Influence of hydroxypropyl cellulose on molecular relaxations of epoxy-amine networks

Abstract

A dynamic mechanical analysis (DMTA) study was conducted on epoxy-amine networks crosslinked in the presence of low contents of hydroxypropyl cellulose (HPC). The epoxy resin chosen was diglycidylether of bisphenol-A (DGEBA) and the crosslinker was 4,4'-diaminodiphenylmethane (DDM). In the glassy region, primary (α) and secondary (β, γ) relaxations originating from the epoxy and HPC components were well detected. Two primary relaxations of neat epoxy and epoxy/HPC systems, referred to as αepoxy and α'epoxy, could be detected, showing a particular glassy behavior for the systems studied in comparison with systems cured in bulk. The main relaxation temperature Tα (at the peak of αepoxy relaxation) of the epoxy systems increased slightly with the addition of HPC. The activation energy for this transition (Tα) of the epoxy-amine networks was determined both from tan δ and the peak temperatures for the loss modulus measured at various frequencies. The activation energy of the αepoxy relaxation determined from the loss modulus was more reliable than that based on tan δ. The addition of HPC lowered the activation energy of this αepoxy relaxation.

Keywords

• Epoxy
• relaxations
• hydroxypropylcellulose
• activation energy