Biodegradable Polyurethane Pressure-Sensitive Adhesives Using Biobased Polyols with Distinct Intrinsic Properties

Polyurethane pressure-sensitive adhesives (PSAs) were synthesized by reacting isophorone diisocyanate (IPDI) with mixtures of different biobased polyols, where polylactide diol (PLA 1000) acted as a hard polyol and cashew nut shell liquid (CNSL)-derived diol and castor oil (CO) acted as soft segments. Besides, CO played another role in the synthesis of the polyurethanes as a cross-linker to enhance the cohesion of the prepared PSAs. The effects of different ratios of polyols and NCO/OH on microphase separation, thermal, rheological, and adhesive properties of the polyurethane were comprehensively studied. A balanced PSA with excellent tack and sufficient peel strength was prepared by adjusting the ratio of different polyols at PLA1000/CNSL diol/CO = 4:4:2 and a suitable NCO/OH value of 0.70. Eventually, the biodegradability of PSA 442-0.70 was investigated, and the biodegradation rate reached 64.47% within 8 weeks, making it a promising environmentally friendly adhesive tape for packaging applications.