Research On The Influence Of 3D Printing Process Parameters On The Shape Memory Properties Of Polyurethane And Polylactic Acid Materials

4D printing is a 3D printed object that can produce geometric shapes or changes in physical and chemical properties.This kind of change occurs under certain external stimuli,including heating,lighting or applying electromagnetic effects,etc.,and the way of change can be pre-designed and programmable.Shape memory polymers are commonly used 4D printing materials.The printed parts can be given a temporary shape,deformed under heating or light,and restored to a permanent shape.The deformation characteristics of 4D printing shape memory polymers,including shape fixation rate,shape recovery rate,deformation speed,and deformation trigger temperature,are related to the thermodynamic processes experienced during processing.In the printing process,the effects of heat and force experienced by the material are related to process conditions and parameters such as printing temperature,cooling temperature,and printing speed.Studying the influence of printing process conditions and parameters on shape memory polymers,revealing the process-performance relationship,can optimize process parameters and obtain required material properties,including material mechanical properties and shape memory properties.However,the current 4D printing of shape memory polymers only uses 3D printing to form permanent shapes,and there are few studies on using printing process parameters to adjust the properties of materials,and the advantages of 3D printing processes to control the properties of materials are not used.4D printing can be used to develop drivers and replace traditional smart components.It has high reliability and self-driving capabilities.It has huge application potential and potential value in aerospace,biomedical,flexible robots,etc.,and can be applied to In many fields,it has very broad application prospects.The difficulty and core of 4D printing that need to be broken through is how to control 4D changes,and give the change method to the printing process,so that the material can produce the response behavior we set,so that it can produce more deformation functions,and expand 4D.The design space of the print can be applied.Polyurethane and polylactic acid are the most commonly used4 D printing shape memory materials,and their deformation characteristics are affected by the printing process conditions.However,there are few researches on the effects of printing conditions and process parameters on its performance at present.In this paper,the following researches are carried out to address these issues:1)A new type of 4D printing device with adjustable parameters has been developed.Printing parameters such as printing temperature,substrate temperature,printing speed and material conveying speed can be adjusted in order to study the influence of process conditions on printing materials.In addition,changing the way of extruding materials from gear propulsion to pneumatic extrusion,replacing the previous filamentary materials with granular materials,reduces the impact of thermal history on material properties during processing,and expands the range of printable materials.2)The polylactic acid(PLA)and polyurethane(PU)materials were tested,characterized and analyzed,including differential scanning calorimetry,dynamic thermomechanical and rheological analysis,and the melting temperature,glass transition temperature,and The rheology and thermomechanical properties provide a basis for the selection of the printing test and shape memory test parameters.3)The effects of printing process parameters(printing temperature,printing speed,extrusion speed,substrate temperature,etc.)on the deformation performance and mechanical properties of 4D printed samples are studied.Firstly,a method for measuring the recovery rate and recovery time of shape memory polymers is established.Then,the shape memory recovery rate and recovery speed of 4D samples with different printing process parameters were quantitatively tested and analyzed,and the influence of process parameters on the shape change of 4D printing shape memory polymer was analyzed.The effect of heat treatment process conditions on the shape memory performance and mechanical properties of the material is explored.Finally,according to the law of change,a variety of actuators with multi-stage 4D deformation were designed and printed,which verified the feasibility of using process parameters for 4D printing deformation control.