Monte Carlo simulation of the peroxide curing of ethylene elastomers

• Published in: Rubber chemistry and technology Vol. 76; no. 1; pp. 174 - 201
• Main Author: JOHNSTON, Robert T
• Format: Conference Proceeding Journal Article
• Language: English
• Published: Akron, OH American Chemical Society 01.03.2003; Rubber Division
• Subjects: Applied sciences; Chemical reactions; Chemical reactions and properties; Chemistry; Copolymers; Crosslinking, vulcanization; Efficiency; Exact sciences and technology; Experiments; Molecular weight; Monte Carlo simulation; Organic polymers; Physical properties; Physicochemistry of polymers; Polymers; Polyolefins; Radiation; Rubber; Sulfur; Viscosity; Monte Carlo method; Olefin copolymer; Conversion rate; Elastomer; Theoretical study; Modeling; Vulcanization; Ethylene copolymer; Curative; Numerical simulation; Measurement method; Chemical reactivity; Comparative study; Organic peroxide
• ISSN: 0035-9475; 1943-4804
• DOI: 10.5254/1.3547732

Abstract Four ethylene octene copolymers covering a range of 0.87–0.91 g/cc density and 0.5–30 melt index were crosslinked using 0.25–8.0 phr dicumyl peroxide and characterized by sol-gel analysis and dynamic viscometry in an RPA 2000 rheometer. Using Monte Carlo simulation, the peroxide initiation efficiency (45–57%) and scission/crosslinking ratio (0.10–0.26) were determined. After using these sol-gel results to calibrate the simulation, the simulation was used to predict and analyze the crosslinked network structure as a function of extent of peroxide reaction. From the simulation output, the RPA 2000 dynamic storage modulus was successfully modeled using a three component model comprised of: (a) an affine modulus contribution related to the number of elastically active chains; (b) a Pearson-Graessley trapped entanglement contribution related to the weight fraction of elastically active network chains and the plateau modulus (which was in turn related to copolymer composition through a polymer backbone weight fraction model); and (c) a relaxation modulus component related empirically to network defects. These results show how misleading curemeter (ODR, MDR, RPA) data can be without application of an appropriate analytical or simulation model for their interpretation, but also how useful, when appropriately analyzed, these data can be for developing a fundamental understanding of polymer structure-network-property relationships.