Study On In-situ Induction Of Isotactic Polypropylene β Crystals By Zinc Oxide/phthalic Anhydrid

Isotactic polypropylene（i PP）has good regularity,high crystallinity and excellent performance,which is widely used in construction,packaging,fishery and forestry and other fields.As a typical homogeneous polycrystalline polymer,i PP has five crystal forms,therein,βcrystal form of isotactic polypropylene（β-i PP）can be used to prepare gas exchange microporous films,oil prone capacitor film and micro fiber with good water absorption because of its loose crystal structure.Meanwhile,βcrystal form slip can absorb energy leading to good toughness and excellent low-temperature impact resistance performance,β-i PP also can be applied to hood,automobile bumper,electronic container slot and so on.β-i PP is the focus of research and development in recent year.However,β-crystal form is a metastable and can only be obtained under specific conditions,the addition ofβnucleating agent（β-NA）is the most effective and commonly used method.Recently,theβ-NA,zinc oxide and phthalic anhydride（ZnO/Pht）have attracted the attention of industry because of their good dispersion,strong stability and simple operation.However,there is a lack of systematic research on the nucleation properties of ZnO/Pht.Therefore,ZnO/Pht was used to inducingβ-i PP in-situ sythsis in this paper,the crystallization behaviors,isothermal kinetics and mechanical properties of i PP were investigated by adjusting the size,ratio and concentration of ZnO/Pht.Its mechanism was characterized by infrared spectroscopy（FTIR）,wide-angle X-ray diffraction（WAXD）and thermogravimetry infrared（TG-IR）.The main research contents and results are as follows:（1）Size effect of ZnO/Pht onβ-i PP performance.The results of crystallization behavior,isothermal kinetics and mechanical properties show that Nano-ZnO/Pht has stronger nucleation efficiency for i PP than Macro-ZnO/Pht,the value of k_β（DSC）is78.18%,and the impact strength is 110%higher than that of pure i PP.The in-situ reaction process of ZnO/Pht was simulated and the size action mechanism of ZnO/Pht was established.FTIR and WAXD tests showed that Macro-ZnO and Nano ZnO reacted with Pht to generate zinc phthalate（Zn Pht）,which was the main component of inducedβ-crystal.TG-IR test shows that the content of Zn Pht produced by Nano-ZnO/Pht is more than that of Macro-ZnO/Pht.Nano-ZnO has higher reaction activity because the proportion of surface chemical oxygen is higher than Macro-ZnO.In addition,Nano-ZnO has more particles because the particle size is much smaller than Macro-ZnO.Therefore,the reaction of Nano-ZnO/Pht is more sufficient,the content of Zn Pht is higher,resulting in strongerβnucleation efficience.（2）Ratio effect of ZnO/Pht onβ-i PP performance.The results of crystallization behaviors,isothermal kinetics and mechanical properties show that Nano-ZnO₄/Pht₄has the bestβnucleation efficience.The value of k_β（DSC）can reach 86.09%,and the impact strength is 250%higher than that of pure i PP.To simulate the in-situ reaction process of different ratio of ZnO/Pht,and establish the action mechanism of ZnO/Pht.TG-IR test shows that the content of Zn Pht is different that generated by different ratio of Nano-ZnO/Pht.The content of Zn Pht is the highest when Nano-ZnO₄/Pht₄,resulting in highest of k_β（DSC）value and impact strength.（3）Concentration effect of ZnO/Pht onβ-i PP performance.The results of crystallization behaviors,isothermal kinetics and mechanical properties show when the concentration of Nano-ZnO/Pht is 0.4wt%,the nucleated i PP had the bestβnucleation efficience,and the value of k_β（DSC）can reach 86.53%,as well as the impact strength is256%higher than that of pure i PP.Nano-ZnO/Pht has the bestβnucleation efficience when the concentration of Nano-ZnO/Pht is 0.4wt%.When the concentration of Nano-ZnO/Pht is 1.0wt%,the nucleated i PP had the fastest crystallization rate.