Thermally activated parameters of self-adhesion in acrylic pressure-sensitive adhesive-like networks

We have conducted an experimental study of acrylic pressure-sensitive adhesive-like networks (PSA-LN) with the goal of establishing deconvolution of interfacial and bulk processes in adhesion. For contact adhesion testing, four types of cylindrically shaped samples were created, each synthetically modified to attain distinct bulk and surface properties. Introduction of small amounts of polar comonomers during synthesis increased the intrinsic adhesion energy, G o , from 65 mJ/m 2 for an unmodified acrylic PSA-LN to 129, 158, and 218 mJ/m 2 for PSA-LNs modified with 10 wt% of acrylic acid, amino acrylate, and acrylonitrile comonomers, respectively. Following a reversed trend, the critical rate of separation, nu* (below which deadhesion is an intrinsically interfacial process) was more than halved from 496 nm/s for the unmodified PSA-LN to 201, 188, and 212 nm/s for those modified with the same three comonomers (same order, respectively). The adhesion energy was found to be dependent upon the crack propagation rate and sensitive to it at all rates of interfacial separation, including those below the critical crack propagation rate, nu*. In addition, the dependence of the adhesion energy on crack propagation rate was measured at three temperatures. It was found that nu* displayed an Arrhenius dependence on temperature from which an activation energy could be calculated. Those activation energies, as a function of chemical composition, are compared with activation energies derived from shift factors determined from measurements of bulk modulus as a function of temperature. A direct correlation between those activation energies was noted.