The effects of polybenzimidazole and polyacrylic acid modified carbon black on the anti-UV-weathering and thermal properties of polyvinyl chloride composites

In this study, the effects of polybenzimidazole (PBI) and polyacrylic acid (PAA) modified carbon black (MCB) on the anti-UV-weathering and thermal properties of PVC composites were investigated. The optimal mass ratios of PBI and MCB to PVC are 0.1 wt% and 0.2 wt%, respectively, and the resultant 1PBI/2MCB/PVC composite membrane with a thickness of about 60 μm can block over 99% of UV light below 380 nm. The UV absorption mechanism was investigated by the optional band gap (Eg) and the fluorescence spectroscopy. The incorporation of PBI and MCB results in a decrease in Eg, from 4.96 eV for PVC membrane to 2.90 eV for 1PBI/2MCB/PVC composite membrane, and MCB can quench the fluorescence of PBI by photon-induced electron transfer to further protect PVC. The results of accelerated UV-weathering experiment indicate that the incorporation of PBI and MCB can improve the anti-UV-weathering property of PVC. The thermal degradation behaviors of PVC and its composite membranes in air and N2 atmosphere were also investigated. The highest char residue (13.7 wt%) is obtained in 1PBI/2MCB/PVC composite membrane at 800 °C in N2 atmosphere, with an increase of 73.4% compared with that of PVC membrane, which may be because PBI and MCB can synergistically accelerate the carbonization of PVC molecules to rapidly form stable char residue.