Synthesis of chloromethyl benzimidazole grafted polybenzimidazole with enhanced UV absorption and its effect as a stabilizer on the ultraviolet‐aging behaviors of poly(vinyl chloride) films

ABSTRACT Poly(vinyl chloride) (PVC) is particularly susceptible to UV damage, and its durability can be reduced substantially when it is exposed to outdoor environments. In this study, high‐molecular‐weight polybenzimidazole (PBI) was synthesized and then grafted with 2‐chloromethyl benzimidazole. The polybenzimidazole grafted with 2‐chloromethyl benzimidazole (PBI‐ g ‐CMBeIm) could absorb over 99% of UV light in the region 220–420 nm. Then, PVC–PBI‐ g ‐CMBeIm blend films were prepared by a solution‐casting method, and the effects of the PBI‐ g ‐CMBeIm content and UV‐irradiation time on the properties of these films were investigated. The results show that the benzimidazole moieties incorporated into the macromolecular chain of PBI provided additional conjugation units, and this allowed the films to have a stronger UV absorption and broader λ range. The yield strength of the PVC–PBI‐ g ‐CMBeIm blend films irradiated for 1000 h ranged from 16.5 to 27.7 MPa; this increased 3.2–14.4 MPa compared with that of the pure PVC. The strength retention rate of the pure PVC was 28.8%, whereas that of the PVC–PBI‐ g ‐CMBeIm blend films was in the range 34.1–55.2%. The addition of PBI‐ g ‐CMBeIm also effectively increased the thermal degradation temperature of the blend films and slowed down their thermal degradation rate. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136 , 47626.