Effect of diisocyanates on the properties and morphology of epoxy/polyurethane interpenetrating polymer networks

Abstract

The present work investigates the effect of epoxy resin (EP) modification with polyurethanes (PURs) based on polyethylene glycol and two different diisocyanates: 4,4'-diphenylmethane diisocyanate (MDI) and 2,4-toluene diisocyanate (TDI). The impact strength of the material based on 15 wt% PUR with TDI was enhanced by 130%, while the critical stress intensity factor and the flexural strength of epoxy composition based on 5 wt% PUR with MDI increased by approximately 140% in comparison with unmodified EP. Fourier transform infrared spectroscopy confirmed the occurrence of chemical reaction between the hydroxyl groups of EP and isocya-nate groups of PUR, explaining the improvement in the mechanical properties of EP. Moreover, scanning electron micrographs showed a rough surface with plastic yielding and several microcracks in the compositions containing TDI-based PUR and deformed leaf-like morphology with more elongated structure for the EP modified with MDI-based PUR.

One-Pot Synthesis and Characterization of Novel Shape-Memory Poly(ε-Caprolactone) Based Polyurethane-Epoxy Co-networks with Diels–Alder Couplings

“…Epoxy resins (EPs) are well-known for their versatile applications covering coatings, adhesives and matrices of composites [1][2][3][4]. The widespread use EPs is mostly due to their good mechanical The synthesis of the DA adduct -see the above scheme-was performed similarly to those reported in Ref.…”

Graft‐interpenetrating polymer networks of epoxy with polyurethanes derived from poly(ethyleneterephthalate) waste

“…Earlier studies have revealed that blending of epoxy with poly(oxyethylene) (PEG 400)‐based polyurethane led to 60% improvement in the impact strength, while in a separate study introduction of polyurethane (40% w/w) reportedly increased the impact toughness by 46% . In comparison, the improvement in impact strength is larger (190%) when poly(oxypropylene)‐based polyurethanes are blended with epoxy.…”

“…In comparison, the improvement in impact strength is larger (190%) when poly(oxypropylene)‐based polyurethanes are blended with epoxy. Interestingly, blending of epoxy with polyester polyurethanes leads to larger improvements in impact strength (200%), as compared with polyether polyurethanes which may be attributed to the additional sites of hydrogen bonding available with the former. However, irrespective of the type of polyurethane being blended, the main cause behind the toughened nature of blends is the elastomeric nature of the polymer.…”

“…However, irrespective of the type of polyurethane being blended, the main cause behind the toughened nature of blends is the elastomeric nature of the polymer. The introduction of this rubbery phase hinders the process of crack propagation in the brittle epoxy matrix . The decrease in properties at higher loadings (>10%), can be attributed to the formation of large separated phase domains at higher loadings …”

“…In this context, blending of epoxy with elastomeric polyurethanes has been attempted to improve the fracture toughness of the base brittle thermoset . Epoxy‐polyurethane blends offer interesting properties, as polyurethanes are associated with excellent elasticity, abrasion resistance, and damping properties, while the epoxy resins possess excellent mechanical properties along with strong adhesion to metals.…”