Preparation And Properties Of Polycaprolactone/polyurethane-based Shape Memory Composites

Shape memory polymer is a new type of intelligent materials that can deform and deformation can be controlled under the external stimulation.Low temperature thermoplastic is a typical shape memory material as a new medical polymer material applied in the field of rehabilitation medical devices,mainly used in the production of rehabilitation orthotics and orthopedic devices,relative to the traditional plaster material,has the advantages of good permeability,convenient production,light quality and so on.At present,low-temperature thermoplastic mainly suffers from the lack of mechanical strength of the material and has a large mass and poor fit,which cannot be used in environments with high stresses such as those of the lower limbs and spine.Therefore,in this paper,polycaprolactone/polyurethane(PCL/TPU)with good mechanical properties and biocompatibility was used as the matrix to prepare shape memory composites low-temperature thermoplastic plates by two strategies of constructing organic-inorganic hybrid structures and adding rigid inorganic fillers to improve the mechanical strength of the materials.1.The organic-inorganic structure was constructed by polyhedral oligomeric silsesquioxane(POSS)to obtain nanofillers with good compatibility with the substrate and improve the mechanical strength of the material.Epoxy group was introduced on POSS by epoxidation reaction by using vinyl-POSS as raw materials.PCL/TPU/POSS nanocomposites were prepared by melt blending of epoxy-vinyl-POSS,PCL and TPU as raw materials.The mechanical and thermal properties of the materials were tested by the universal testing machine,differential scanning calorimeter and thermogravimetric analyzer.The thermotropic shape memory properties of the materials was investigated by a high temperature universal testing machine.The results showed that the mechanical properties,thermal stability and shape memory properties of the materials are improved with increasing POSS content.When the POSS content was 3 wt%,the comprehensive performance of the materials was greatly improved,the modulus of the materials was increased by 40%,and the shape recovery ratio of the materials was increased by 6%.2.PCL/TPU/PHGM photo-thermal dual-response shape memory composites were prepared by adding polydopamine modified glass microsphere(PHGM).The surface of HGM was modified by a layer of polydopamine via dopamine oxidation self-polymerization.The chemical structure and surface morphology of the glass microsphere before and after modification were characterized by using FT-IR,XPS,SEM and TEM.The results showed that the surface of the glass microsphere was successfully coated with a polydopamine layer.The polydopamine modified glass microsphere(PHGM)were then melt-blended with PCL and TPU to produce a PCL/TPU/PHGM light and thermal dual-response shape memory composites.The thermal and mechanical properties of the PCL/TPU/PHGM materials were tested using a universal testing machine,and the thermotropic shape memory properties of PCL/TPU/PHGM composites was tested by high temperature universal testing machine.The results showed that the addition of PHGM improved the mechanical properties and thermal stability of the materials and maintained the good shape memory properties of the material.The composites also has excellent photoluminescent shape memory properties,and the composites can recover to the initial shape of the materials within 7 s under the irradiation of 900m W/cm~2 near infrared light at the PHGM content of 5%.