Para-Aramid Manufacturing Process
topic
Kevlar production: (1) low-temperature solution polymerization of p-phenylenediamine and terephthaloyl chloride in amide solvent (NMP, DMAc) with calcium chloride at -10 to 0°C yielding PPTA, (2) dissolution in concentrated (>99%) sulfuric acid at 80-100°C forming liquid crystalline anisotropic solution (20-22% polymer), (3) dry-jet wet spinning through spinneret into water coagulation bath with air gap allowing orientation, (4) washing, neutralizing, (5) drying under tension at 200-250°C, (6) heat treatment at 400-550°C for crystallization and property development.
Role
Liquid crystal spinning and extreme tension during coagulation-washing-drying achieve 95-98% molecular orientation along fibre axis, creating exceptional axial properties (strength 3.0-3.6 GPa, modulus 70-130 GPa) but poor compression.