Macromolecular Modification of EPDM: Wettability, Miscibility, and Morphology Study MILENA GINIC-MARKOVIC, 1 NAMITA ROY CHOUDHURY, 1 MARIA DIMOPOULOS, 1 JANIS MATISONS, 1 CHANDIMA KUMUDINIE 2 1 Polymer Science Group, Ian Wark Research Institute, University of South Australia, The Levels, South Australia 5095, Australia 2 Polymer Research Center, Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221-0172 Received 2 May 2000; accepted 2 June 2000 Published online xx Month 2001 ABSTRACT: The present investigation deals with studies on wettability, miscibility, and morphology of the macromolecularly modified EPDM. Two different maleated EPDM rubbers (grafted rubber) were chosen (0.5 and 1% maleation) for such modification and they were used in various proportions. Wettability of the rubber substrate, as observed from dynamic contact angle measurement, was improved using these grafted rubbers. Results of X-ray photoelectron spectroscopy showed an increase in oxygen level with higher levels of grafted rubber in the blends. Morphology study by transmission electron microscopy showed a smaller domain size for the blend with higher maleic anhydride content in the grafted rubber. The viscosity versus blend ratio results showed a negative deviation behavior for blends with 1% grafted rubber, whereas a positive negative deviation behavior was observed in blends with 0.5% grafted EPDM. As the strength of interaction increased, the glass transition shifted to a higher temperature. All blends were heterogeneous, as indicated by different degrees of dispersion. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2647–2661, 2001 Key words: blends; EPDM rubber; grafted rubber; miscibility; morphology; wetta- bility INTRODUCTION Elastomeric compounds are selected for a partic- ular application on the basis of their specific phys- ical, electrical, or chemical properties. Not all the elastomers possess the required physical and chemical properties. For example, ethylene–pro- pylene– diene rubber (EPDM) is selected for auto- motive window-seal application because it has very good ozone and weather resistance, although its hydrocarbon nature leads to relatively poor surface chemical properties and hydrophobicity, making it difficult to bond to polyurethane (PU) coating. Because the hydrocarbon nature of EPDM rub- ber results in poor bondability, many attempts have been made by several workers to improve it. Vanderaar et al. 1 reported a new aqueous bond- ing system, to improve the adhesion of EPDM rubber to stainless steel. To improve wettability of the surface and biocompatibility of the ethyl- ene–propylene rubber (EPR), grafting with 2-hy- droxyethylene methacrylate (HEMA) and N-vi- nylpyrrolidone (NVP) was undertaken using CO 2 - pulsed laser as an excitation source. 2 Later, Haddadiasi and Burford 3 extended previous stud- ies by modification of four vulcanized EPR with Correspondence to: N. Choudhury (E-mail: Namita. Choudhury@unisa.edu.au) Journal of Applied Polymer Science, Vol. 80, 2647–2661 (2001) © 2001 John Wiley & Sons, Inc. 2647