Epoxy resins tensile strength

Fibre-glass reinforced epoxy resins are used particularly in the power transmission, building products and pressure vessel markets. In the case of epoxy resins, tensile strengths fall from 600 in the virgin polymer to 68 MPa while the flexural modulus falls from 3 to 1.1 GPa. 

Both tensile strength equations are iRustiated in Figure 12 using data typical of graphite fibers in epoxy resin. 

Fig. 12. (a) The variation of the tensile strength of unidirectional carbon-fiber-reinforced epoxy resin as a function of the fiber volume fraction, (b) The variation of the tensile strength of unidirectional carbon-fiber-reinforced epoxy resin as a function of the fiber volume fraction for low fiber volume... 

A systanatic investigation of isomeric phenylaie diamines and ring-alkylated MPD s as epoxy curing agents was performed. Initial studies on blends of phenylene diamine isoners shewed that 20% substitution of OPD in MPD increased the Tg of the cured resin but decreased the tensile strength and elongation. When used alone, OPD resulted in resins of inferior properties. 

Table III. Tensile Shear Adhesive Strength of Ozonized Lignin/Epoxy Resins. (Normal Test)...

Fig. 6. Shear strength of aluminum/epoxy joints and tensile strength of epoxy resin after exposure to water and ethanol at 90 °C 66) (Reprinted from Ref. 66, p. 63, by courtesy of Society of Chemical Industry)...

Because of their low viscosity, cycloaliphatic epoxies are often used to dilute other epoxy resins. These resins, however, have not achieved general importance in adhesive formulations because of relatively low tensile strength and because they do not cure well at room temperature. One major application for cycloaliphatic epoxies, however, is for adhesives and coatings that can be cationically cured by exposure to uv light. 

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