Research On Shape Memory Materials Based On Crystalline Polymers And Their Performance

Crystalline polymers are a class of polymer materials characterized by a highly ordered arrangement of polymer chains in a crystalline lattice structure.The presence of crystallinity in these materials contributes to their exceptional properties,including high mechanical strength,stiffness,and thermal stability.Crystalline polymers also exhibit shape memory behavior,where they can undergo significant reversible deformation under specific conditions.The study of crystalline polymers involves investigating their crystallization kinetics,crystalline structure,and the relationship between structure and properties.This research provides a foundation for the development of advanced materials with tailored properties for various applications.In various shape memory materials constructed from crystalline polymers,functional fillers have become a primary approach for preparing high-performance polymer shape memory materials with specific responsiveness,due to their low cost and excellent mechanical properties.However,the responsiveness of such shape memory materials is largely constrained by the content of functional fillers and the crystalline polymer structure in the composite materials.On one hand,polymer composites with a high content of functional fillers can better absorb external energy and facilitate energy conversion,thereby exhibiting improved responsiveness.However,the high loading of functional fillers in the polymer matrix often leads to aggregation,resulting in decreased mechanical performance,non-uniform deformation under external stimuli,and insufficient mechanical properties.In this paper,the preparation methods and properties of various shape memory polymer were studied.The effects of solid fillers on shape memory recovery rate,recovery time and cycle stability were analyzed.(1)First,we prepared and studied PVA-Py/CNTs fast photo-responsive composites.By using polyvinyl alcohol(PVA)modified with pyrene group as the matrix and adding carbon nanotubes as the photo-thernal conversion agent,the high proportion of carbon nanotubes in the polymer matrix was well dispersed with π-π due to the stacking effect between pyrene and carbon nanotubes.At the same time,π-π stacking establishes stable cross connection and fonns shape memory effect.Therefore,the high-quality part of carbon nanotubes is used to endow the material with rapid photothennal response.Dynamic π-π stacking is used to realize self-healing of polymer networks.(2)After that,we use 3D printing direct ink printing technology to manufacture smart deformable composites.Shape memory polymer with high solid content was studied to prepare ε-caprolactone-butyl polyacrylate(PCL-PBA)composite.The effects of solid fillers on the shape memory recovery,recovery time and cycle stability of PCL-PBA samples were analyzed.The results show that the recovery time of the shape memory polymer with high solid content is 18s under the optimum printing parameters,which shows good shape memory cycle performance.In addition,PCL-PBA composite also has excellent mechanical properties,and the ultimate tensile strain can reach 1.4.(3)Then the two crystalline polymers PTHF and PEG are crosslinked by isocyanate and mixed into the existing resin materials to obtain the bidirectional shape memory materials.By using the different crystallization and melting temperatures,and through the pre-designed deformation and crystallization of the materials,it can show the true bidirectional shape memory effect.First,the initial sample is deformed at high temperature Treset(Treset>Tm,PEG)by applying a certain external force,and then cooled to low temperature Tfix(Tfix<Tm,PTHF)for fixation.After the external force is removed,the shape A can be obtained.Then,the sample is heated to a certain temperature Ti(Tm,PTHF<T1<Tm,PEG).At this time,the sample becomes shape B.When the cooling and heating process is repeated between T1 and Tfix,The sample can undergo multiple reversible transformations between shape A and shape B.(4)Finally,we explored the modification of hydroxyl-terminated polybutadiene(HTPB)to prepare shape memory polymer actuators,and explored the preparation method of adding high solid content.