulfone-PDMS [42], polyamide-PDMS [43], poly(phenylsilsesquioxane)-PDMS [44], and even polycar-bonate-PDMS [45] and polyacrylate-PDMS [27] were prepared and doped with dyes to carry out permeability tests for optical sensing purposes. 

Development of several new siloxane-imide copolymers for commercial applications have also been reported by Lee 181) and Berger58). Although no information was given in terms of the chemical compositions of these materials, most of these polymers were reported to be processable by solution or melt processing techniques, most probably due to their high siloxane contents. However, due to the presence of low (—20 to —120 °C) and high (>230 °C) temperature Tg s, it was clear that multiphase copolymers have been synthesized. Molecular weights and thermal stabilities, etc, were not reported. 

During the reactions backbone compositions of the siloxane oligomers employed have been varied between all dimethylsiloxane to 50/50 by weight dimethylsiloxane/ diphenylsiloxane and dimethylsiloxane/(trifluoropropyl,methyl)siloxane. Block molecular weights of the siloxane oligomers have been kept between 3,000-5,000 g/mole, whereas the overall level of siloxane incorporation into the copolymers have been varied between 0 and 60 weight percent. In most cases the ratio of terephthalate to... 

The polyoxyalkylene units in the copolymer have a molecular weight below 500, and the polysiloxane units have 3 to 50 silicon atoms. The resin has a phenol/aldehyde ratio of 2 1 to 1 5 and an average molecular weight of 500 to 20,000 Dalton. The composition shows synergistic demulsification activity when compared with the individual components. The siloxane units can be either in blocks [979,980] of the polyoxyalkylene-polysiloxane copolymer or randomly distributed [728,729]. 

Table V. Influence of Siloxane Graft Molecular Weight and Composition on Surface Composition of PMMA-g-PSX Copolymers by Variable Angle XPS (ESCA) (Copolymers 5 wt.% PSX)...

Table VI. ESCA Study of Styrenic-Siloxane Block and Graft Copolymers (Copolymer Composition 10 wt.% PSX)...

Although being qualitatively in agreement with experimental results, disagreements between experiment and theory remain. Besides the composition, /a, and the total degree of polymerization, N, all theoretical works refer to the segmental interaction parameter x This parameter can be estimated from a relationship to the solubility parameters. The ODT as a thermodynamic measure of the incompatibility was used to compare a set of symmetrically composed diblock copolymers from different hydrocarbons, polydimethyl-siloxane and poly(ethylene oxide) (PEO) [33]. While the behaviour of hydrocarbon diblock copolymers was successfully described by a consistent set of solubility parameters, this procedure failed for systems containing PEO. The... 

Block copolymers of styrene(A)/dimethyl siloxane (B) are even more unusual in the respect that in many solvents t>A and nB are roughly of similar magnitude, but the former is positive and the latter negative156. Hence, depending on the composition WA [cf. Eq. (97)], the value of v for the copolymer can be positive, negative... 

In this study our aim was to systematically synthesize a, oraminopropyl terminated (dimethyl-diphenyl)siloxane oligomers having low molecular weights (1000-3000 g/mole) and to subsequently analyze the composition and thermal behavior of the copolymers. 

---