Synthesis And Structure-Property Relationships Of Sis-G-Pb Copolymers And Their Application In Hotmelt Pressure-Sensitive Adhesives

A "graft onto" method was combined with an epoxidation reaction and living anionic polymerization to successfully synthesize a series of SIS-g-PB copolymers with defined branch numbers and branch lengths. These copolymers were utilized to formulate various hot-melt pressure-sensitive adhesives (HMPSAs). Their molecular structure and bulk properties were characterized by 1H-nuclear magnetic resonance (1H-NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and rheometry. The adhesion performances were characterized in terms of holding power and 180 degrees peel strength. The epoxidation reaction alone would negatively influence the rheological properties of the parent SIS copolymers, particularly for low-temperature applications. Controlled addition of the low-Tg PB blocks can significantly improve the low-temperature properties of the SIS copolymers. Both eta* and G' increased in the lower shear frequency regime (< 10(1) rad s(-1)) but decreased in the higher shear frequency regime (> 10(1) rad s(-1)) with branch number and branch length, in which branch length had a greater effect than the branch number. As a result, the 180 degrees peel strength of the SIS-g-PB based HMPSAs displayed reached 0.23 kN m(-1), which is more than twice the value for SIS-based HMPSAs.