Influences of cellulose nanofiber on the epoxy network formation

The effects of cellulose nanofiber on the curing behavior, dynamic mechanical, and morphology properties of epoxy/diamine systems were investigated. The studies were conducted using an aliphatic triamine, diethylentriamine (Dien), and an aromatic diamine, diaminodiphenylmethan (DDM), as the curing agents in the presence of three different levels of 0.5, 2, and 5 phr of cellulose nanofiber. Calorimetry experiments were used to probe the changes in the reaction enthalpy and in the glass transition temperature (Tg) as a function of the fiber concentration. The results showed that both the Tg and the heat of reaction were increased with increasing the fiber concentration up to 2 phr. The experimental cure data obtained from in situ FT-IR measurements were used to evaluate the kinetic parameters using the modified Avrami theory of phase change. The results showed that the kinetic parameters were less sensitive to the epoxy composition. DMTA measurements showed that the storage modulus and the Tg of the composites were dependant on the level of fiber loading. SEM studies revealed that a reasonable dispersion and adhesion have been achieved between the fiber and the epoxy matrix at low concentration of fiber. It is concluded that the fiber agglomerated at high concentration of cellulose fiber prevented the formation of a homogeneous mixture, thus resulting in weak thermal and mechanical properties.