Structural evolution of PPR, PP/PE, and maleic anhydride-grafted PP/PE blends during uniaxial stretching and cooling studied by in situ SAXS and WAXD

In situ SAXS/WAXD experiments were conducted to investigate the structural evolution and crystal growth of maleic anhydride (MAH)-grafted PP/PE and PPR blends (represented by PPR/EP55M), as well as their un-grafted blends (represented by PPR/EP55) during uniaxial stretching and cooling. Special attention was paid to the effect of MAH on pore formation under different stretching rates in the plastic deformation mechanism. The results show that the PPR/EP55 blend undergoes plastic deformation and forms micro-pores in the yield zone of PE. When stretched further in the MD direction, a long period increased through recrystallization and PE delayed the formation of holes caused by PP chain fracture. However, due to the incompatibility between PP and PE, the interfacial adhesion was poor and toughness of PPR/EP55 blends was significantly reduced compared to PP. The addition of MAH could increase the compatibility between PP and PE in the PPR/EP55M blends, allowing PE to enter the PP enrichment zone and promoted the conversion of PP-β to more stable α crystals with polymers that had stable properties. This improved the tensile strength of PE molecules and further delayed the fracture of PP molecular chains without affecting their toughness. We improved the research content on the impact of MAH on the mechanical properties of the PP/PE blends which has important guidance values for producing the protective pipes necessary for high-performance gas production drill pipes.

Graphical abstract