Morphologies and mechanical and thermal properties of highly epoxidized polysiloxane toughened epoxy resin composites

Abstract

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), 29 Si nuclear magnetic resonance spectroscopy ( 29 Si NMR), and gel permeation chromatography (GPC). The T g increased by approximately 8 ºC after introducing HEPSO. TGA in air showed that the initial degradation temperature for 5% weight loss (T d 5%), the temperature for 50% weight loss (T d 50%) and the residual weight percent at 800 ºC (R 800 ) were increased after introducing HEPSO. The addition of 4 phr HEPSO2 resulted in the highest increase in tensile strength, impact strength and fracture toughness (K IC ). 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.

Effect of Atmospheric-Pressure Plasma Treatments on Fracture Toughness of Carbon Fibers-Reinforced Composites

“…The potential of nano-scale fillers in multi-scale composites is a key factor in improving K IC , especially for automotive and aerospace applications where practical brittleness is essential [ 51 , 52 , 53 , 54 , 55 ]. Figure 5 shows a comparison of K IC , which represents the overall mechanical properties of SCE and P-SCE composites using each ASTM equation.…”

Liquid Rubbers as Toughening Agents

“…Other elastomeric modifiers studied are acrylate elastomers [57,58] and polysiloxanes [59]. Liquid polyethers such as poly(propylene oxide) [60] as well as hydroxylterminated polybutadiene (HTPB) [61,62], styrene-butadiene rubber (SBR), and acrylonitrile-butadiene rubber (NBR) [63] have also been used as toughening agents for different type of thermosets.…”

Phase separation of ternary epoxy/PEI blends with higher molecular weight of tertiary component polysiloxane

“…27,28 However, polysiloxanes are rarely used as a toughening agent because of the poor compatibility between so segments of polysiloxane and carbon-based epoxy resin. 29 Various methods have been developed to improve the miscibility of polysiloxanes with epoxy resins, including using silane coupling agents, 30 introduction of functional groups, such as hydroxyl, 31 amino, [32][33][34] epoxy [35][36][37][38] and carboxyl group. 39 On the other hand, polysiloxanes can signicantly compromise the storage modulus and glass transition temperature (T g ) of epoxy resins.…”