Xu G, Shi WF, Gong M, Yu F, Feng JP (2004b) Photopolymerization and toughening performance in polypropylene of hyperbranched polyurethane acrylate. European Polymer Journal 40(3), 483-491. [In English]
Web link: http://dx.doi.org/10.1016/j.eurpolymj.2003.11.005
Keywords:
polypropylene; hyperbranched polyurethane acrylate; morphology; mechanical property; environmental-stress cracking; pvc-cpe; pvc/cpe blends; abs; polyesters; mechanisms; particles; kinetics;
Abstract: A novel UV-curable hyperbranched polyurethane acrylate (HUA) was synthesized and found to polymerize rapidly in the presence of 5 wt.% benzophenone in N-2 under UV exposure. The photopolymerization kinetics of HUA was studied by differential photocalorimetry (DPC). Its toughening effect for polypropylene (PP) was investigated by tensile and impact tests of the UV irradiated PP/HUA blends. The morphological structures and thermal behavior were determined by polarized optical microscopy, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). The obtained results demonstrate that (1) the maximum photopolymerization rate increases with raising temperature up to 140 degreesC, whereas decreases at above 150 degreesC. The activation energy of 19 kJ mol(-1) for the photopolymerization was obtained at below 140 degreesC from the Arrhenius plot, while it is negative at above 150 degreesC. (2) The incorporation of 5 wt.% HUA greatly improved the notched impact strength of PP matrix with a slight improvement in the tensile strength and without obvious decline in breaking elongation. These results correlate well with SEM observation. (3) During the UV irradiation of PP/HUA blends, PP can be crosslinked/grafted with the cured HUA particles, resulting in the increase of the impact strength of PP matrix. (4) The cured HUA particles in the PP/HUA blends act as heterogeneous nucleation agent for PP, which results in the decrease of spherulite size and less perfection of PP crystals. (C) 2003 Elsevier Ltd. All rights reserved.
