| Intumescent flame retardant (IFR) is a kind of phosphorus-nitrogen based flameretardant, in which the acid source, char forming agent and blowing agent can reactbeyond a certain temperature to form cellular charred layer on the surface of condensedphase to slow down heat and mass transfer between gas and condensed phases andinterrupt the self-sustained combustion of the polymer. IFR is one of the environmentfriendly flame retardant to produce low smoke halogen free flame retardant polymericmaterials. Nowadays, most IFR is mainly used in flame retardant coating. Small part ofIFR with high quality can be filled in polyolefin as flame retardant for application in wireand cable, construction materials, electric equipment and vehicles. IFR only has verysmall percentage in flame retardant market of China. There are two technical aspectswhich limit the wide application of IFR, the first is improvement of the flame retardantefficiency, decrease of the required filling level and cost, the second is increase of thedecomposition onset temperature (Tonset) and decrease of the solubility. The research targetof this dissertation focuses on the two aspects mentioned above and making a primaryevaluation to the quality of commercial available IFR in domestic market.Addition of synergist is helpful to get intumescent flame retardant system with highefficiency. Generally, chemical catalysis is needed to promote the reaction betweencomponents of IFR and polymer matrix to produce more char yield and improve thequality of charred layer. Rare earth oxides (REO) including La2O3and Nd2O3wereemployed as synergists in intumescent flame retardant thermalplastic olefin (FRTPO)based on polypropylene (PP). The limiting oxygen index (LOI) increased. Peak of heatrelease rate (pHRR) and peak of mass loss rate (pMLR) decreased. The synergistic effect(SE) of Nd2O3is higher than that of La2O3. REO increases the thermal stability in hightemperature range and final char yield but decrease the Tonsetof IFR and FRTPO slightly.The presence of REO changes the viscous-elastic behavior of FRTPO during thermal degradation process and is helpful to suppress the melt dripping and damp the pressaroused by release of gas to keep the intactness of charred layer. Addtion of REOincreases the tensile strength of FRTPO slightly and has no remarkable effect onelongation at break.Natural silicate can be used as multi-functional filler with low cost in plastics andrubber. There are lots of categories in natural silicate, which differs much in surface traitand metal content. Addition of0.5~7wt%unexfoliated vermiculite (VMT) or exfoliatedvermiculite (EVMT) can increase the LOI values of intumescent flame retardant PP(FRPP). EVMT has better performance than VMT to increase LOI values. LOI values canbe further increased if VMT was modified by titanate coupling agent containingphosphorus. pHRR and pMLR of FRPP can be lowered by addition of vermiculite andperformance of EVMT is better than VMT. Peak of smoke production rate (pSPR) andtotal smoke production (TSP) also can be lowered by addition of EVMT. The residual charof FRPP with vermiculite after combustion is more compact than that of FRPP withoutvermiculite and so has better barrier property. Addition of vermiculite increase the TonsetofFRPP and final residual char. Original montmorillonite (MMT), attapulgite (ATP) andzeolite (ZLT) also can increase the LOI values of FRPP and decrease pHRR and pMLR.Organic montmorillonite (OMMT) using dioctadecyl dimethyl ammonium bromide asintercalation agent and OMMT modified by zirconium ion (Zr-OMMT) has no effect onthe LOI values of FRPP but can change pHRR, pMLR and pSPR. Zr-OMMT has betterperformance than OMMT. Zr-OMMT has excellent smoke suppression performance.Synergistic affectivity (SE) values of EVMT, VMT, ZLT, MMT and ATP in FRPPcalculated based on the increase of LOI values is1.6,1.4,1.4,1.3and1.2, respectively.Addition of silicate decreases the fire growth rate index (FIGRA) and fire performanceindex (FPI) of FRPP. EVMT has the best synergistic performance. Synergistic effect ofsilicate has close relationship with the summary weight content of transition metalincluding Fe and Ti, but is not determined by this factor only.To lower the solubility of ammonium polyphosphate (APP) and improve its thermalstability, encapsulation is essential. Diisocyanate was in-situ polymerized in solution witha charring agent tri(2-hydroxyethyl) isocyanurate (THEIC) in the presecne of APP toprepare encapsulated APP (CUAPP). Solubility of CUAPP in water was greatly decreasedcompared with that of mixture of APP and THEIC.The Tonsetof CUAPP was also increased. Flame retardant efficiency of CUAPP is lower than that of mixture of APP and THEIC buthydrolytic stability of FRPP containing CUAPP is improved compared with that of FRPPcontaining APP and THEIC. FRPP containing CUAPP can pass UL94V-0rating afterhydrolytic stability test.To make a primary technical evaluation on the quality of commercial available IFR inChina, the effect of one imported IFR and four kinds of domestic IFR on the flammability,hydrolytic stablity, mechanical and rheology properties of toughened PP (TGPP) andthermalplastic olefin elastomer (TPE) was investigated in detail. IFR with brand nameDeflam EM82, JLS-PNP1D and Budit3167has no remarkable discrepancy in flameretardant efficiency, but only flame retardant TG (FRPP) or flame retardant TPE (FRTPE)containing Budit3167can pass UL94V-0rating after hydrolytic stability test. FRPP orFRTPE containing Budit3167has higher Tonsetthan FRPP or FRTPE containing other IFR.The innovative points of this dissertation are listed as follows:(1) Synergistic effect of REO with different catalytic activity in FRTPO wasinvestigated systemically. The change of viscous-elastic behavior of FRTPO duringthermal degradation was detected by thermal scanning rheology tests and mechanismresponsible for the synergistic effect was revealed in detail. REO increases the thermalstability in high temperature range and final char yield but decrease the Tonsetof IFR andFRTPO slightly. The presence of REO changes the viscous-elastic behavior of FRTPOduring thermal degradation process and is helpful to suppress the melt dripping and dampthe press aroused by release of gas to keep the intactness of charred layer.(2) The synergistic effect of various silicates including unexfoliated vermiculate,exfoliated vermiculite, original montmorillonite, organic montmorillonite, organicmontmorillonite modified by zirconium ion, attapulgite and zeolite in FRPP was studied indetail. Exfoliated vermiculite is the optimal synergist with high synergistic efficiency andlow cost. Organic montmorillonite modified by zirconium ion (Zr-OMMT) with highsynergistic efficiency was prepared. Zr-OMMT has excellent smoke suppressionperformance.(3) Diisocyanate was in-situ polymerized in solution with a charring agenttri(2-hydroxyethyl) isocyanurate (THEIC) in the presence of APP to prepare encapsulatedAPP (CUAPP). CUAPP is a novel IFR with good thermal stability and hydrolytic stability. Use of CUAPP in PP can produce flame retardant materials with good thermal stabilityand hydrolytic stability. |
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