Effects of different polyolefin copolymers on properties of melt mixed polypropylene blends

Abstract

Polypropylene (PP) is an affordable plastic commodity but lacks massive use in engineering applications given its limited mechanical properties including significantly low impact strength. In this work, three polyolefin-based copolymers including ethylene-octene random block (Engage, E), ethylene-octene multiblock (Infuse, I), and ethylene-propylene copolymer (Versify, V) were blended with PP. It was found that the V copolymer was miscible while the rests were immiscible in the PP matrix. Mechanical testings indicated that the addition of the 20% E and 20% I copolymers significantly enhanced the impact toughness of PP up to 83% and 108% at À20 C, respectively. At a higher temperature such as 25 C, the impact toughness of the PP/E20 and PP/I20 were 400 and 571%, respectively. The enhancement of the PP impact toughness was governed by the particle size of the added immiscible copolymers. Experimental results also revealed that the good compatibility between PP and copolymers has an insignificant influence on the mechanical properties of PP while the essence of added copolymer plays a key role instead. The findings from this work provide significant insights into the design of PP-based products with desirable properties to satisfy requirements demanded by engineering applications.

Advances in Nonreactive Polymer Compatibilizers for Commodity Polyolefin Blends

“…In separate studies of 50:50 LDPE/iPP blends compatibilized with 5 wt % of an EPDM copolymer, Vervoot et al and Fortelný et al reported approximately 6- and 3-fold increases in impact strength, respectively. In another study, Radonjič et al reported a 4-fold improvement in the impact strength for 80:20 LDPE/iPP recycled blends compatibilized with 10 wt % of an EPR or EPDM copolymer . These findings are consistent with impact resistance increasing with the introduction of a rubbery phase capable of absorbing energy, thereby preventing failure at the PE/PP phase boundary.…”

“…In part, this is due to the chemical similarities of branched polyolefins (e.g., LLDPE and LDPE), the covalent copolymerization of olefins (e.g., PP copolymers), and the intentional blending of virgin resins (e.g., impact modified iPP). For example, reactor blending and postreactor blending of iPP with ethylene- co -propylene rubber (EPR), ethylene- co -propylene- co -diene monomer (EPDM), and other amorphous polyolefins is a common practice for enhancing impact strength, toughness, and processability. ,− It should be noted that although compatibilization to improve the performance and consistency of secondary plastics is an urgent need, the technologies covered herein also apply to virgin blends, which can result in superior properties, new applications, and material reduction.…”