Preparation And Flame Retardancy Of Series Epoxy Resin Composites

Epoxy resin was widely used in many fields due to its excellent performance, however,the limit oxygen index(LOI) of epoxy resin is about 20, which is a flammable material. To broad the application of epoxy resin when flame retardancy was needed, epoxy resin should be modified by flame redardant. With the development of flame retardant technology, the flame redardant used today should be environment friendly, low poison, high efficiency and multi-functionalization. Using several kinds of environment friendly flame retardants, this dissertation prepared series epoxy resin composites and studied their flame retardancy and thermal conductivity properties, the main contents are briefly introduced following:1. A series of diglycidyl of bisphenol-A/Polyhedral oligomeric silsesquioxane(DGEBA/OGPOSS) nanocomposites were prepared, using 4, 4’-diamino diphenyl methane(DDS) as curing agent. The results showed that OGPOSS dispersed homogeneously in DGEBA. As the content of OGPOSS was increased, the glass transition temperature(Tg), heat release rate(HRR) and total heat release(THR) decreased significantly, while the LOI increased.Carbon residue analysis showed that OGPOSS can form a stable residual carbon layer in the condensed phase, while silicone dioxide(SiO2) accumulated in the surface of the carbon residue. It was inferred that SiO2 can reduce HRR value and protect composites further damaged in the process of burning.2. Using methylhexahydrophthalic anhydride(MHHPA) as curing agent, the thermal conductivity and flame retardantbehavior of DGEBA/Multi-walled carbon nanotubes(MWCNTs) composites was studied. At the same time, the thermal conductivity and flame retardantbehavior of DGEBA/MWCNTs/ Hexaphenoxycyclotriphosphazene(HPCTP)composites was studied. The results showed that part of MWCNTs aggregated as the concentration of MWCNT was increased to 1.5 wt. %. As the concentration of MWCNTs was increased, the Tg, thermal decomposition temperature with 5 wt. % weight loss and thermal conductivity increased and then decreased. The HRR decreased with concentrationof MWCNTs, so the flame redundancy property of epoxy resin improved. For DGEBA/HPCTP/MWCNTs composites with 1 wt. % MWCNTs, the Tg, thermal decomposition temperature, HRR and THR were all larger than that of DGEBA/HPCTP composites. It was apparent that MWCNTs can improve thermal stability and flame retardancy of DGEBA/HPCTP epoxy resin composites.3. Using nano aluminium nitride(AlN), aluminium hydroxide(Al(OH)3) and magnesium hydroxide(Mg(OH)2) as flame redardants, the flame redardancy and thermal conductivity of these composites was studied.The conclusion are as following: as the content of AlN was increased, AlN nanoparticles aggregated in DGEBA, Tg, the thermal decomposition temperatures at 50 wt. % and maximum weight loss all increased. However, thermal decomposition temperatures at 5 wt. % weight loss, and thermal conductivity both increased then decreased with the concentration of AlN. It was observed that the degradation process of DGEBA/Al(OH)3 composites can be classified to two steps: the temperature scope of first step was 220~300 oC, and Al2O3 was formed in this step as inert endothermic compound; the second step happed in 300~440 oC where hydrate alumina was formed. The degradation of DGEBA/Mg(OH)2 composites maily happened in 300~550 oC, Mg(OH)2 released bound water during heat decomposition, which deceased the temperature of composites during flaming process, inhibited the further decomposition of combustible gas and increased the quantity of residual carbon. As the flame redardant of DGEBA, it was concluded that Al(OH)3 and Mg(OH)2 exhibited the solid phase flame redardant mechanism.4. Using diglycidyl-4-glycidyloxyaniline(AFG-90) as epoxy matrix and MHHPA as curing agent, the curing kinetics of AFG-90/MHHPA was studied by non-isothermal differential scanning calorimetry(DSC) method, while the curing reaction kinetics model was calcuated by Kissinger and Ozawa method. The gelation temperature(Tgel), curing temperature(Tcure) and post-treating temperature(Ttreat) were calculated to be 64.06 °C,136.42 °C and 162.35 °C, respectively. According to above results, the curing condition of AFG-90/MHHPA was setted as 80 oC/2 h + 140 oC/2 h + 160 oC/1 h.5. Using 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO) and ammonium polyphosphate(APP) as flame retardant, the flame retardancy properties ofAFG-90/DOPO and AFG-90/APP composites was studied. The results showed that AFG-90/DOPO was transparent and the internal structure of AFG-90/DOPO composties was homogenous. During the process of thermal degradation, crosslinking reaction happened between DGEBA and phosphorus element which existed in DOPO, forming a carbon diffusion layer which can hinder heat and inhibit further degradation of composites. It was also observed that APP dispersed homogeneously in epoxy resin and didn’t form bigger aggregates. As the concentration of APP was increased, the thermal decomposition temperature at 5 wt. %, 50 wt. % and the max weight loss decreased. It was concluded that AFG-90/APP composites exhibited the intumescent flame redardant mechanism during the buring process. The formed intumescent foam layer can effectively prevent the overflow of gas phase pyrolysis products, and accordingly, reduced the value of HRR and THR and enhanced the flame redardancy of AFG-90 epoxy resin.