Analysis of Water Vapor Permeability in Spunlace Nonwoven Fabric
Abstract : Medical dressing products were prepared by the company All Clean Natural spunlaced technology with the same viscose parameter fiber and polyester fiber as raw materials to quantitatively analyze the water vapor permeability of the conventional nonwoven fabric used as the functional layer of dressing. Various water pressure and different angles were used to test the pore structure of dressings.
Based on the dressing application environment, the water vapor permeability of nonwoven dressing with different compositions was discussed ．The results show that hydrophilic-hydrophobic properties are present in the pore structure and provide a significant effect on water vapor permeability. The water vapor permeability of nonwoven fabric composed of viscose ranges from 9 300 to 11 000 g ／ (m ：。 24 h) , While the one of nonwoven fabric made of polyester ranges from 8 800 to 9 700 g ／ (m2·24 h). The results CaD reach the primary requirement of dressings water vapor permeability ．
Dressings are materials used as a wound covering or a substitute product to protect skin impairments while administering an environment conducive to wound healing. Wound improvement and management are always challenging to hurt patients, specialists, and doctors. Mostly, wound infection always accompanies healing hygiene. The reason being wound dressings play crucial roles in wound procedures. A good dressing can increase wound healing and free the wound from germ contamination. Moreover, we often need to switch different types of wound dressings during the whole process of a case treatment. A dressing needs to be used together with other dressings to create a suitable environment for wound recovery and wound protection. Skin cuts or wound moist conditions healing dressing mouth should have the following purposes:
- stain superior permeability features
- Absorb excess exudate.
- Keep the cut at a steady temperature (37°C).
- Keep a particular humidity when the dressing is in contact with the wound.
- Stop microbes, dangerous particles, and other damaging substances or textile from contaminating the wound.
Thus, considering the dressing structure's impact on the wound microenvironment's moisture permeability is essential for efficiently treating wound dressings supervising significance. In expanding to traditional cotton gauze, commercial dressings use new medical components, chitosan, alginate, hydrogel, hydrocolloid, and other hydrophilic product materials, polycaprolactone with hydrophobic dressing cloth. Today, the analysis of the factors affecting dressings' moisture permeability mainly starts from the combination of multiple materials, physical and chemical modifications, and biological substances, and most of them are combined with electrospinning technology.
In the conventional nonwoven fabrics industry, the spunlace process modifies the material's pore composition by changing the areal density, web angle, and spunlace strength; polyester and viscose are used as raw materials for insertion—wetness observation, study dressing spunlace base cloth pro.
The impact of hydrophobicity and pore structure affects the moisture permeability of the dressing; compared to the sample's moisture permeability with two typical commercial dressings. The dressing with excellent moisture permeability provides a reference for the design to explore the changes in the traditional nonwoven fabric's moisture permeability when the material and pore structure change for the design. The dressing with excellent moisture permeability provides reference.
General Types of Wound Dressings Explained
- Foams
Clinical Indications: For partial or full-thickness injury. Medium to massive exudation of wounds. They are absorbing effluent.
Advantages:
•Soft
•Disposable
•Comfortable and easy to use.
•Conservative replacement frequency.
•They can absorb many wound secretions to reduce the influence of impregnation on wounds.
•Easy to remove from the wound without hurting the skin. Insulation and heat protection shield outside impulse/pressure.
- Gauze
Clinical Indications: Best for one-time use, hemostasis bandaging, or hygienic care of surgical or local wounds in medical units.
One-time use for operation and wound care in medical units.
Advantages:
•Affordable and readily available.
•Handy to protect cuts and reduce bacterial intrusion.
•Simple to use and suitable for many kinds of wounds.
•They are widely used in the clinic.
•Low cost and suitable for various consumption levels.
- Transparent membrane
Clinical Indications: Suitable for healing external wounds. Protection of skin inclined to abrasion or external infection. It is used mainly for the maintenance of the first layer dressing.
Advantages:
•Prevent the friction and bacterial infection of the wound bed.
•Transparency and easy wound observation with no removal.
•Keeps humidity in the wound bed surrounding skin.
•Low cost, good fit.
