Meltblown hair "brittle" - must be "targeted" for solution

text/polymer

With outbreak of global epidemic, raw materials factories, modified plastic factories, hardware factories, textile factories and other enterprises have joined meltblown camp. They met each other, but they met each other in huge rivers. and lakes. But after all, "weave like a mountain". Now many customers raise problem of "fragility" of meltblown produced after a few days. The appearance of such problems with production technology is normal. Did you find it? ?

1. Know structure of polypropylene from "root"

Let's look at structural formula of polypropylene:

Meltblown hair "brittle" - must be "targeted" for solution

On carbon atoms of main chain, methyl groups are alternately located, which can be divided into three stereoisomers according to location of CH3- in molecule (position, arrangement, order, etc.), i.e. isotactic polypropylene, syndiotactic polypropylene and atactic polypropylene. All methyl groups of isotactic polypropylene are located on one side of plane, methyl groups of syndiotactic polypropylene are evenly distributed on both sides of plane, methyl groups of syndiotactic polypropylene are evenly distributed on both sides of plane, as shown in Figure 1.

Figure 1. Polypropylene spatial structure

Among three stereoisomers, isotactic and syndiotactic polypropylene belong to tactical polypropylene. Since it is a crystalline polymer resin, its crystallization behavior, crystal shape and spherulite size directly affect final characteristics of product. Combining previous articles of official report, it can be seen that more ordered polymer chains are with each other, higher crystallinity and better mechanical properties. This is also reason why polypropylene homopolymer should be selected as base material of melt-blown polypropylene.

Second, why is meltblown fabric "brittle"

The fragility of meltblown fabric is closely related to each customer's production equipment, process and raw materials. First, meltblown material (PP) must have stable and ultra-high fluidity, extremely narrow molecular weight distribution, extremely low ash content, no other product residue, excellent spinning ability and other functions. Uneven spinning can easily lead to uneven heat dissipation, resulting in internal stress and brittleness; according to analysis of raw materials, it may be that low-melting fat spinning is used, and threads are relatively thick; this is due to high content of raw materials. and processing temperatures.

A third, "targeted" solution to hair breakage

Some technicians advise manufacturer to increase amount of "elastomer". Big mistake! We analyze it from a chemical point of view. The material we use is melt blown, obtained by oxidative decomposition. Peroxide is a vulcanizing crosslinking agent that is often used to vulcanize rubber. What is an elastic body? It is an ultra-high molecular weight polymer (eg block) cross-linked physically or chemically. Do you think about consequences of adding elastomers during twin screw extrusion? This will not only affect overall fluidity of meltblown material, but also cause strong crosslinking of meltblown material.

There are many issues that are causing meltblown fabrics to be "brittle" right now. Toughness Brother™ MSTO 666 Soft Masterbatch is based on ultra high MFR and soft polypropylene. and high quality compound lubricants are dispersed in base material. This can reduce processing temperature of meltblown polypropylene nonwoven fabric, prevent secondary severe thermal degradation of polypropylene, improve crystallization shape of polypropylene, and greatly improve brittleness of meltblown polypropylene fabric. Its physical properties are shown in table below.

Table 2-1 Soft Masterbatch Physical Properties

4. Conclusion

For now, fastest solution is to add an appropriate amount of soft polypropylene masterbatch. Of course, each customer's production equipment, processes, and raw materials are different, and manufacturers must carefully analyze and process them according to their specific conditions. .