Abstract
Toughened epoxy has been widely used in industrial areas such as automotive and electronics. In this study, nanosized hyperbranched polymers (HBPs) as a flexibilizer are synthesized and embedded into epoxy resin to enhance the toughness and flexibility. Two different HBPs, hyperbranched poly(methylacrylate-diethanolamine) (poly(MA-DEA)) and poly(methylacrylate- ethanolamine) (poly(MA-EA)), were prepared and blended with both epoxy and polyetheramine, a curing agent. The molecular size of HBPs was estimated to be 6 ~ 14 nm in diameter. The molecular weight of HBPs ranges from 1500(1.5 K) to 7000(7.0 K) g/mol. In cured epoxy/HBP blends, no phase separations are occurred, indicating that HBPs possess sufficient miscibility with epoxy. The tensile toughness of the blends increased with changing the molecular weight of HBPs without sacrificing tensile strengths. The impact strength of the blends increases stiffly until the loading % of HBPs in the blends reaches 10 wt%. In addition, the experimental studies showed that impact resistance also increased with an increase in molecular weight of HBPs. The obtained impact resistance of the epoxy/HBP blends with 10 wt% was 270% more effective compared to that of cured neat epoxy.
Highlights
Toughened epoxy resins exhibit excellent mechanical properties and are widely used in high performance composites and structural adhesives [1,2,3,4]
We investigated the effect of nanosized hyperbranched polymers (HBPs) particles, possessing hydroxyl or carbonyl end groups, on the toughness and flexibility of epoxy resins
The ATR-IR spectrum shows the evidence for the synthesis of intermediates for hydroxy-terminated polyamine esters (HBP1) and methoxycarbonyl-terminated polyamine esters (HBP2)
Summary
Toughened epoxy resins exhibit excellent mechanical properties and are widely used in high performance composites and structural adhesives [1,2,3,4]. Many of the research works have been conducted to overcome the low impact resistance and low toughness properties of epoxy resins. Block copolymer particles as tougheners have attracted considerable attention [15, 16]. These block copolymers tend to be self-assembled to form certain nanostructures in the epoxy matrix during the cure process. These self-assembled nanostructures can improve the fracture toughness without affecting the Tg (glass transition temperature) and tensile strength of cured epoxy resins. Nanoscale hyperbranched polymers (HBPs) are synthesized as tougheners and incorporated into epoxy resin to improve the toughness and flexibility of epoxy resins
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