Preparation And Properties Of Synergistic Toughening Modified Polypropylene With ?-nucleating Agent And Nano-Silica

Polypropylene(PP)is the most widely-produced general-purpose plastic.It has the advantages of good mechanical strength and chemical stability.However,the major drawbacks of poor impact toughness and low-temperature brittleness greatly limit its application.Therefore,it's necessary to toughen PP.In order to study the ?-nucleation effect of phenyl-substituted aromatic diamide compounds,N,N'-diphenylterephthalamide(DPTH)was synthesized by the amidation reaction of terephthaloyl chloride and aniline.The results of FT-IR and 1H NMR confirmed that high-purity ?-nucleating agent DPTH was prepared through the amidation reaction.XRD and DSC were used to study the effect of DPTH on the crystallization behavior of PP,and the results showed that DPTH effectively induced the formation of ? crystals.The relative content of ? crystals was increased with the increasing DPTH content.The crystallization rate and crystallization temperature of PP were both increased by DPTH.The non-isothermal crystallization kinetics of PP were calculated according to the Avrami-Jeziorny equation.It was found that DPTH played a role in heterogeneous nucleation.The crystallization activation energies of PP and PP containing DPTH were calculated by Kissinger formula.PP/SiO₂ nanocomposites were prepared using surface-modified nano-SiO₂ and the polypropylene grafted with maleic anhydride(PP-g-MA)was added as a compatibilizer.The effect of modified nano-SiO₂ on crystallization behavior and mechanical properties of PP was studied under the action of compatibilizer.The results of FT-IR and SEM proved that there was an interaction between PP-g-MA and nano-SiO₂,and the dispersion of nano-SiO₂ in PP was improved.DSC was used to study the crystallization/melting behavior of PP.The results indicated that nano-SiO₂ accelerated the nucleation and crystallization rates of PP,and increased its crystallization temperature.But it had no effect on the crystal form of PP.The results of mechanical properties showed that PP was effectively strengthened and toughened by nano-SiO₂ at certain nano-SiO₂ content.The voids generated by the exfoliation of nano-SiO₂ were the internal reason for toughening.Moreover,with the increasing nano-SiO₂ content,the Young's modulus of PP increased,while the elongation at break decreased.DMA results showed that the storage modulus and glass transition temperature of PP were increased by nano-SiO₂.PP/SiO₂/TMB composite with ?-crystal PP matrix was prepared by combining modified nano-SiO₂ and ?-nucleating agent TMB-5 into PP.The composite effect of nano-SiO₂ and TMB-5 on the crystallization/melting behavior of PP was studied.XRD results showed that ? crystals effectively induced by TMB-5 were inhibited with the addition of nano-SiO₂.DSC results confirmed that the compounding of nano-SiO₂ and TMB-5 increased the crystallization temperature and crystallization rate of PP/SiO₂/TMB composites.Both TMB-5 and nano-SiO₂ induced the heterogeneous nucleation of PP,accroding to the results of non-isothermal crystallization kinetics.The crystallization activation energy of PP/SiO₂/TMB composite was increased by TMB-5 due to its ?-nucleation ability,and was reduced by nano-SiO₂.The interaction between nano-SiO₂ and TMB-5 was studied by FT-IR and SEM.The results confirmed the existence of hydrogen bonds between nano-SiO₂ and TMB-5,which improved the dispersion of nano-SiO₂.The mechanical properties result indicated that the synergistic effect of TMB-5 and nano-SiO₂ comprehensively increased the tensile and impact properties of PP.A synergistic toughening effect of TMB-5 and nano-SiO₂ was found at 1 phr nano-SiO₂ content.This was because the loose layered structure of ?-crystal PP made it easier to cause plastic deformation of the matrix around nano-SiO₂ when it was peeled off.DMA results indicated that TMB-5 promoted the movement of molecular chains in the amorphous region due to the formation of ? crystals.Thus,the storage modulus and glass transition temperature of PP were decreased together.