Moisture absorption capacity of polyamide 6,6 fabrics surface functionalised by chitosan-based hydrogel finishes

Abstract

The present study aims at investigating the moisture absorption capacity of polyamide 6,6 fabrics when their surface is functionalised by chitosan-based hydrogels. For the finishing procedure, bulk hydrogels of chitosan (CS) with different contents of embedded thermosensitive microparticles of poly(N-isopropylacrylamide-co-acrylic acid) (PNIAA) were used. In practice, hydrogel incorporation into the fabric surface layer was achieved by crosslinking primary amine groups of chitosan with the end amine groups of polyamide, using the natural crosslinker genipin. Among other analytical techniques, Scanning Electron Microscopy (SEM) was used to characterize the surface morphology of both hydrogel and fabric samples, Differential Scanning Calorimetry (DSC) to determine the Lower Critical Solution Temperature (LCST) of PNIAA, and X-ray Photoelectron Spectroscopy (XPS) to analyse the fabric surface chemical composition. The fabric moisture contents were determined by weight measurements at different temperatures and relative humidity values (RH). Liquid porosimetry, water vapour transmission (WVT) and dynamic wetting measurements were also performed to assess the fabric pore volume distribution, permeability and wetting times, respectively. It was found that the moisture absorbed by the functionalised polyarnide fabrics can be regulated at different conditions of temperature and relative humidity according to the PNIAA/CS ratio in the hydrogel. For example, at 40 degrees C (i.e. above the PNIAA LCST) and even at high RH (85%), the higher the PNIAAJCS ratio was in the incorporated hydrogel, the lower were the moisture contents of the functionalised fabrics, compared to the reference. In all cases, the presence of CS increased significantly the polyamide fabric wetting times.