Epoxy thermoplastics liquid crystalline

Dow Chemical developed liquid crystalline polymers (LCP) based on diglycidyl ether of 4-4 -dihydroxy-o -methylstilbene in the 1980s (62,63). Liquid crystal thermoplastics and thermosets based on this novel chemistry showed excellent combinations of thermal, mechanical, and chemical properties, imachievable with traditional epoxies. However, commercialization of these products has not materialized. 

In practice, it is necessary to avoid using amorphous resins in structural applications above, or even near to, the T. (This restriction applies to all thermosets, because they are invariably amorphous, but it does not apply to crystalline thermoplastics, otherwise polypropylene chairs, with a of around -15°C, could only be used safely in Alaska and in Siberian winters). A margin of safety of 20°C is required for reasonable durability, and a much larger one in humid conditions. Traces of water, or any other solvent, lower the Tg to below its usual value, so the maximum safe working temperature of a load-bearing amorphous resin is lower in humid conditions than in a dry environment. There is a widely quoted rule of thumb that each 1% moisture absorbed by the matrix lowers the Tg by 20°C. This comes from epoxy resin data in wet atmospheres and different figures apply to other resins and liquids. 

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