Impact energy absorption of block copolymer/tackifier blends: Effect of compatibility, viscoelasticity, and laminate structures

This work studied the effects of tackifiers on the impact energy absorption properties of block copolymers (BCPs) comprising poly(styrene)-b-poly(isoprene)-b-poly(styrene) (SIS) and poly(methyl methacrylate)-b-poly(n-butyl acrylate)-b-poly(methyl methacrylate) (MAM). A rosin ester resin (RE) and an aliphatic petroleum resin (C5PR) were compared as the tackifiers. Analyses of Hansen solubility parameters and observations using electron microscopy indicated that both tackifiers were highly compatible with the poly(isoprene) component of the SIS, while the RE also showed good compatibility with the poly(n-butyl acrylate) phase of the MAM. The impact energy absorption characteristics of laminates made by applying layers of BCP/tackifier blends to cured epoxy substrates were evaluated using a pendulum impactor. The extent of energy absorption by these laminates was found to increase within specific tackifier concentration ranges. However, the C5PR showed poor compatibility with the MAM and had almost no effect on the energy absorption of the laminates. The energy absorption of the laminates could be described based on the calculated loss factor, eta, determined using the RUK equation including the viscoelastic parameters (both tan delta and storage modulus) for the BCP/tackifier blends, considering the time-temperature superposition principle, and for the laminate structures.