Synthesis And Properties Of Novel Heat Resistant, Flame Retardant Epoxy Resins And Curing Agents

Novel heat resistant, flame retardant epoxy resins and curing agents were synthesized. The properties of the cured polymers were investigated by several methods. The relationship of these properties of the cured polymers with the structure of the epoxy resins or curing agents were studied. The cure kinetics of some curing systems were also carefully investigated.A new epoxy resin containing both naphthalene and dicyclopentadiene (DCPD) group was synthesized to produce a highly heat-resistant network, and the curing behavior was investigated using diaminodiphenylsulfone (DDS) as curing agent. The chemical structures were characterized by Fourier Transform Infrared (FTIR) spectroscopy, Nuclear Magnetic Resonance (NMR), Mass Spectrometry (MS), and Gel Filtration Chromatography (GPC) analyses. Dynamic curing behavior was investigated using differential scanning calorimetry (DSC). The physical properties of the resulting polymers were evaluated with dynamic thermal mechanical analyses (DMTA) and thermogravimetric analyses (TGA). The cured polymer showed great improvement in heat resistant property including remarkably higher glass transition temperature (Tg) and thermal stability.A novel novolac curing agent containing both naphthalene and dicyclopentadiene (DCPD) moieties was prepared. The thermal properties of the resulting polymer from diglycidyl ether of bisphenol A (DGEBA) epoxy resin cured with the novel curing agent were evaluated using DMTA and TGA. Compared with the conventional curing agent, the resulting polymer cured with naphthalene/DCPD novolac shows considerable improvement in heat resistant properties such as higher glass transition temperature (T_g) and thermal stability. The result also shows better moisture resistance because of the hydrophobic nature of naphthalene/DCPD structure.A reactive phosphorus-containing compound, bis-phenoxy (3-hydroxy) phenyl phosphine oxide (BHPPO) was successfully synthesized to produce the phosphorus-containing flame retardant epoxy resin (BHPPO-EP). The chemical structures were characterized with FTIR, MS, NMR spectra and elemental analyses. Thermal degradation behaviors and flame retardant properties of the cured epoxy resins were investigated by TGA and the limiting oxygen index (LOI) test using DDS as curing agent. The cured BHPPO-EP exhibited better stability than the regular bromine containing epoxy resin. The high char yields and the high limiting oxygen index values 34 were also found to certificate the great flame retardancy of this new phosphorus-containing epoxy resin.The cure kinetics of naphthyl/dicyclopentadiene epoxy resin and bis-phenoxy (3-hydroxy) phosphine oxide (BHPPO) was investigated by differential scanning calorimetry (DSC) under nonisothermal and isothermal condition. The advanced isoconversional method (AICM) was used to study the nonisothermal DSC data, the effective activation energy of the curing system in the early stage agreed with the value calculated from the Kissinger model and then increased because of the hindrance of molecular mobility. Autocatalytic behavior was shown in the isothermal DSC measurement, which was well described by Kamal model in the early curing stage. In the later stage, a crosslinked network structure was formed and the curing reaction was mainly controlled by diffusion. The diffusion factor was introduced to optimize the Kamal model and correct the deviation of the calculated data. The physical properties of the cured polymer were evaluated by DMTA, TGA and limiting oxygen index (LOI) test, which exhibited relatively high glass transition temperature, good thermal stability and flame retardance.A novel epoxy resin containing imide and naphthyl groups was synthesized to produce heat resistant polymer. The chemical structures were characterized by ¹H-NMR, ¹³C-NMR, FTIR spectra and elemental analyses. The curing behavior was investigated by DSC using DDS as curing agent. The physical properties of the cured polymer were evaluated with DMTA and TGA. The cured polymer exhibited great improvement in heat resistant properties including higher glass transition temperature (T_g) and better thermal stability.