Tacky-Free Polyurethanes Pressure-Sensitive Adhesives by Bio-Based Thermoplastic Polyurethane Design from Eco-Friendly Isosorbide

A series of Isosorbide-based thermoplastic polyurethanes (ISB-TPUs) were newly developed through the synthetic process by reacting methylene diisocyanate, poly(ethylene glycol) (PEG), and bio-based material isosorbide (ISB) for chain extender based on the different HDI/HDI trimer ratios. The structures of ISB-TPU series were analyzed by Fourier transform infrared spectroscopy and gel permeation chromatography. The changes in the thermal and physical properties due to the hard segment crystallinity were also measured by thermogravimetric analysis, differential scanning calorimetry and universal test machine. The sticking properties of polyurethane pressure-sensitive adhesives (PU-PSAs) depended on both the HDI/HDI trimer ratio and crosslinking-agent composition in the formulation. The differences in the crosslinking-density significantly affected the cohesion, adhesion, and tack in PU-PSA. The formulation of 50 wt% 600PEG and 50 wt% crosslinking-agent and an HDI/HDI trimer ratio of 1.0 led to the optimal balance between the adhesion and cohesion properties owing to the sufficient tack, high 180-peel strength, and good cohesion. The results showed that biopolyol used in polyurethane can be applied according to the characteristics required in eco-friendly products fields.