Evaluation of solvent and thermal induced modifications in polyamide 6 fibres: an optical approach

Optical investigation has been conducted on chemically treated polyamide (nylon) 6 fibres using a strongly interacting solvent, dimethylformamide (DMF). A comparison has been carried out between the effect of solvent treatments and the effect of thermal treatment on the structure and properties of the fibres. The two-beam interference Pluta microscope is used to calculate the refractive indices parallel and perpendicular to the fibre axis and the birefringence. Optical and structural parameters related to the refractive indices and birefringence are evaluated. Crystallinity, specific refractivity of the isotropic dielectric, polarizability per unit volume and orientation functions are among the parameters obtained and plotted versus the time of treatment. Increases in the birefringence, crystallinity and orientation functions with time of treatment are obtained. The results indicate that DMF modifies the fibre structure and enhances its optical anisotropy. Moreover, immersion of the fibre samples in DMF prior to thermal treatment gives rise to different results for the optical and structural parameters than those immersed in DMF and thermally treated at the same time. The study revealed a considerable change in the molecular orientation of the nylon 6 fibres due to solvent and thermal treatments. This could enhance and expand their utilization in industrial applications