| Two types of adhesive formulations, RFL (Resorcinol-Formaldehyde-Latex) and CRFL (Chlororesorcinol-Formaldehyde-Latex), were used to bond rubber to polyethylene terephthalate (PET) cord. Chlorophenol (DK) and chlororesorcinol condendsates (CR) were used to promote adhesion. The effect of heat treatment, test temperature, aging, and cure conditions on adhesion were studied. Overcure conditions were used to simulate long service time. Adhesive strength was evaluated by a pull-out test (H-test) (ASTM D4776-95a). Many of the adhesives result in adhesive strength sufficient to break the cord at room temperature. Adhesive strength decreases with increasing test temperature, and deteriorates with overcure. Bond strength increases with increasing heat treatment time and temperature. In addition, adhesion increases with an increasing ratio of DK or CR to RFL.; Addition of the chlorophenol condensate improves tensile strength of the adhesive film. This is attributed to increased crosslink density.; Failed specimens were examined by scanning electron microscopy to determine locus of fracture. Overcure changes the mode of failure from mostly cohesive failure in the rubber to mixed mode in which interfacial failure between the adhesive and fiber is dominant. |
