Silane functionalized ethylene/diene copolymer modifiers in composites of heterophasic polypropylene and microsilica

• Published in: Polymers & polymer composites Vol. 15; no. 5; pp. 343 - 355
• Main Authors: LIPPONEN, S, PIETIKÄINEN, P, VAINIO, U, SERIMAA, R, SEPPÄLÄ, J. V
• Format: Journal Article
• Language: English
• Published: Shrewsbury Rapra Technology 01.01.2007; Sage Publications Ltd. (UK); Sage Publications Ltd
• Subjects: Applied sciences; Chemical properties; Composites; Copolymers; Exact sciences and technology; Forms of application and semi-finished materials; Materials science; Polymer industry, paints, wood; Polypropylene; Polypropylene fibers; Silane; Silica; Technology of polymers; Finland; Olefin copolymer; Propylene polymer; Ethylene propylene rubber; Mechanical properties; Hydrosilylation; Dispersion reinforced material; Experimental study; Property processing relationship; Compatibilizer; Silicon copolymer; Silica; Diene copolymer; Composite material; Structure processing relationship; Chemical modification; Impact strength; Morphology; Preparation; Ethylene copolymer; Olefin polymer; Fracture mode
• ISSN: 0967-3911; 1478-2391
• DOI: 10.1177/096739110701500501

Ethylene/1,7-octadiene copolymer was polymerised with metallocene catalyst and hydrosilylated to form silane functionalised polyethylenes (PE-co-SiX, X=Cl, OEt, Ph). The functionalised species were tested as modifiers in composites of rubber toughened polypropylene (heterophasic PP, hPP) and microsilica filler (μSi). A metallocene-based functionalised PE (PE-co-SiF) produced earlier in our laboratory and three commercial grades of functionalised polyolefins (one PE- and two PP-based) were used as reference modifiers. Major differences were seen in the toughness of the composites both above and below the glass transition temperature (T g ) of PP. In addition to increasing the stiffness, the microsilica filler enhanced the toughness of the heterophasic polypropylene by over 200% at ambient temperature. Below the T g of PP (at −20 °C), the influence of μSi was the opposite and the impact strength of the hPP/μSi composite was below that of unfilled hPP. With the addition of just 2 wt% of functionalised polyethylene, the poor cold toughness of hPP/μSi composite was improved by nearly 100%. With the same addition, the toughness of the composites at ambient temperature was improved by 50 to 100% compared with the unfilled hPP. This behaviour was explained by significant changes in the fracture mechanism. Addition of functionalised PE increased the concentration of microsilica in the rubbery phase, allowing the crack to enter that phase. The rubbery phase was also able to absorb a large amount of impact energy below the glass transition temperature of PP.