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Abstract

This paper summarizes an investigation of the effects of interactive chemical solvents on the structure and properties of Nomex®, a fibrous aromatic polyamide. Dynamic and isothermal shrinkage experiments were performed on Nomex yarn in dimethyl formamide (DMF), dimethyl acetamide (DMAc), and dimethyl sulfoxide (DMSO) over wide temperature ranges. The rate of the solvent-induced shrinkage was established as being dependent on solvent diffusion. Over a wide temperature range, the equilibrium shrinkage in DMF and in DMAc was found to be independent of temperature. In DMSO, on the other hand, the equilibrium shrinkage was strongly temperature-depeddent above a postulated transitional region around 42°C. The molecular-relaxation mechanism manifest as shrinkage in DMF, in DMAc, and in DMSO below 42°C is postulated to proceed via a rigid chain-slippage process. Above 42°C in DMSO the glass-transition relaxation mechanism involving micro-Brownian motion is postulated. There is evidence for microvoid formation in the Nomex after treatments in the three solvents at 100°C. Improved dyeability is evident in prelimi nary experiments.

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