Synergistic effects of phenylsilane and isopropyl titanate-modified montmorillonite nanofillers on the thermal and flame-retardant properties of PVA films

Poly (vinyl alcohol) (PVA) films are limited by their low thermal stability and inherent flammability. In this work, a synergistic surface modification of montmorillonite (MMT) was achieved using phenyltriethoxysilane (PTES) and isopropyl tri (dioctyl pyrophosphate) titanate (IPPTO) to produce co-modified nanofillers (IPMMT) that are uniformly dispersed within PVA, forming a hierarchical porous network. The dual modification transforms MMT from a slit-like structure into a mesoporous architecture while enhancing interfacial bonding via Si–O–C/Si–O–Si and Ti–O–M linkages. Compared with pristine PVA, the IPMMT–PVA nanocomposite exhibits dramatically improved thermal performance: the char yield exceeds 40% at 600 °C in air (vs. ∼1% for PVA), Td 20 rises from 293 °C to 377 °C, Td 30 from 312 °C to 506 °C, and the maximum mass-loss rate decreases by more than an order of magnitude. Infrared thermography further confirms superior heat-shielding capability, with the time to reach 200 °C prolonged to 52 s—an increase of 372.8% relative to pure PVA. Mechanistically, phenylsilane grafting enhances polymer stability below 300 °C and constructs low mesopores that confine volatile degradation products, while titanate modification yields in situ TiO 2 above 600 °C, forming an inorganic barrier and promoting char densification. This cooperative silane–titanate strategy provides an environmentally friendly route to high-performance, thermally insulating, and flame-retardant PVA materials.