1. Research Background
Medical protective masks can be used for medical personnel and related staff to protect against airborne respiratory infections, to stop the spread of blood, body fluids and splashes during invasive operations, and to be worn by medical personnel in outpatient clinics, laboratories, operating rooms and other workplaces with high environmental requirements, with strong protection against bacteria and viruses and a relatively high safety factor. Many cross-infections were produced in hospitals using traditional gauze masks, and the role of gauze masks was questioned, and gauze masks did not have protective functions before people began to pay attention to the application of disposable masks and medical protective masks.
The physical indicators that need to be tested for medical protective masks include filtration efficiency, airflow resistance, synthetic blood penetration, pressure difference, flame retardant and other properties. At present, the instruments for testing the physical gas exchange performance of medical protective masks in the domestic market include filtration efficiency tester, airflow resistance tester, synthetic blood penetration tester and flame retardant tester, but there is no pressure difference tester. The high or low pressure difference value on both sides of the mask determines the fluency and comfort of human breathing. Medical mask gas exchange pressure difference is in the constant flow of gas flow through a certain area of the mask, both sides of the gas exchange pressure difference value, that is, the mask on the damping of airflow. To achieve better protection effect, the gas exchange pressure difference value of the mask is very critical, so the medical mask gas exchange pressure difference value becomes an important indicator to judge whether the mask is qualified and the protection level.
In view of the lack of pressure difference tester, we have researched the key technology of gas exchange pressure difference detection for medical masks and developed a special instrument. At the same time, the instrument can also be used to test the gas exchange pressure difference of common fabrics.
2. Instrument structure design features
2.1 Overall structure design
The gas exchange pressure difference performance tester for medical masks is mainly composed of a body, a sample clamping device, a four-bar self-locking sample clamping device, and a control box. The instrument has the characteristics of wide application range, high efficiency, easy operation and convenient sample installation. In order to facilitate the clamping of the sample, the mounting surface of the sample holder is specially designed as a 60° slope, and in order to ensure the flatness of the reference plane for the sample clamp installation, the sample clamp mounting plate is made of a steel plate with a thickness of 8 mm, and its surface The grounding process is carried out to make the installation reference of the front and rear parts of the movable chuck seat and the fixed chuck seat uniform, and ensure the installation coaxiality of the front and rear parts of the sample holder. The structure design of the whole instrument body satisfies the principle of ergonomics, which makes the operation of the experimenter comfortable and convenient.
2.2 Structural design of sample clamping device
The inner hole of the fixed chuck seat is matched with the outer circle of the fixed chuck, and the fixed chuck is loaded from the inner hole of the fixed chuck seat, and it is installed in place by the positioning shoulder on the fixed chuck. The set screw of the fixed chuck is fixed. During the test work, the fixed chuck cannot move because the fixed chuck seat is fixed, and the movable chuck is located under the fixed chuck, and the movable chuck can slide back and forth on the movable chuck seat relative to the movable chuck seat. In order to reduce frictional resistance, a copper sleeve is inlaid on the movable chuck seat, and the copper sleeve is embedded in the movable chuck seat with an interference fit. The movable chuck is loaded from the inner hole of the copper sleeve. When the movable chuck slides in the copper sleeve, The friction between the two is reduced, and the movable chuck plays a supporting and positioning role. This device ensures the coaxiality of the sample during the clamping process and ensures the accuracy of the test results.
When the movable chuck moves upwards and the movable chuck enters the positioning cavity of the fixed chuck, the sealing ring on the end face acts as a seal, which not only ensures the accuracy of the effective area of the test, but also provides a guarantee for the accuracy of the test results , the test results have good reproducibility.
2.3 Working principle
A digital display gas flowmeter is used to control the flow of gas flowing through the sample. The flowmeter adopts advanced microcomputer technology and high-performance integrated chips, and uses micro-power consumption technology to reduce the power consumption of the whole machine. The gas exchange pressure difference tester for medical masks is mainly used to measure the pressure difference between the two sides of the mask for gas exchange. During the working process of the tester, the differential pressure sensor is used to detect the differential pressure value; the gas flow is controlled by the regulating valve.
