Mechanism of Significant Improvement of Large Strain Elasticity in Soft Propylene–Ethylene Random Copolymer via Blending with Hard Propylene–Ethylene Coplymer

Abstract

The deformation behavior of propylene–ethylene copolymers with 23 mol % of ethylene (iPPcoE23) and its blend (90/10 w/w) (iPPcoE23b) with propylene–ethylene copolymer (6 mol % ethylene) (iPPcoE6) at room temperature was studied by in situ small-angle X-ray scattering and wide-angle X-ray diffraction techniques. The 10 wt % copolymer with 6 mol % ethylene counits dispersed as small domains in the matrix of iPPcoE23. During stretching, longer and thinner fibrils and better elasticity properties were shown in the blend iPPcoE23b at large strain regime. The higher elasticity for iPPcoE23b at large strain regime was ascribed to the weak ability of strain-induced crystallization due to cocrystallization of the crystallizable long chain sequences of iPPcoE23 with the high crystalline iPPcoE6 during cooling, leaving fewer long crystallizable sequences in the matrix in iPPcoE23b. In addition, the phase-separated domains contributed stronger network modulus in the late stage of stretching compared with that of the recrystallized network of iPPcoE23.

Structure Evolution of Polyethylene in Sequential Biaxial Stretching along the First Tensile Direction

“…The average length of fibril ( L fibril ) along the tensile direction can be determined via the formula put forward by Ruland and Perret. − where B obs and B φ represent the integral breadth of the azimuthal integrated curve and misorientation of fibrillar structure, respectively. The method for obtaining B obs and L fibril is provided in Figures S7 of the Supporting Information.…”

Influence of ethylene/propylene sequences on the thermal and mechanical properties of propylene‐based elastomers

“…In addition, PBEs can be a perfect candidate for polyolefin compounding modification benefit from the excellent compatibility. For example, PBEs blended with polypropylene can improve the transparency and impact resistance of the product and improve its processing performance 6–9 . Exxon Mobil has blended PBE (16 wt%) with iPP (84 wt%) to prepare an SMMS nonwoven that can be used in a three‐dimensional leak‐proof nappy partition design.…”

“…For example, PBEs blended with polypropylene can improve the transparency and impact resistance of the product and improve its processing performance. [6][7][8][9] Exxon Mobil has blended PBE (16 wt%) with iPP (84 wt%) to prepare an SMMS nonwoven that can be used in a threedimensional leak-proof nappy partition design. Heidari et al 10 significantly improved the impact strength with the increase of PBEs concentration.…”