Modifications Of Poly(?-caprolactone)-Based Materials Towards Green Polymeric Blends And Composites

With the continuous deepening of the social process,people are more and more aware of the importance of the concept of sustainable development,and biodegradable polymers are popular among more researchers.Poly(?-caprolactone)(PCL)has been widely used in people's production and life because of its good biocompatibility,rheological properties,and solubility.However,PCL's slow degradation rate,poor wettability,and mechanical properties,low cell adhesion,and other disadvantages greatly limit its broader application prospects in the preparation of green materials.Therefore,researchers have proposed two methods for preparing green materials based on poly(?-caprolactone):nanoparticle composite and polymer blending modification.It is a good consideration to select cellulose nanofibers(CNF)with abundant natural reserves and high strength and modulus to enhance the PCL.Based on the fact that CNF is easy to agglomerate in the PCL matrix,the surface of CNF is modified with a silane coupling agent to enhance the interfacial bonding of the materials and achieve a better reinforcement effect.Some scholars have set their sights on poly(lactic acid)(PLA).PLA is a biodegradable polymer with high strength,which can improve the mechanical properties of materials without destroying the biodegradability of PCL.In this paper,PLA was selected to modify PCL by blending,and PCL/PLA blends were modified by two different treatment methods to achieve better reinforcement effect by improving the compatibility between PLA and PCL and enhancing the interface connection strength.One way is using glycidyl methacrylate(GMA)to graft with the end groups of PLA and PCL molecular chain respectively under the action of initiator,and then blend the graft products with PCL/PLA blends.The other way is to directly carry out reactive extrusion of PCL and PLA,and then melt blend with the PCL/PLA blend.This paper is mainly based on the blending and compound modification of poly(?-caprolactone)to prepare green materials,and the performance testing and analysis of these green materials.The main research contents are as follows:(1)The PCL/CNF composites were prepared by melt processing.The dispersion of CNF in the PCL matrix could be obtained by SEM cross-sectional observation.Silane coupling agents with different polarities were used to modify CNF.The rheological properties,thermal properties,and mechanical properties of the PCL/CNF nanocomposites were tested.The results showed that CNF modified by different surface treatments enhanced the affinity and interface binding of CNF and PCL matrix,and achieved a good enhancement effect on the PCL matrix.Among them,n-octyltriethoxysilane(OTES)coupling modified CNF had the best dispersion effect in the PCL matrix,and promoted the crystallization of PCL,which had the best reinforcement effect.(2)The PCL/PLA blended material was prepared by the melting.From the SEM,it was observed that PLA existed in the form of spherical droplets in the PCL matrix.Combined with the interfacial tension test results,it was found that the PCL/PLA blended material was two phases incompatible system.Compared with pure PLA and PCL,PCL/PLA blends showed different rheological responses,and the blends had higher storage modulus in the low-frequency region.The addition of PLA significantly increased the strength and modulus of PCL,but decreased the plasticity.With the addition of PCL-g-GMA(GPCL)and PLA-g-GMA(GPLA),the size of the dispersed phase(PLA)decreased,and the strength of the material was further improved.Among them,GPLA had a better enhancement effect.(3)The reactive extrusion of PCL and PLA(Blend)was prepared by melting,and then Blend was added to PCL/PLA blends.Through the observation of the surface morphology of the blends and the characterization of the thermal properties,rheological properties,and mechanical properties,it was found that Bend with different content reduced the size of the dispersed phase.Among them,10 phr Blend contributed the most to the particle size of the dispersed phase(PLA).The results of the mechanical tensile test also showed that the addition of Blend increased the yield strength of the blended material,and the blend with 10 phr Blend had the highest strength and modulus.Compared with the PCL/PLA blend material,the interfacial tension measured by the fiber retraction of the PCL/PLA/Blend ternary Blend material had a lower value,indicating that the reactive extruder had a thermodynamic capacity increasing effect.