Zhengyu Feng, Jia Guo, Yongxin Yan, Jun Sun*, Sheng Zhang*, Wenjia Wang, Xiaoyu Gu, Hongfei Li. Modification of mesoporous silica with phosphotungstic acid and its effects on the combustion and thermal behavior of polylactic acid composites. Polymer Degradation and Stability, 2019, 160, 24-34

https://doi.org/10.1016/j.polymdegradstab.2018.12.004

Abstract

Highly ordered mesoporous silica (SiO₂) modified with phosphotungstic acid (PWA), was successfully prepared by vacuum impregnation. The chemical structure of as-designed PWA-mesoporous silica (PWA-SiO₂) was characterized by tran**ission electron microscopy, scanning electron microscopy, Fourier transform infrared spectra and **all-angle X-ray scattering. PWA-SiO₂, in association with intumescent flame retardant (IFR), was introduced into polylactic acid (PLA) by melt blending to obtain flame resistant composites. The flammability evaluation indicated that the presence of 19.0 wt% IFR and 1.0 wt% PWA-SiO₂ in PLA achieved the maximal LOI value of 47.2%, passed the UL-94 V-0 rating, and significantly decreased the peak heat release rate from 622.4 kW m⁻² of neat PLA to 182.3 kW m⁻². The introduction of PWA-SiO₂ could also slightly improve the mechanical properties of PLA composites. It is proposed that PWA-SiO₂, which exhibits excellent catalytic effect, can play roles together with IFR in both condensed phase through promoting the formation of continuous dense char layer and gas phase through releasing non-flammable gas.