Synthesis And Application Of Hypophosphites As Flame-retardant For PBT

Poly (1,4-butylene terephthalate)(PBT) is a widely used engineering plastics, mainlyused in electronics, machinery, automobile and other fields. Nevertheless, its flammability andserious dripping during combustion limited its potential applications. It is necessary to modifyPBT in order to meet the requirements of industrial and life technology. In this paper, we haveprepared hypophosphite, and they were added to PBT as flame retardants. Subsequently,thermal degradation properties of PBT with additives were investigated by using TGA-DTG,TGA-FTIR, TGA-MS and cone calorimeter. More details are as follow:Firstly, Aluminum hypophosphite, lanthanum hypophosphite monohydrate and ceriumhypophosphite monohydrate were synthesized, and characterized through X-ray diffraction(XRD), energy dispersive spectrometer (EDS) and scanning electron microscopy (SEM). Thedegradation process and degradation produats were studied by TG-DTG、 TG-FTIR andTG-MS, and study on the dynamics of degradation process.Secondly, the fire retardant effect, thermal stability and mechanical properties of PBTsystem containing hypophosphite were discussed. The LOI of flame-retardant PBT increasedabout7-8%when25wt%hypophosphite was introduced into PBT. UL-94rating V-1and V-0were respectively obtained when aluminum hypophosphite and lanthanum hypophosphitewere introduced into PBT at a total loading of25wt%. The hypophosphite can promote PBTto form more stable char layers and reduce the amount of released gas.Thirdly, flame-retarded PBT has been prepared using aluminum hypophosphite (AHP)and Trimer. The combustion properties of flame-retarded PBT were evaluated using LOI,UL-94and cone calorimetry. The cone calorimeter data indicated that the presencePBT/AHP/Trimer imported a significant smoke-suppressing effect. The thermal degradationproperties of flame-retarded PBT were also investigated using TG-FTIR and TG-MS. Theresults showed that addition of AHP and Trimer, not only decreased T-5%(defned as thetemperature at which5%of the initial weight has been lost), but also promoted stability of thechar residue. For the samples of PBT, PBT/25%AHP and PBT/AHP/Trimer, the main gas pyrolysis products were CO2and butadiene, while the sample of PBT/AHP/Trimer generatedless CO2and butadiene, and consequently retained more carbon in the matrix. The amount ofphosphorus-oxygen radicals of PBT/25%AHP was1.3times that of PBT/AHP/Trimer, whichindicated that AHP alone showed slightly stronger gaseous phase effect than the combinationofAHP and Trimer.