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Toughening mechanism of rubber reinforced epoxy composites by thermal and microwave curing
Author(s) -
Xi Jiaojiao,
Yu Zhiqiang
Publication year - 2018
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.45767
Subject(s) - materials science , epoxy , composite material , curing (chemistry) , ultimate tensile strength , scanning electron microscope , mooney viscosity , glass transition , polybutadiene , toughness , fracture toughness , dynamic mechanical analysis , natural rubber , izod impact strength test , nitrile rubber , polymer , copolymer
The carboxyl terminated polybutadiene (CTBN) is utilized to improve the toughness of diglycidylether of bisphenol A epoxy cured by heat and microwave. The change of viscosity, chemical groups, and the glass transition temperature ( T g ) of system are analyzed. The impact performance is characterized to evaluate the fracture toughness, and tensile properties also are investigated. The fracture morphologies are observed by the scanning electron microscopy for exploring toughening mechanism. The viscosity results indicate that viscosity of system increases with increasing of CTBN, demonstrating the formation of precrosslinking and interpenetrating network structure of two phases. The Fourier transform infrared spectrometer results show that effective chemical bonds are formed between CTBN and epoxy resins. The T g decreases with introducing CTBN, indicating the decline of crosslinking density, which further suggests inherent three‐dimensional structure have been changed. The impact strength and energy increase with increasing of CTBN, and reach a maximum value of 5.92 kJ/m 2 and 0.13 kJ at 15% for thermal curing, respectively, increased by 36.8% and 23.1% relative to microwave curing system, while tensile strength and modulus reach the optimum at 5%. Scanning electron microscopy observation finds that “plastic tensile” and “microvoid” deriving from “sea‐island” structure exist, presenting the ductile fracture features. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135 , 45767.