Rheological and Mechanical Study of Polypropylene Ternary Blends for Foam Application

Melt strength of polymer is one of the main primaries for the success of fabricating low-density extrusion foam and thermoforming process. Polypropylene (PP) as a linear polyolefin has low melt strength for bubble stabilization and sagging. Large molecules and long chain branches of PP cause higher molecular entanglements and increase elongational strength of PP melt. In this paper the rheological behaviour, melt elasticity, mechanical properties, and crystallinity of linear PP blends are studied and compared with blends containing a long chain branched PP resins. It is found that ternary blends of linear PP improve the melt elasticity in a certain composition, comparing to binary blends. Branched PP resins increase molecular entanglements, which it leads to higher melt elasticity. The results of this study help to understand the effects of chain size and chain architecture in increasing the melt strength and melt drawability of PP blends. These are the most important factors for producing low density PP foam and high quality thermoformed products.