Preparation And Properties Of Silk/PLA And PCL Composites

Most of the existing composite materials are not easy to recycle after the service life is reached,can not be naturally degraded,and cause environmental pollution.The problem of natural resource protection,recycling and reuse has aroused new interest in natural fiber reinforced composite materials.Biodegradable fibers are commonly used as reinforcements,and biodegradable polymers are used as the matrix.Silk is a natural protein fiber that is softer than other natural fibers.It not only has good elongation at break and good breaking strength and modulus,but also has good biocompatibility and biodegradability.Polylactic acid(PLA)is a material with good thermoplasticity and biodegradability,but PLA is poorly heat-stable,brittle and tough.For this reason,PLA has been blended and modified with polycaprolactone(PCL).Therefore,the use of silk as a reinforcement and PCL modified PLA as a matrix to prepare silk reinforced composite materials provides a theoretical and experimental basis for the production and application of silk reinforced composite materials.After fully understanding the silk,PLA and PCL,silk was used as the reinforcement,and PLA was used as the resin matrix to prepare the composite.The silk/PLA composite yarn is prepared by wrapping the silk yarn with the PLA filament.And the composite yarn is used to weave plain,four-layer orthogonal,five-layer orthogonal,five-layer angular interlock,five-layer orthogonal/quasi-orthogonal,five-layer orthogonal/angle interlock,and six-layer orthogonal structure fabric.The degumming treatment was carried out,and the woven fabric after degumming was used as a reinforcing body,and the PLA mixed substrate treated with PCL was modified,and the silk/PLA and PCL composite materials were prepared by laminating hot pressing.In this paper,the preparation of PCL modified PLA resin matrix,the preparation of composite yarn and the proportion of silk content are optimized for the preparation process of silk/PLA and PCL composites.It provides certain theoretical and experimental basis for the preparation of silk/PLA and PCL composites.For the prepared composite materials,the MTS universal testing machine and the NI series pendulum impact testing machine were used to test the mechanical properties and characterize other related properties.The composite materials were prepared by weaving six.kinds of three-dimensional woven fabrics,and the effects of three-dimensional structural fabrics on the mechanical properties of silk/PLA and PCL composites were studied.The main research contents and conclusions are as follows:(1)In order to prepare the best performance PCL/PLA blend matrix,and provide the basis for the preparation of later composite materials,The PCL/PLA blend matrix with different PCL content was prepared in this paper.The mechanical properties of the PCL/PLA blend matrix system were tested and characterized by SEM,FTIR,TG and DSC.To study the effect of PCL content on the performance of PCL/PLA blend matrix system.The research shows that when the PCL content is 5%,the tensile strength,elongation at break,and impact strength of the blended matrix system reach the maximum values of 20.26 MPa,1.68%,and 18.89 KJ/m2,respectively,Increased by 43.88%,34.4%,54.23%respectively;FTIR analysis shows that the two are physically mixed;TG test shows that the thermal decomposition temperature of the blended matrix when the PCL content is 5%reaches 329.769?;DSC test results The addition of surface PCL can improve the crystallization properties of PLA.(2)In order to facilitate the weaving of the woven fabric and improve the strength of the woven fabric,the silk/PLA composite thread is prepared by wrapping the silk with the PLA filament through a wrapping device.The structure and properties of silk and PLA filaments were studied.The basic properties such as appearance,structure,linear density,tensile strength and friction characteristics of the raw materials before wrapping and the composite wires after wrapping were observed and tested.The research shows that when the outer yarn is PLA filament of 15.8 tex,the minimum surface friction coefficient of the composite yam is 0.84,and the tensile strength is 23.37 cN/dtex.The silk is relatively straight in the composite yarn,and the yarn quality is good,which is convenient for weaving the fabric(3)In order to prepare the reinforcement of the composite material,the plain weave fabric was woven,and the semi-automatic weaving prototype was modified,the three-dimensional woven fabric was woven,and the basic parameters of the fabric and the tensile strength of the fabric were tested.The research shows that the breaking strength of the angle interlocking structure fabric is the lowest;the tensile breaking strength of the three-dimensional fabric with the same orthogonal structure increases with the increase of the number of fabric layers;The fracture strength of the orthogonal structure is the highest among the five layers of four different structures:five-layer orthogonal structure,five-layer angular interlocking structure,five-layer orthogonal/quasi-orthogonal structure,and five-layer orthogonal angle interlocking structure.(4)The effects of silk content on the mechanical properties of silk/PLA and PCL composites were studied.The mechanical properties were tested and characterized by FTIR,SEM and TG.The research shows that when the silk content is 16%,the tensile strength and impact strength of the prepared silk/PLA,PCL composite materials reach the maximum,which are 23.127 MPa and 18.01 8 KJ/m2,respectively;after degumming treatment,the silk and PLA/PCL mixed matrix are more closely combined;The thermal decomposition temperature of silk/PLA and PCL composites is 311.0?,which is between silk and PLA/PCL blends.(5)Study the effect of three-dimensional structure fabric on the mechanical properties of silk/PLA and PCL composites.The research shows that the mechanical properties of the three-dimensional woven fabric reinforced composites are closely related to the fabric structure.The tensile strength of the composites is related to the straightening state of the warp yarns.The orthogonal structure of the fabrics is good,so the orthogonal structural composites the tensile strength is better,and the tensile strength of the corner interlocking composite is the lowest;The impact strength of the composite material is related to the structure of the material thickness direction.The results show that the orthogonal/quasi-orthogonal structure and the orthogonal/angle interlocking structure reinforced composites have better impact resistance.The orthogonal structure composites have poor impact resistance.