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What are the types of non-woven fabrics for face masks? Difference between 5 types of non-woven fabrics and 11 types of mask raw materials!

Non-woven fabrics for face masks

When Covid-19 began to spread, the shortage of non-woven fabrics for face masks made people panic and hoarded masks frantically, and everyone began to pay attention to the importance of this thin piece of masks. At the same time, the shortage of supply resulted in many counterfeit products on the market. Some face mask manufactures claimed that their products were medical masks, but they were actually made of regular non-woven fabrics without any filtering effect. Below we will introduce various types of non-woven fabrics first, and then we’ll have an in-depth analysis of the non-woven fabrics for face masks!

Non-woven fabric is the most important raw material for medical masks, and it is also the key to the virus and bacteria filtering effect. There are many medical masks on the market that claim to be medical masks, but in fact they’re just fake products without any filtration effect! Special attention should be paid when choosing medical masks!


We’ve introduced woven fabrics and knitted fabrics when we introduced the weaving methods of fabrics in the previous article. The topic of this article is “non-woven fabrics”, as the name implies, “fabrics that are made not by the traditional plain weaving or knitting process“. In other words, it is a fabric directly combined from chemical fiber raw materials through chemical or physical methods.

“Non-woven” fabric covers a wide variety of fabrics. In fact, according to the different raw materials and manufacturing process, there are a very diverse and widely used non-woven fabric types to choose from. Based on the different manufacturing methods, we’ll introduce 5 common non-woven fabrics below:


Types of non-woven fabrics


1.Spunbond Nonwoven:

Using web formation process, the molten polymer particles are extruded, stretched into continuous filaments, then laid into a web and combined by reinforcement technology to form a fabric. The fiber diameter is about 10-20 microns (μm). Polypropylene fiber is the commonest raw material of spunbond non-woven fabrics, and the fiber itself is slightly water repellent, so it is often used in the outer layer of face masks. Although polypropylene has antibacterial properties, it can still be processed as required to enhance the antibacterial effect.


2.Melt-blown Nonwoven:

Melt-blown Nonwoven is also made by web formation technology, but it is different from the extrusion process used in spunbonded nonwovens. Instead, hot air is used to disperse the meltable polymer particles and spray them to produce ultra-fine fibers that fall onto the collecting web to form a fabric. Its fiber diameter is thinner than spunbond nonwoven fabric, about 2-5 microns (μm).  The main raw material is also Polypropylene. Because meltblown nonwoven fabric is a high-density nonwoven fabric, it is often used in the middle filter layer of face masks.


3.Spunlace Nonwoven:

Using high-pressure jets of water (40-120kg/cm2; 0.1mm) to entangle carded fibers and thereby provide fabric integrity. Spunlace non-woven fabrics can be made of 100% pure natural fibers without any chemical adhesives. The products produced are the most environmentally friendly and best for the skin, but the cost is also higher than the use of blended fibers (mixed natural fiber and polyester fiber ) or 100% polyester fiber; due to the finer and more comfortable characteristics of spunlace non-woven fabric, it is a common material for facial masks on the market. It can also be used to produce medical products, such as ointment fabrics, antipyretic patches, alcohol cotton sheets, facial towels, etc., or as a base material for sports goods or industrial materials.


4.Heat-bonded Nonwoven:

Mixing the hot-melt fiber into the fiber raw material at the initial stage, the fiber is fused into a fabric by hot air during the reinforcement step. The material is mostly PE/PP or PE/PET mixed. The heat-bonded non-woven fabric has the characteristics of soft and fluffy, good hydrophilicity, and the surface is smooth and lint-free. It is mostly used to make diapers, sanitary napkins, nursing pads or cleaning products. Due to its hydrophilic and lint-free properties, it has also been widely used in the inner layer of face masks during the epidemic.


5.Pulp Air-Laid Nonwoven:

It is also called dust-free paper and dry paper-making non-woven fabrics. Because of the name “dust-free paper”, it is often misunderstood as paper, but in fact it is non-woven. The raw material is wood pulp fiber. First, air-laid technology is used to make the fibers reach a loose single fiber state and form a net, and then spray water-soluble adhesive to heat and reinforce the fabric. Commonly used in production lines of various semiconductors and precision products.



<Medical Mask Manufacturing Process>


About medical masks

After understanding the common types and production methods of non-woven fabrics, we can now have an in-depth analysis of the non-woven fabrics used for face masks.  Generally, medical mask is composed of three layers of nonwoven fabrics as listed below.


