At present, there are odor problems in non-woven masks. There are always complaints from consumers. Through consumer evaluation of Tmall's major brands of non-woven masks, it can be concluded that mask odor is a pain point that is urgently needed for such products and is a demand point for consumers.

What is the cause and effect of the odor of the mask?

1 Start with raw materials

The material of mainstream non-woven masks is PP nonwoven. The raw material of PP nonwovens is polypropylene. PP non-woven fabrics are formed by drawing polypropylene particles or powders. The physical and chemical properties of polypropylene can be seen from the figure below

The original polypropylene is odorless and non-toxic. Then the question is, why do masks have bad smells?

Still followed by the polypropylene pellets of raw materials, the production process of polypropylene pellets involves a lot of technical requirements. In general, polypropylene pellets lead to polypropylene due to their own degradation and use of various additives during the production process. Pellets have a odor (Paper Reference: Luoyang Petrochemical Polypropylene Co., Ltd. CLC number TQ325.14) As for odor components, as mentioned below.

So far we have come to the conclusion that the original mask odor is because the odor of the non-woven fabric, odor of the non-woven fabric because of its raw material polypropylene granules have odor.

Can you improve this problem? The answer is yes, China has a very high technical level in the polypropylene field, Sinopec, PetroChina polypropylene pellets quality is very good. ExxonMobil's polypropylene pellets abroad are also quite good. Of course, the cause of the mask odor is not the problem of raw materials alone. The following will be mentioned step by step.

At this point, we initially concluded that improving raw material sources can improve the odor problem of raw materials. My point is: There are many homes in non-woven factories all over the country. There are also many homes that produce polypropylene pellets. Find a non-woven fabric manufacturer with a high level of technology and strict requirements on its polypropylene pellet sources (PetroChina, Sinopec, or ExxonMobil, etc.). Can produce "low odor" non-woven fabrics.

However, there are very few non-woven fabric suppliers that do both at home and at the same time. Because for the entire nonwovens industry, the number of non-woven fabrics used in masks is small, while other non-woven fabrics are used in situations where the level of their own odor is not very high, so the polypropylene material is inexpensive. The grain "makes use of it." I consulted the people in the non-woven industry. Since the competition in the non-woven industry is fierce, the profit of a ton of non-woven fabrics is actually lowered to around RMB 1,000. If a good polypropylene raw material is used, the cost per ton will increase by 500. Yuan, directly cut 50% of profits. As a result, unless the customer explicitly requests the use of good polypropylene pellets, they will not increase this part of the cost. The end result is an odor problem caused when these non-woven fabrics are used on masks.

Then we began to introduce the second point. I also mentioned above why non-woven fabric suppliers need excellent technology in addition to raw materials.

In the case of polypropylene pellets, polypropylene breaks above 150 degrees and generates a series of oxidation products, which are precisely one of the sources of odors. Improper use of additives, catalyst residues, etc., will produce odors. To control the generation of odors, it is necessary to efficiently remove the equipment, control the use of additives, use categories, control catalyst residues, etc. I will not describe it further. (Can refer to the paper: Ningxia Engineering and Technology in June 2013 Volume 12, No. 2) So need to have a considerable size and technical conditions of the supplier. Individuals who have learned excellent non-woven suppliers during long-term exposure have their own unique processing methods to reduce this problem.

So far we have come to the conclusion that with excellent pellets, it is also necessary to have excellent techniques for processing pellets in order to ensure that the PP nonwovens produced have a “low odor” level. Finished non-woven fabrics with low odor, I only found 2 in China.

Next, let's study, if I get a good "low odor" non-woven fabrics can solve the problem of mask odor? the answer is negative.

First of all, the non-woven fabric itself has a strong ability to absorb the ambient odor. If it happens improperly during storage and transportation, the non-woven fabric will have an odor. This involves the manufacturer needing at least a separate warehouse for storage of non-woven fabrics, and to achieve good preservation, no moisture, no mold, no insect infestation. This is the first point.

The second point is that there is still a long way to go to save the transportation, from the low odor of a mask, or without odor. Then, let's just say, what is still affecting the problem of non-woven odor? ------produce!

The third point is the production problem. This is an important part that cannot be ignored!

At present, the forming process of the non-woven fabric is ultrasonic welding, and we can only use this method to process it before there is no other processing technology. Does the processing method affect the odor problem? The answer is yes.

So what do we mean by the effect?

Let us first look at a few pictures (Table 1 Reference Paper: "Materials Science and Technology" 2004, 11 (3): 311-314)

In other words, when the temperature is higher than 420 degrees, the polypropylene is completely decomposed, and the decomposition process is doped with an oxidation reaction, which produces a series of irritating gases. While the instantaneous temperature of ultrasonic welding cannot be measured, the opinion of the insiders is as follows

It can be roughly understood that the temperature range of “a few hundred degrees or more is even higher” should cover the critical decomposition temperature of polypropylene. The product will have a pungent oily taste.

