Toughening Epoxy Thermosets with Block Ionomer Complexes: A Nanostructure鈥揗echanical Property Correlation

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• 作者：Shuying Wu ; Qipeng Guo ; Shuhua Peng ; Nishar Hameed ; Martin Kraska ; Bernd St眉hn ; Yiu-Wing Mai
• 刊名：Macromolecules
• 出版年：2012
• 出版时间：May 8, 2012
• 年：2012
• 卷：45
• 期：9
• 页码：3829-3840
• 全文大小：682K
• 年卷期：v.45,no.9(May 8, 2012)
• ISSN：1520-5835

文摘

Block ionomer complexes based on sulfonated polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SSEBS) and a tertiary amine-terminated poly(蔚-caprolactone), denoted as SSEBS-c-PCL, were used to toughen epoxy resin. Well-dispersed spherical microdomains, consisting of a poly(ethylene-ran-butylene) core surrounded by a sulfonated polystyrene shell, were revealed by transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) in the cured epoxy blends with 10 wt % SSEBS-c-PCL of various compositions. Structural parameters, core radius (R_c), effective hard-sphere radius (R_hs), and shell thickness (T_s) were obtained by fitting the SAXS data with a core鈥搒hell model and, for the first time, correlated with the fracture toughness (critical stress intensity factor K_IC and strain energy release rate G_IC) of the epoxy blends. K_IC and G_IC were found to increase with increasing R_c and R_hs but decrease with T_s. The blend containing SSEBS-c-PCL with least PCL, i.e., 2.4 wt %, shows nanostructure of the largest R_c and R_hs, and smallest T_s, displaying highest K_IC and G_IC. Examination of the fracture surfaces indicates that the increased toughness arises from interfacial debonding of spherical microdomains and plastic expansion of resultant nanovoids, followed by small-scale matrix shear deformation. The correlations between nanostructure parameters and fracture toughness have provided a fundamental understanding of nanostructure toughening of thermosets via an innovative strategy based on block ionomer complexes.