ABSTRACT
The overall performance of polymer composites depends on not only the intrinsic properties of the polymer matrix and inorganic filler but also the quality of interfacial adhesion. Although many reported approaches have been focused on the chemical treatment for improving interfacial adhesion, the examination of ultimate mechanical performance and long-term properties of polymer composites has been rarely investigated. Herein, we report carbon fiber (CF)/epoxy composites with improved interfacial adhesion by covalent bonding between CFs and the epoxy matrix. This leads to the improved ultimate mechanical properties and enhanced thermal aging performance. Raman mapping demonstrates the formation of an interphase region derived from the covalent bonding between CFs and the epoxy matrix, which enables the uniform fiber distribution and eliminates phase separation during thermal cycling. The covalent attachment of the CF to the epoxy matrix suppresses its migration during temperature fluctuations, preserving the mechanical performance of resulting composites under the thermal aging process. Furthermore, the finite elemental analysis reveals the effectiveness of the chemical treatment of CFs in improving the interfacial strength and toughness of silane-treated CF/epoxy composites. The insight into the mechanical improvement of CF/epoxy composites suggests the high potential of surface modification of inorganic fillers toward polymer composites with tunable properties for different applications.
ABSTRACT
Objective:To evaluate inhibitory potential of sevenKorean thistles against the advanced glycation endproducts(AGE) formation as well as to identify responsible compounds from the most active species.Methods:We used anin vitroAGE inhibition assay to evaluate the anti-diabetic complication potential of the methanol extracts of the selectedKorean thistles.Results:Among the sevenKorean thistles, the leaves ofCirsium maackii(C. maackii) exhibited the most significant inhibitory activity againstAGE formation.By means of bioassay-directed fractionation, a lignan, chlorogenic acid and14 flavonoids were isolated from the active ethyl acetate soluble fraction of a methanol extract fromC. maackii leaves.Luteolin and its5-O-glucoside have been previously isolated; however, a lignan and13 known compounds were isolated for the first time fromC. maackiileaves in this study.Most of the isolated compounds exhibited inhibitory activities against potentialAGE formation.Among them, cernuoside was shown to be the most potentAGE inhibitor with anIC50 value of21.21 μmol/L.Most importantly, two major flavonoids, luteolin and its5-O-glucoside, also significantly inhibitedAGE formation, withIC50 values of 36.33 and37.47 μmol/L, respectively.Structure activity relationship revealed that the presence of free3' and4' dihydroxyl group in flavonoids skeleton played an important role inAGE inhibition. Conclusions:These results indicate thatC. maackii andC. maackii-derived flavonoids might be explored further to develop therapeutic agents for the prevention of diabetic complications due to their significant inhibitory activity againstAGE formation.
