Study On Preparation And Properties Of Rare Earth Cerium Modified Polylactic Acid Functional Film

Polylactic acid（PLA）is one of the most promising biomaterials to replace polymers derived from petrochemicals due to its full biodegradability.PLA has been applied extensively over the years in medical treatment,food packaging,tableware,water cups,buffer packaging of electronic products,and other areas,which successfully effectively reduce"white pollution".Despite being one of the most popular degradable plastics,PLA has some drawbacks,including a slow crystallization rate,singular functionality,a lack of toughness,etc.,that make it difficult to replace petroleum-based non-degradable plastics or broaden applications.This study focuses on improving the crystallinity of PLA and considers of improving PLA’s poor UV resistance,weak antibacterial performance,and high brittleness.Based on the different functional characteristics of rare earth cerium,this study uses diverse compounds of rare earth cerium and polyethylene glycol（PEG）as multifunctional additives to modify PLA.Four functional films of rare earth cerium modified PLA were prepared and their comprehensive properties were analyzed.The following are the main research contents and conclusions:（1）Study on preparation and properties of modified functional PLA film with high crystalline and heat-resisting.In response to the low crystallization rate of PLA,this study uses rare earth Ce F₃ for PLA modification.The results show that Ce F₃ can be used as a transparent crystallization nucleating agent for PLA,and it can synchronously improve mechanical properties and thermal stability.When the addition amount of Ce F₃ in PLA is 1%,the visible light transmittance retention of the modified film is 82.36%,and the crystallinity,tensile strength,and elongation at break are increased by 58.14%,8.77%,and 23.24%compared to pure PLA,respectively.（2）Study on preparation and properties of modified functional PLA film with high crystalline and UV resistance.The above basic exploration has been done on the crystallization performance of Ce F₃ modified PLA,proving that rare earth Ce can significantly promote PLA crystallization.However,PLA not only has a demand for high crystallization,but its single functionality also limits its expansion of application range.This study considers the dual need of PLA for high crystallinity and UV resistance.Ce O₂ was used to modify the crystallization performance and UV resistance of PLA simultaneously.The results show that Ce O₂ can be used as a nucleating agent and ultraviolet absorber for PLA.When the amount of Ce O₂ added to PLA was 2%,the average UVA transmittance of the modified film decreased by99.33%,and the crystallinity,tensile strength,and elongation at break increased by20.59%,10.06%,and 199.3%,respectively,compared to pure PLA.（3）Study on preparation and properties of modified functional PLA film with with high crystalline and antibacterial.Above research has modified the crystallization performance and UV resistance of PLA simultaneously.In addition,there is a clear demand for the antibacterial function of PLA in practical use.Based on the above research foundation,this study is intended to further improve the crystallization performance of PLA while also improving its antibacterial performance.A new environmentally friendly rare earth cerium lactate complex（Ce-LA）was synthesized by lactic acid（LA）and rare earth Ce.That used to modify PLA.The results show that Ce-LA can be used as a nucleating agent and antibacterial agent for PLA.Ce-LA not only significantly improves the crystallization performance of PLA,but also synchronously enhances its antibacterial performance.When the addition of Ce LA in PLA was 1.8%,the crystallinity of the modified film reached 37.99%,71.75%higher than that of pure PLA.In addition,antibacterial rates against Staphylococcus aureus and Escherichia coli reached 93%and 85%respectively.（4）Study on preparation and properties of modified functional PLA film with high crystallinity and good toughness.Above research has modified the crystallization performance and antibacterial of PLA simultaneously.However,the modified film still has the defect of brittleness.To address the problem,this study using PEG and Ce-LA to toughen and crystallinity modification of PLA.The results show that PEG can effectively modify the toughness and crystallinity of PLA in collaboration with Ce-LA.The addition amount of Ce-LA is fixed at 1.8%.With the increase of PEG addition,the fracture elongation of the film gradually increases,and the tensile strength slightly decreases,achieving the expected toughening effect.When the PEG addition amount is 15%,the comprehensive performance of the modified film is the best,with its elongation at break and crystallinity increased by 1645%and 177%,respectively,compared to pure PLA.