•Conducive to self-dissolving debridement.
•Prevent wound bed friction and bacterial contamination.
- Alginates
Clinical Indications: Injuries with partial to full-thickness wounds.
Average to extensive exudates. Pit/hole or sinus tract.
Advantages:
•Can handle strong exudate retention capability, used for contagious wound, with no wound adherence.
•It can provide autolysis debridement.
•It can provide wet healing conditions to keep the nerve ends moist.
•Relieve pain, avoid dehydration and promote epithelial regeneration.
•Form hydrate with necrotic tissue to help wound autolysis and debridement.
•Easy to use and remove, no toxicity, no allergy.
- Composites
Clinical Indications: Surgical wounds, infectious wounds, grade II burn, small range grade III burn wounds, chronic refractory wounds for debridement of infected granulation wounds, and old granulation wounds.
Advantages:
•Easily use and available.
•They are used as one or two coats of dressing.
•They are used for a variety of wound types.
•Strong absorptive capacity.
•It provides endless debridement, stimulating necrotic tissue exfoliation.
•control infection and promote wound healing.
•It is the adequate protection of skin grafts to prevent infection and necrosis.
- Hydrocolloids
Clinical Indications:
Superficial, moderately deep wounds with small to moderate exudation and desquamated or necrotic tissue.
Advantages:
•Implement moist conditions for clean cuts and granulation tissue.
•Promote autolysis debridement of necrotic tissue.
•Providing a hypoxic and wet healing environment
•Flake self-adhesive, sealing wound bed, without the second layer of dressing, to prevent bacterial invasion and waterproof.
•Comfort and decrease irritation, relieve pain, and promote epithelial migration and granulation tissue growth.
7. Hydrogel
Sheet or amorphous with rich water used for auxiliary and autolysis debridement and softening eschar.
Clinical Indications: Use as partial or full-thickness injury.
Necrotic or desquamate wounds small to medium exudation.
Hydration promotes self-dissolving debridement.
Advantages:
•Positively contributing water to dry injuries and keeping a wound moist.
•No wound adherence.
•Increasing autolysis debridement for scab debridement.
•Helpful to epithelial migration and granulation completion
•Non-sticking wound.
•Pain relief protecting germ infection.
1 Test supplies
1.1 Test materials
ALL CLEAN NATURAL CHINA provides the test materials. The specifications of the materials are shown in Table 1.
Table 1
Specification of fibrous materials
(on below table, 1Material type 2 Linear density 3 Length 4 Width 5 Curl)
1.2
Preparation process
Applying polyester and viscose fibers as raw materials, the manufacturers production of combing with a parallel carding machine, and when laying the web at three angles (0°, 45°, and 90°) respectively, using the spunlace process to consolidate the web to obtain the conclusive dressing Spunlace fabric. All units use the same amount of spunlace applications, and the spunlace weights listed in the article are the maximum spunlace pressures. The method of the preparation process is shown below, Figure 1.
1-Opening 2*-Carding 3-Laying 4-Spunlace Reinforcement 5-Dry Winding
1.3
Development method
Tested spunlace nonwoven dressing is prepared, and the resultant density of the dressing was set at value 0, 120, and 180 g/㎡ on the specific test.
The devices and test techniques are shown in Table 2. Among them, the study on the moisture permeability of spunlace nonwoven fabrics is tested according to dressings standards.
2 Conclusions and analysis
2.1
Study of agents altering the thickness of the dressing nonwoven fabric
2.1.1
Impact of areal density on the thickness
The areal density and thickness affect each other. Under the hydroentanglement pressure of 1000 N/c㎡, the connection among the areal density and thickness of viscose and polyester fibers is shown in Figure 2. The standard thickness of each sample of the dressing measures ten times the average.
Figure 2 shows that the thickness and areal density of both polyester and viscose nonwoven dressings are correlated. With areal density.
With fiber content increase, the thickness of the nonwoven fabric also continuously increases.
Comparing the two product materials of polyester and viscose, the thickness of viscose nonwoven fabric is larger than that of polyester nonwoven fabric. The viscose fiber has better hydrophilicity, and the consolidation and entanglement effect between the fibers is better under the spunlace process. The fiber as a whole tends to shrink.
