Development of cardanol-derived epoxidized and Si-modified pressure-sensitive adhesives (PSAs)

Abstract

This research attempts to create a pressure-sensitive adhesive (PSA) from cardanol as an outset material. The two kinds of formulations were established; the first scheme followed the epoxidation of cardanol, dihydroxylation, and PSA development. In the latter system, cardanol was pretreated with dichlorodimethysilane (DCDMS) in the second scheme, continuing the same procedure to obtain PSA resin. The chemical nature and structure confirmation were done using FTIR and NMR spectroscopy, hydroxyl value, epoxy equivalent weight (EEW), etc. To evaluate PSA resin's crystallinity, thermal stability and hydrophilicity the film was separately obtained for both the schemes by curing whereas to obtain PSA tapes the obtained PSA and tackifying resins were applied onto PET sheets. XRD analysis showed a decrease in the degree of crystallinity after incorporating DCDMS. The gel content values decreased, whereas the water absorption values increased, which could be related to the increase in the hydrophilic nature of PSA with an increasing number of tacky sites. TGA and DSC showed the formation of a high amount of char yield (∼31%) and a higher Tg (−37.72 °C) in Si containing film. The probe tack, peel strength, and shear strength values were high for the formulation with equal amounts of PSA and tackifying resin. Finally, the contact angle measurements showed that the hydrophobicity of film was also improved after incorporating DCDMS. The materials resembling PSA tape and including only small amounts of tackifying resins and crosslinkers displayed the ideal characteristics with satisfactory results.