Autohesion in the Presence and Absence of Interfacial Mass Transfer
A study has been conducted to investigate time-dependent autohesion in a series of polybutadiene systems, both with and without diffusing components greater than the entanglement molecular weight Me. Diffuse interfaces were prepared by joining surfaces of high molecular weight polybutadienes. An equilibrium adhesive fracture energy G∞ of 2.5kJ/m2 (T=-35°C and c=lmm/s) was measured for these interfaces. Non-diffuse interfaces were produced using a telechelic polybutadiene crosslinked using NCO/OH reactions. Extraction of a sol component was possible in each of these networks, however, subsequent GPC analysis demonstrated that the molecular weight of the mobile sol fraction to be less than Me. Measured G∞ values for the non-diffuse interfaces were greater than those of the diffuse interfaces, G∞8.5kJ/m2 for NCO/OH=1.0, tested at corres-ponding rates. The incorporation of low molecular weight polybutadiene dramatically decreased t∞, but only slightly influenced G∞.
KeywordsFracture Energy Diffuse Interface Isophorone Diisocyanate Polymer Diffusion Experimental Time Scale
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