Enhanced crystallization property and equilibrious mechanical properties of a novel self-assembly nucleating system based phosphate for polypropylene

The macroscopic properties of isotactic polypropylene (iPP) are closely related to the microscopic crystallization characteristics. It is significant to design and fabricate nucleating agent which can regulate the crystallization property of iPP efficiently. Here, a novel self-assembly nucleating system (MBP-Z13Xa) was tailored by impregnating 2,2′-methylene-bis-(4,6-di-tert-butylphenyl) phosphate (MBP) on zeolite carrier 13X (Z13X). The excellent system endowed iPP with brilliant crystallization performance and mechanical properties including rigidity and toughness. The results showed that the binding energy (BE) between MBP and Z13X calculated by using density functional theory (DFT) was 35.6 kcal/mol, much higher than that of MBP themselves (6.5 kcal/mol), which meant that MBP tended to associate with Z13X more easily than with itself. As a result, the novel self-assembly nucleating system MBP-Z13Xa embodied well dispersion was obtained at the driving of hydrogen bonding interaction between Z13X and MBP verified by FTIR. In point of the novel nucleating system, the incorporation of Z13X made MBP disperse uniformly. The structure matching between MBP-Z13Xa and iPP finally enhanced the crystallization and mechanical properties of iPP. The better mutual interaction between appropriate structure of MBP-Z13Xa and iPP segments obtained when the mass ratio of Z13X to MBP was adjusted to 1.4. MBP-Z13X1.4 not only increased the crystallization peak temperature about 7.5 °C, but also enhanced flexural modulus and impact strength of iPP by 23% and 15% respectively, showing equilibrious improvement between rigidity and toughness.