Silanization of functionalized PET fabric to improve PET-nitrile rubber (NBR) adhesion; effects of functionalization type and silane concentration

Surface modification could increase affinity of PET fibers to polymer matrix by changing the interfacial physical interactions to covalent bonds. In this research, surface modification of a superfine polyethylene terephthalate (PET) fabric was performed by bis(triethoxysilylpropyl)tetrasulfide (TESPT). The surface grafting was performed at different silane concentrations (i.e. 1, 5 and 10X). Before silanization, the fabrics were functionalized using photochemical method (i.e. irradiation of UV light in presence of glutaric acid peroxide (GAP)) and also hydrolysis by Sodium hydroxide (NaOH). Due to functionalization, carboxyl and hydroxyl groups were formed on the PET surface that made it ready to condense with hydrolyzed silane molecules. The fabrics were characterized using FTIR, TGA, FE-SEM, XPS analysis for evaluation of grafting performances. XPS analysis confirmed the presence of new peaks of Si and S after surface modification with TESPT. Comparing the results of TESPT-grafted functionalized PETs, it was found that the silane grafting content on PET surface is dependent not only to the silane concentration but also to the functionalization method. Finally, the influences of silane grafting on the functionalized PET fabrics to NBR adhesion were evaluated using H-pull and T-peel tests. The results showed that silane grafted-carboxylated PET fabric illustrated more adhesion to NBR than silane grafted-hydroxylated PET (i.e. 33 and 12% improvement in the pullout strength and T-peel adhesion, respectively).