Glycerol based tough hyperbranched epoxy: Synthesis, statistical optimization and property evaluation

• Hyperbranched epoxy was synthesized by A2+B3 approach, using glycerol as B3 unit.
• Curing conditions were optimized by multi-response surface methodology.
• Epoxy thermosets exhibited good toughness and excellent adhesive strength.
• Synthesized material may be used as tough engineering adhesive.

Synthesis of three glycerol based hyperbranched epoxy resins (HBGEs) with varying amounts of glycerol is reported. The chemical structure is authenticated from FTIR, 1H NMR and 13C NMR studies with degree of branching from 0.70 to 0.88. The resins exhibit Newtonian flow behavior as indicated by a rheometric study. Time, temperature and amount of glycerol for the best cured epoxy thermosets (cured with poly(amidoamine)) are optimized by the multi-response surface methodology via a composite desirability function. The poly(amido amine) cured epoxy thermosets exhibit high gloss (84.5–90.7 at 60°), good impact resistance (>100 cm), high scratch hardness (up to 10 kg), good tensile strength (24.59–48.6 Mpa), moderate elongation at break (16.6–28.1%), high strain energy or toughness (611, 590.29 and 483 MPa) exceptionally high adhesive strength (1578 MPa for aluminum) and good chemical resistance. Thus, the glycerol based hyperbranched epoxy resin possesses good toughness to be used as an advanced adhesive/binder for different advanced applications.

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