Study On Polylactic Acid Based Shape Memory Polymer And 4D Printing

With the rapid development of science and technology,more and more new materials draw people's attention.Among various kinds of materials,smart material as a new type material which owns unique properties,is becoming more and more popular.Among them,shape memory polymers?SMPs?is a typical candidate and have outstanding shape memory effect,which is widely used in biomedical,machinery manufacturing,aerospace,civil engineering,and other important fields.Polylactic acid?PLA?with excellent biocompatibility,biodegradablity,and mechanical performance indicates widespread use in the biomedical field.However,its glass transition temperature is too high for human body to realize thermal drived shape memory effect.This article focuses on decreasing the transition temperature of SMPs by modifying to adapt the human body.The traditional method of actuating SMPs,direct heat,limits the practical applications in human body.There for,this article also study remotely actuation to achieve controllable shape recovery process.Thermo-gravimetric analysis?TGA?,differential scanning calorimetry test?DSC?,dynamic thermal mechanical properties test?DMA?,fourier infrared spectrum?FTIR?and shape memory performance test were carried out on the material thermal properties,thermal and mechanical properties,shape memory performance analysis and the possibility of magnetic drive and 4D print performance.We used polylactic acid as raw material,and prepared shape memory Polylactic acid material,which underwent four steps,physical mixing,injection molding,curing and demoulding.And its structural parts were successfully prepared by blending extrusion and 4D printing method.The results showed its their thermal decomposition temperature was about 310? which indicated a good thermostability.The crystallization ability was weak,Tg was 66.9?,and the cold crystallization temperature was 110.5 ?.The mechanical properties were good,and the modulus of elasticity of the material was up to 2.75 GPa at low temperature.The polylactic acid material showed a good shape memory performance,the shape fixity was 99.1%,and the shape recovery was 99.4%.Moreover,the printing process had no influence on the shape memory property of the material,so it could realize the 4D printing of the material.The modified polylactic acid?PLA?shape memory polymers were prepared by the physical blending method.Polybutylene succinate?PBS?,polycaprolactone?PCL?,polybutylene succinate?PBS?and polyethylene glycol?PEG?are selected as the modified material.The results showed that,the modified materials has excellent thermal performances.The initial thermal decomposition temperature?TD?was higher than 300? which showed a good thermostability.At the same time,the material has good mechanical properties,in spite of low temperature.The elastic modulus was up to 2.48 GPa,and could also reach more than 100 Mpa in the middle of glass transition.By adding different modified materials,the glass transition temperature of poly?lactic acid??PLA?decreased significantly.The biggest drop of temperature was 15.6?.The shape fixity was 96%.The shape recovery speed is fast,and the shape recovery was 98%,and it could be used for 4D printing.At last,we prepared the multifunctional composite material printing line with the addition of nano iron oxide?Fe₃O₄?.The hybrid particles conferred the magnetic properties of the polylactic acid materials.PLA/Fe₃O₄ realized the remotely driving behavior under the driving of alternating magnetic field,and the magnetic field was 32 KHz.After recovering by magnetic drive,the material's recovery performance was almost the same as that by direct heat.At the same time,the thermal properties and the shape reply performance were very good.The storage modulus increased 1Gpa than that of the undoped material improving the mechanical properties.The materials realized not only 4D printing eventually,but also a functional drive.