Properties and morphologies of UV‐cured epoxy acrylate blend films containing hyperbranched polyurethane acrylate/hyperbranched polyester

Abstract

The properties and morphologies of UV‐cured epoxy acrylate (EB600) blend films containing hyperbranched polyurethane acrylate (HUA)/hyperbranched polyester (HPE) were investigated. A small amount of HUA added to EB600 improved both the tensile strength and elongation at break without damaging its storage modulus (E′). The highest tensile strength of 31.9 MPa and an elongation at break around two times that of cured pure EB600 were obtained for the EB600‐based film blended with 10% HUA. Its log E′ (MPa) value was measured to be 9.48, that is, about 98% of that of the cured EB600 film. The impact strength and critical stress intensity factor (K1c) of the blends were investigated. A 10 wt % HUA content led to a K1c value 1.75 times that of the neat EB600 resin, and the impact strength of the EB600/HPE blends increased from 0.84 to 0.95 kJ m−1 with only 5 wt % HPE addition. The toughening effects of HUA and HPE on EB600 were demonstrated by scanning electron microscopy photographs of the fracture surfaces of films. Moreover, for the toughening mechanism of HPE to EB600, it was suggested that the HPE particles, as a second phase in the cured EB600 film, were deformed in a cold drawing, which was caused by the difference between the elastic moduli of HPE and EB600. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3159–3170, 2005

Superiority of nanosized over microsized hyperbranched polymer second phase in modifying brittle epoxy resin

“…However, as HBP concentration increases to some certain value, no further increase in fracture toughness could be observed11 or a small decrease in impact strength was observed at high HBP concentrations 23. On the contrary, the tensile strength was significantly reduced by the addition of HBPs 10, 20, 23. As mentioned above, the HBP‐modified epoxy systems would generally show a separate phase morphology.…”

“…The improvements in the fracture toughness10–12, 19, 22 and the impact strength20, 23, 24 were observed with adding HBPs to epoxy resins. However, as HBP concentration increases to some certain value, no further increase in fracture toughness could be observed11 or a small decrease in impact strength was observed at high HBP concentrations 23. On the contrary, the tensile strength was significantly reduced by the addition of HBPs 10, 20, 23.…”

“…Hyperbranched polymers (HBPs) are a relatively new group of polymers called dendrimers that are a novel and intriguing new class of modifiers for brittle epoxy resins 8–24. The chemical structure of a HBP (H30) is shown in Figure 1.…”

“…For example, HBPs are known to exhibit a very low degree of chain entanglement and typically have relatively low‐melt viscosities even with high molecular weights compared with linear polymers, which gives HBPs a great potential as modifiers for brittle epoxy resins. Therefore, there has been a great research work done on HBPs as modifiers for brittle epoxy resins 8–24. The curing evolution and the curing kinetics were investigated for the HBP‐modified diglycidylether of bisphenol A resin system 16.…”

Synthesis and characterization of hyperbranched polyesters and polyurethane coatings

“…Fornof et al24 synthesized the highly branched poly(ether urethane)s based on TMP and isocyanate endcapped polyethers by A2+B3 methodology. Xu et al25 studied the properties and morphologies of UV‐cured epoxy acrylate blend films containing hyperbranched polyurethane acrylate and HB polyester. Asif et al26, 27 synthesized the waterborne hyperbranched polyurethane acrylates for UV curable aqueous dispersions from hydroxy‐functionalized HB aliphatic polyesters (Boltorn) of varying generation number.…”