UV absorber co-intercalated layered double hydroxides as efficient hybrid UV-shielding materials for polypropylene

Abstract

Two kinds of UV absorbers 2-hydroxy-4-methoxy-benzophenone-5-sulphonic acid (HMBA) and cinnamic acid (CA) were successfully co-intercalated into the interlayer of Mg₂ZnAl layered double hydroxides (LDH) by a modified coprecipitation method to prepare novel UV-shielding material HMBA–CA-LDH for improving the anti-photoaging capability of polypropylene (PP). The characterization results reveal the presence of host–guest interactions between the LDH host layers and HMBA/CA guest anions as well as guest–guest interactions between guest anions in HMBA–CA-LDH, and the HMBA–CA-LDH has much stronger UV absorption capability than the HMBA intercalated LDH (HMBA-LDH) in the whole UV band and a much broader UV absorption band than the CA intercalated LDH (CA-LDH). A series of LDH/PP composites with evenly dispersed LDH nanosheets were prepared by incorporating the prepared LDHs into the matrix of PP via the solvent casting method. As expected, LDH/PP composites show higher thermal stability and better anti-photoaging ability than pristine PP. Interestingly, HMBA–CA-LDH/PP shows better anti-photoaging performance in comparison with HMBA-LDH/PP and CA-LDH/PP because of its better UV-shielding ability arising from the synergistic UV-shielding effects of both HMBA and CA, and the HMBA–CA-LDH can reduce the photodegradation of PP by about 85%. Hence, the prepared novel HMBA–CA-LDH has potential application in the field of PP as an efficient and promising UV-shielding material.