Synthesis, Curing Behavior And Properties Of Novel Thermal Resistance Epoxy Resins

In this dissertation, a series of novel phenyl or naphthalene bridging groups containing novolac epoxy resins were synthesized to meet the need in high-tech applications which required higher thermal resistance and better moisture resistance. The structure-propeties relationships of the resulting epoxy thermosets were investigated. The curing kinetics and mechanism of the epoxy systems were explored.1．A series of naphthalene containing bisphenol A (BPA) based novolac epoxy resins (bis-NANER) were synthesized. Compared with direct refuxing method, the azeotropic distillatiom method resulted in higher molecular weight ((?)_n) and narrower polydispersity index (PID) The (?)_n and PID of bis-NANER increased with increasing fraction of 1-naphthaldehyde. When the mole ratio of 1-naphthaldehyde to bisphenol A exceeded 1．25, gellation occurred. The epoxy value of bis-NANER decreased with increasing the fraction of 1-naphthadehyde. Bis-NANER was cured with 4,4'-diaminodiphenyl sulphone (DDS) and the resulting products were characterized with dynamic mechanical thermal analysis (DMTA), thermogravimetric analysis (TGA), and moisture absorption measurement. Compared with those based on regular diglycidyl ether of bisphenol A (DGEBA), the cured bis-NANER showed remarkably higher glass temperatures (T_gs), enhanced thermal stability and better moisture resistance. For cured bisphenol A, the T_gs, storage modulus (E') and moisture resistance decreased after reached a maximum, and hydrophobicity increased all alone with increasing the fraction of 1-naphthadehyde.2．Three bisphenol A based novolac epoxy resins with different bridging groups: methylene, methane-phenyl and methane-naphthyl, respectively, between bisphenol A phenyl rings were prepared via the condensation of bisphenol A with formaldehyde, benzaldehyde and 1-naphthaldehyde, respectively, followed by the epoxidation. The PIDs of three bisphenol A based novolac epoxy resins were comparable, their M increased, epoxy value decreased with increasing the size of bridging groups. The methane-naphthyl-bridged epoxy network cured by DDS possessed the highest storage modulus, T_gs, thermal stability and moisture resistance.3．Two 1,5-naphthalenediol based novolac epoxy resins with methane-phenyl and methane-naphthyl briging groups and 1,5-di(2,3-epoxypropoxy)naphthalene (DEN) were synthesized. The PIDs of three 1,5-naphthalenediol based epoxy resins were similar, their M_n increased, epoxy value decreased with increasing size of bridging groups. The methane-naphthyl-bridged and methane-phenyl-bridged epoxy networks cured by DDS possessed higher storage modulus, T_gs, thermal stability and moisture resistance than DEN cured network.4．Multifunctional novolac epoxy resin were synthesized via the condensation of bisphenol A with p-hydroxyphenylaldehyde, followed by the epoxidation. Compared with BPA/benzaldehyde novolac epoxy, the above synthesized expoxy resin netwok cured by DDS possessed higher storage modulus, Js, thermal stability and moisture resistance.5．The dynamic curing kinetics of bis-NANER/DDS and 1,5-naphthalenediol based epoxy resins/DDS were evaluated with both Kissinger and Ozawa methods, the calculated activation energy showed that the reaction activity of the resins decreased with increasing size of the bridging groups, i.e., methine-naphthyl-bridged novolac epoxy resins possessed the lowest reaction activity, methine-phenyl-bridged novolac epoxy resin was intermediate, which may be owing to the bulky rigid naphthalene moiety briding group, it decreased the reactive activity of epoxy.6．The isothermal curing reaction of bis-NANER/DDS and 1,5-naphthalenediol based epoxy resins/DDS exhibited an autocatalytic behavior and the curing kinetics was described with the Kamal kinetics model, accounting for both autocatalytic and diffusion-control effect.