Melt Synthesis and Characterization of Aliphatic Low-Tg Polyesters as Pressure Sensitive Adhesives

Polyesters, which are readily synthesized in the absence of solvent, are excellent candidates for a new generation of pressure sensitive adhesives (PSAs) due to their low cost and potential biodegradability. In this study, linear, all-aliphatic polyesters with low glass transition temperatures (Tg) were synthesized using a solvent-free, environmentally friendly melt polycondensation methodology. Polyesters of various compositions were synthesized from different diol and diester monomers to adjust the glass transition temperature and achieve optimum adhesive properties. Melt polycondensation of an isomeric mixture of dimethyl-1,4-cyclohexane dicarboxylate (DMCD), dimethyl adipate (DMAP), diethylene glycol (DEG), and triethylene glycol (TEG) generated a series of linear low-Tg polyesters. The synthesized polyesters were characterized using size exclusion chromatography (SEC), differential scanning calorimetry (DSC), and 1H NMR spectroscopy. The frequency- and temperature-dependent properties of the low-Tg polyesters were characterized using dynamic mechanical analysis (DMA). The adhesive performance of the polymers was evaluated using tack, peel, and shear strength measurements at ambient humidity and temperature. The low-Tg polyesters exhibited peel and tack properties comparable with commercial acrylic adhesives.