The melt-blown process is a term that’s seeing an increasing amount of research these days. What was once an obscure fabric is now one of the most in-demand materials in the world.
Melt-blow extrusion is the full name of the manufacturing process. It creates a type of fabric that falls under the category of non-woven fabric that’s made of polymers. These polymers are known as polypropylene.
Traditional fabrics are often made using natural materials like silk or cotton that are woven together. Non-woven fabrics, in this case, melt-blown fabric, are thermally bound together material created from individual fibers of molten polymers. The end result is a fabric that has a web-like structure, and it becomes desirable for a number of reasons. These are absorbency, bacterial protection, cushioning, resilience, softness, and sterility. They’re also washable as well.
Given the different numbers of features they offer, there are a number of diverse products that can be made using the melt-blown fabric. These include filters, face masks, medical masks, and surgical masks as well. The versatility of the cloth means that it’s used to produce many different products. However, because of the COVID-19 pandemic, the main use of melt-blown fabric is now in the production of masks. If you’re looking to learn more about how the melt-brown process is used to make face masks, then keep on reading!
How Is Melt-Blown Fabric Made?
Melt-blown fabric is created through a process which is known as melt-blown extrusion. It is a single-step process that involves a stream of high-velocity air, that blows molten thermoplastic resin from extruder tip. The resulting material goes onto a conveyor or a take-up screen. It’s a process that’s been around since 1950 and has never been more important until today.
There are four basic components of the process; these are the resin feed system, extruder assembly, metering pump, melt-blown die assembly, collector, and the winder unit.
Resin Feed System
Thermoplastic resin is the main raw material for the melt-blown process. There are several different polymers that are adaptable for use in the melt-blown extrusion process. The different polymers include; Polypropylene, Polycarbonate, Polybutylene terephthalate, and Polyamide, among others.
Raw material from the resin feed system is fed into the extruder assembly. There are three different zones in the assembly. These are the feed zone, transition zone, and metering zone. The feed zone is where material enters the extruder and begins to melt.
In the transition zone, the polymer is homogenized and compressed. Once the polymer enters the molten state, it’s fed into the metering zone. The pressure increases as the material are getting ready for discharge through the melt-blown die assembly.
The molten polymer output enters the metering pump pressurized and, at a temperature of 250-300C, enters the metering pump. This pump is designed to deliver clean polymer mix to the die assembly at a constant volume.
It’s a sophisticated piece of machinery that accounts for variations in pressure, temperature, and viscosity. After the metering pump, the resulting output is feed into the die assembly.
Melt-Blown Die Assembly
The die assembly contains three key components; the feed distribution, die nosepiece, and the air manifolds. An absolutely critical component is the die nosepiece. It impacts the uniformity of the web of melt-blown fabric coming out of the machine. The air manifolds then supply high-velocity hot air to the extruded fibers.
The high-velocity hot air causes the polymer to turn into microfibers. These microfibers have a diameter that ranges from 0.1 to 15 microns.
The last step of the process is the winder unit, where the fabric from the collector is wound onto a cardboard core.
Now that you’ve learned how the material is made, we can move on to how you manufacture the masks.
How Is Melt-Blown Fabric Used To Make Masks?
The non-woven melt-brown fabric is the primary material used in the production of medical masks and surgical masks. Medical Masks are typically produced by stacking together three layers of non-woven material. The inner layer, which comes in contact with the wearer’s face, absorbs any moisture.
While the outer layer of non-woven fabric is a waterproof barrier that stops any liquids, the patient spills out. In between the inner layer and the outer layer is the middle layer that serves as a filter. This middle layer is where the melt-blown fabric comes into action.
Additionally, for face masks that meet technical standards, they also get electret treatment. The process adds electrostatic properties to the filter, which enables the electrostatic absorption, which helps trap aerosolized particles through electrostatic attraction.
The mask-making process follows seven basic process steps; these are the same for surgical masks and medical masks. All the steps in the process are as follows;
- The machine combines three layers of materials together to produce the three-layer face masks. It’s initially a large piece of fabric that needs to go through the cooking process.
- Attach a metal nose strip. The machine has to stitch the metal wire into the melt-blown fabric face masks. These metal strips are crucial for masks as they allow the wearer to bend the mask to fit around their nose.
- Add the necessary folds and pleats. Once again, the machine will use a folding device that adds all the requirements. It allows companies to adjust the standard mask to fit all the different wearers.
- Cutting and stitching. The next step in the process is cutting the large piece of three-material fabric to individual size masks. After the cutting process, you can stitch the melt-blown fabric to join all the layers.
- Attach Ear Loops. These are crucial as they need to stick to the mask properly. To ensure they stick, the adhesive makes use of a thermal press. Alternatively, companies can make use of ultrasonic welding.
- Disinfect properly. If face masks need to meet the technical standard, they must be subjected to a sterilization process. After this treatment, the mask needs to stay in isolation for seven days until the ethylene oxide dissipates.
- This is the final step in the process, and it involves simply packaging the completed masks for shipment.
In the case of N95 respirators, the process is slightly different and involves the use of a polyester shell and cover web. The key in all the masks is the melt-blown fabric filtration layer.
Due to the dense structure of the fabric, it helps ensure that the smallest particles are filtered out at high efficiency. It’s because of these characteristics that the fabric is crucial for filtering viruses and any other pathogens.
Currently, the worldwide demand for face masks that meet a technical standard is very high. It is currently greatly outweighing the supply. Even though companies are trying to switch towards face mask production, there’s still a need for a greater focus on producing more medical masks. Now that you know more about how these masks are produced, you’ll also want to know the technical standard for masks in different countries.
ASTM International is providing no-cost public access to important ASTM standards that are used in the production and testing of masks. These included several test specifications that analyze different features of the mask.
The tests include an efficiency test of materials used, bacterial filtration efficiency, and standard specifications for the performance of materials used in the mask. However, most of these specifications apply to the high-quality masks that are available in the market.
The CDC recommends that the general public should not use these masks, and should restrict themselves to using standard cloth face masks. These generally don’t need to meet any standard requirements except the standard terminology specifications of protective clothing.
China formulated these following standards for medical face masks: GB19082-2009 technical requirements for single-use protective clothing. The other standards deal more directly with medical face masks.
These are the GB19083-2010 technical requirements, YY/T0969-2013 single-use medical face mask, and YY0469-2011 surgical masks. China is also currently in the midst of updating its technical standards for the masks. They’ve also included a new designation for masks specifically designed for children.
Medical masks also regulated under the category of Class II medical device in China. According to the government’s guidelines, a manufacturing enterprise needs to obtain production licenses issued by a provincial drug regulatory department before production.
The European Committee for standardizations and the European Committee for electrotechnical standardization came together to come up with 14 technical standards that apply to medical masks. They’re hoping the actions will help both EU companies and third-country companies to adhere to a minimum standard of production.
11 of the standards developed have been worked on by CEN while three additional ones are developed jointly with ISO. All these standards are also available for free for public access.
There’s a massive demand for high-quality medical masks given the current climate. The demand is only going to increase as more and more countries encourage their populations to wear masks.
As manufacturers try to operate at optimum capacity to produce as many masks as possible, it’s important that they adhere to international standards as well. Each country has its own specification, but they generally tend to follow the same guidelines!