The Regulation Of Crystallization Properties Of Polylactic Acid And Its Mechanism

Polylactic acid is a kind of environmentally friendly materials which can be regenerated,biodegradable and compatible.The disadvantages of PLA are brittleness,bad impact and poor heat resistance which restrict the further expansion of the PLA's application field.Adding nucleating agents can greatly alter the crystallinity of PLA,and then change the performance of PLA such as machining,mechanical properties,thermal properties and transmittance.Therefore,it is of great significance to study the crystallization and crystallization mechanism of polylactic acid under different nucleating agent.The effects of Colijn Nav101,nano-attapulgite clay and nano-attapulgite nucleating agents adsorbed sorbitol nucleation NX8000 K on the crystalline properties and dynamic thermal mechanical properties of PLA and the effects of different concentrations of nucleation promoter(CBT)on PLA/PPZn0.5crystallization and other properties were investigated in this paper.Firstly,we prepared PLA/Nav101 complexes by melt blending,and we investigated the effect of Nav101 concentration on heat performance,crystallization properties,dynamic mechanical properties and transmission rate.The results showed that the concentration of Nav101 nucleating agent was 0.05% to the optimum state,crystallinity and crystal density were the largest,and continued to increase the Nav101 concentration crystallization performance stabilized,Nav101 did not change the PLA's crystalline type.The DMA test shows that in the glass state area,E' and Tg of the PLA/Nav1010.05 are reach the maximum value,when the Nav101 content exceeds 0.05%,E' gradually decreases.In the entire visible area,the transmittance of PLA decreased markedly after adding a small amount of Nav101 nucleating agent.Continue to increase the Nav101 content,the average light transmittance of PLA decreased trend has slowed.Secondly,PLA/AT Nano-composites were prepared by solvent casting,and the effect of the concentration of nano-attapulgite clay(AT)on the crystallinity and transparency of PLA was investigated.The AT does not alter the PLA's crystalline form.For a solvent directly volatile film,AT will reduce the crystallinity of the PLA,when the AT is 3%,the degree of crystallization of the smallest reduction.However,to eliminate the heat history after the sample,at can improve the crystallization of the PLA.The DMA test found that a minimal AT(0.1%wt)reduces the PLA's energy storage modulus and the glass transition temperature,and the E' and Tg values of the PLA are the largest in the composites with 3% AT.The addition of AT has greatly reduced the transmittance of PLA,and the transmittance of PLA/AT-3 is almostreduced to zero.Thirdly,in order to improve the crystallization and transparency of PLA by nano-attapulgite,treatment of Nano-attapulgite by using N-dimethyl formamide with different concentrations of sorbitol as nucleating agents,and the effect of Nano Attapulgite adsorption different content of NX8000 K on the crystallinity and transparency of PLA was investigated.The XRD test showed that the crystalline structure of nano-attapulgite was not changed after the adsorption of sorbitol nucleating agent,but the crystal characteristic peaks of NX8000 K were not detected.The DSC test shows that AT-NX8000 K reduces the crystallization of the PLA composites with solvent casting film,and the effect of AT1-NX3 on the reduction of PLA crystallinity was minimal.For the composite material after eliminating thermal history,AT-NX8000 K instead improves the thermal crystallinity of PLA,indicating that the nano-attapulgite modified with sorbitol nucleating agent is beneficial to improve the effect of nano-attapulgite on the crystalline properties of PLA.In addition,the modified AT can improve the transparency of composites,and with the increase of the ratio of sorbitol nucleating agent transparency gradually increased,the abnormal phenomenon of PLA/AT1-NX3 is because its crystallinity is larger than the crystallization degree of PLA/AT1-NX1.Finally,the effect of CBT on the crystallization properties of PLA/PPZn Composites was studied.The study found that the Oligomer CBT can promote the crystallization performance of PLA/PPZn0.5,where CBT concentration is 0.4%,the best effect,crystallinity and crystallization rate are the greatest.POM discovers that CBT can promote the formation of the PLA ball crystal more perfect,at 150 ?isothermal crystallization,the CBT content of more than 0.4% of the composite material after the crystal density decreases.The DMA test shows that the amount of energy storage modulus and Tg increase with the CBT content,but abnormal in the CBT content of 0.8%.Adding CBT to the PLA/PPZn0.5 can increase the melt index of the substrate,but still lower than the pure PLA Melt Index,adding 0.6% CBT has reached the PLA/PPZn0.5 material melt liquidity optimum state.The study of Transmittance has found that adding a small amount of CBT(?0.4%)in PLA/PPZn0.5 can increase the transmittance and increase with the content of CBT;add a lot of CBT(?0.6%)when the transmittance of composites decreases with the increase of CBT content.