Study On Structural Properties Of PLA/PCL Thermally-activated Shape Memory Composites Prepared Via Volume Elongational Deformation

Polylactic acid(PLA)/Poly(?-caprolactone)(PCL)thermally-activated shape memory composites can not only spontaneously recover their initial shape under the control of temperature,but also have good biocompatibility and complete biodegradability,so they are widely used in the field of in vivo therapeutic and drug release.During the preparation of PLA/PCL shape memory composites,the dispersion uniformity and compatibility of the two phases directly affect the shape memory performance of the composites.Compared with adding chemical compatibilizer or reaction processing,using special physical processing method to improve the compatibility of shape memory composites and realize its comprehensive performance improvement can better maintain its biological compatibility.The eccentric rotor mixer based on elongational flow field was developed for the first time.By setting two straight sections and a special spiral section on the eccentric mixer rotor,the meshing relationship between the rotor and the internal cavity of the mixer stator during the rotation and revolution is realized.The material is subjected to the cyclic volume elongational deformation in the eccentric rotor mixer,and the strength and action time of the volume elongational force field are controllable.Firstly,the mixing characteristics of the eccentric rotor mixer were studied,and then the effects of processing flow field type,processing temperature,processing speed and mixing time on the structure and properties of PLA/PCL composites were studied.The results show that the interface between the two phases of the PLA/PCL composites prepared by the eccentric rotor mixer is fuzzier and the compatibility of the two phases is better than that of the shear flow field processing equipment.With the increase of processing temperature,processing speed and mixing time,the mixing effect of eccentric rotor mixer gradually increases and then slightly decreases.When the processing temperature is 200 ?,the processing speed is 45 rpm,and the mixing time is 10 min,the elongation at break and impact strength of composites increased by 45 and 2.9 times compared with pure PLA respectively.Based on the optimal process parameters of eccentric rotor mixer,thermally-activated shape memory composites were prepared.Without adding any compatibilizer,the interface between the two phases in composite is blurred,the compatibility is obviously better,and the degree of bending shape fixation and bending shape recovery exceed 95%.With the increase of PLA content,the degree of shape fixation of composites decreases,while the degree of shape recovery increases.After five times of “bending-recovery” shape memory program,the degree of bending shape fixation and shape recovery of the composite are still above 90%.The research show that the eccentric rotor mixer based on volume elongational deformation can effectively improve the compatibility of the multiphase and multicomponent system.Moreover,eccentric rotor mixer can improve the comprehensive performance of the biocompatible shape memory composite system on the premise of ensuring cleaner production.The research results can guide the development of volume elongational deformation dominate polymer processing equipment,and promote the application of environment-friendly PLA/PCL thermally-activated shape memory composites.