Because this temperature cannot provide valid papers and experimental data to testify, its degree of reliability is not very high. Then let's look at a group of pictures, and what exactly is the unpleasant smell component that has been mentioned above. (The following picture references: "Henan Chemical Industry", 2008, 24 (11): 43-45)

Polypropylene in the presence of air, and more precisely in the presence of oxygen, begins to thermally oxidize at 150 degrees to produce so many odorous gases. It is worth mentioning that ultrasonic welding must melt the non-woven fabric, that is, melting polypropylene, and the melting temperature of polypropylene is shown in the following figure:

That is, the mask welding temperature is maintained at at least 160 degrees, typically 240 degrees. As long as the mask can be welded and formed, there must be a thermal oxidation temperature above 150 degrees, (usually 240 degrees welding, just the ideal thermal oxidation temperature) must produce thermal oxidation products, resulting in a lot of odor small molecules. If the temperature is not controlled well, as already mentioned above more than 420 degrees, it is completely decomposed. Produces pungent oily taste.

In addition, some factories are accustomed to ultraviolet disinfection, starting point is good, but ultraviolet light can break the chemical bond of polypropylene, broken bond with oxygen, resulting in aldehydes, ketones and other substances. Therefore, some sellers often say that this is a sterilizing taste. Ultraviolet sterilizing non-woven fabrics can produce tastes, but disinfection and sterilization are more toxic. Regardless of whether it is sterilized or not, there are many phenomena in which odors are regarded as sterilized. Actually, they are also helpless because they do not know why they have odors.

At this point, we came to the conclusion that the reasons for mask odor are as follows:

1 Unwoven fabric raw material Polypropylene pellets have odor

2 improper production process of non-woven fabrics, non-woven fabrics have odor,

3 improper storage and transportation of non-woven fabrics, plant environment restrictions, placing a semi-finished product space smell, resulting in adsorption of environmental odor.

4 Production process limitations, thermal oxidation of polypropylene, and the complete decomposition of polypropylene have resulted in odors.

At this point, we will study in detail the next key! Mask odor components and potential harm.

The first is non-woven raw polypropylene pellets if the source is improper, the raw material particles can produce harmful gases (Reference: Henan Chemical Industry in 2007, Volume 24)

Secondly, assuming that the polypropylene raw material is normal and has a low odor, these harmful gases are produced in the production process of the non-woven fabric (hereinafter referred to as PP product processing).

(Reference: Ningxia Engineering and Technology, Volume 12, Number 2)

Third: Assuming that none of the first two are present, then these gases will be produced during mask making

(Reference: Luoyang Petrochemical Polypropylene Co., Ltd. 471012)

A comprehensive study of these three products found that the main components of the odor on the final mask are carbonyl compounds, formaldehyde, acetaldehyde, ketones, alcohols, acids, acetophenone, etc. These gases are collectively referred to as VOCS organic volatile gases and are harmful to humans. It is beyond doubt. Therefore, smells can be toxic on the other hand.

Personal point of view: Say masks are poisonous and shocking, but there are so many journal papers that come to this conclusion through experimental methods. A large part of the research results brought by these journal articles has been applied to the non-woven fabric manufacturing process. However, the required technical conditions are relatively high and few non-woven manufacturers can do it. Non-woven fabrics are used in a wide range of applications, and these results must be applied to the masks above. In addition, these research results also have a part of the mask (I do not know whether it is intentional or coincidence) but the system uses these research results and provides almost no solutions. Masks that have caused a serious odor in the current mask market account for quite a high proportion.

Masks are toxic, but the concentration of toxic gases has reached a level that can harm human health. Specific analysis is required. If a person can clearly feel that the odor in the mask is unpleasant, nausea, and unacceptable, then there is a certain degree of poisoning. Now. For occupational reasons, I often wear a mask to feel the degree of odor and the size of the resistance. I have rhinitis. I often do this and my nose is blocked. Until I discovered this, I only knew why my nose would be blocked. And for a long time, the throat will still hurt. I sucked quite hard. I inhaled those gases.

Is it possible to determine the gas concentration inside the mask by means of detection? Personally think that is more difficult! In the national standard, the raw materials that describe the mask must be harmless to the human body. However, it is not known that even if the raw materials are not harmful, it will be harmful if it is processed. And in the national standard, only one sentence has been passed on this point, and no in-depth analysis has been conducted.

The volatile gas inside the mask is divided into two parts, one part is the surface layer gas produced by the non-woven fabric, and the other part is the welding gas produced by welding. The surface layer gas can easily fill the packaging bag, and ventilation can eliminate some of the odor of the surface layer. The welding line and other layers of cloth are enclosed in the inner layer, cannot be diffused for a short time, and the evaporation process takes a long time.

Masks as a health-care product, I hope first of all it is harmless. Pregnant women and children, the elderly, the infirm, these people can withstand the concentration regardless of level, try to be the lowest, or even not the best. I am not alarmist, I personally understand.

Do not forget the original intention to do masks!