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Toughening of Epoxy Resin System Using a Novel Dendritic Polysiloxane
Songqi Ma,Weiqu Liu,Chaohui Hu,Zhengfang Wang,Chunyi Tang 한국고분자학회 2010 Macromolecular Research Vol.18 No.4
Dendritic polymers have attracted increasing attention in the field of epoxy resin toughening. This paper is the first report of the use of a novel dendritic polysiloxane (DPSO) bearing high epoxide groups to modify the diglycidyl ether of bisphenol-A (DGEBA). The thermal properties, toughness and morphology of the cured epoxy resins were examined by DSC, TGA, impact testing and SEM. The chemical structure of DPSO was confirmed by FTIR, 29Si NMR and GPC. The Tg increased by approximately 7 oC after introducing the DPSO. The TGA results under N2 and air atmospheres showed that the initial degradation temperature for 5% weight loss (Td 5%), temperature for 50% weight loss (Td 50%) and residual weight percent at 800 oC (R800) all increased after introducing DPSO. Moreover, the addition of 3 phr DPSO100 resulted in a 70.4% increase in impact strength compared to that of the neat epoxy. The morphology of the fracture surfaces shows that the miscibility of polysiloxane with epoxy resin increased with increasing number of epoxy groups in DPSO, and the improved toughness was attributed to the rubber-bridged effect. The high number of epoxy groups in dendritic polysiloxane can react during the curing process,and participate chemically in the crosslinking network. DPSO is expected to improve significantly the toughness and thermal stability of epoxy resin.
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Songqi Ma,Weiqu Liu,Zhengfang Wang,Chaohui Hu,Chunyi Tang 한국고분자학회 2010 Macromolecular Research Vol.18 No.9
A novel highly epoxidized polysiloxane was synthesized to modify the diglycidyl ether of bisphenol-A (DGEBA). The mechanical and thermal properties as well as the morphology of the cured epoxy resins were examined by tensile testing, impact testing, fracture testing, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and environmental scanning electron microscopy (ESEM). The chemical structure of the highly epoxidized polysiloxane (HEPSO) was confirmed by Fourier transform infrared spectroscopy (FTIR), 29Si nuclear magnetic resonance spectroscopy (29Si NMR), and gel permeation chromatography (GPC). The Tg increased by approximately 8 ºC after introducing HEPSO. TGA in air showed that the initial degradation temperature for 5%weight loss (Td 5%), the temperature for 50% weight loss (Td 50%) and the residual weight percent at 800 ºC (R800)were increased after introducing HEPSO. The addition of 4 phr HEPSO2 resulted in the highest increase in tensile strength, impact strength and fracture toughness (KIC). The morphology of the fracture surfaces show that the miscibility of polysiloxane with epoxy resin increased with increasing epoxide group in HEPSO. The high epoxide groups in HEPSO can react during the curing process, and participate chemically in the crosslinking network. HEPSO is expected to improve significantly the toughness and thermal stability of epoxy resin.
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