2.1.2
Influence of spunlace pressure on the thickness.
Fiber web opens the spunlace area after pre-spunlacing. Commonly, as the pressure of the spunlace progresses, the water flows energy increases, and the fibers in the fiber web incorporate water. The more movement energy, the better the fiber web's reinforcement effect and the tighter the fiber entanglement. When the areal density is 120 g/㎡, the fiber entanglement woven result of the sample is presented in Figure 3.
Figure 3 Showing comparison of the fiber entanglement effect of viscose and polyester spunlace under different spunlace pressures. The more significant the spunlace pressure, the fiber entanglement. The more equal the dimension arrangement, the fewer parallel fibers, and the better the entanglement effect. The thickness of the nonwoven fabric under several spunlace pressures is shown in Figure 4. It can be seen from Figure 4 that the thickness of both viscose and polyester spunlace nonwovens lessens with the increase of spunlace pressure, and the decreasing trend is evident. It can be seen that as the pressure of the spunlace increases, the entanglement between the fibers becomes tighter, which decreases the thickness of the spunlace cloth.
2.1.3
Control of Laying Angle on Thickness
After the nonwoven fiber web is carded and then passed through the web-laying process, the orientation degree between the fibers can be changed, thereby affecting the fiber. The degree of entanglement in the method. The influence of the change of the netting angle on the thickness of the spunlace cloth. With the change of the netting angle, the thickness change range is smaller. It can be seen that the change of the web angle only affects the fiber. An adjustment has little effect on the overall thickness of the dressing base cloth.
2.2
Review of circumstances concerning the pore structure of nonwovens for dressings.
The dressing health cloth is mostly nonwoven material, a material composed of multi-directional three-dimensional curved pores and high porosity. The pore-structure has the most significant impact on the permeability of the dressing base fabric. The indicators of pore structure are porosity, pore size, and pore size distribution. Porosity (ε)
The calculation method is shown in formula (1).
2.2.3
Review of circumstances concerning the pore structure of In the formula.
The material density (g/m2); is fiber density (g/cm3); is material thickness (mm); is the material bulk density (kg/m³). Determination of the pore size is based on the difference in the gas flow rate through the dry and wet capillary pores of the sample under pressure, analysis, and calculation of the sample's pore size and arrangement. The calculation formula of the single pore diameter of the sample is shown in the formula.
(2).
Where: is the pore diameter of the i-th hole in the sample (μm); γ is the surface tension of the liquid (10^(-5) N/cm); θ is the contact angle of the same liquid (°); is the size of the i-th hole Instant gas pressure (N/cm²).
2.2.1
The effect of bulk density on pore structure
According to formulas (1) and (2), the porosity and average pore diameter of viscose and polyester spunlace cloth at different bulk densities are calculated, and the results are shown in Figure 6.
Figure 6 That the porosity and standard pore diameter of viscose and polyester spunlace nonwovens steadily decline with the increment of their bulk density. And the decreasing trend is evident. As the density per unit volume of the material improves, the volume occupied by the fibers per unit volume increases so that the volume occupied by the pores per unit volume decreases, and the overall porosity and average pore diameter of the material decrease.
Compare polyester and viscose, two materials with more significant differences in hydrophilicity and hydrophobicity. Their pore structure is significantly different. Compare the porosity under the same process, it can be seen that the volume density of the viscose water-laid cloth has a small variation range, and the corresponding porosity reduction is also small, only 2.514%;
The mass density of the spunlace cloth differs widely, and the identical porosity reduction is larger than that of viscose. The porosity reduction is more important than that of viscose by 7.928%. Compare to the average pore diameter. It can be seen that the average pore diameter of polyester spunlace nonwovens is higher than that of viscose as a whole. The former is 55-64μm,
The latter is 25-40μm. It is mainly because polyester fiber has greater rigidity than viscose fiber. In the process of web reinforcement, the flexural cohesion ability is worse than that of viscose fiber, so the degree of interpenetration between fibers is less than that of viscose fiber.
2.2.3
The effect of laying angle on the pore structure.
