Effect Of Nucleating Agents Talc And Plasticizers TBC On The Properties Of Poly(L-lactic Acid)

Growing oil resources shortage and environmental awareness have motivated researchers to develop high-performance, low-cost, renewable resources, safe non-toxic and environmental development products. Poly(L-lactic acid)(PLLA), is a well-known renewable and biodegradable polyester that can be produced from renewable sources. It is decomposed into CO2and H2O finally by the enzymes of plants and animals, or by various microbes in nature. PLA shows brilliant future as eco-friendly packing materials. Polylactic acid has many disadvantages, such as brittle performance, and poor impact resistance, which limit its application.In order to improve the crystallability and flexibility of the polylactic acid, Talc, modified talc and tributyl citrate were chosen as additives to improve the performance of polylactic acid. The effects of nucleating agent, plasticizer and process conditions on mechanical properties, crystallability and thermal stability were investigated.It was found that the nucleating agent and the plasticizer could improve the melt index of the polylactic acid. With the increase of the talc content, the tensile strength, flexural strength and impact strength of the coposite improved first and then decreased. With the increase of TBC content, the tensile strength decreased, but the flexural strength and impact strength increased. When adding both nucleating agent and plasticizer, the mechanical properties improved.Polarizing Light was used to observe the changes of spherulite size of pure polylactic acid after adding nucleating agents and plasticizer. It was found that the size of the spherulites was almost unchanged. But spherulite size decreased after adding nucleating agents, and largened after adding plasticizer.With the increase of the talc content, cystallization temperature (Tc) of the polylactic acid decreased and degree of crystallinity increased by DSC. TBC improved crystallization rate of PLLA. Synergies of them could improve the crystallability. Modified talc could effectively improve the crystallinity of polylactic acid after extrusion.Non-isothermal crystallization kinetics research of Polylactic acid revealed that the crystallization temperature range increased and half crystalline time(t1/2) decreased gradually with the increase of cooling rateβ. Nucleation model was mainly homogeneous nucleation, but heterogeneous nucleation existed at the same time. The result showed that crystal growth pattern was three dimensional growth.The research showed that talc improved the thermal decomposition temperature of the polylactic acid by TG analysis, which may be attributed to the increase of crystallinity which made thermal decomposition more difficult. Adding plasticizers reduced the thermal degradation temperature, because dilution effects of plasticizer reduced intermolecular force and enhanced segmental mobility. Synergies of them could commendably improved the thermal decomposition temperature of poly (lactic acid). The study also found that the thermal decomposition temperature moved to high temperature with the increase of heating rate by the thermal degradation kinetics of polylactic acid.