Study On Synthesis Of Biphenyl Phenol Novolac Epoxy Resin And Its Kaolinite Nanocomposites

Recently, traditional epoxy molding compounds are facing great challenges for both of the voice from ever-rising environmental protection and the requirements of improving the properties of electronic encapsulating materials. The conventional epoxy resins are unable to satisfy some applications, which require higher thermal and moisture resistance. Thus, it is necessary to design and develop epoxy resin systems with high thermal resistant and low moisture absorption for these applications.In this paper, factors that affects on the epoxy value and chlore content of BPNE were discussed through the selection of reaction temperature, reaction time, the quantity of the catalyst, according to the existed problem of the high chlore content of biphenyl phenol novolac epoxy resin (BPNE) in our previous research. The optimal synthesizing conditions were found when the reaction temperature was 65℃; reaction time was 2h and ratio of catalyst to hydroxyl value was 1:1.The curing kinetics of BPNE in presence of 4,4’-diamino biphenyl sulfone (DDS) was explored by non-isothermal differential scanning calorimetry (DSC) technique. The basic cure process was determined through extrapolation. The Flynn-Wall-Ozawa isoconversional method and Kissinger method were used to evaluate the effective activation energy (Ea). The curing mechanism was given by the Malek method. A two-parameter (m, n) autocatalytic model (Sestak-Berggren equation) was found to be the most adequate model to describe the cure mechanism of the studied epoxy resins.The physical properties of the resulting polymers were evaluated with DSC and thermogravimetric analyses (TGA). The kinetics of the thermal degradation BPNE/DDS in nitrogen was investigated by TGA. The lifetime of cured expoxy resin was estimated by Dakin equation. The cured polymer showed great improvement in the resistant properties including remarkably higher glass transition temperature (Tg=167℃), higher thermal stability and lower moisture absorption (1.09%). Flynn-Wall-Ozawa method and Coats-Redfern method were used to determine the three kinetic parameters (activation energy E, decomposition order n, frequency factor A) of degradation. The results showed that the reaction order was 1. The activation energy of thermal degradation of BPNE/DDS was 209.74 kJ/mol. The lifetimes of heated at 288.1℃in nitrogen could reach 10 days at a weight loss of 50%.Epoxy/kaolinite nanocomposites were prepared by adding the organically modified layered kaolinite to BPNE with DDS as a curing agent. The dispersion state of the kaolinite within crosslinked epoxy-resin matrix was examined by X-ray diffraction (XRD) and transmission electron micrograph (TEM). The effects of kaolinite on thermal properties were investigated and discussed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Experimental results showed that BPNE/kaolinite nanocomposites exhibited improved thermal properties compared with pure BPNE. However, the moisture absorptions of BPNE/kaolinite nanocomposites were found to increase with adding kaolinite.