Dielectric properties polymers with polar bonds

Poly(vinylidene fluoride), PVDF or PVF2, is usually manufactured from radical initiated batch polymerization process in aqueous emulsion or suspension of CH2=CF2 monomer. PVDF is a thermoplastic that exhibits interesting properties, such as piezoelectric, pyroelectrical, and ferroelectric behaviors. PVDF has even superior dielectric permittivity arising from the strong polymerization originating from C—F bonds, and the spontaneous orientation of dipoles in the crystalline phases makes it a polar polymer with good compatibility with polar chemicals. 

The thermoplasticity of material proteins has been utilised to produce materials using thermal or thermomechanical processes under low hydration conditions, as already employed for starch- or polyolefin-based materials [136, 152]. According to the thermoplastic behaviour of synthetic polymers, the Tg of the proteins involves sudden variations in their physical properties (thermal, mechanical, dielectric properties and so on). The molecular response associated with the transition from the glassy to the rubbery state involves an overall increase in the free volume and macromolecule mobility [153,154]. As for synthetic polymers, the Tg of the proteins is affected by the MW, chain rigidity, size and polarity of the lateral groups, presence of intermolecular bonds or crystalline zones, and also by the plasticiser type and concentration [155,156]. 

Very little chemistry may be needed to destroy the mechanical properties of a polymer. If 1% of the (3—C bonds in a hydrocarbon fluid are broken, the effect is to form a small fraction of impurities, usually of little significance. The same fraction of breaks in a polyolefin will reduce it from a hi molecular weight polymer to an oligomeric wax. Thus in pol3rmers a very low level of chain breaks will cause failure, and polymers may lose their mechanical properties rather easily with negligible changes in mass. Some other properties, for example the dielectric constant, may be even more sensitive to formation of polar groups by oxidation. 

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