Abstract : In order to solve the problems of superimposed compression, complicated wear and tear and exposure risk of traditional protective clothing and its supporting head and face equipment, a new type of high-comfort medical protective clothing with multiple functions was developed by using injection molding, point hot melting, re-injection molding and pressing hole process. The breaking strength of the head and face structure of the integrated protective clothing prepared by this process can reach more than 105 N, and the moisture permeability of the sweat-prone parts of the human body such as the head and back can reach more than 8 705 g / ( m2 · d ). The results of three groups of clinical trial studies show that the comfort of the new protective clothing is better than that of the traditional protective clothing, the wear-off efficiency is higher than that of the traditional products, and the safety has been greatly improved. The product quality is stable, and the qualified rate of the finished product of the pilot line reaches 99.8 %, which provides a guarantee for improving the safety, convenience and comfort of medical protective clothing in clinical application.
Keywords : medical protective clothing ; injection molding ; head and face integration ; moisture permeability ; breaking strength

 

From the outbreak of atypical pneumonia ( SARS ) to the spread of coronavirus disease 2019 ( COVID-19 ) in the world, a large number of people were infected or even died in both special periods [ 1-4 ]. Studies have found that most viruses can directly or indirectly contact the human body through carriers such as liquid and aerosol particles suspended in patients ' body fluids, blood and droplets, and the infectivity of close contact is more intense [ 5 ]. Therefore, when medical workers are in close contact with the source of infection, in addition to wearing protective clothing, they also need to wear medical masks, medical caps, face screens, goggles, rubber gloves, shoe covers and other highly closed personal protective equipment for treatment and self-protection [ 6-7 ]. The wearing of traditional protective clothing and its supporting equipment has the risk of poor individual matching, superimposed compression, cumbersome wearing and taking off, and secondary pollution of stripping in clinical applications [ 7-8 ]. Especially in the long-term use, the hot flashes caused by human respiration and body temperature can easily make users feel psychological and physiological irritability and discomfort [ 8-9 ]. In order to solve these problems, the research of protective clothing in recent years has focused on the integrated design of head and face [ 8-10 ]. At present, the listed head and face integrated products are basically used in conjunction with the air supply device, with high cost, heavy self-weight, and the risk of secondary pollution of recycling and disinfection.

To address the pain points mentioned above, this article starts from three aspects: structural design, raw material selection, and process improvement of protective clothing. It studies the processing technology suitable for passive medical integrated protective clothing, explores the development of medical disposable protective clothing that combines safety, convenience, and comfort, and conducts clinical trials on the new type of protective clothing.

1 Experiment

1. 1. Structural design

The new protective clothing designed in this paper is based on the traditional protective clothing, and adds components such as eye protection area, mouth and nose protection area and shoe cover area, which completely covers the wearer 's head and face, trunk, limbs and feet, forming a more closed integrated structure product, as shown in Figure 1.

The head and face integration of new protective clothing is the core of product design. The structure is to overlap and fix the patch of the head sleeve ( A1 ) and the mouth and nose ( A2 ) ( referred to as the head and face patch ) with the windward side of the eye mask ( B ) and the skin-friendly side of the eye mask ( C ) to form an internal and external sandwich structure, as shown in Figure 2.

Fig．1 A new product show of high comfort integrated medical disposable protective clothing

Fig．2 Structure design of head and face

1. 2. Experimental materials

The main raw materials involved in the product experiment are shown in Table 1.

1. 3. Processing technology

As shown in Figure 3, cut the head cover A1 and mouth and nose protection A2 separately, and use the Brother brand S-7300A-303 computer flat sewing machine to sew the A1 and A2 flat cars to form a head and face joint, which serves as a soft multi-layer non-woven fabric area for the head and face.

Firstly, B was injected into the windward surface of the composite sheet, and then C was injected into the skin-friendly surface. The C face of the B-A-C sheet was placed on the shaped nylon plate, and the A material between B and C was removed by pressing the knife mold to obtain the head-face integrated product. In order to select suitable materials, different injection molding materials and fabrics in Table 1 were processed into head and face integrated products according to the same process and compared.

Tab．1Ｒaw materials for product testing

Fig．3 Schematic of head and face integration technology

In addition to the head and face, the rest of the parts are connected and closed by the traditional process of sewing and hot air press strip, and then the PC lens is installed into the eye cover. The sterile products were packed into the outer box after the inner packaging was completed and sterilized with ethylene oxide.

1. 4. Test

1 ) Breaking strength and breaking elongation. The breaking strength of the materials in the chest, arms, back position and shoe cover of the protective clothing was tested according to the strip method specified in GB / T 3923.1-1997 ' Textile fabrics--Part 1 : Determination of breaking strength and elongation at break '. The test equipment was HD026PC-200 multi-functional electronic fabric strength tester.

Because the integrated part of the head and face is a three-dimensional structure, it cannot be directly clamped, and it needs to be preprocessed to test its breaking strength. The pretreatment method is as follows : a plain cloth strip with a longitudinal direction of 20 cm and a latitudinal direction of 5 cm is cut, and the latitudinal end of the cloth strip is sutured to the injection part inside the eye mask area with a needle pitch of 12 needles / 3 cm, and the head and tail ends of the suture position are fixed with two back and forth needles, as shown in Fig.4. The strength test equipment is the same as the above, and the equipment fixtures respectively clamp the 2 and 3 parts in Figure 4, as shown in Figure 5. Test at least 3, take the lowest value as the strength test results.