The automatic control system of the instrument is composed of the panel control system, the differential pressure detection system, the flow adjustment system, and the alarm system. The error ensures the test accuracy and improves the test efficiency.
During the test, control the control links of each part of the instrument through the control buttons on the operation panel. The current differential pressure value can be dynamically read in real time from the digital display, and the accuracy of the differential pressure value is 1%. When the value on the digital display is in a stable state, press the "test stop" button, and the ZD differential pressure value that occurs during the test is locked on the screen of the display. If the differential pressure value detected by the differential pressure sensor exceeds the range of the range, the tester will send out an alarm signal and stop the test automatically. During this process, the digital display will also lock the ZD differential pressure value transmitted by the sensor on the display. on the screen.
Usually, when the air permeability of the sample is better, the pressure difference value obtained by the tester is smaller. On the contrary, when the air permeability of the sample is poor, the pressure difference value obtained by the tester is larger. When using the Medical Face Mask Air Exchange Pressure Difference Tester for the test, the test data is recorded in real time, and the average value M is taken as the result.
According to the requirements of the standard, the test area S=4.9 cm2. Then the pressure difference per unit area ΔP=M/4.9. Comparing the obtained pressure difference per unit area with the requirements in the standard (the pressure difference ΔP on both sides of the mask is 49), it can be inferred whether the sample meets the requirements.
3. Analysis of test results
3.1 Test conditions and specimen selection
All tests were conducted in a constant temperature and humidity room with temperature (21±1)℃ and relative humidity (60±2)%. Five kinds of mask products were selected, namely, daily mask (cotton), nonwoven mask, skimmed gauze mask (cotton), seaweed fiber mask, and PM2.5 mask. Each material is cut according to the standard requirement size, and then the specimen is put in the constant temperature and humidity room for more than 24 h to reach the moisture balance and then start the test.
3.2 Test scheme and content
Through the comparison of the test results in Table 1, it can be seen that the fabric of skimmed gauze mask (cotton) is skimmed cotton, which is made of gauze folded and sewn in 10 layers, and its fabric tissue is loose, and the measured gas exchange pressure difference performance is good; secondly, it is a non-woven mask made of non-woven fabric folded and sewn in 2 layers after several hydrophilic treatments; thirdly, it is an ordinary daily mask made of ordinary knitted cotton fabric folded and sewn in 3 layers; fourthly, the tissue is 3 layers of non- PM2.5 masks have the worst gas exchange pressure difference performance because they are made of many kinds of fabric stacked together and sewn. Through the data in Table 1, it can be concluded that: the gas exchange pressure difference performance of daily masks (cotton), non-woven masks, skimmed gauze masks (cotton), and seaweed fiber masks is better; PM2.5 masks have poor gas exchange pressure difference performance because the tissue is too dense.
4. Conditions and prospects for promotion and application
In recent years, with the strengthening of national attention to personal safety protection and the growth of occupational disease incidence, the market space for professional masks is huge. Professional masks keep occupying the market, while the market share of low-end all-gauze masks will keep decreasing, which is an inevitable trend. And with the improvement of people's living standards, people also continue to pay attention to health, civilian masks will also develop to specialization. Medical mask gas exchange pressure difference detection key technology research and special instrument development, for medical mask performance evaluation provides a technical guarantee, solve the domestic only the corresponding test standard, but no corresponding test instrument problem, the production of enterprises has a positive guiding significance, but also makes the competent departments at all levels of the mask product quality supervision has a basis to follow. The development and production of the medical mask gas exchange pressure difference testing instrument provides a proven means for the detection of masks, provides a technical guarantee for the overall improvement of mask quality, and promotes the sustainable development of the mask industry. After the instrument enters the market, it will effectively improve the quality of mask products and make a qualitative leap, which will play a positive role in promoting economic development and improving people's quality of life.
The Medical Face Mask Air Exchange Pressure Difference Tester is developed according to the requirements of the pharmaceutical industry standard YY 0469-2011, and is suitable for testing the gas exchange pressure difference of medical masks. The instrument has the characteristics of wide range of use, high efficiency, easy operation, convenient sample installation, accurate test results and high test efficiency. It provides an effective way for enterprises and testing institutions to accurately test the quality of mask products.