Development Of Polyether Block Amide Hollow Fiber Tube For Minimally Invasive Interventional Medical Device And Regulation Of Structures And Properties

Hollow fiber tube is a key component of the minimally invasive interventional medical devices.In order to go through in the complex blood vessels,it is highly necessary for hollow fiber tubes to possess sufficient axial and radial strength,suitable flexibility,certain rigidity and excellent torsion control performance,but also stable biocompatibility to meet the complex requirements of hollow fiber as a minimally invasive interventional medical devices,such as crossing,tracking,pressure and torsion control.Polyether block amide(PEBA)hollow fiber tube is widely used in micro-trauma interventional medical devices because of its wide range of hardness,excellent physical and mechanical properties and easy processing.However,there are some problems in PEBA,such as the poor biological stability of low-hardness materials.While it is also unclear that the relationship between the structure and the properties during the preparation of hollow fibers balloon.Moreover the insufficient strength,toughness and torsion control performance of hollow fibers tube also limited its further applications.These problems have been restricted the development and application of the polyether block amide hollow fiber in high-performance medical devices.In view of the above problems,this thesis has carried out in-depth research on the key scientific and technical problems in the preparation of polyether block amide hollow fiber tubes.The key technology of improving biocompatibility of low hardness polyether block amide hollow fiber tube by surface coating was established.The mechanism of improving the strength and toughness of the polyether block amide hollow fiber tubes by controlling condensed statethe and blending modification were systematically studied.The improvement of torsion control performance of polyether block amide braided reinforced composite hollow fiber tube wire surface coating modification was also established.The method lays a foundation for the industrialized production of polyether block amide for high-performance micro-traumatic interventional medical devices,and has theoretical significance and application value.1.Influencing factors of biological compatibility of polyether block amide.PEBA in the range of Shore hardness 25 D ~ 72 D were selected to prepare PEBA hollow fiber tubes by melt extrusion.The microstructures of hollow fiber tubes were analyzed by Fourier transform infrared spectroscopy(FT-IR),X-ray diffraction(XRD)and dynamic mechanical thermal analysis(DMA).It was found that with the increase of the Shore hardness,the content of the PA12 in the hard segment increased gradually,while the content of PTMO in the soft segment decreased gradually.Due to the good crystallinity of hard segment PA12 and the different polarity of hard and soft segment molecules,there are obvious micro-phase separation structures in PEBA hollow fiber tubes.It can be clearly observed by scanning electron microscopy(SEM)and atomic force microscopy(AFM)that the microphase separation of PEBA hollow fiber tube increases with the increase of the hardness.In addition,the wettability of PEBA hollow fiber tube was studied by contact angle.The cytotoxicity and hemolysis properties of the PEBA hollow fiber tubes were tested by MTT method.The results showed that the cell proliferation rate of the PEBA hollow fiber tubes increased with the increase of microphase separation and surface hydrophobicity.It can be inferred that the biocompatibility of polyether block amide is closely related to the degree of microphase separation and surface properties.However,PEBA hollow fiber tubes with low Shaw's hardness(25D-55D)showed poor cell proliferation rate and low biological safety in vitro.Therefore,it is necessary to biologically modify a low hardness polyether block acyl hollow fiber tubes.2.Study on the modification and the mechanism of surface biocompatibility of the low hardness polyether block amide hollow fiber tubeLow hardness PEBA hollow fiber tubes were prepared by single screw extruder taking Shaw's 35 D low hardness polyether block amide.Following that,PEBA hollow fiber tubes with lower hardness were coated with polydopamine(PDA)and poly-levodopa(L-PDOPA),respectively.Then the heparin was grafted onto the surface of coated PEBA hollow fiber tubes.T-IR results showed that polydopamine and poly-levodopa can adhere to the surface of PEBA hollow fiber tubes.When the concentration of the heparin is 3 mg/ml and levodopa is self-polymerized by 5 layers,heparin can be grafted onto the surface of the PEBA hollow fiber tube in a most efficient way.SEM and AFM results showed that dopamine could self-polymerized on the surface of PEBA hollow fiber tubes to form polydopamine,which increased the surface roughness of the hollow fiber tubes.However,the surface of the PEBA hollow fiber tubes became smooth again after being grafted with heparin.When the number of layers of levodopa reaches five layers,the surface of the PEBA hollow fiber tube is smooth and flat.When the concentration of heparin was 3 mg/mL,the thickness of heparin was uniform.Meanwhile,there was no agglomeration,and the roughness was slightly increased.The dynamic contact angle test results show that the contact angle of the PEBA hollow fiber tube decreased with the increase of the number of layers of poly-L-dopa.When the heparin concentration reached 3 mg/mL,the contact angle of the PEBA hollow fiber tube is minimized.Continued increase the concentration of heparin,the contact angle of PEBA hollow fiber tube will increase.With the increase of the heparin concentration,the cell growth rate of PEBA hollow fiber tube increased gradually,the hemolysis rate decreased gradually,the APTT gradually increased,the cell growth morphology gradually improved,and the cell density gradually increased,indicating that the dopamine self-polymerized grafted heparin coating was a suitable approach to improve the blood compatibility of the PEBA hollow fiber tubes.With the increase of the number of levodopa,the cell growth rate of PEBA hollow fiber tube increased gradually,the hemolysis rate decreased gradually,the APTT gradually increased,the cell growth morphology gradually improved,and the cell density gradually increased,indicating that the layer assembled levodopabide graftingheparin coating is a good way to