Epoxidation of styrene-isoprene-styrene block copolymer and its use for hot-melt pressure sensitive adhesives

The epoxidation of styrene-isoprene-styrene block copolymer (SIS) with performic acid generated in situ from hydrogen peroxide and formic acid was studied, and the hot-melt pressure sensitive adhesives (HMPSA) were prepared with epoxidized SIS (ESIS), SIS and the tackifier ESCOREZ-2203LC. The H-1 nucleal magnetic resonance and Fourier transform infrared spectra revealed that the epoxidation reaction mainly occurred in 1,4-isoprene units of SIS, and the reactivity of the cis-1,4-structure was higher than that of the trans-1,4-structure. Analysis by Gel Permeation Chromatography (GPC) showed that the molecular weight of SIS increased and the molecular weight distribution widened after epoxidation. Differential scanning calorimetry analysis showed that ESIS was compatible with SIS and ESCOREZ-2203LC. The addition of certain amount of polar ESIS in the HMPSA was beneficial to the improvement of 180 degrees peel strength when the substrates were polar materials, such as PVC and steel. With the increase in peeling rate, the peel failure mode changed to adhesion failure from cohesion failure.