1. Outer layer of face mask

The first layer of the mask is mostly using polypropylene spunbond (PPSB) nonwovens. The material is water-repellent and can block droplets and dust. Its weight is between 25-30gsm (=g/m2, which is the weight of gram per square meter).


It is worth mentioning that if you need to use heat transfer/sublimation technology to print the outer layer of a customized mask, the printing temperature of heat transfer is generally about 150 degrees Celsius and sublimation is about 200 degrees Celsius. So before printing it is necessary to confirm whether the melting point of the fabric used exceeds the temperature of printing; for example, when using the sublimation technology to print, the non-woven material of the mask cannot be made of polypropylene (PP), because its melting point is only about 167 degrees Celsius, which is less than the temperature of heat sublimation (200 Celsius). We recommend to use: PET (polyethylene terephthalate) spunbonded non-woven fabric, which has a melting point of 265 degrees Celsius and can withstand the high temperature of the printing process without melting.


In addition to PET spunbond non-woven fabrics, PET spunlace non-woven fabrics can also be used for printing. The difference between the two fabrics is the manufacturing process, which results in different effects of printing:

(1) 100% PET spunbonded non-woven fabric: The advantage of the fabric is breathable and water-repellent. Generally, it is recommended to use 30-40gsm PET fabric for printing. The disadvantage is that its handfeel is close to paper, and the surface of the fabric is uneven. Therefore, when the printing pattern contains very thin lines or the color is solid and dark, the printing effect may not be as good as expected.

(2) 100% PET spunlace non-woven fabric: The advantage of the fabric is delicate and soft. When printing a darker design pattern, the color is more solid and closer to the original design. Usually we recommend to use 40-45gsm PET spunlace fabrics for printing. The disadvantage is that the fabric itself is heavy and thick. Using it in the outer layer of face mask is not as breathable as PET spunbonded non-woven fabric in summer. Also, spunlace is not water repellent and it needs to be processed additional treatment to achieve the water repellent effect.


2. Middle layer of mask – Melt-blown Nonwoven

Middle layer is the main filter layer of the mask, so it needs to use high-density melt-blown non-woven fabric to achieve the filtration effect. Polypropylene (PP Melt-blown, also called MB or PPMB) is the commonest material for melt-blown fabrics. Using “electrostatic electret technology” in the melt-blown process can make the melt-blown non-woven fabric generates static electricity and make the middle layer of face mask have electrostatic adsorption function, which can filter bacterial particles and pollutants. Usually the weight of melt-blown fabric is 25-30gsm.


The storage conditions of the melt-blown fabric will affect the electrostatic electret effect. It is recommended to store the fabrics in a dry and cool storage environment at 20 degrees Celsius and avoid high temperature and high humidity environments. Also, when the storage time is longer, its electrostatic electret effect will inevitably decline. The filtering effect of the mask will also declines, which makes the bacterial filtration efficiency (BFE) lower than 95%. This is the least thing that every mask manufacturer doesn’t want to see. Since Covid-19 continues to spread in recent years, a melt-blown fabric with stable quality, long-lasting electrostatic electret performance, and low pressure difference is desired by every mask manufacturers. This demand has resulted in significant improvement and development in the manufacturing process of melt-blown fabrics.


Regarding the electrostatic electret technology, different manufacturing process will affect the filterability and the time electrostatic staying on the non-woven fabric:

(1) Corona charging method: Also known as low-temperature plasma discharge method. Its technology is to charge the fibers by corona charging method by adjusting the applied voltage, charging time, charging distance, and charging temperature and humidity. “Thermally stimulated charging method” will be used during corona charging. A large percentage of melt-blown fabrics on the market are made by corona charging method because the equipment is relatively simple and easy to operate; but the disadvantage is that this kind of implanted charges can only be stored on the surface of electret materials, so the static electricity is relatively unstable and easy to lose. The melt-blown fabrics have to be stored in a cool and dry storage environment otherwise the charge of electret materials will decay in a short period of time.


(2) Electrospinning method: This method is to dissolve the polypropylene to polymers solvent, charge it through a high-voltage electric field, then eject it to continuous filaments, cool them and form random laid nonwoven fabrics. The output of this machine is comparatively low, and the quality of fabrics is not good enough to meet the filtration efficiency of a satisfactory melt blown fabric. Therefore, this technology is not popular on the market and still needs to be continuously improved to a better level.


(3) Frictional electrification method: The electrification method is relatively simple, yet the static electricity is just temporary and easy to lose. Static electricity occurs when two surfaces are rubbed together. But the electrostatic performance can be easily affected by the quality of fiber. It is generally used in the basic carding process and is not suitable for making filters for face mask.


