Investigation of Barrier Effectiveness and Comfort Properties of Biodegradable PLA Nonwoven Fabrics Coated with Unmodified Lignin/Water-Borne Polyurethane Composite Coatings

Abstract

In this study, the main aim is to prepare unmodified lignin/water-based polyurethane (WPU) composite coatings with varying lignin concentrations and apply them to polylactic acid (PLA) spunlace nonwoven fabrics (PNFs). The effects of lignin concentrations were investigated in terms of color values, hydrophobicity, air permeability, and antibacterial properties of PNFs. The analysis of chemical groups in the structures of lignin/WPU composite films after curing was performed using Fourier Transform-Infrared (FTIR) spectroscopy, and their thermal properties were analyzed by Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). The coatings applied to the fabrics were examined by scanning electron microscopy (SEM) through surface images. The fabric coated with the X4 formulation, containing 4% concentration of lignin, displayed the highest water contact angle recorded at 93.6º. As the lignin concentration increased, the air permeability of the fabrics decreased. Regarding color measurements, the PNF sample coated with the X4 formulation showed the highest K/S value of 7.45. In antibacterial activity tests, no inactivation was observed against E.coli bacteria. However, inhibition zone measurements against S. aureus bacteria were 12±1.41 mm and 16.05±0.7 mm on fabrics coated with X3 and X4 formulations having lignin concentration 2% and 4%, respectively. The results indicated that an increase in lignin concentration effectively contributed to the inactivation against S. aureus bacteria. In this respect, this study represents the potential usability of unmodified lignin/WPU coatings providing barrier and comfort properties on biodegradable PNFs.