Factors Affecting The Quality Of Melt Blown Fabrics
1. MFI of polymer raw materials
Melt blown fabric, as the best barrier layer for masks, is an extremely fine material composed of many crisscrossing ultra-fine fibers stacked in random directions inside. Taking PP as an example, the higher the MFI, the finer the wire pulled out during melt blown processing, and the better the filtration performance.
2. Hot air flow rate
Under the same temperature, screw speed, and receiving distance (DCD) conditions, the faster the hot air speed, the smaller the fiber diameter, and the softer the hand feel of the non-woven fabric. The more tangled the fibers, the denser and smoother the fiber mesh, and the higher the strength.
3. Hot air injection angle
The angle of hot air injection mainly affects the stretching effect and fiber morphology. Reducing the angle will promote the formation of parallel fiber bundles in the fine flow, resulting in poor uniformity of non-woven fabrics. If the angle tends towards 90 °, a highly dispersed and turbulent airflow will be generated, which is conducive to the random distribution of fibers on the mesh curtain, and the resulting melt blown fabric has good anisotropy performance.
4. Receiving distance (DCD)
Excessive acceptance distance can lead to a decrease in longitudinal and transverse strength, bending strength, and a fluffy texture of non-woven fabrics. In melt blown processes, it can lead to a decrease in filtration efficiency and resistance.
5. Screw extrusion speed
Under constant temperature, the screw extrusion rate should be maintained within a certain range. Before a certain critical point, the faster the extrusion speed, the higher the quantity and strength of the melt blown fabric; When the critical value is exceeded, the strength of the melt blown fabric actually decreases, especially when the MFI is greater than 1000. This may be due to the insufficient stretching of the filament due to the high extrusion rate, which leads to severe wire breakage, resulting in a decrease in the bonding fibers on the fabric surface and a decrease in the strength of the melt blown fabric.
