Effect of tackifiers on the properties of natural rubber-based adhesive used to bind canvas fabric and rubber shoe sole

Abstract

In this study, the influence of various tackifiers, including C9 hydrocarbon resin (PR), phenolic resins (P803L and P2402), and cumaron, on the basic properties of natural rubber-based adhesives was thoroughly investigated. The test application materials used to evaluate the performance and properties of the adhesive are canvas and shoelace rubber, which are used to produce high-end export canvas shoes at enterprises in Vietnam. The study results reveal that tack and peel strength progressively increase with a rise in tackifier content until reaching an optimal threshold, beyond which these properties begin to decline when this content exceeds the optimal value. Thermal-ageing resistance was mainly affected by the chemical nature of the tackifiers. An adhesive formulation containing 7 phr of PR exhibited the highest peel tensile strength at 4.158 N/mm and the best ageing coefficient of 0.81. Furthermore, the bonding failure mechanism was identified as a mixed-mode failure mechanism. This result is significant for the development of the material combination and the manufacturing of natural rubber-based adhesive used in the production of high-end footwear.