Nucleation efficiency of substituted aromatic heterocyclic phosphoric acid metal salts as nucleators for isotactic polypropylene
Nucleation efficiency of 2,2′-methylene-bis (4,6-di-tert-butylphenyl)phosphoric acid metal salts as the nucleators for isotactic polypropylene (iPP) were investigated with differential scanning calorimeter (DSC), their effects on mechanical and optical properties of iPP were also studied. The results showed that monovalent metal salts of substituted aromatic heterocyclic phosphoric acid such as sodium salt, lithium salt and potassium salt had good nucleation efficiency. With 0.2%(mass) of sodium salt, lithium salt and potassium salt blended with iPP, the crystallization peak temperature of PP could be increased by 13.5℃, 13.6℃ and 15.0℃, respectively, the mass fraction of crystallinity of iPP could be increased by about 5%, and crystallization rate was enhanced increasingly.Meanwhile the tensile strength and flexural modulus of iPP could be increased by about 10% and 30%, respectively,and the haze value of iPP could be decreased by about 40%. But bivalent and trivalent metal salts of the phosphoric acid had little effect on properties of iPP. Furthermore the studies on non-isothermal crystallization kinetics of iPP showed that the addition of sodium salt, lithium salt and potassium salt could change the crystallization growth pattern of iPP.