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6834674 
Journal Article 
The effect of phenyl content on the degradation of poly(dimethyl diphenyl) siloxane copolymers 
Deshpande, G; Rezac, ME 
2001 
1 
Polymer Degradation and Stability
ISSN: 0141-3910 
74 
2 
363-370 
WOS:000172112600018 
Inert atmosphere thermal degradation of polysiloxanes having different side groups (–CH3 and –Ph) was studied at 364 °C. The process was characterized using gas chromatography-mass spectrometry, 29Si NMR and elemental analysis. The polysiloxanes studied included polydimethylsiloxane (PDMS), poly(3.5%diphenyl-96.5%dimethyl)siloxane (DP-3.5) and poly(25%diphenyl-75%dimethyl)siloxane (DP-25). The degradation products were primarily cyclic oligomers ranging from hexamethylcyclotrisiloxane and octamethylcyclotetrasiloxane for PDMS with benzene as an additional product for PDPDMS. No cyclic oligomers with phenyl substituents were observed. Various mechanisms for degradation of PDPDMS were reviewed and discussed in relation to the 29Si-NMR results and elemental analysis. The 29Si NMR analysis shows the mechanism for generation of benzene to be thermally induced random free-radical reaction. 
PDMS; Silicone rubber; Partial pyrolysis; Oxidation; Organic/inorganic materials; Composites