Wholly aromatic polyamides containing bridged biphenylylene groups, 2. Copolyamides

Abstract

A number of wholly aromatic copolyamides containing bridged biphenylylene groups were synthesized from a mixture of aromatic diamines and terephthaloyl chloride, on one hand, and from a mixture of aromatic diacid dichlorides and 1,4-phenylenediamine, on the other hand. Each mixture of diamines and of diacid dichlorides was constituted of a phenylene derivative and a bridged biphenylylene derivative. The copolyamides synthesized were dissolved in high concentration sulfuric acid and spun into fibers. The fibers spun showed fairly high tensile strengths and high initial moduli, but annealing caused further increase in strength and modulus. All the copolyamides studied had very high thermal resistances. a) Part I : cf. I).

Effect of the molecular weight of poly-para-aramids and structural changes in heat treatment on the mechanical indexes of the fibres

“…Although PPTA and copolyamide D differed insignificantly in this characteristic, copolyamide C should be less rigid-chain. This follows from the fact that its molecular chains have significant kinks in the 2,7-diphenylenesulfone groups with an angle of deviation from the initial direction of 19 ~ [6] (in addition to the kinks in the amide groups with an angle of deviation of 7-10 ~ [7,8]. Homopolyamide C, prepared from the indicated diamine and terephthaloyl chloride, forms a LC state in sulfuric acid solutions which are distinguished by higher viscosity than polyamide D and PPTA with similar concentrations of the LC solution --by approximately 20 times for a 20 wt.…”

“…The strength of PPTA fibres and copolyamide D fibres decreases slightly [15]. However, as a result of thermal drawing of copolyamide C fibres, both the modulus of elasticity and the strength increase [5,6]. Thermal drawing of copolyamide C fibres was investigated and the structural changes in copolya_mides C and D that take place as a result of thermal drawing of the fibres were also examined.…”