Interfacial strengthening of high-impact polypropylene compounds by reactive modification

Abstract

The effects of reactive modification on the interfacial strength in high-impact polypropylene materials have been investigated using a model system and demonstrated in two specific examples on high flow materials for thin wall injection moulding and reinforced compounds for engineering applications. Using Borealis' proprietary modification technology, the modification degree was controlled by varying the free radical initiator and co-agent content, respectively. The influence of the modification degree on the formation of ethylene-propylene copolymer grafted to polypropylene, which is believed to be the main reason for the strengthened interface between the PP matrix and EPR particles, the phase morphology and material properties was investigated. Depending on practical application requirements, a well defined material performance such as toughness, flowability, surface stability, etc. could be adjusted.

Heterophasic copolymers of polypropylene: Development, design principles, and future challenges

“…For heterophasic PP, the influence of the EPR design and PE addition on the visbreaking reaction was studied by Sheng et al They analyzed the effect of the molecular weight of an ethylene‐ block ‐ co ‐PP on the crystallization behavior, morphology, and fracture behavior after peroxide‐induced degradation, whereas a combination of radical modification and recombination in the presence of a coupling agent led to a high‐melt‐strength PP with long‐chain branching when a PP homopolymer was used as the base material. This reaction led to the so‐called reactive‐modified copolymers when a heterophasic PP was the base material . The addition of a free‐radical initiator and a co‐agent such as a diene causes the formation of ethylene–propylene grafted to PP.…”

“…This grafted copolymer is thought to strengthen the interface between the PP matrix and the EPR particles and thus reduces the tendency of the particles to agglomerate. These materials show a refined morphology and a strongly increased impact strength …”

The Production of High-Impact and High-Flow PP/EPDM/talc Composites by Reactive Extrusion

“…At the same time, in the development of the examined composites, the potential of methods of reactive compounding of PP/EPDM blends has remained virtually untapped. The high effectiveness of these methods in terms of increasing the compatibility of components and producing high-flow blends with increased impact strength is clearly indicated by data from elsewhere [4][5][6].…”

Binary Blends of Ethylene-α-olefin Elastomers for Improving the Balance between the Impact Strength and Individual Deformation and Strength Properties of Polypropylene Composites Produced by Reactive Extrusion

“…A great advantage of the above dynamic vulcanisation systems -peroxide/polar vinyl monomer coagent -is the possibility of controlling the melt flow of the products obtained within a certain framework, without significantly reducing their impact strength [6][7][8].…”