Effect of side group and crosslinking on the copolyesters as solvent-free pressure-sensitive adhesives

Abstract

Pressure-sensitive adhesives (PSAs) are extensively employed in various applications due to their ability to instantly adhere upon the application of light pressure. Towards a sustainable future is the major driving force for the development of PSAs without solvent. In this study, a two-step melt polycondensation method was used to synthesize a series of copolyesters with varying contents of propanediol (PDO), 2-methyl-1,3-propanediol (MPO), and glycerol. These copolyesters were composed of different molar ratios of PDO/MPO (80/20, 50/50, and 20/80, respectively) and varying glycerol loading in polymer backbone (0, 0.5, and 1.0 mol%, respectively). The influence of the short side group from MPO and the slight crosslinking from glycerol on the thermal and rheological behavior of the copolyesters was investigated. The glass-transition temperature of these copolyesters range from −58.0 to −52.1 °C. Furthermore, the adhesive strength of these copolyesters was evaluated through T-peel and 180° peel testing. The 180° peel strength ranged from 81.1 to 600.6 Pa, while the T-peel strength ranged of 52.5–156.6 Pa. By adjusting the balance of side group and crosslinking content, it was possible to control the relationship between cohesion, adhesion, and tack. This study provides a potential material design for polyester-based and solvent-free PSAs.