Effect of N-isopropyl-N-phenyl-p-phenylenediamine antioxidant on the adhesion properties of (zinc oxide)-filled (epoxidized natural rubber 25)-based pressure-sensitive adhesives

The effect of antioxidant, namely, N-isopropyl-N-phenyl-p-phenylenediamine (IPPD), on the adhesion properties of epoxidized natural rubber (ENR 25)-based pressure-sensitive adhesive was investigated. The concentration of the IPPD was varied from 0 to 5 parts by weight per hundred parts of rubber (phr). Coumarone-indene resin, zinc oxide, toluene, and polyethylene terephthalate were used as the tackifier, filler, solvent, and substrate, respectively. A Lloyd Adhesion Tester operating at different testing rates (10-60 cm/min) was used to determine the loop tack, peel strength, and shear strength at 60-mu m and 120-mu m coating thicknesses. Results indicate that adhesion properties increase with IPPD up to 2 phr of content, after which it decreases with further addition of the antioxidant. This observation is attributed to the culmination of wettability and compatibility at the optimum IPPD concentration. The 60-mu m coated sample consistently shows higher adhesion strength than that of 120-mu m coated sample. Loop tack and peel strength increase with testing rate up to 30 cm/min. However, shear strength increases with increasing testing rate in the testing rate investigated in this study. J. VINYL ADDIT. TECHNOL., 21:111-115, 2015. (c) 2014 Society of Plastics Engineers