Effect of aromatic dihydrazide compounds on crystallization behavior and mechanical properties of isotactic polypropylene

we prepared a series of aromatic dihydrazide compounds which were used as nucleating agents (NAs) in isotactic polypropylene (iPP). Differential scanning calorimetry (DSC) was used to study the influence of aromatic dihydrazide compounds with different structures on the crystallization behavior of iPP. The optimum concentration and mechanical properties of 1-N′,3-N′-dibenzoylbenzene-1,4-dicarbohydrazide (PTADH-Ph-3) with the best nucleation effect were investigated. The results of DSC demonstrate that all synthesized compounds have strong α-nucleating ability for iPP. When the para position of phenylenedihydrazide is substituted by phenyl, the crystallization peak temperature (Tc) of nucleated iPP is 14.4 °C higher than that of pure iPP. The Tc of iPP nucleated by dihydrazide compounds first raises sharply and then reduces slowly with increasing the number of carbon atoms in straight chain alkyl. When the number of carbon atoms in straight chain alkyl is two, the nucleation effect of nucleated iPP is the best, and the Tc of iPP nucleated with PTADH-CH-1 is higher 11.2 °C than that of pure iPP. While the addition amount of PTADH-Ph-3 is 0.2 mass%, the Tc of nucleated iPP can reach the maximum at 130.6 °C. The rigidity of iPP nucleated with PTADH-Ph-3 is improved. Compared with pure iPP, the impact and tensile strength of iPP nucleated with 0.2 mass% PTADH-Ph-3 have little change, but the flexural modulus and flexural strength increased significantly.