| Polylactic acid(PLA)has attracted much attention due to its biodegradability,transparency and excellent mechanical strength.However,the application of PLA is greatly restricted as its brittleness,high costs and flammability.Therefore,in this thesis,the PLA/PBAT/starch ternary blends were prepared with poly(butylene adipate-co-terephthalate)(PBAT)as toughening agent and cheap starch together with self-made bio-based flame retardant by melt blending.The major research contents and results were summarized as following:(1)PLA/PBAT blends were prepared by melt blending in the presence of chain extender(ADR)which was used as a compatibilizer.The effects of the ADR and PBAT content on the mechanical,compatibility,thermal stability and processing performance of the blends were investigated in detail.In the case that ADR content is 0.55 phr and the weight ratio of PLA/PBAT is 60/40,the toughness of the PLA/PBAT blend was optimal,namely,the elongation at break and impact strength were increased by 57.5 times and 117 % compared with pure PLA,respectively.Meanwhile,the melt flow rate value of the blend is minimum,indicating that the melt strength was supreme and was helpful to the film formation process.Scanning electron microscopy(SEM)and dynamic mechanical analysis(DMA)demonstrated that the incorporation of ADR improved the compatibility between the blend matrix,and the adhesion between the two-phase interfaces was thus enhanced.Thermal stability analysis(TGA)showed that the content of ADR and PBAT had little effect on the thermal stability of PLA/PBAT blends.(2)The rheological study of the compatibilized PLA/PBAT blends showed that the storage modulus and loss modulus of the blends increased whilst the complex viscosity decreased as angular frequency increased.As the content of ADR and PBAT increased,its storage modulus,loss modulus and complex viscosity increased.The Han curves demonstrated that the compatibility of the blends was improved by the addition of ADR.And the time dynamic scan showed that the time had obvious effect on the storage modulus of PLA/PBAT blends in contrast to the slight effect on the storage modulus of pure PLA and PBAT.(3)The compatibilized PLA/PBAT/TPS ternary blends were prepared by melt blending in the presence of diphenylmethane diisocyanate(MDI)as the compatibilizer for the thermoplastic starch(TPS)and polymer matrix.The effects of MDI and TPS content on the mechanical,compatibility and melt flow rate of the blends were investigated in detail.The PLA/PBAT/TPS(54/36/10,w/w/w)ternary blends with 0.2 phr of MDI and 0.55 phr of ADR exhibited excellent comprehensive mechanical properties.Both SEM images and the dynamic rheological results showed that the blends containing 10 wt% TPS had good compatibility.The melt flow rate test and the TGA results demonstrated that the blends containing 10 wt% TPS had the highest melt strength and the best thermal stability,respectively.(4)A bioderived flame retardant(marked as ATMP-A)was synthesized via the ionic exchange between adenine and amino trimethylene phosphonic acid(ATMP).The incorporation of ATMP-A endowed the PLA/PBAT/TPS ternary blends with improved fire safety.The PLA/PBAT/TPS blend containing 18 wt% ATMP-A alone achieved a UL-94 V-0 rating with a higher LOI value(28 %).Meanwhile,its peak of the heat release rate(PHRR)and total heat release(THR)were reduced by 60.5 % and 34.1 % as compared to the PLA/PBAT/TPS ternary blend,respectively.Such excellent flame retardancy was mainly attributed to the formation of the intumescent flame retardant system(IFR)in which ATMP-A acted as both acid and gas sources together with TPS as a natural carbon source.Based on the analysis of the volatile gases and the char residues,a possible flame retardant mechanism including gas phase and condensed phase was proposed.This work provides a novel and effective idea for improving the fireproof performance of PLA/PBAT/TPS blends and will broaden its practical application fields. |
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