Under the same areal density (120 g/m2) and the same spunlace pressure (1 000N/cm2), changing the laying angle, the obtained material pore structure characteristics are shown in Figure 7.
Fig．7
Effect of different paving angles on porosity and average pore size
Figure 7 Proves that the netting angle has varying effects on the porosity and average pore size of the spunlace nonwoven fabric. For viscose spunlace nonwovens, the porosity and average pore diameter persist consistently with the web angle change. In contradiction, for polyester spunlace nonwovens, the porosity and average pore diameter show a slow reduction trend with the web angle increase. Under the spunlace process, the hydrophilic material's cohesion performance is better than that of the hydrophobic material, and the variance of the netting angle has less influence on the hydroentanglement of the hydrophilic material than the hydrophobic material.
2.3
Analysis of determinants considering the moisture permeability of dressing nonwovens.
Moisture permeability is a crucial indicator for evaluating the efficacy of dressings. There are three ways to transmit moisture in the dressing base cloth:
a. When the dressing treats the wound lack of water vapor to the outer conditions through pores of the base fabric is due to the incomplete pressure of water vapor in the air layer is higher than the partial pressure of water vapor in the enclosing environment.
b. Once the wound surface liquid evaporates in the microclimate zone, it will remain on the fabric fiber surface. The gap holes condense into a liquid form, which is then transported to the fabric's outer surface, thus evaporating again into water vapor to diffuse and transport to the external environment.
c. It is maintaining the balance of moisture absorption and desorption. The moisture retention of the dressing material makes the wound area. The first and second dressing base cloth pathways are called hydrophobic material—three ways of moisture permeability. The pore structure is the fundamental carrying medium of the above three types of transmission paths.
Three ways of moisture permeability. The pore structure is the fundamental carrying medium of the above three types of communication paths. Unlike manufacturing nonwovens, the moisture permeability test method of dressing nonwovens is based on the wound environment. The main characteristics are: (1) The experiment heat is close to the human body temperature, which is (37±1)℃, and the relative humidity must be lower than 20%; (2) The measured inner diameter of the breathable cup is 35.7 mm. The cup depth is 32 mm, which is distinct from the inner diameter of the industrial nonwoven fabric moisture permeability test, which is 60.0 mm, and the cup depth is 22 mm; (3) The industrial nonwoven fabric utilizes the micro-environment of outside wetness and inner dryness. Measure the desiccant's property change in the moisture-permeable cup to absorb external moisture as the moisture permeability. Simultaneously, the dressing base fabric resembles the wound area environment with the micro-environment of "outside dry and internally wet", and measures the evaporation of water vapor in the moisture-permeable cup as the specific calculation method for moisture permeability is shown in formula (3).
X=δX1000X24/t
Where: X is the water vapor transmission rate (MVTR) (g/(m2·24 h)); δ is the absolute mass difference between the vapor-permeable cup and the sample during the test period (g) ; t is the test time (h), The test time is generally 18-24 h.
The attraction of the pore structure of various dressing nonwovens on the moisture permeability is shown in Table 3.
The pore structure's impact on the moisture permeability is calculated . The link between the porosity of the dressing nonwoven fabric and the moisture permeability value (ie, water vapor transmission rate) is shown in Figure 8.
Fig ．8 Effect of porosity on the MVTR
Figure 8 explains that the moisture permeability of viscose and polyester nonwovens are the same.
As the porosity rises, it shows an upward trend, and the moisture permeability increases by 10.663% and 9.862%, respectively. The reason is the pores of the same material. The greater the rate, the greater the number of crevices and holes, which is more helpful to the diffusion of moisture, thereby enhancing the moisture permeability. This can be observed from Table 3 that the average pore size is the influence of moisture permeability is consistent with porosity. To increase the dressing's moisture permeability, you can suitably reduce the water jet pressure under the same areal density; To make the dressing nonwoven fabric fluffy and porous, decreased the surface density appropriately under the same process. It is going to reduce the thickness so that moisture can penetrate the dressing quickly.
