Enhanced heat resistance of acrylic pressure-sensitive adhesive by incorporating silicone blocks using silicone-based macro-azo-initiator

To improve the heat resistance of acrylic-based pressure-sensitive adhesive (PSA), silicone-block-containing acrylic PSAs (SPSAs) were synthesized using a polydimethylsiloxane (PDMS)-based macro-azo-initiator (MAI). To evaluate the heat resistance of the PSA films, the probe tack and 90^◦ peel strength were measured at different temperatures. The acrylic PSA showed that its tack curves changed from balanced debonding at 25^◦ C to cohesive debonding at 50^◦ C and exhibited a sharp decrease. However, in the case of SPSA containing 20 wt% MAI (MAI20), the balanced debonding was maintained at 75^◦ C, and its tack value hardly changed with temperature. As the MAI content increased, the peel strength at 25^◦ C decreased due to the microphase separation between PDMS-and acryl-blocks in SPSA, but the shear adhesion failure temperature (SAFT) increased almost linearly from 41.3 to 122.8^◦ C. Unlike stainless steel substrate, SPSA showed improved peel strength on a polypropylene substrate due to its low surface energy caused by PDMS block. Owing to the addition of 20 wt% silicone-urethane dimethacrylate oligomer and 200 mJ/cm² UV irradiation dose, MAI20 showed significantly increased 90^◦ peel strength at 25^◦ C (548.3 vs. 322.4 gf/25 mm for pristine MAI20). Its heat resistance under shear stress assessed by shear adhesion failure test (SAFT) exhibited raising in failure temperature to 177.3^◦ C when compared to non-irradiated sample.