Hybrid Organic-inorganic Flame Retardation Modification Of Epoxy Resin

Epoxy resins are globally used on a large scale for microelectronicspackaging materials, biotechnology, mechanical engineering and environmentengineering, as their excellent adhesion, mechanical strength and insulativity,etc. Neat cured epoxy resins belong to firesensitive polymer, exertingfragmentation of chemical bonds by the action of a significant extent of heat.Thus, there is an increasing demand of epoxy resin with better flame retardancyto meet new requirements or to replace existing materials.In this thesis，progress in applications、flame retardation modificationmechanism and research hot spots of epoxy resins were reviewed. Then severaltypes of novel organic-inorganic hybrid fire retardants were prepared andcharacterized. By utilizing the synergy between flame proofing elements anddesigning difffernet nanometer materials, applications of phosphorus-alumina,phosphorus-silicon, and phosphorus-silicon-alumina hybrids in bisphenol-Adiglycidyl ether type epoxy resin (DEGBA) were investigated, in order to revealflame-retardant mechanism. The main research contents are as follows:1. Aluminum-phosphorus hybrid nanorods (APHNRs) with regularmorphology were prepared by hydrothermally reacting diphenylphosphinic acid(DPPA) with aluminium hydroxide (ATH) based on the resultant structure ofaluminophosphates mainchains and phenyl side chains.（1）FTIR, Raman, XRD,SEM and TEM showed that the crystal structure of ATH have been completelydestroyed in the hydrothermal reaction, meanwhile, a rod-like, long-rangeorderly structure containing bidentate PO2formed.（2）The aryl face-to-face π-πstacking evidenced in the range of2θ=22.0~25.0oin XRD pattern supplied thedriving force of assembling into nanorods.（3）SEM and XRD spectroscopyfurther revealed a “decomposing-assembling-propagating” process for theformation of nanorods.（4）Size-controlled and morphology-adjustable nanorodshave been also prepared by using this growth mechanism.（5）DTA resultsshowed APHNRs have a pronounced thermal stability and char yield. Therefore,it was expected to be applied in the flame-retardant modification of polymers.2. New phosphorus-alumina hybrid nanorods (AOPH-NR) have been prepared by reacting dibenzylphosphinic acid (DBPA) with aluminum hydroxide(ATH) in organic solvent and used to prepare nanocomposites with epoxy resin.In order to determine the structure-property relationship of these composites,several other phosphinic acids of the general formula (R(CH2)n)2POOH, with R=ester, allyl and nitrile, and n=1or2, and corresponding AOPHs weresynthesized.（1） FTIR, Raman, TGA, and XRD examinations showed that onlyAOPH-NR possesses highly hybrid structure and nanorod morphology， asmentioned growth mechanisms before.（2）DTA results showed AOPH-NRexhibited high thermostability than other AOPHs.（3）The characteristics ofAOPH-NR caused the good dispersion in epoxy resin, the ability to acceleratethe curing reaction, and the improvement of mechanical properties.（4）Limitingoxygen index (LOI) determination and cone calorimeter analysis showed thatthe incorporation of only4.25wt%AOPH-NR remarkably improved the LOIvalue to as much as28.0，led to a23%reduction in peak heat release rate (PHRR)and prolonging of the ignition time to79s. Thus, these properties weresignificant for personnel evacuation in the fire.3. Novel silicon-/phosphorus-containing flame retardant,3-((methoxy-diphenyl-silyl)oxy)-9-methyl-2,4,8,10-tetraoxa-3,9-diphosphaspiro [5,5] unde-cane3,9-dioxide (SDPS) was synthesized. The chemical structure of SDPS waschartered by FTIR，1HNMR，13CNMR.（1）TGA，EDX，FTIR，TG-IR furthershowed the thermal decomposition of SDPS not only contained the chemicalcomponent promoting char formatting, but also thermal-stability inorganicsilicon.（2） Compared with dicyclic nitrogen-/phosphorus-containing flameretardant (SPDM), SDPS showed the ability to retard the initial decompositionof resins but low char yield. It was effective to play role on either gas phaseflame retardant or condensed-phase flame retardant by cooperative SDPS andSPDM.（3）On the macroscopic view，SEM showed a ‘‘honeycomb’’ coherentchar structure can efficiently isolate heat and oxygen form the degreedvolatiles，as the good interaction of SDPS and SPDM and appropriate viscosityof the melting mixture. On the microcosmic view, Raman showed the formationof nanoscaled structure of residues can improve heat shielding efficiency.（4）SDPS can dispersed in the network structure of resins uniformly, simultaneously,increase the toughness of composites as the existence of-Si-O-Si-units. Therefore, SDPS can be used improving the mechanical performance oftraditional intumescent flame-retardant epoxy resin.4. Al2O3grafted with3-((methoxy-diphenylsilyl)oxy)-9-methyl-2,4,8,10-tetraoxa-3,9-diphosphaspiro [5.5] undecane3,9-dioxide， SAlu, has beenprepared.（1）The characterization of FTIR, Raman, XRD, SEM and NanoZSshowed SDPS can be grafted into the surface of Al2O3and thus increase particlediameter（.2）TGA results showed that the SDPS grafting amount is more than40wt%（.3）Introduction of SAlu into epoxy network can improve thermal stabilityand char residues. The carbonization of epoxy composites showed that SAlu canpromote cured resins to form a similarly ceramic-carbon coking structure withinner multihole morphology; and therefore isolating heat and oxygen from thedegreed volatiles, improving fire resistance.（5）SAlu can dispersed in thenetwork structure of resins uniformly, simultaneously, increase storage modulusand glass-transition temperature.