Thermal breakdown, electrical properties polymers

The formation of radical intermediates influences not only the chemical state of irradiated polymers, but it brings also about physical characteristics solubility, fusion enthalpy, heat capacity, crystallinity, mechanical features, electrical properties permittivity, dielectric loss, breakdown tension, thermal conductivity. The new formed structures may be unlike in comparison with initial material, because intermolecular bridges, new organic functions appeared on macromolecular backbones, general molecular order or free volumes attain other values. 

As a result of these properties, silicone fluids find application for example as heat transfer media, hydraulic fluids, brake fluids, lubricants and vacuum pump oils. One of their earliest uses was as dielectrics the dielectric constant changes very little with temperature and is also essentially independent of frequency over the range 10 -10 Hz. On thermal breakdown organic polymers have the disadvantage that they commonly produce carbon, which conducts electricity. Organosiloxanes are more robust and also tend to decompose or oxidize to products which are themselves insulators, such as silica or volatiles of low molecular weight. 

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