improve the blood compatibility of PEBA hollow fiber tubes.3.Blowing-induced flow(BIF)regulates the condensed structure and properties of the polyether block amide hollow fiber tube balloonThe blowing-induced flow(BIF)was used to prepare PEBA hollow fiber balloon from the hollow fibers.The condensed structure and properties of the PEBA hollow fiber balloon were control by the conditions of BIF.According to the calculation formula of balloon blowing ratio,different sizes of PEBA hollow fiber tubes were designed using 72 D Shore hardness PEBA and prepared by single screw extrusion.Then balloons of equal thickness were prepared by blowing-induced flow(BIF).At the same inflation ratio,equal thickness balloons were prepared using different blowing temperatures.The effects of different blowing ratio and blowing temperatures on the crystallization,thermal and mechanical properties of the PEBA balloons were studied by DSC,XRD and DMA.It was found that as the blowing ratio and the blowing temperature increased,the regularityof the PEBA molecular chain increased under the action of the blowing flow field.Further more,the crystallinity and the melting of the balloon increased slightly.And the glass transition temperature of both the soft segment and the hard segment were also found to increase thus also the heat resistance of the balloon is improved.The effects of blowing ratio and blowing temperature on the mechanical properties of PEBA balloons were studied by means of tensile and blasting resistance.The results show that the tensile strength of the PEBA balloon and the bursting strength of the balloon increase with both the increase of the blowing ratio and the blowing temperature.However,the compliance of the balloon decreases as the blowing ratio and the blowing temperature increasing,demonstrating that the degree of tolerance of the balloon increases as the blowing ratio and the blowing temperature increasing.The microstructures of the PEBA balloon were observed by AFM and SEM.The results illustrated that with the increase of blowing ratio,more regular layered structure appeared inside the balloon.This may be due to the orderly increase of the crystals generated by the blowing process,which tends to be staggered and layered gradually.This structure might absorb more energy under the action of external force,thereby improving the tensile strength of the PEBA balloon and the bursting strength of the balloon.4.Study on structures and properties of thepolyether block amide hollow fiber tubes blended with TPUThe polyether block amide(PEBA)was toughened through blending with the thermoplastic polyurethane(TPU).The TPU/PEBA hollow fiber tubes were obtained by single-screw extrusion molding.FT-IR,XRD and DMA were used to study the effect of TPU with different contents on the structures of PEBA/TPU blend hollow fiber tubes.It was found that even addition of a small amount of TPU could form strong hydrogen bonds within the intermolecules of PEBA.When TPU content was 3%,the blend present higher crystallinity and more ordered crystalline structures.The addition of the TPU also increases the microphase separation of the PEBA/TPU hollow fiber tubes,and the degree of microphase separation becomes more severe as the content of TPU increases.The mechanical properties of PEBA/TPU blended hollow fiber tubes with different contents of TPU were studied by three-point bending,drawing and bursting pressure test system,repectively.The fracture morphology of PEBA / TPU blended hollow fiber tubes was analyzed by SEM and AFM in details.The results show that when the content of TPU is 3%,the elongation at break,the breaking strength,the flexural strength and the bursting strength of the PEBA/TPU hollow fiber tubes are optimized,which are increased by 12.4%,21.5%,19.05% and 25%,respectively.At this time,the cross sections of the hollow fiber tube show much rough surfaces with many small cracks,which is highly respective with to the features of the typical ductile fractures.Therefore,low content of TPU can be uniformly dispersed into the PEBA matrix,which results in hydrogen bonding between PEBA and TPU.The crystallization regularity of the blend was improved,and the toughness and strength of the hollow fiber tube were also improved.5.Study on the torsion control performance of the braiding reinforced hollow fiber composite tube with coated stainless steel wire and heat treatmentThermoplastic polyurethane coating modification of the stainless steel wire were carried out by immersion pulling process.The effects of the different pulling rates and the different emulsion viscosities on the thickness of the coating were studied systematically.The wetting properties of the surface coatedstainless steel wire were studied by contact angle test.The surface morphologies and the roughness of the stainless steel wire before and after the coating modification were characterized by SEM and AFM carefully.The mechanical properties of the stainless steel wirec braiding reinforced omposite hollow fiber tube were characterized by the methods of torque control,tensile strength,three-point bending,ILSS and impact strength,respectively.The results show that the coating thickness increases with the increase of the pulling rate.When the pulling rate reaches V=4.0 m/min,the coating thickness becomes maximum.After that,the coating thickness does not change substantially with thepulling rate increasing.At the same time,the coating thickness increases as the viscosity of the emulsion increases.By analyzing the contact angle of stainless steel wire before and after coating,it is foud that the contact angle of stainless steel wire after coating decreases dramatically.This shows that the wettability of the modified stainless steel wire is improved,which is conducive to the impregnation and interfacial bonding of the resin matrix.The test of the mechanical properties shows that the torsion control performance of the composite hollow fiber tube braiding reinforced by the coated stainless steel wire is significantly improved.The maximum forward torsion control can be increased by nearly 14.8%,while the reverse torsion control can be increased by nearly 41.4%.The shear strength of the composite hollow fiber tube is also significantly increased with braiding reinforced by the coated the stainless steel wire,which is increased by 28% compared with the composite hollow fiber tube braiding reinforced by the uncoated stainless steel wire.