| Over the past few decades, more attention has been focused on the preparation of the ?-crystal form of isotactic polypropylene (?-iPP) for better impact resistance, in comparison to the traditional a-form of iPP (a-iPP). At present, adding highly efficient and selective ?-nucleating agents (?-NAs) is considered as the most reliable method for the production of the (3-iPP, however, the few kind of efficient and selective ?-NAs limits the development of ?-iPP. Therefore, the development of low-cost, highly efficient and selective ?-NAs has important significance for the application and development of ?-iPP.Firstly, Zinc adipate(Adi-Zn(Solution) and Adi-Zn(Semisolid)) was synthesized through semi-solid method and solution method. The molecular structure, crystal structure and morphology of ?-NAs were characterized by fourier transform infrared spectroscopy (FTIR), wide-angle x-ray diffraction (WAXD) and scanning electron microscopy (SEM). The effects of Adi-Zn that synthesized through above methods on the ?-crystals content and the mechanical properties of nucleated iPP were investigated. The results showes that, the Adi-Zn that synthesized through above methods are capable of inducing ?-iPP from the polypropylene and substantially improved the toughness of iPP. The kp value remained at 0.95 when Adi-Zn(Solution) was added at a concentration of 0.2-0.8 wt%, kp reaches a maximum of 0.97 when it with a concentration of 0.1. Nucleated polypropylene obtain maximum impact strength, respectively,1.8 times and 2.8 times that of neat polypropylene when Adi-Zn (Semisolid) and Adi-Zn (Solution) added at a concentration of 0.2 wt% and 0.6 wt%. The above results show that Adi-Zn that synthesis through semi-solid method is a more effective ?-NAs. This may be due to a smaller size of Adi-Zn crystals from semi-solid method, better dispersion in the polypropylene, so the higher the nucleation efficiency.Secondly, the effect of Adi-Zn that synthesized by two methods on crystallization behavior and kinetics of polypropylene was investigated using differential scanning calorimetry (DSC). The results showes that, Adi-Zn (Semisolid) is more efficient than Adi-Zn (Solution) with a higher crystallization peak temperature (Tcp) of polypropylene, a shorter half crystallization time, which is consistent with the results of mechanical properties. Meanwhile the effect of cooling rate on the Adi-Zn and Adi-Zn(Semisolid) nucleation polypropylene ? polymorph formation was investigated using flash scanning calorimeter(FSC). At cooling rates below 3000?/min, only ?-crystals existed. However, at cooling rates above 6000?/min,?-crystals failed to form.Based on the effect of cooling rate on Tcp of polypropylene, we proposed an exponential decay of Tcp (x) with the cooling rate (y): y= Ae-x/B+CFinally, the process the nucleating agent is prepared in situ was proposed, in this study, two kinds of Adi-Zn(Adi-Zn-Nano(In situ) and Adi-Zn(In situ)) were synthesized in situ method, respectively by nano-zinc oxide and zinc oxide as ordinary raw materials reacted with adipic acid during processing, and also the nucleation effect of them was investigated. It showes that both of them are capable of inducing ?-iPP from the polypropylene, kp value reaches the maximum of 0.99 with a concentration of 0.05 wt% added. However, they have defferent improvement on polypropylene impact strength and crystallization peak temperature, Adi-Zn-Nano(In situ) can improve the impact strength of polypropylene increase to 3.9 times, Tcp increase 9.1?, better than Adi-Zn(In situ). This shows that the nucleating agent with nano zinc oxide as a starting material dispersed more evenly in the polypropylene matrix, and with a higher nucleation efficiency. |
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