| Polylactic acid(PLA),a degradable polymer prepared from renewable resources,has good processing properties and excellent mechanical properties,and its high cost limits the wide application of PLA materials.PLA/reed composites are highly flammable and require flame retardant treatment.In this paper,flame retardant reed,phosphorylated flame retardant reed and reed-based lignin flame retardant were prepared to prepare flame retardant PLA/reed composites,and the mechanical properties and flame retardant properties of reed-based flame retardant on PLA composites were investigated by using universal testing machine,thermogravimetric analyzer(TGA),limiting oxygen index(LOI)and cone calorimeter(Cone).Details are as follows.In the first part,flame retardant reed powder(IFRF)was prepared by the impregnation method using amidinium urea phosphate(GUP)as flame retardant,and the effects of impregnation time,impregnation pressure and other factors on the impregnation effect were investigated,and the flame retardancy of IFRF increased with 800 ~oC residual mass after impregnation treatment.IFRF was applied to PLA,and the effect of impregnated flame retardant method and direct mixed flame retardant method on the performance of flame retardant PLA composites was investigated.The experimental results showed that at the same flame retardant dosage,the flame retardant performance of the composite obtained by the impregnation method was similar to that of the direct mixed method,while the mechanical properties were better.When IFRF was added at 40 wt%,the bending strength of the flame retardant composites was only reduced by 11.3%to 233.7 MPa and the tensile strength was reduced by 18%to 43.7 MPa compared with the non-flame retardant composites;the mechanical properties of the composites directly mixed with flame retardants decreased more,and the bending strength and tensile strength decreased to 199.8 MPa and 29.5 MPa,respectively.Meanwhile,the ultimate oxygen index(LOI)of the flame retardant PLA composites reached 25%,and the peak heat release(p HRR)decreased to 264 k W/m~2,which was 51.7%lower compared with that of the non-flame retardant PLA/reed composites.In the second part,reed fibers,phosphorus pentoxide and urea were used as raw materials to modify reed fibers with phosphorylation by mechanical force chemistry in a grinder to obtain phosphorylated reed fibers(MPRF)with flame retardant effect,and the optimal phosphorylation ratios were optimized by designing orthogonal experiments to adjust the raw material ratios.The experiments showed that the residual carbon rate of MPRF was increased from 22%to 36.6%of pure reed.When MPRF was added at 40 wt%,the LOI of the composite was 25.1%,and its residual carbon rate at 800 o C was significantly improved to 15.8%compared with 10.7%for the pure composite.Its p HRR was 336.9 k W/m~2,while the p HRR of the unflamed composite was 547 k W/m~2,indicating that MPRF has a flame retardant effect.The bending strength of the composites after adding 40 wt%MPRF was 277 MPa tensile strength was 44.7 MPa,which was less compared to the bending strength(298 MPa)and tensile strength(57.2 MPa)of the pure composites.In the third part,lignin from the reed fraction was selected as the raw material,and the reed-based lignin flame retardant(PNr-lignin)was prepared by successfully grafting polyethyleneimine and polyphosphoric acid on reed-based lignin through a two-step process.The flame retardant PLA composites were prepared by compounding PNr-lignin with MPRF.When the PLA addition in the composites was 70%,the LOI of the composites could reach30.8%at 20 wt%and 10 wt%for PNr-lignin and MPRF,respectively,and their UL-94 was V-0.Cone results showed that PNr-lignin lignin addition reduced the p HRR during combustion(214.37 k W/m~2),while the addition of PNr-lignin had less effect on the mechanical properties of the composites.The experimental results indicate that PNr-lignin is an excellent flame retardant for PLA/reed system. |
PDF Full Text Request