Abstract:

Objective In order to solve the problem of insufficient water and solvent resistance of linear waterborne polyurethane (WPU) adhesives due to the lack of cross-linking sites, A cross-linking modification strategy was proposed to optimize their comprehensive performance, aiming to develop eco-friendly WPU adhesives and expand their applications in reflective textiles.

Method A cross-linked WPU adhesive was prepared using a prepolymer mixing method, with polycarbonate diol (PCDL) as the soft segment, isophorone diisocyanate (IPDI) and dimethylolpropionic acid (DMPA) as the hard segments, and glucose as the green crosslinking agent. The influence of glucose mass fraction on the properties of WPU was characterized by Fourier transform infrared spectroscopy (FT-IR), mechanical testing, thermogravimetrico analysis (TG) and other methods, and the optimized WPU with organic silane coupling agent (KH560) and transparent paste were incorporated for the preparation and performance evaluation of reflective fabrics.

Results The result showed that glucose was successful in constructing a three-dimensional cross-linked network. As its mass fraction increased, the breaking strength of WPU increased from 6.58 N to 21.47 N, and the elongation at break decreased from 188.08% to 64.87%. The solvent resistance was enhanced, and the water washing resistance was improved by virtue of the compactness of the cross-linked network. Subsequently, the increase in glucose mass fraction caused functional group imbalance, decreased cross-linking efficiency, and many hydrophilic groups remained, resulting in a decrease in cross-linking degree and water resistance. When the glucose mass fraction was 1.0%, the comprehensive performance was found the best, with breaking strength being 10.28 N, the elongation at break 94.11%, and the heat and alkali mass residual rate 80.3%. After applying this WPU to reflective fabrics, the change rate of the reverse reflection coefficient of polyester/cotton fabrics and cotton fabrics after 3 water washing cycles was lower than 2%, while that of pure polyester fabrics increased by 2.55%, demonstrating excellent washing stability.

Conclusion Glucose reacts with —NCO to form a three-dimensional cross-linking network, making the emulsion from transparent to milky white with good stability. In terms of mechanical properties, the breaking strength is improved while the elongation rate decreases. The water washing resistance is superior first and then inferior (the mass fraction of 1.0% is the best), the solvent resistance and thermal stability are significantly enhanced, and the heat and alkali resistance remain stable (the mass residual rate is about 80%). The reflective fabric prepared by optimizing the adhesive composite has excellent performance, with polyester/cotton fabric as the optimal substrate. The fabric is solvent resistant, acid resistant, and washing durable, but not resistant to strong alkalis. The glucose modified WPU adhesive proposed utilizes its multifunctional group to construct a three-dimensional interpenetrating network, significantly improving the mechanical strength and solvent resistance of the film, as well as enhancing the integrity and cohesion of the film formation, thereby strengthening the interface bonding between the coating, reflective microbeads, and fabric substrate. Compared with existing systems, it can anchor microbeads more effectively, greatly improving the reflectivity coefficient and water washing resistance of reflective fabrics, providing a new solution for the environmentally friendly replacement of conventional solvent-based adhesives and the high-performance development of reflective fabrics.

Key words: waterborne polyurethane, adhesive, glucose modification, cross-linked network, reflective fabric, biobased crosslinking agent, water washing resistance