2.3.2
The impact of material's hydrophilicity and hydrophobicity on moisture permeability
The function of moisture absorption and desorption of the fiber material influences the moisture permeability for wet wipes. Therefore, the hydrophilicity and hydrophobicity of the material will also affect the nonwoven dressing moisture permeability of the fabric.
It can be seen from Fig. 8 that under similar porosity conditions (87.5% in the figure). The moisture permeability of polyester fiber is greater than that of viscose fiber. It is because polyester fiber's moisture release effect is better than that of viscose fiber. The water vapor is barely attached when passing through the polyester fiber and is directly lost from the holes. In nonwoven fabrics with high porosity, the moisture distribution effect of holes plays a leading role in water vapor transmission.
According to Table 3, compare and analyze the areal density and spunlace of the two materials and the effect of pressure on moisture vapor transmission rate. When the areal density (60 g/㎡) of polyester and viscose nonwoven fabrics increased by 1 and 2 times, the corresponding moisture permeability of polyester decreased by 7.9% and 8.97%, respectively. The moisture permeability decreased by 3.62% and 3.58%, respectively, indicating that polyester's areal density has a more significant effect on moisture permeability than viscose. Under the condition of an areal density of 120 g/㎡, when the spunlace pressure of polyester and viscose nonwovens increases by 200 and 400 N/cm2 respectively in 2020, the corresponding moisture permeability of polyester decreases by 0.87% and 5.56%, respectively. The related moisture permeability of viscose decreased by 9.13% and 9.29%, indicating that the hydroentanglement pressure of viscose nonwoven fabric has a more significant effect on its moisture permeability than polyester.
2.3.3
The relationship between the moisture permeability of the dressing and wound healing.
The wound conditions play a vital role in wound healing, and the most healing idea was concluded in 1958. The idea refers to the construction of moist.
3 The microenvironment suitable for wound healing, the moisture permeability requirements
(1) The moisture permeability is not easy to be too large, and the moisture permeability is too large, which will cause the water vapor to dissipate too quickly and cause the wound to dry out, the color of the wound turns black and purple, and the healing ability becomes poor and easy to adhere to the dressing;
(2) The moisture permeability is not easy to be too short. The moisture permeability is too short. The moisture cannot be discharged in time, which generates the vapor essence to condense in the skin area near the dressing, increasing the amount of fluid buildup in the wound area and causing wounds deterioration. The moisture permeability of self-made nonwoven materials (viscose, polyester) and cotton gauze was tested. The results are shown in Table 4.
The vague group is the evaporation of water vapor when the dressing is not covered. In the commercial dressing group, the viscose nonwoven fabric from ALL CLEAN NATURAL CHINA belongs to the test group's commercial dressings with better wound healing effects.
Table 4 shows the moisture permeability of the vague control sample and cotton-gauze dressing.
In useful utilization, the use of cotton gauze dressing is for temporary absorbent and protection. When used for wound dressing for some time, due to extreme moisture permeability, the wound will be dry and adhered to the damage and challenging to treat; self-made viscose nonwoven material's moisture permeability is within a moderate scale. According to the exact application, polyester fiber can be mixed with viscose fiber for nonwoven preparation. The characteristics of polyester and viscose fiber can be used to optimize the moisture permeability of the sample. Overall, 9 500～10 000 g/(rfl2·24 h) is the dressing material's standard moisture permeability.
4 Analysis Completion
- The dressing wet wound healing idea analysis shows that the moisture permeability of dressing materials suitable for wound healing is not easy to be too large or too small but should range at 9 500～10 000 g/(㎡24 h).
- The greater the thickness, the greater the spunlace pressure, the smaller the thickness; the laying angle has no evident influence on thickness. For the same material, both the porosity and the average pore size decrease with the increase of the bulk density; under the same process conditions, the porosity of the viscose spunlace cloth is greater, while the average pore size is smaller than that of polyester.
- Same quality material, the average pore size, and porosity affect the dressing. The moisture permeability of nonwoven fabrics has a greater impact. The larger the porosity and average pore size, the better the moisture permeability. Under the condition of high porosity, the moisture permeability of the dressing plays a principal role, and the hydrophobicity of the material itself plays a minor role in the moisture permeability.
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| Spunlace Nonwoven Fabric |
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