New Epoxy-Anhydride Thermosets Modified with Multiarm Stars with Hyperbranched Polyester Cores and Poly(ϵ-caprolactone) Arms

Abstract

Multiarm star polymers with hyperbranched aromatic or aromatic-aliphatic cores and poly(ϵ-caprolactone) arms have been used as toughness modifiers in epoxy-anhydride formulations catalyzed by benzyldimethylamine. The curing process has been studied by dynamic scanning calorimetry, demonstrating little influence of the mobility of the reactive species and the hydroxyl content on the kinetics of this process. The obtained materials were characterized by thermal and mechanical tests and the microstructure by electron microscopy. Homogeneous thermosets have been obtained with a remarkable increase in impact strength without compromising glass transition temperature, thermal stability or hardness.

Keywords:

• Epoxy resins
• Hyperbranched
• Multiarm star
• Toughness

Notes

Glass transition temperature of the samples cured at 10°C/min T _g , calculated glass transition temperature, using DSC data and Fox equation T _g,Fox , and conversion at the gel point α _gel and gelation time t _gel .

^a Temperature of maximum of the tan δ at 1 Hz.

^b Modulus in the rubbery state determined at temperature of maximum tan δ + 50°C.

^c Temperature of the onset decomposition determined by TGA in nitrogen atmosphere at 10°C/min calculated for a 5% weight loss.

^d Temperature of the maximum decomposition rate determined by TGA in nitrogen atmosphere at 10°C/min.

^e Char residue at 800°C determined by TGA in nitrogen atmosphere at 10°C/min.

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