Study On Modification Of Polypropylene

In this paper, a kind of new titanium nucleating agents were prepared by isopropyl titanate, p-tert-butyl-benzoic acid and tetraethyl orthosilioate, and their performance were investigated. The feasibility of melt-grafteded polypropylene(PP) by maleic anhydride(MAH), N-glycine amide maleic acid (GMA), N-glycine amide maleic calcium (GMACa) and N-diacetic acid maleimide (DAMI) were explored, and the performance of modified polypropylene were also studied.The modified polypropylene with new nucleating agents were tested by the methods of thermogravimetric analysis (TG), X-ray diffraction analysis(XRD), differential scanning calorimetry(DSC), polarizing microscopy and biomechanical testing, and vicat softening point and melt index were also tested.The results of TG show that titanium nucleating agent begin to decompose at the temperature of 254.1℃. They are stable in the polypropylene's processing temperature (200-220℃) , so they can be used as nucleating agent of polypropylene.The results of DSC, XRD, vicat softening point and polarizing microscopy show that the titanium nucleating agent are effectiveαcrystalline nucleating agent of polypropylene, the crystallinity, crystallization temperature and crystallization rate of modified polypropylene have been increased in varying degrees. Compared with pure PP, the crystallization temperature and crystallinity are increased 15.62℃and 3%, the difference of crystallization onset temperature and crystallization peak temperature reduced from 4.4℃of the pure PP to 2.8℃, vicat softening point of modified polypropylene increased 7.7℃. Polypropylene's spherulite size are decreased significantly, and the boundaries between grains are weakened.The crystallization rate and crystallinity of modified PP by melt grafting have been improved to some extent, Compared with the cross-linking blank in 2% of GMA's mass fraction, polypropylene's crystallization temperature and crystallinity are increased 9.18℃and 5.6%; vicat softening point of modified polypropylene increased 18.1℃, the grains of modified polypropylene are refined significantly, and the boundaries between spherulites are not obvious.The mechanical properties of PP modified with titanium nucleating agents are improved in varying degrees, the maximum of tensile strength is 40.54MPa, and the largest increase is 15.2%; the maximum of anti-bending is 61.35MPa, and the largest increase is 26.3%; the maximum of impact strength is 13.02kJ/m2, and the largest increase is 114.9%.The melt grafted polypropylene's tensile strength, flexural strength and impact strength have been significantly increased compared with cross-linked blank of PP. The mechanical properties of grafted polypropylene by N-glycine Maleic acid amide are the best, their largest tensile strength, flexural strength and impact strength are 41.18MPa, 51.74MPa and 17.35kJ/m2.