High strain thermomechanical properties of IBMA‐functionalized poly(butyl acrylate) films

Abstract

AbstractBatch emulsion polymerization was used in order to obtain latexes from a mixture of butyl acrylate (ca. 90% mole), and a hydrophobic crosslinkable functional monomer called N‐isobutoxymethyl acrylamide (ca. 10% mole). Films were then cast from these latexes, and their thermomechanical properties were studied before and after a heat treatment intended to provoke crosslinking of the functional groups. The differential thermal analysis and the dynamic mechanical analysis of the film samples proved that the functional monomer copolymerized with butyl acrylate; the dynamic mechanical analysis revealed also that crosslinking took place after the heat treatment. Different kinds of high strain experiments (among which there were stress relaxation tests) were carried out in a tensile testing machine Important differences were thus shown to appear between the “as‐dried” and “annealed” samples. In the case of stress relaxation experiments, simple mechanical models were used in order to fit the experimental data, both during the stretching experiment and the stress relaxation following it. The analysis of the high‐strain experiments and their simulation led to the conclusion that the films contained high molecular weight polymers having a broad molecular weight distribution, and that their crosslinking enhanced the entropic elastic behavior, even though a viscoelastic, large relaxation time contribution was kept; the hypothesis of its coming from a trapped‐entanglement effect was proposed.