Reduction of High-Temperature Thermal Shrinkage of Polyvinyl Alcohol Fiber Using Organometallic Compounds

Polyvinyl alcohol (PVA) fibers exhibit excellent mechanical and chemical properties but suffer from severe thermal shrinkage at elevated temperatures, limiting their applicability in high-temperature environments. This study proposes a novel, halogen-free surface modification strategy to enhance the thermal dimensional stability of PVA fibers through a two-step treatment process. In the first step, zirconium-based compounds modify the fibers surface through coordination with hydroxyl-rich PVA chains, while in the second step, metal alkoxides such as tetraethoxysilane or zirconium(IV) butoxide are applied to reinforce the modified surface via hydrolysis-driven deposition of thermally stable inorganic species. Rather than assuming the formation of a fully characterised skin layer or hybrid barrier structure, the sequential treatment is conservatively interpreted as generating an inorganic-rich surface-modified region, inferred from surface morphology and bulk thermal behaviour. Differential scanning calorimetry results are discussed in terms of treatment-induced changes in thermal transition behaviour without direct attribution to crystallinity variation, while thermogravimetric analysis indicates an increase in inorganic residue without assigning specific oxide phases. These effects are associated with suppressed fibers contraction under thermal stress. Comprehensive characterisation utilising scanning electron microscopy, thermomechanical analysis, thermogravimetric analysis, and differential scanning calorimetry indicates significantly enhanced thermal behaviour, including the onset temperature of shrinkage being raised from 135 °C for untreated fibers to approximately 188 °C for the dual-treated fibers. Moreover, the treated fabric visually retains its woven structure after exposure to 250 °C for 5 min. The halogen-free surface modification approach provides a simple and applicable method to enhance the thermal dimensional stability of PVA fibers, which opens an avenue for their applications in high-performance technical textiles in large-scale production.