Chitin Whisker Reiforced Poly(?-Caprolactone)Fibers Via Melt-spinning

Polycaprolactone(PCL)was developed in 1989 by the Daicell chemical company.PCL has a good application prospect in the field of biomedical materials due to its excellent biological properties like biocompati-bility,biodegradability and non-toxic properties.The strength and hardness of PCL can't reach the standard for cardiovascular stents and artificial bone plates.The poor mechanical properties of PCL limited its applications.Chitin also has some excellent biological properties like non-toxic,antibacterial,biocompatibility and biodegradability,and it can be made into fibers and membrane easily.Chitin was widely used in textile,printing,papermaking,bio-engineering,medicine,food,chemical industry and other fields.Chitin whisker(CW)can be prepared by hydrochloric acid towards hydrolysis under some conditions.CW has high modulus.The longitudinal modulus is up to 150GPa and radical modulus is up to 15GPa.CW can form a three-dimensional network structure as the reinforcing phase in matrix material,which can improve the mechanical properties of the material.This work takes advantage of chitin whisker,a kind of good reinforcement nanofiller with excellent biological properties as PCL,to enhance PCL with polyoxyethylene(PEO)as a compatibilizer,compares the microstructure and mechanical properties between CW/PCL system and CW/PEO/PCL system,and chooses the better system to study the rheological properties.Based on that,the CW/PCL blend fibers are prepared by melt-spinning.Mek-spinning is an environment-friendly method compared with wet-spinning and electrospinning.The strength and hardness of PCL is improved and biocompatibility,biodegradability and non-toxic properties retained.At last,the vascular stent has been made by the blend fibers,and the compression property increase by 75%compared to that made by PCL fibers.The main results are as follows:(1)The obtained rodlike nanocrystals have a size of 25-50nm in width and 200-600nm in length,The research shows that CWs are uniformly dispersed in the PCL matrix in CW/PCL system.In the CW/PEO/PCL system,CWs are wrapped in a small "ball",and the "balls" are distributed in the matrix of PCL.The mechanical properties of CW/PCL composites are better than that of CW/PEQ/PCL composites.In CW/PCL system,when the CWs loading is 6%,the mechanical properties are the best The yield strength reaches 26MPa,and the elastic modulus reaches 474MPa.The CWs loading decreases the crystallmity and thermal stability of nanocomposrtes.(2)The melt index of CW/PCL system declines with the increase of CWs at 180 ?.Steady rheological tests show that with the increase of the temperature,the viscosity declines.The increasing temperature and increasing shear rate take the same effects on flow.With the increase of the CWs,the viscosity rises.As the shear rate increases,the flow activation energy declines.Frequency sweep rheological tests show the G' and G" rise with the increase of frequency,and the melts mainfy present viscous response.In the low frequency region,CWs forms three-dimensional network structure.As the frequency increases,the three-dimensional network structure is destroyed.(3)When the spinning temperature at 180?,winging speed at 18.5m/min,the mechanical properties of CW/PCL blend fibers are the best When the CWs loading is 6%,the breaking strength of fibers reaches 2.63cN/dtex(70.7%higher than the PCL fiber),and the elastic modulus reaches 9.24cN/dtex(1.04 times higher than the PCL fiber).The compressive mechanical property of vascular stents made by CW/PCL is 1.75 times higher than that made by PCL.