Abstract
Diglycidyl ether of bisphenol-A (DGEBA), having number average molecular weight (Mn) 375, was modified by incorporating the hydroxyl terminated polybutadiene (HTPB) based prepolymer using isophorone diisocyanate as a coupling agent. To increase the compatibility between the epoxy resin and HTPB part, polar groups were introduced in the later to achieve physical and chemical interactions between the two phases. The finally modified DGEBA system was cured with amine based hardener. FTIR and 1H-NMR were used to monitor the whole modification procedure. The rubber particles size and distribution was monitored as a function of HTPB contents in the resin system using scanning electron microscopy (SEM). The mechanical, thermal and thermo-mechanical properties have shown that the tensile strength, toughness, ductility and impact strength of the modified cured system have been successfully increased at some optimum HTPB contents without affecting the inherent thermal and thermo-mechanical stability associated with DGEBA resin system. Some of the mechanical properties like flexural modulus, tensile modulus and compressive strength decreased with increasing rubber contents.
Highlights
Thermo set resins form a rigid network which is dimensionally stable under many conditions, having good chemical and thermal resistance
The mechanical, thermal and thermo-mechanical properties have shown that the tensile strength, toughness, ductility and impact strength of the modified cured system have been successfully increased at some optimum hydroxyl terminated polybutadiene (HTPB) contents without affecting the inherent thermal and thermo-mechanical stability associated with Diglycidyl ether of bisphenol-A (DGEBA) resin system
The molar ratio 2:1 (16% w/w of isophorone diisocynate (IPDI) with respect to HTPB) was considered ideal as it could leave one NCO group free to react with one epoxide group of epoxy resin, in the sec ond step of reaction
Summary
Thermo set resins form a rigid network which is dimensionally stable under many conditions, having good chemical and thermal resistance As a result these polymers are very important engineering materials, accounting for nearly 20% of the polymer market, including use in composites, coatings and adhesive applications [1,2,3]. Epoxy resins are thermo sets with extraordinary adhesion accompanied by simple cures, good strength, creep resistance, heat tolerance, chemical durability and relatively low shrinkage. These polymers are brittle and have a high degree of cross linking. The secondary rubber can improve the impact strength without loss in polymer other properties [4]
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