Research On Wet Transfer Performance Of Nonwoven Dressings Based On Spunlaced Process

A good microenvironment provided by dressing is important for wound healing.Since the theory of wound wet healing has been put forward,numerous new type wound dressings that people are striving to develop has been emerging.The wet transfer performance in the special system of"dressing-wound" involves three kinds of substance action,namely,the absorption and diffusion of dressings to liquid wound exudate,the volatilization and diffusion of vapor-state perspiration,and the exchange of gaseous air.However,the present research on dressings stays in the selection of new biomedical materials and modification of substance' chemical and biological properties,in which lacking of systematic research on the influence of the wet transfer performance factors in"dressing-wound" system.And relevant literatures have not been reported the superior indicator of wound dressing provided for liquid absorption and water vapor permeability that suitable for various types of wound dressings.Thus there still exists a blank on the analysis of dressings' material and pore structure for affecting the wet transfer effect.The internal pore structure of fibrous materials and materials itself is the main medium for wet transfer of dressings,therefore,this paper chose hydrophilic viscose fiber and hydrophobic polyester fiber as two kinds of dressing raw materials for the fabrication of nonwovens.It was studied the influence on pore structure changed by process parameters,namely,mass per unit area,water jet pressure and paving angle.The influence of the pore structure,hydrophilic and hydrophobic characteristics of the dressing on the liquid absorption ability and the liquid transportability under the condition of a large number of wound exudate was fully discussed,and the design direction of dressings' superior debridement ability was pointed out.Besides,the moisture permeability mechanism of hydrophilic and hydrophobic materials is discussed under the condition of less or no amount of wound exudate,and the key factors affecting the moisture permeability of the dressing were pointed out.Furthermore,by comparing with two kinds of typical commercial dressings wet transfer performance,the effects of different wet transfer properties on wound healing in microenvironment were analyzed.The main conclusions were as follows:(1)Under the spunlaced process,it was found that fiber's disordered arrangement could be enhanced by the increase of mass per unit area,water jet pressure and the mesh paving angle,which would increase the entanglement of the fiber and influence the pore structure.Specifically,porosity,average pore size and pore size distribution of the dressing decreased with the volume density increasing;the average pore size and pore size distribution range decreased with the paving angle increasing,while,the change of porosity of the dressing was not obvious.What's more,the structure of high porosity and small average pore size was more easily obtained by the hydrophilic viscose than hydrophobic polyester under the spunlaced process.(2)Wetting is the prerequisite for dressing's good suction ability,and the key factors affecting dressing's suction ability of wound exudate are the dressing materials' porosity,surface energy and liquid surface tension.Dressing has a bigger suction ability when the material has a bigger surface tension.When the surface tension of the material is bigger than the liquid',the suction capacity of different materials depends on the material's porosity,and the greater porosity always has a bigger suction capacity on the condition of same equivalent radius of the dressing,that is to say the fiber's thickness or specific surface area has no change.What's more,hydrophilic materials are easier to absorb liquid than hydrophobic materials because of larger surface tension.The amount of wound exudate decreases when dressing has a bigger suction capacity,which will be more beneficial to debridement of wound,and it is of great significance to the wound healing.(3)The liquid transportability of dressing for the simulate wound exudate can reflect the dressing's liquid absorption ability,liquid transportability and liquid diffusion ability to a certain extent.With the decrease of average pore diameter of nonwoven dressing,the maximum wicking height has an upward trend.What's more,the hydrophilic fiber has better liquid absorption and permeation ability than hydrophobic fibers',and the capillary effect of hydrophilic fiber is more obvious than hydrophobic fibers'.The parallel spreading fiber network is advantageous to the fiber's orientation entanglement,and it can form a better liquid diffusion channel to reach the diversion function.Based on the Laplace equation,the design suggestion for multi-layer compound dressing was proposed.(4)Through the analysis of the mechanism of "dressing-wound" system,it was concluded that conventional nonwovens based on dressing's volume density and pore structure was not easy to find the water condense phenomenon in the process of vapor transmission,therefore,the main way of dressing's moisture permeability is fiber's "moisture absorption and release" effect and pore channel.In low humidity conditions(according to the test method of contact wound dressings,part 2:Moisture permeability of breathable membrane dressings,relative humidity ? 20%),the hydrophilic and hydrophobic properties of dressing's material have less influence on dressing's moisture permeability,and the greater porosity of the dressing always has a stronger moisture permeability.