(4) Low-energy electron diffraction method (LEED): Use low-energy electrons to bombard the dielectric of the non-woven fabric, and then the fabric is electrified by obtaining and storing static electricity in the dielectric. This method requires high technique to control the current density and bombardment time of the electron beam, and the operation process is quite complicated, so it has not yet become an easy-to-implement process technology.


(5) Pure water jet electret method: Water electret melt-blown fabric is made by the most outstanding and contemporary technique – pure water jet method. This method is to use a high-pressure water pump to spray pure water onto the non-woven fabrics, make the water and the fabric rubbed and generate the static electricity via friction. The static then is retained in the fabric through the conductive material, and the electricity can be locked by the hot air drying. After these two high-humidity and high-temperature processes, all the virtual electricity on the surface can be eliminated, and only the static electricity is stored in the electret material. Water electret melt-blown fabric has the best filtration efficiency, and the shelf life is very long – generally up to 10 years; this material is very suitable for making mask stockpiles in the COVID-19 pandemic.


Nowadays, more and more manufacturers are dedicated to the production and development of high-end melt blown fabric, for example, using HEPA (High-Efficiency Particulate Air) air purification grade fabric to be the filters, or replacing the melt-blown fabric with nanofiber membrane. Although the filtration effect of these types of filter layer is excellent, the cost of production is quite high, which results in an increase in the unit price of face masks. Their prices will determine whether they can stay in business but there is no doubt that it is every supplier’s goal to develop high-quality melt-blown fabrics.


3. Inner layer of face mask

Because people have to wear face masks all day during COVID-19 pandemic and the inner layer of face mask will be in contact with our facial skin for a long period of time, it is better to use a material that is soft and not hairy. Some mask manufacturers use polypropylene spunbond (PPSB) nonwoven fabrics, same material as the outer layer, to be the inner layer of face mask in order to reduce the cost, but PPSB is hairy and will make face itchy and irritated. Also, hydrophilic treatment on the inner layer is also not good for allergy-prone skin. Therefore, ES composite fibers (Ethylene-Propylene Side By Side) spunbond non-woven fabric are more commonly used in the market as inner layer material of masks now. There are two types of ES nonwoven fabrics according to the fiber composition:


(1) Polyethylene (PE) + polypropylene (PP), is often abbreviated to “EP”.

(2) Polyethylene (PE) + polyester fiber PET (Polyester), is often abbreviated to “ET”.


Most mask manufacturers in Taiwan prefer to use EP with hydrophilic treatment because EP is softer than ET, lint-free and can absorb mouth foam or facial sweat/grease. The fabric weight is usually around 20gsm.


Most important thing for face masks – Filtration efficiency!


Besides colors and shape of mask, we recommend that you should pay attention to the filtration efficiency marked on the packaging, such as BFE, PFE, or even VFE. The numbers (>95% or 99%) represent the filtration efficiency of the mask and usually mask manufacturers will test the masks in the laboratory before they claim their masks pass the standard. Higher numbers in the test indicate better barrier efficiency.


Three types of filtration efficiency:


(1) BFE (Bacterial Filtration Efficiency): A measurement of a filter material’s resistance to penetration of bacteria (usually tested by using particles of size 3.0 μm).

(2) PFE (Particle Filtration Efficiency): A measurement of a filter material’s ability to filter fine particles at sub-micron levels (such as 0.75μm).

(3) VFE (Viral Filtration Efficiency): A measurement of a filter material’s ability to filter viruses in the air. The Viral Filtration Efficiency (VFE) test follows the same procedure as BFE but using different challenge organism to test.


Some countries have their own standards and regulations for medical/surgical masks and others follow the testing method of ASTM F2100. In Taiwan the standard for medical/surgical mask is CNS14774. According to CNS14774, medical mask’s BFE should be higher than 95%, and differential pressure (respiratory impedance) should be lower than 5 (mm H2O/cm2). CNS14774 is compiled and revised according to ASTM F2100. ASTM F2100 classifies medical masks into 3 levels (Level 1 to 3). Level 1 mask needs to reach BFE & PFE ≧ 95%, and differential pressure (respiratory impedance) should be lower than 5 (mm H2O/cm2).

In order to meet the standards, mask manufacturers need to carefully evaluate and control the quality of each layer of face masks. We recommend to choose reliable filter suppliers that can provide stable quality and up-to-date test reports, to ensure the filtration efficiency and differential pressure of face mask!

ASTM F2100

<ASTM F2100 V.S. EN14683>


If you have any questions, please feel free to contact ILLUME!





‘National Standard (CNS) Web Service System Search (cnsonline.com.tw)




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