| Polylactic acid (PLA), a non-petroleum-based biodegradable polymer material, canalleviate the issues of increasingly serious environmental pollution and dwindling petroleumresources and has become a hot research topic. However, brittleness of PLA limits itsapplication in many fields. In this work, PLA alloys were fabricated by melt blending in orderto improve its toughness and expand its application in many fields. Mainly related to thefollowing aspects:1. PLA was toughened by the full-vulcanized powdered rubber of carboxylstyrene-butadiene (SDB) and carboxylated nitrile (SDQ). The results showed that the meltblending of PLA with SDB or SDQ could improve the impact strength and elongation atbreak of PLA. Adding a certain amount of compatibilizer, the impact strength was furtherimproved. Between them, SDQ exhibited better toughening effect for PLA. SEM resultsshowed that powdered rubbers have a poor dispersion in the PLA matrix due to a largedifference between their solubility parameters, wherein the SDQ particles were dispered inmatrix with a smaller size. DSC results showed that the addition of SDB or SDQ decreasedcrystallinity of PLA.2. PLA was toughened by biodegradable poly(butylene adipate-co-terephthalate)(PBAT),meanwhile adding compound compatibilizer of2,2’-(1,3-phenylene)bis-2-oxazolin (BOZ) andphthalic anhydride (PA). It was found that BOZ/PA could significantly improve the toughnessof PLA/PBAT alloys. PLA/PBAT alloys showed the best mechanical properties withcompound compatibilizer of1phr BOZ and1phr PA, which elongation at break and tensilestrength were improved to515%and45.3MPa respectively. SEM results revealed that the sizeof the dispersed phase was significantly decreased and more uniformly, and the two-phaseinterface became blurred. Thus BOZ/PA improved the compatibility of PLA and PBAT, thusthe mechanical properties of PLA/PBAT alloys. GPC and DSC results show that the additionof BOZ/PA increased the molecular weight of PLA/PBAT alloys, and decreased thecrystallinity. DMTA results indicated that, compared with PLA, the storage modulus and lossmodulus of PLA/PBAT alloys decreased. In addition, the Tgof PLA declined with the additionof BOZ and PA.3. An appropriate amount of compatibilizer ADR4370S (ADR),1,6-hexanedioldiglycidyl ether (HDE) or dicumyl peroxide (DCP) used as compatibilizer significantlyimproved the mechanical properties of PLA/PBAT alloys. The tensile elongation at break ofPLA/PBAT (80/20, wt) was212%. The tensile elongation at break of PLA/PBAT alloys wasincreased to460%and430%respectively by adding1phr ADR and HDE. By adding0.1phrDCP, the tensile elongation at break was increased to476%. Besides, the tensile strength ofPLA/PBAT alloys was also improved. SEM results showed that the addition of ADR, HDE orDCP reduced the PBAT particles. Among them ADR displayed the best compatibilizationeffect for PLA/PBAT alloys. GPC data suggested that the molecular weight of PLA/PBATalloys increased with the addition of ADR, HDE or DCP. By adding1phr ADR, themolecular weight was increased from5.97×10~4for sample of PLA/PBAT (80/20, wt) to 10.22×10~4, exhibited the most chain-extending effect.4. The accelerated degradation experiments indicated that the weight loss rate of samplesincreased and the molecular weight decreased with increasing of the degradation time. Aftereight weeks of degradation time, the weight loss rate for PLA was39wt%, but only4wt%forPBAT. The results revealed the degradation rate of PBAT was slower. Furthermore, theaddition of ADR, HDE or DCP retarded the degradation rate of PLA/PBAT alloys, and ADRexhibited the most retarded effect. The pH value of degradation liquid decreased withincreasing of degradation time. The change of pH value were similar for PLA/PBAT (80/20,wt) with addition of ADR, HDE or DCP. |
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