Importance of Medical Protective Coveralls

What special functions do medical protective overalls provide that ordinary clothing does not? Accordingly, what are their special requirements for materials?

1. Importance of Medical Protective Coveralls

In the current situation where Covid-19 is still rampant, medical protective overalls are essential for the safety of medical workers, public health workers, patients, and people entering the infected areas to visit patients. They provide functions including isolating germs, harmful ultra-fine dust, acid and alkaline solutions, etc., which guarantees the life and work safety of the relevant persons and maintains a clean environment.

The main performance indicators of medical protective overalls are protection, comfort, physical and mechanical properties, etc. Among them, protection is the most vital performance requirement for medical protective overalls, which consists of liquid barrier, microbial barrier, and barrier to particulate matters, etc; comfort refers to air and moisture permeability. In order to enhance the protection performance, the clothing fabrics of protective overalls are usually laminated, making them heavy, breathable, and moisture permeable. Prolonged wear of medical protective overalls poses requirements on air and moisture permeability, and sweat and heat dissemination; the physical and mechanical properties mainly pertain to the requirements for resistance to tearing, puncture, and abrasion, in order to avoid becoming a gateway for bacteria and viruses spread.

2. Breathability of Medical Protective Coveralls

Disposable medical protective coveralls are made from micro- and nano-level materials that meet the "three resistances and one anti" (i.e. resistance to water, blood, alcohol and anti-static). This type of composite material can be made by laminating different materials, such as laminating spun-bonded nonwovens of polyethylene and polypropylene with breathable microporous films or other nonwovens, or spunlace nonwovens with breathable microporous films, or pulp compound with spunlace nonwovens. In addition, several types of films prepared from PTFE can also be used to manufacture high-end protective overalls. In these composites, the breathable microporous films are especially important.

The so-called breathable films are made by homogeneously blending a functional inorganic product into the polyolefin raw materials. The finished product is stretched at a high rate during film formation, eventually bringing in the air and moisture permeability functions; in short, the functions of the breathable film are water barrier and water (moisture) permeability. We take the most commonly-used PE-based breathable film as an example.

(1) The principle of air permeability

The principle is simple: Inorganic + stretching = micropores, the process is in fact very delicate. Only the homogeneously distributed micropores of the appropriate size are effective.

Insufficient stretching will result in the micropores being too small or even no micropores at all. The poorly stretched and undersized micropores can only be disposed as scrap.

(2) The basic principle of breathable film formation

The principle of breathable film formation: PE+CaCO3 (masterbatch)---film formation---stretching---breathable film. Breathable PE film is made by adding approximately 50% of special calcium carbonate to LDPE/LLDPE polyethylene resin carrier for blending, and then extruded into film and orientation-stretched at a certain ratio. The fact that polyethylene resin is a thermoplastic material that can be stretched and crystallized under certain circumstances makes the polymer peel off from the calcium carbonate particles, resulting in interconnected meandering pores or channels formed around the calcium carbonate particles. It is these meandering pores and channels that give the film air (moisture) permeability, thus connecting the environments on both sides of the film.

(3 ) The function principle of breathable film

When the vapor concentration on one side of the film is greater than that on the other side, a gradient pressure of moisture difference is formed, which provides the basic condition of air (vapor) convection. The breathable film, when used as waterproof film, can serve as a barrier against liquid because of the numerous channels within it. The winding channel it forms offers a great value of "length to diameter ratio (L/D)", which can be seen as a capillary. Therefore, under the circumstance where the liquid (such as water) and the pressure is the same, as long as the liquid-column height of the capillary is shorter than the length of the capillary, there will be no liquid leakage.