%0 Journal Article
%T Dependence of Adhesion Property of Epoxidized Natural Rubber (ENR 25)/Ethylene-Propylene-Diene Rubber Blend Adhesives Crosslinked by Benzoyl Peroxide
%A B. T. Poh
%A Y. Y. Teh
%J Journal of Coatings
%D 2014
%R 10.1155/2014/526369
%X The loop tack, peel strength, and shear strength of crosslinked epoxidized natural rubber (ENR 25)/ethylene-propylene-diene rubber (EPDM) blend adhesives were investigated. Coumarone-indene resin, toluene, and benzoyl peroxide were used as the tackifier, solvent, and crosslinking agent, respectively, throughout the experiment. The adhesive was coated on a polyethylene terephthalate (PET) substrate using a SHEEN hand coater at 60£¿¦Ìm and 120£¿¦Ìm coating thickness. It was cured at 80¡ãC for 30 minutes before testing on a Lloyd adhesion tester operating at testing rates from 10 to 60£¿cm£¿min£¿1. Results show that loop tack and peel strength of the ENR 25/EPDM adhesive pass through a maximum value at 2 parts per hundred parts of rubber (phr) of benzoyl peroxide content. This observation is attributed to the increase in crosslinking which enhances the cohesive strength of the adhesive. Further addition of the crosslinking agent decreases the tack and peel strength due to the decrease in wettability of the over-crosslinked adhesive. Shear strength, however, increases steadily with benzoyl peroxide content, an observation which is associated with the steady increase in the cohesive strength. The adhesion properties increase with increasing coating thickness and testing rate. 1. Introduction Natural rubber has been widely used to prepare pressure-sensitive adhesives [1]. One of the main reasons is that natural rubber is a renewal bioresource material. Natural rubber is known to exhibit several outstanding properties due to its ability to crystallize under stretching, that is, strain-induced crystallization [2, 3]. In formulating a rubber-based pressure-sensitive adhesive, an elastomer provides the elastic component while a low molecular weight tackifying resin imparts the viscous component. However, natural rubber alone has low tack and adhesion to surfaces. Hence, it is necessary to add tackifying resins to the rubber to increase its adhesion properties. It is generally accepted that adhesion properties of pressure-sensitive adhesives depend strongly on the viscoelastic properties of the adhesives. Many studies on the uncrosslinked natural rubber have been carried out. However, the adhesion properties of crosslinked rubber-based adhesives are scarcely reported in the literature. Hamed and Preechatiwong [4] found that during peeling action, strain-induced crystallization occurs for uncrosslinked and lightly crosslinked natural rubber. In the case of highly crosslinked natural rubber, no strain-induced crystallization was observed. Neoh et al. [5] studied the
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