Application Of Flame Retardants Based On Aluminum Hypophosphite For PBT

Poly(1,4-butylene terephthalate)(PBT) with excellent properties is an important thermoplastic engineering plastics, which is widely used in electronic industry, automotive industry and other fields. However, the flame retardancy are relatively required highly in these fields. PBT is flammable and dripping seriously, which limit the application of PBT. Aluminum hypophosphite(AHP), zinc stannate(ZS), reduced graphene oxide(RGO), aluminum hypophosphite/reduced graphene(AHP/RGO) hybrid material are synthesized in this paper,then AHP, ZS synergistic flame retardant, AHP, RGO synergistic flame retardant and AHP/RGO hybrid material are applied in PBT, as a result, thermal degradation properties and flame retardancy of PBT composites are investigated by thermogravimetric analysisdifferential thermogravimetry(TG-DTG), thermogravimetric analysis-Fourier transform infrared spectroscopy(TG-FTIR) and cone calorimeter test(CCT). More details are as following:Firstly, AHP and ZS are added to PBT as flame retardants, the flame retardancy of PBT system are discussed by limiting oxygen index test(LOI), UL-94 test, and microscale calorimetry(MCC); the results show that the LOI of flame-retarded PBT increases to 24.1% from 21.8% of neat PBT when 1.4wt% ZS(at a total loading of AHP and ZS is 20 wt%) is introduced, at the same time, UL-94 rating V-0 is obtained. The results indicate that AHP and ZS in appropriate proportion can significantly improve the anti-dripping performance of PBT. The results from MCC show that the peak heat release rate(PHRR) of the sample(when the content of ZS is 1.4wt%) is decreased to 538.57 W/g from 561.40 W/g of pure PBT, which is beneficial in the actual fire.Secondly, the flame-retarded PBT has been prepared using AHP and RGO. The combustion properties and thermal degradation properties of flame-retarded PBT are evaluated using LOI, UL-94, MCC, TG and TG-IR. The results show the flame retardancy of PBT composites is best at the loading of RGO was 0.5 wt%(the total loading of AHP and RGO is 20 wt%), LOI increases to 24.5% from 21.8% of virgin PBT, UL-94 rating reaches to V-0 level. The results of MCC test show that the PHRR of PBT/AHP-RGO(0.5%)(the content of RGO in the sample is 0.5wt%) reaches a 16.52 % reduction than PBT/AHP(20%)(the content of AHP is 20wt% in the sample). The results of TG-IR test indicate that RGO plays a role of physical barrier, which effectively hinder the escape of small molecules from the the substrate.Thirdly, AHP/RGO hybrid materinal is prepared through a simple in situ hydrothermal route. The as-prepared sample is characterized by FTIR, X-ray diffraction(XRD), Raman spectroscopy(Raman), X-ray photoelectron spectroscopy(XPS), Scanning electron microscopy(SEM), and Transmission electron microscopy(TEM). It turns out that the target product is synthesized successfully.Fourthly, the obtained sample is used as a flame retardant for PBT, and the flame retardancy of the composites is investigated by LOI, UL-94, and CCT. The mechanism is studied by TG-DTG and TG-IR. When 20 wt% of AHP/RGO is added to PBT( abbreviated as PBT/AHP/RGO(20%)), LOI of PBT/AHP/RGO(20%)is lower than PBT/AHP(20%), however, UL-94 obtains V-0 level. The CCT datas indicate that the presence AHP/RGO significantly reduce PHRR, the reduction of which reaches to 78.7%. The results of TG-IR test suggest that AHP/RGO can promote PBT to form more stable, compact char layers and reduce the total smoke production.