Have you produced meltblown cloth up to N95 standard? If not, what factors affect the quality of the melt blown cloth?

- May 02, 2020-

Have you produced meltblown cloth up to N95 standard?

If not, what factors affect the quality of the melt blown cloth?


Factors affecting the quality of melt blown cloth

MFI of polymer raw materials

As the best barrier layer of the mask, the melt blown cloth is a very fine material, which is made of many crisscross microfibres stacked in random direction. Taking PP as an example, the higher MFI is, the finer the wire drawn out during melt blown processing, and the better the filtration performance.

 

Hot air injection angle

The hot air injection angle mainly affects the drawing effect and fiber morphology. The smaller the angle, the parallel fiber bundle will be formed, which will lead to the poor uniformity of the non-woven fabric. If the angle tends to 90 °, a highly dispersed and turbulent air flow will be generated, which is conducive to the random distribution of fibers on the screen, and the anisotropic property of the final melt blown cloth is good.

 

Screw extrusion speed

Under the condition of constant temperature, the extrusion rate of screw should be kept in a certain range: before a certain critical point, the faster the extrusion speed is, the higher the quantity of melt blown cloth is, and the greater the strength is; when the critical value is exceeded, the strength of melt blown cloth will decrease, especially when MFI > 1000, which is more obvious. It may be because the high extrusion rate leads to the insufficient draft of wire rod and the serious silk, so the cloth surface is sticky The results show that the strength of the melt blown fabric is decreased.

 

Hot air velocity

At the same temperature, screw speed and receiving distance (DCD), the faster the hot air speed, the smaller the fiber diameter, the softer the hand feel of the non-woven fabric, and the more tangled the fibers, resulting in the denser, smoother and higher strength of the fiber mesh.

 

Receiving distance (DCD)

Too long acceptance distance will lead to the decrease of longitudinal and transverse strength, bending strength, fluffy handle of non-woven fabric, and the decrease of filtration efficiency and filtration resistance in melt blown process.


Melt blown die head

Many spinneret die materials on the market are not standard materials. Some low-end die steels are used instead. During the use process, there will be some small cracks that can not be seen by the eyes. The hole diameter processing is rough and the accuracy is poor. It is directly used without polishing. It causes uneven spinneret, poor toughness, different spinneret thickness and easy to produce crystallization.