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4.3.1.1 effect of antoxidantThe effect of the added amounts of antioxidants on the mechanal and melt properties of the composites comprised of 100 parts of PP, 100 parts of RGP, 1 part of MAH, and 0,5 part of TBPB by weght were determined and the the result s are shown in figure 4.1. The apparent melt viscosities of the composites increased with ncreases in the antioxidant contents. That s, the addition of antioxidant suppressed the man chain sciccion (depolymerization).As for the one step process, all components (for example, radical ntiator, MAH, and antioxidant) existed altogether in the system during kneading. When kneaded at a high temperature, the primary radicals generated by the peroxide decomposition attacked the PP molecules, eliminating hydrogen atoms to generate PP macroradicals. The latter result in either a MAH addition or a man chain scission of PP. because the antoxidants can react with radicals, it can be considered that the antioxidants take the role of supressng the main chain scission and of maintaining the molecular weight of PP at a high level. On the other hand, the maxmum tensile is recognized in fgure 4.1 when the antioxidant are added in 0,6 parts amounts as a whole. It is also favorable for composite strengths to keep the molecular weight of the matrix polymerat a high level. When the antioxidants exist in excess however, the addition of MAH nto the PP is retarded and MPP cannot be formed in sufficient amounts within the kneading system. As a result, the composite lacks the MPP compatibilizer and sufficient strength cannot be attained. In any case, the strength of a composite is determined by the balance of these positive and negatve effects and thus, the maximum strength of the omposite obtained in figure 4.1 is at most 320 kgf/cm2, which is much less than that of a composite prepared by the two step process of chapter 3 that is 420 kgf/cm2.
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