Properties Of Polylactic Acid And Triglyceride Blends

Poly (lactic acid), PLA, is a biodegradable thermoplastic that can be producedfrom renewable resources. PLA not only has excellent mechanical properties, but alsopossesses brilliant optical properties, low toxicity, processability and so on. But itsinherent brittleness limits its application in a lot fields such as bait. Using glyceryltriacetate (GTA) and glyceryl tripropionate (GTP) as plasticizers to toughen PLA, thecomposites blended with the batchwise mixer at five concentrations,5,10,15,20wt%. Compared with pure PLA, the blends plasticized with GTA or GTP had gainedimprovement of toughness to different extent in elongation at break and impactstrength. When GTA or GTP content reached15wt%, the PLA blends underwentbrittle-ductile transition, correspondingly, the tensile strength of the blends decreased.PLA/GTA15or PLA/GTP15blends showed the greatest impact strength and thesamples didn’t break in unnotched Charpy impact test. The Tgs of PLA blends shiftedto lower temperature due to the facts that GTA or GTP reduced the polymerchain-to-chain interactions. Two pronounced melting peaks appear on thethermograms of PLA blend, this is an indication of a simultaneous melting andrecrystallization during the temperature scan of unstable crystals at temperaturesbetween cold crystallization and melting. Compared with unaged samples, the dropsteps in the storage modulus of the aged samples widened, this is the due that increaseof the crystalline region induced enrichment of GTP in the decreased amorphousregion. Above glass transition, a rise step occurred on the curve of the aged samples,while can’t be seen on the curve of the unaged samples. This is because that theunaged samples undertook cold crystallization at the step temperature, while the agedsamples completed crystallization during aging. Because of the volatility of theplasticizers, a decrease in thermal properties of plasticized formulations compared tothe neat polymer can be seen. But owing to good compatibility between GTA or GTPwith PLA, the blends still had great thermal stability.