Study on degradation and crosslinking of impact polypropylene copolymer by dynamic rheological measurement

The structural stability of impact polypropylene copolymer (IPC) melt under high temperatures was explored by dynamic rheological measurement. The structure changes including degradation and crosslinking of IPC were discussed through examining the influence of temperature and additive antioxidant on dynamic rheological functions. A plateau of dynamic storage modulus (G′) appeared in low frequency region at high temperatures under air atmosphere. Furthermore, when IPC sample was annealed at 230 °C, its viscoelasticity presented a dramatic change. The time dependences of G′ for pure IPC at different temperatures were investigated. At 190 °C, a slight drop and a succedent rise of G′ for IPC0 appeared. The decrease period of G′ generally shorted and the increase of G′ became more remarkable with the increase of temperature. The decrease of G′ was ascribed to the degradation in IPC and the G′ increase was due to the crosslink reaction. Through incorporation of antioxidant into IPC, the crosslinking in IPC could be effectively inhibited, and the degradation and crosslinking in IPC were believed to result from PP component.

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