Preparation And Performance Of Anti-Migration Polypropylene Antioxidants With Supramolecular Structure

Polypropylene (PP) has become an integral part of life and production materials due to rich source of raw materials, light weight, high mechanical strength and excellent corrosion resistance. PP is seriously suffered from oxidative degradation due to environmental factors such as light, heat and oxygen. Generally, a certain amount of antioxidants are required to retard the aging and degradation of PP during the procession. Yet, most of the used antioxidants are organic molecules and have a trenency of migrate to the surface of polymer because of good compatibility between organic antioxidants with organic polymer. Undoubtedly, the loss of the anti-oxidants will cause the weakness of anti-thermal oxidantive stability of polymer. Therefore, it is of interest and importance to explore novel polypropylene antioxidants with high performance and long duration.Layered double hydroxides (LDH) is one kind of two-dimensional anionic-inorganic functional materials with adjustable chemical composition and tuneable charge density in the host sheet, and changeable guest anions in the interlayer regions. LDHs has been widely used as various functional additives for polymers. It is possible to obtain novel intercalated antioxidants with high performance and long durability because of potential host-guest interactions and interface effect. In this work, the organic anions (MP) of antioxidant 1425 were used as guest anions and a series of intercalated antioxidants MP-LDHs were prepared by one-setp co-precipitation method. The following results were obtained:(1) A series of intercalated antioxidants of CaAl-, CaMgAl- and CaZnAl-MP-LDH were successfully prepared by co-precipitation method. The corresponding characterizations on crystal structure and chemical composition were carried out. MP-LDH/PP composite with different loadings were prepared by solvent mixing method. The MP-LDH nanoparticles were well dispersed in PP and did not change the crystalline structure of PP.(2) The loading of CaAl-MP-LDH in MP-LDH/PP has influenced the anti-light, thermal oxidantive stability of PP composites and the migration behavior of anion MP in the composite. When the loading of MP-LDH in PP was 1.0 wt%, the anti-light oxidantive stability of LDH/PP composite was more than 2 times and anti-thermal oxidantive time extended by 30 times related to the pure PP (no MP-LDH); furthermore, the migration rate was reduced by 50% due to the barrier effect and interface effect compared with MP/PP composite with the same loading of MP in PP.(3) The influence of the chemical compositions was investigated on the performance of LDH/PP composites against photo- and thermal-degradation and migration of MP. Among the examined samples, when Ca:Zn:Al was 1:1:1, the anti-light oxidantive stability and anti-migration performance of CaZnAl-MP-LDH/PP composite was best; additionaly, appropriate amount of Zn2+ incorporated in the host sheet favored to enhance the performance against photo-, thermal-oxidative degradation and anti-migration capcity of MP in the MP-LDH/PP composites.