Rigidity of plastics

Electrical Properties. CeUular polymers have two important electrical appHcations (22). One takes advantage of the combination of inherent toughness and moisture resistance of polymers along with the decreased dielectric constant and dissipation factor of the foamed state to use ceUular polymers as electrical-wire insulation (97). The other combines the low dissipation factor and the rigidity of plastic foams in the constmction of radar domes. Polyurethane foams have been used as high voltage electrical insulation (213). 

Talc is an imusually soft mineral that occurs naturally in many parts of the world, but the composition varies considerably from one place to another. Commercial grades have plate-like particles that impart reinforcement to polypropylene at low cost. They have a high surface area and a high aspect ratio that improves the rigidity of plastics. Unlike wollastonite (see later), it is acid-resistant. It is also relatively cheap. 

Kurt Uberreiter joined the Institute in 1937 as a doctoral student under Jenckel. He grew to be an important member of the Institute staff and carried out essential research into the structure and rigidity of plastics. Uberreiter developed two fundamental concepts in early plastics research. First he characterized the glass-like... 

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