Study on autoclave foaming properties of metallocene polypropylene
The melting and crystallization behavior of two types of polypropylene,named as mPP and ZNPP,were stud-ied by using differential scanning calorimeter(DSC)and polarized microscope(POM),and their rheological characteris-tics were analyzed through frequency scanning and melt stretching.Autoclave foaming experiments were conducted to in-vestigate the melting crystallization behavior,foaming ratio,and cell structure of the expanded polypropylene(EPP)beads.The results indicated that ZNPP had a higher complex viscosity and more obvious shear thinning,leading to high-er molecular weight size and distribution.ZNPP exhibits higher melting strength than mPP at higher temperatures due to more intense molecular chain entanglement.However,its melt strength is similar to that of mPP at lower temperatures.The quality of the cell structure needs to be improved,when mPP is used to produce EPP beads with similar ratios to ZNPP.
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