Preparation And Properties Study Of Antibacterial Catheter By Gas-assisted Extrusion

Plastic catheters have become indispensable disposable medical supplies in the diagnostic and therapeutic process.The issue of infections associated with catheter use remains a significant challenge in interventional treatments.Constructing surface functional coatings to endow antimicrobial properties is one of the most effective methods to solve this problem.However,the existing processes for preparing antimicrobial catheters are plagued by complex procedures and poor adhesion of coating.Aiming to shorten the antimicrobial plastic catheter processing time and avoid secondary pollution,this study adopts the gas-assisted extrusion technology.By introducing an auxiliary gas containing antimicrobial particles into the die,a stable gas cushion layer is formed on the melt surface,enabling the simultaneous extrusion of the plastic catheter and the preparation of the surface antimicrobial coating.In order to verify the feasibility of the gas-assisted extrusion process for preparing antimicrobial catheters,and explore the relationship between process parameters,the stability of the gas cushion layer,catheter dimensions,and antimicrobial performance,the following works were carried out in this paper:(1)Mechanism study on the influence of process parameters on catheter crosssection deformationBased on rheology,multiphase flow theory,and computational fluid dynamics theory,a numerical model was established considering the coupling effect between the inner and outer layers of auxiliary gas and melt.The finite element numerical analysis method was used to study the distribution of melt pressure field,velocity field,and stress field under different gas cushion layer pressure differences,and to analyze the effect of the pressure differences between the inner and outer gas cushion layers on the dimensions of the antimicrobial catheter.This provides a reference for setting reasonable process parameters for the gas-assisted extrusion of antimicrobial catheters.The researches indicate that the drag effect produced by the gas cushion layer on the melt causes the axial velocity of the melt to gradually increase along the axis,leading to a significant difference in the first normal stress and a radial velocity difference towards the interior of the melt at the entrance of the gas cushion layer.These factors lead to shrinkage in the wall thickness dimensions and cross-sectional deformation of the plastic catheter.In addition,when the pressure of the outer gas cushion layer is slightly less than that of the inner gas cushion layer,the radial velocity difference on the melt surface significantly decreases,which contribute to reduce the cross-sectional deformation of the catheter.(2)Impact of die gas chamber structure on flow field distribution and gas cushion layer stabilityFocusing on the formation of a stable gas cushion layer and the continuous extrusion of antimicrobial catheters during the gas-assisted extrusion process,the study intensively explores the flow field distribution at the annular gap gas outlets of the gasassisted die.Numerical models of various gas intake methods and chamber structures were established,and the flow field and velocity uniformity distribution at the annular gas outlets of the die were analyzed.To reduce the deformation rate of the catheter,the chamber structure of the extrusion die was optimized.Numerical results indicate that using a dual gas chamber structure results in a lower velocity non-uniformity coefficient at the die outlets compared to a single gas chamber die,which contributes to forming a stable gas cushion layer,thereby improving the wall thickness uniformity of the catheter.(3)Establishment of gas-assisted extrusion experimental platform for antimicrobial cathetersAccording to the theories of pneumatic dispersion and mechanical conveying,a dispersion device for transporting antimicrobial particles suitable for the gas-assisted extrusion process and a dual-chamber gas-assisted die were developed.Integrated with gas-assisted systems and single-screw extruders,an experimental platform for gasassisted extrusion of antimicrobial catheters has been established,providing the equipment foundation for preparation of antimicrobial catheters.The impact regularities of dispersion nozzle size structural parameters and process parameters on the dispersion effectiveness of aggregates was analyzed,and the equipment has been optimized based on orthogonal simulation experiments.The results show that the dispersion effectiveness of agglomerates initially increases and then decreases with the increase in the throat length and diameter of the nozzle,and improves with increasing nozzle inlet pressure.(4)Experimental study on the gas-assisted extrusion molding and antimicrobial performance testing of antimicrobial cathetersIn the gas-assisted extrusion experiments of plastic catheters,the effect of technological parameters on the gas-assisted extrusion process and the size deformation of antibacterial catheter was studied.The results show that the outer diameter of the extruded catheters decreases with increasing pressure of the external gas cushion layer.The glossiness and transparency of the melt increase with the increase of temperature,and appropriately increasing the melt temperature contributes to forming a stable gas cushion layer.Various specifications of antimicrobial catheters were prepared,and their surface morphology was observed using scanning electron microscopy and photoemission spectrometer to confirm the feasibility of the gas-assisted extrusion process for embedding antimicrobial particles.Appearance tests and antimicrobial experiments on the catheters indicate that increasing nozzle inlet pressure results in smaller antimicrobial particle size on the catheter surface.Moreover,the density of antimicrobial particles on the catheter surface and antimicrobial effectiveness are positively correlated with the screw rotation speed,and the antibacterial coating has good stability.