The main factors affecting the barrier properties of SMS non-woven fabrics

The main factors affecting the barrier properties of SMS non-woven fabrics are as follows:

1. Product Quantity: The larger the product's quantification (g/㎡), or the greater the proportion of the meltblown layer fiber web , the hydrostatic pressure is also higher, but the strength of the product will decrease, the cost of raw materials will increase, the energy consumption will also increase, and the production cost will also increase.

2. Temperature: The higher the temperature of the melt and the drafting wind, the easier it is for the thin stream of the melt to be drawn into fine and thin, the smaller the diameter of the fiber, the smaller the average pore size of the product, the smaller the hydrostatic pressure higher.

3. DCD of melt-blown system: The size of receiving distance DCD affects fiber drafting, cooling and product density. When the DCD is small, the product uniformity is good, the density is high, the barrier performance is good, the hydrostatic pressure is high, and the air permeability is poor; Good breathability and feel good. DCD has an optimal value, generally between 100 and 200mm.

4. Melt flow rate or spinning pump speed: The diameter of the fiber is proportional to the melt flow rate, that is, is proportional to the rotational speed of the spinning pump, and is inversely proportional to the flow (speed) of the drafting wind . When producing products of the same specification, reducing the speed of the production line can improve the barrier properties of the product, that is, when the output is low, the product will have a higher hydrostatic pressure, which is a process measure that is often used in the production process. Controlling the barrier performance of the product by changing the flow rate of the melt, the rotational speed of the spinning pump, or the output is essentially changing the flow rate of the melt in the spinneret hole.

5. The hole density of the spinneret: When using a spinneret with a high hole density for production, the hydrostatic pressure of the product is higher than that produced with a spinneret with a lower hole density. The essence is that under the same spinning pump speed, the single-hole flow rate of the high-hole density spinneret is smaller and the fiber is thinner. At present, the hole density of domestic general meltblown systems is 35-42 inches, with a maximum of 50 per inch; that is, equivalent to 1378-1654 per meter, with a maximum of 1969 per meter.

6. The uniformity and fiber fineness of the spunbond web: The uniformity of the spunbond web has a great influence on the barrier properties of the product. The worse the uniformity, the more discrete the hydrostatic pressure distribution; The fiber fineness determines the coverage and average pore size of the fiber web. The smaller the fiber diameter, the better the barrier performance of the product.

7. Finishing processing: When the product is cut off-line, if the tension is not properly controlled, the excessive winding tension will damage the structure and barrier properties of the product. Similarly, the post-finishing of the product will also affect the barrier performance of the product. For example, during antistatic finishing, if the finishing agent contaminates the meltblown layer, the barrier performance will decrease or even disappear. In addition to affecting the hydrostatic pressure of the product, the post-finishing process of the product will also affect the physical properties of the product, such as a decrease in breaking strength, a decrease in elongation, and a poor feel.

8. Raw materials: The flow characteristics of raw materials will affect the quality of products. The higher the MFI, the better the fluidity of the melt, the easier the drawing of the melt stream, and the better the barrier properties of the product. The MFI of the currently commonly used polypropylene (PP) raw materials is between 1200 and 1500.

9. Environment: The melt-blown fiber web is self-bonded to become a melt-blown cloth by relying on waste heat. The temperature of the environment will affect the cooling effect. The lower the temperature, the faster the cooling of the melt-blown cloth, and the quality of the product. Better, especially 'crystal points' are not easy to appear. Therefore, for a meltblown system, a product produced in the winter or at night would be better than a product produced in the summer or during the day. Some meltblown systems are equipped with cooling devices. The biggest advantage is that the environmental conditions are stabilized, crystal points rarely appear, and the controllability of product quality is improved.