Synthesis And Application Of 1,3,5-benzenetricarboxylic Acid Amides Nucleating Agent For Isotactic Polypropylene

With development of science and technology,isotactic polypropylene(iPP)was more and more widely used in different fields.However,iPP also has some disadvantages,so modification of iPP with different methods is needed to improve comprehensive properties of iPP.Addition of nucleating agents during processing of iPP can improve flexural and tensile properties and decrease haze value of iPP obviously.Therefore,research and development of novel and highly-efficient nucleating agents is one of the important research fields in polypropylene modification.In this paper,nucleating agents 1,3,5-benzenetricarboxylic acid tris(cyclohexylamide)(BTA-99)and 1,3,5-benzenetricarboxylic acid tris(phenylamide)(BTA-93)were prepared from 1,3,5-benzenetricarbonyl trichloride,cyclohexylamine and aniline by adjusting mixing conditions of the reactants,reaction temperature and reaction time.The structures of the obtained products were verified by FT-IR and differential scanning calorimetry(DSC)and effects of the nucleating agents on crystallization behaviors and crystallization kinetics were investigated.The results showed that characteristic absorbing peaks of BTA-99 and BTA-93 were observed in FT-IR spectrums,respectively.The DSC melting curves of these two products were analyzed and were compared with that of 1,3,5-benzenetricarboxylic acid.The results showed that the synthesized products were the expected products and no other impurities exist in the products.The studies on the effect of BTA-99 and BTA-93 on crystallization and melting behaviors of iPP nucleated with different amounts of nucleating agents revealed that both of these two nucleating agents were highly efficient nucleating agents for iPP.When the addition amount of the nucleating agents in iPP was very low(0.04wt% for BTA-99 and 0.07wt% for BTA-93),compared to that of pure iPP,the crystallization temperature was increased by 7.0oC and 5.8oC,respectively,which was comparable to that of a highly effective commercial nucleating agent Hyperform HPN-68,indicating that both BTA-99 and BTA-93 are highly effective nucleating agent for iPP.The melting curves of iPP nucleated with both BTA-99 and BTA-93 show only one melting peak around 165 oC,which indicates that both BTA-99 and BTA-93 are ?-nucleating agents.Isothermal crystallization behaviors of pure iPP and iPP nucleated with BTA-99 were investigated by the classical Avrami theory.The results showed that the value of Avrami exponent n for nucleated iPP was close to that of pure iPP,indicating that the spherulite growth patterns of iPP didn't change after addition of BTA-99.iPP nucleated with BTA-99 had Zt,smaller crystallization half time(t1/2)and smaller time at maximum crystallization rate(tmax),and the crystallization activation energy ?E of iPP was decreased by 58KJ/mol when compared to that of pure iPP,indicating that addition of BTA-99 increased the overall crystallization rate of iPP.The Mo method was adopted to study the non-isothermal crystallization kinetics of iPP nucleated with BTA-99.The results showed that the crystallization peak of iPP became wider and the crystallization peak temperature was decreased with increasing of the cooling rate,indicating that the super-cooling degree will be higher when the cooling rate is increased.The plot of ln? versus lnt is a straight line,which illustrated the Mo method was applicable for study of non-isothermal crystallization kinetics of iPP nucleated with BTA-99.A high value of F(T)means a high cooling rate needed to reach this relative crystallinity in unit crystallization time,which reflects the difficulty extent of the crystallization process.The value of F(T)increases when the relative crystallinity increases,indicating that the cooling rate should be increased in order to reach a given relative crystrallinity in unit crystallization time.The cooling rate of iPP nucleated with BTA-99 needed for reaching the same relative crystallinity is far lower than that of pure iPP,indicating that the addition of BTA-99 increases the crystallization rate of iPP efficiently.