Preparation And Performance Of Semi-soluble Knitted Spacer Structure Hemostatic Dressing

The skin is the body’s defense layer,it is extremely vulnerable to damage.For better wound healing,spacer fabrics have received much attention because of their excellent comfort and mechanical properties.Yarn modification or structural changes can make the dressing hemostatic and biocompatible,and the spacer fabric one-piece process also shortens the dressing preparation process,so weft-knitted spacer structural dressings show great potential in wound healing and mass production.This paper describes the preparation process and properties of carboxymethyl cellulose fiber,viscose filament/PTFE braided yarn,Coolmax/nylon monofilament wrapped yarn and weft-knitted spacer structural dressing.Firstly,this thesis investigated the carboxymethylation process of viscose filaments using the one-factor variable method.The experimental results showed that when the pre-alkalization parameter Na OH concentration was 30%,together with a shorter alkalization time of 30 min and a lower alkalization temperature of 40°C,the viscose was more likely to undergo etherification reaction,after which the etherification parameter chloroacetic acid concentration was 5%,the etherification time and etherification temperature were higher than the alkalization conditions,2 h and 70°C,respectively,and the better degree of substitution of the modified viscose filaments was 1.33.After that,the properties of carboxymethyl cellulose fiber were analyzed for yarn morphology,group changes,crystallographic changes and thermal stability.It was confirmed that the carboxymethylation of viscose filament occurred and the modified viscose had enhanced hygroscopicity and could dissolve quickly and stop bleeding.Secondly,in this thesis,different sizes of yarns were prepared by varying the skin yarn pitch and core yarn diameter.The raw material of skin contact surface is defined as the lining yarn,which is a braided yarn composed of viscose filament(shell yarn)and PTFE(core yarn).The larger the braiding pitch,the worse the mechanical properties of the braided yarn.The braided yarn with a pitch of 2 mm has a greater tensile breaking strength(79.49N)and slip resistance(3.64 N),and X-ray energy spectroscopy(EDS)analysis confirmed the uniform carboxymethylation reaction of the braided yarn and the hemostatic effect of the carboxymethyl cellulose fiber.The spacer yarn is an entangled yarn composed of Coolmax(shell yarn)and nylon monofilament(core yarn).The larger the core yarn diameter,the less the effect of the wrapping pitch on the elasticity of the wrapped yarn.too high or too low a pitch reduces the elasticity and core-absorbing properties of the wrapped yarn.The wrapped yarn prepared with core yarn with a diameter of 0.2mm and shell yarn with a pitch of 2mm has a faster suction speed,a cyclic tensile stress of 144.37 MPa,good slow elasticity of the spacer yarn,residual strain of 2.46%,and good fatigue resistance of the spacer yarn.After that,the tissue structure of the weft-knitted spacer structural dressing is studied and analyzed in this thesis.Experimentally,the No.7 flat machine was selected to satisfy the feeding of braided and wrapped yarns,and the surface tissue consisted of full stitch and one spacer tissue,which could prevent the protrusion of spacer filaments.The spacer filaments span 4,6 and 8 needle gauges with different spacer filament lengths corresponding to F1,F2 and F3 dressings.The spacer filaments change the fabric pore space,thickness and moisture absorption,thus affecting the comfort properties of the fabric,and the angle between the spacer filaments and the horizontal plane affects the mechanical properties of the fabric.F2 has high air permeability,suitable water vapor permeability,insulation rate,high blood absorption rate(159.09%),and minimum liquid diffusion area.After F2 cyclic compression,the strain and thickness changes are minimized,and the buffering capacity and fatigue resistance are the best.In addition,UHMWPE makes the outer surface of the weft-knitted spacer structural dressing hydrophobic.Finally,this thesis compared and analyzed the hemostatic properties of gelatin sponge,hemostatic gauze,unmodified dressing f2 and modified dressing F2.F2 absorbs blood through wrapped yarn and clots through carboxymethyl cellulose sodium.The clotting time is5 minutes,and the clotting index is as low as 7.96%.The hemolysis rate is only 0.98%,and the hemostatic effect is the best.In summary,carboxymethylated modified viscose filaments and Coolmax fibers are used for multi-channel hemostasis,PTFE maintains the structural integrity of the dressing,and nylon monofilament provides the elasticity of the dressing.This article prepared new weft-knitted spacer structural dressing with excellent comfort properties,mechanical properties and hemostatic properties based on the three-dimensional structure of spacer fabric.The semi-soluble hemostatic spacer structure dressing can be used as a competitive wound dressing.