Preparation And Properties Of Flame-retardant And Reinforced PP/EPDM Thermal Plastic Elastomer With Lanthanum-containing Compounds

Polypropylene/ Ethylene-Propylene-Diene-Monomer Thermal Plastic Elastomer(PP/EPDM TPE) is a typical TPE with extraordinary comprehensive properties. Since it could be processed in common equipments, it is applied into many industries including auto part, electric and cable, etc. However, because the poor mechanical properties and flame retradancy have limited the application fields of PP/EPDM TPE severely, it is imperative to improve these two properties. Although traditional flame retardants could impart PP/EPDM TPE with good flame retardancy, it would damage mechanical properties greatly due to the poor compatibility between additives and polymer matrix. While traditional reinforcing agents could enhance the mechanical properties of PP/EPDM TPE, it could not improve the flame retardancy of the material. The good synergic effects between rare earth compound and flame retardant have been widely proven and this gives us useful guidance in finding a mutli-functional additive. In this paper, firstly, lanthanum tri-methacrylate(La TMA) reinforcing PP/EPDM TPE with great mechanical properties was prepared by using lanthanum oxide(La2O3) and methacrylic acid(MAA) through in-situ dynamic vulcanization and the reinforcement mechanism of La TMA was studied. Secondly, in order to improve both flame retardancy and mechanical properties of PP/EPDM TPE, lanthanum phosphate methacrylate(La PMA) reinforcing flame retardant PP/EPDM TPE was prepared by using 2-hydroxylethyl methacrylate phosphate(HEMAP) and La2O3. Finally, 2,6,7-Trioxa-1-phosphabicyclo[2.2.2]octane-4-ethanol 1-oxide(PEPA) was added into PP/EPDM/La PMA TPE to prepare PP/EPDM/IFR TPE with good flame retardancy and mechanical properties, the synergistic flame retardant effect between La PMA and PEPA was studied as well. The main research contents and results are listed as follows:Firstly, PP/EPDM/La TMA TPE reinforced by La TMA was prepared via in-situ dynamic vulcanization by using La2O3 and MAA as raw materials and dicumyl peroxide(DCP) as a curing and evocating agent. The influences of the dosage of La2O3, MAA and DCP on the mechanical properties, flame retardancy and crosslink density were investigated, the reinforcement mechanism of La TMA were characterized by scanning electron microscopy(SEM), rubber process analyzer(RPA), differential scanning calorimetry(DSC), etc. The results showed that when the amount of La2O3 was 4.96 phr, MAA was 7.86 phr and DCP was 1.20 phr, PP/EPDM/La TMA TPE had the best comprehensive mechanical properties. Compared with PP/EPDM TPE, the tensile strength, elongation at break and tear strength were increased to 15.4MPa, 366%, 87.7k N/m from 6.3MPa, 148%, 44.3k N/m respectively. This proved La TMA possessed great reinforcement capability and the reinforcement mechanism may be that La TMA could form ionic crosslink inside the polymer matrix because of the interaction between positive ion and negative ion, therefore when this kind of crosslink was destroyed; it could reconstruct automatically and form new ionic crosslink which could eliminate the energy from external force again.Secondly, flame retardant PP/EPDM/La PMA TPE reinforced by La PMA was successfully prepared through in-situ dynamic vulcanization by using La2O3 and HEMAP as raw materials and DCP as a curing and evocating agent. The influences of the dosage of La2O3 and MAA on flame retardancy were investigated by using cone calorimetric test(CCT), the thermal stability was tested by thermogravimetry analysis(TGA) and the flame retardant mechanism of La PMA was characterized by FTIR and thermogravimetry-Fourier transform infrared(TG-FTIR). The results showed that when the amount of La2O3 was 5.42 phr, HEMAP was 10.48 phr and DCP was 1.20 phr, PP/EPDM/La PMA TPE had the best comprehensive properties. Compared with PP/EPDM TPE, the tensile strength, elongations at break and tear strength were increased to 10.9 MPa, 299%, 68.0 k N/m from 6.3 MPa, 148% and 44.3k N/m. In addition, the peak heat release rate(p HRR), average mass loss rate(av-MLR) and total smoke production(TSP) were decreased to 595.1k W/m2, 44.9m2, 0.042g/s from 767.4k W/m2, 61.2m2, 0.054g/s repectively, while the limit oxygen index(LOI) and fire property index(FPI) were increased to 22.5%, 0.055s·m2/k W from 17.0% and 0.047s·m2/k W. This implied La PMA could improve the mechanical property and flame retardancy of PP/EPDM TPE.Lastly, PEPA was added into PP/EPDM/La PMA TPE so that a novel IFR was formed with PEPA and La PMA, and PP/EPDM/IFR TPE with good flame retardancy and mechanical properties was prepared. The influence of the mass ratio of La PMA to PEPA on the mechanical properties, flame retardancy and thermal stability were investigated. Moreover, the synergistic flame retardant effect between La PMA and PEPA were studied by FT-IR, SEM, TGA and TG-FTIR. The results showed that when the amount of IFR was 20wt% and the mass ratio of La PMA to PEPA was 12:8, PP/EPDM/IFR TPE possessed the best comprehensive properties. Compared with PP/EPDM TPE, the tensile strength, elongation at break, tear strength were 11.1MPa, 213%, 74.2k N/m respectively; in addition, the p HRR, av-MLR and TSP were decreased to 360.5k W/m2, 0.031g/s, 24.7m2 from 767.4k W/m2, 0.054g/s, 61.2m2, while the LOI and char residue were increased to 28.5%, 13.2wt% from 17.0% and 0. This good flame retardancy of PP/EPDM/IFR TPE may be that La could efficiently catalize the char forming reaction of IFR and polymer matrix.