Improved surface quality and hygrothermal performance of epoxy based prepreg by liquefied dicyandiamide with enhanced solubility and dispersibility

• Liquefied dicyandiamide (L-DICY) was fabricated.
• The solubility and dispersibility of L-DICY in epoxy resin were enhanced.
• The transparency of L-DICY cured epoxy resin films was improved.
• The hygrothermal performances of L-DICY cured epoxy based prepregs were improved.

Liquefied dicyandiamide (L-DICY) was fabricated by pretreatment of DICY with polyetheramine (PEA)/diglycidyl ether of bisphenol A (DGEBA) adduct, and physicochemical properties of L-DICY, mechanical, thermal and optical properties of L-DICY cured epoxy resins and hygrothermal performance of L-DICY cured epoxy based prepregs were evaluated to compare with those of DICY and PEA/DICY blends. Amine hydrogen equivalent weight of L-DICY was increased with inferior reactivity to PEA/DICY. The solubility of PEA/DICY and L-DICY in epoxy resin was increased due to good dissolving ability of PEA and PEA/DGEBA adduct. The dispersibility of PEA/DICY and L-DICY in epoxy resins was improved, while dispersion stability of L-DICY was superior to that of PEA/DICY. The mechanical and thermal properties of three kinds of resin matrix changed little, while transparency of L-DICY cured resin films was higher than those of DICY and PEA/DICY. The surface qualities and hygrothermal properties of epoxy based prepreg composites were improved notably, which was attributed to DICY crystal reduction in cured resin films resulted from enhanced solubility and dispersibility of L-DICY.

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