Synthesis and Characterization of para-Aramid Copolymers Containing Cyano Groups
Vol. 51, No. 3, pp. 134-139,
Jun. 2014
10.12772/TSE.2014.51.134
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Abstract
Poly(p-phenylene terephthalamide) (PPTA) and poly(2-cyano-1,4-phenylene terephthalamide) (CNPPTA)-based copolymers were synthesized using a low temperature polycondensation reaction between terephthaloyl chloride, 2-cyano-1,4-phenylene diamine, and/or 1,4-phenylene diamine in a N-methylpyrrolidinone solvent containing 2% CaCl2. The molecular structures and thermal stabilities of PPTA, CNPPTA, and copolymers of the two with different cyano group contents were characterized using FT-IR spectroscopy and thermogravimetric analysis, respectively. The liquid crystalline states and polymer concentration-dependent viscosities of NMP/CaCl2 solutions containing different CNPPTA copolymer concentrations were investigated using polarized optical microscopy and viscometry, respectively. It was found that CNPPTA polymers with higher cyano group contents were more soluble in polar organic solvents, such as NMP, DMAc, and DMF, and that CNPPTA polymer solutions based on the NMP/CaCl2 system formed liquid crystalline structures above certain critical polymer concentrations. In addition, TGA results revealed that, although the initial degradation temperatures of CNPPTA copolymers were quite comparable to that of PPTA, their char yields at 800 oC were far higher.
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