Synthesis and properties of 4,4 '-biphenyldicarboxylic acid and 2,6-naphthalenedicarboxylic acid

This article describes the synthesis and the properties of polyesters and c opolyesters prepared from ethylene glycol, terephthalic acid, 4,4' biphenyl dicarboxylic acid (BDA), and 2,6-naphthlenedicarboxylic acid (NDA). The eff ect of incorporating varying levels of BDA and NDA on polyethylene terephth alate (PET) is described. Depending on the concentration, incorporation of BDA into PET leads to an improvement in glass transition temperature (T-g), strength, modulus, and barrier properties. Copolymers of PET containing up to about 50% BDA derived units are clear and have T-g's ranging from 85 to 105 degrees C, making them suitable for applications where a high T-g alon g with clarity is important. Copolymers with higher BDA concentration are h ighly crystalline, with high rates of crystallization from the melt. Copoly merization of NDA with oligoethyleneterephthalate leads to copolymers that are generally amorphous. Crystallinity can be developed in copolymers with low concentration of NDA by thermal annealing. (C) 1999 John Wiley & Sons, Inc.