Mechanical and Thermal Properties of Epoxy Resin Modified with Polyurethane

Abstract

Epoxy resin was modified with polyurethane having different isocyanate index. Impact strength, tensile strength, elongation at break and flexural strength were estimated as functions of polyurethane content and isocyanate index. Hardness, linear expansion coefficient and the deflection temperature under load were estimated for selected compositions. Infrared spectroscopy was carried out for unmodified epoxy resin and compositions with improved mechanical properties. Maximum improvement in the fracture toughness was reached with polyurethane with highest content of isocyanate. Hardness was not affected but elastic modulus decreased, implying a softening of epoxy-based compositions. The infrared spectra indicated that an excess of isocyanate groups leads to a grafting process between the modifier and the matrix, explaining the toughening of the latter.

Preparation and property evaluation of nanocomposites based on polyurethane‐modified epoxy/montmorillonite systems

“…24 The largest improvement in the fracture toughness was achieved with the PUR having the highest isocyanate content. The infrared spectra have indicated that the excess of isocyanate groups has produced grafting reactions between the modifier and the epoxy matrix, which explained the observed toughening effect.…”

“…[11][12][13][14][15] Epoxy resin's properties have also been improved by using nanoparticles [16][17][18][19][20] as well as other cross-linkable polymers to form full-or semi-interpenetrating polymer networks. [21][22][23][24][25][26][27][28][29] Yilmazer and co-workers 16 have used unmodified montmorillonite (Cloisite Na + ) and organically modified Cloisite 30B as reinforcing agents for diglycidyl ether of bisphenol-A (DGEBA), Their results have shown an increase in the glass transition temperature (Tg) by more than 10°C with the addition of 9 wt% of a modified montmorillonite (MMT). The addition of 0.5 and 1 wt% of Cloisite 30B resulted in a maximum improvement in the impact strength of DGEBA.…”

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

“…Recently, the effect of isocyanate index of TDI-based PUR on the mechanical and thermal properties of diglycidyl ether of bisphenol A cured with triethylenetetramine was investigated, 11 and the positive effect of the reactive groups was confirmed.…”

“…1,[3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] In this respect, polyur-ethanes (PURs) proved to be successful, mainly due to their high flexibility and versatile structure. 18 PUR/EP grafted IPN with combined advantages of both the polymers were first reported by Frisch et al 6 It was demonstrated that PUR can be linked to EP through physical entanglements and chemical bonding to form graft IPN.…”

Properties and Morphologies of Epoxy Resin Based Composites Reinforced by Polyurethane and Graphene Oxide

“…The evolution of tensile properties indicates that the polyurethane prepolymer terminated with hydroxyl groups and GO have the synergistic effect on improving tensile properties of neat EP. On one hand, the introduction of polyurethane prepolymer terminated with hydroxyl groups provides additional free volume, leading to more facilitated segmental movements 13) . On the other hand, the wrinkled topology at the nanoscale of GO results in an enhanced mechanical interlocking with the polymer chains, while the abundant oxygen-containing groups on GO s basal plane and edges may form covalent bonds with polymer matrix 14) .…”