Fig．4 Sketch of clamping rig for the strength test of preprocessed specimen

2 ) Moisture permeability. According to GB / T 12704.1-2009 ' Textile Fabric Moisture Permeability Test Method Part 1 : Moisture Absorption Method ', the moisture permeability of each part of the product was tested by YG501D-II moisture permeability tester.

3. Filtering efficiency of non oily particulate matter. Test the filtration efficiency of various parts of non oily particulate matter using a particle filtration efficiency meter with model G506 based on GB 19082-2009 "Technical Requirements for Medical Disposable Protective Clothing".

Fig．5 Strength test of head-face part integration process

4 ) Liquid barrier properties 1 : Water impermeability. Samples were taken from various parts of the product, and tested with a fabric water permeability tester model YG812C. The test was performed according to the method A moisture absorption method specified in GB / T 12704-1991.

Fig.5 ) Liquid barrier performance 2 : Anti-synthetic blood penetration. Samples were taken from various parts of the product and tested with a synthetic blood penetrometer of WDJY-001-01. The test was performed according to the method in Appendix A of GB 19082-2009.

6 ) Clinical comparative test. The medical staff working in the hospital were selected to carry out the test in a continuous wearing manner. The clinical was divided into three groups. Finally, the number of effective tests in each group was 31 in the first group, and each person tried it on three times. The second group of 32 people, each try on 3 times ; the third group of 20 people, each try on 1 times. The first and second groups compared the clinical trial speed and effect of traditional protective clothing and new protective clothing. The third group only observed the wearing process of the new protective clothing and tested the products after wearing [ 13 ]. The participants involved in the clinical trial included men and women aged 18-66 years, and also covered people who wore glasses and did not wear glasses, worked indoors and outdoors. The main items of the assessment in different groups are shown in table 2. 92 respectively.

 

Tab．2 The main observation and assessment items of clinical try-on test

 

2 Results and discussion

Based on the integrated structure design, in order to ensure the basic respiration of the human body and achieve the necessary protective effect, the moisture permeability, particle filtration efficiency and strength of the material are the elements of the project assessment. Therefore, it is very important for the selection of materials.

 

2.1 Material screening

The safety performance of the fabric is evaluated by testing the filtration efficiency, liquid barrier properties and breaking strength of the fabric. The comfort performance of the fabric is evaluated by testing its moisture permeability. While considering the comfort and safety, the cost of the material is comprehensively considered to determine the application site of the material. The test data are shown in Table 3.

 

Tab．3 Material test results of different parts of protective clothing

The test results show that although the filtration efficiency of PP-PET material is slightly lower than that of PP PE and PU micro-porous fabrics, it can still reach 98 %, which can fully meet the requirements of the national standard for the filtration efficiency of non-oily particles not less than 70 % [ 14-15 ]. Its moisture permeability is second only to PU micro-porous fabric, reaching more than 8 490 g / ( m2 · d ), with better comfort. Considering that the PU micro-porous fabric is thin and it is difficult to realize the integration process with the multi-layer material of the mouth and nose, the PP PET fabric is applied to the head area with the largest sweating amount of the human body, and the PU micro-porous fabric is applied to the back area of the human body, so that the comfort of the product is greatly improved while ensuring cost control.

The frame part of the traditional goggles is generally made of PVC injection. In order to reduce the hardness of PVC, phthalate plasticizers are usually added. Studies have shown that long-term contact or inhalation of phthalates with the skin can cause certain harm to the human body. [ 16 ]. For this reason, the injection molding materials for the eye mask frame were optimized and screened, and the results are shown in Table 4. It can be seen that : 1 ) Due to the polarity difference between PVC and PP-PE, PVC ( polarity ) and PP-PET ( polarity is very weak ) are not sticky, and they cannot be injected together. 2 ) The injection molding of TPE, TPO, TPU and PP-PET is better than that of PP-PE. The reason may be that TPE, TPO, TPU and PP-PET have different polarity, but PP-PE is a non-polar material, and the difference in polarity leads to different compatibility. Similarly with PP-PET injection molding, TPE is superior to TPU and TPO, because the melting temperature of TPE and PP-PET material is close, the molecular chain motion activity of the material in the processing state is similar, and because of the existence of PP molecular chain structure, it has good compatibility. However, the processing temperature of TPU is relatively low, and the processing temperature of TPO is lower. The melting state of the two is not enough to soften the PP-PET material and cause the movement of the molecular chain. Therefore, only weak bonding force exists. Although the breaking strength of TPE and PP-PET after injection molding is higher, there is still a problem of weak penetration of the inner layer of the injection molding with the head and face piece, resulting in the overall breaking strength of the product is not high.

 

Tab．4 The strength of eyecups after injection of different materials

2.2 Process improvement

In order to further improve the permeability of the eye mask frame material and the inner layer of the head and face piece, and improve the overall breaking strength of the head and face integrated product, the process was partially improved on the premise that TPE was selected as the eye mask frame material. In the case of basically the same injection conditions, after the injection of part B into the windward surface of the head and face piece, the ' spot hot melt ' treatment process of the inner fabric part of part B is added to open the connection channel between the multi-layer fabrics, so as to solve the problem that the frame can only be bonded to the surface fabric by relying solely on the ' injection molding ' process, and the infiltration of the sandwich layer material is not uniform and the adhesion is not strong, so that the strength index can only be improved by increasing the pressure, increasing the temperature and prolonging the injection time, which leads to the accelerated aging, brittleness and even hole breaking of the fabric.

Compared with the simple injection molding process, the breaking strength of the head and face integrated product is increased by 32.5 N, reaching more than 105 N, and the hole problem is reduced by 7 % after adding the ' dot hot melt ' treatment process. The integration of the process improves the quality stability and qualification rate of the product. The trial production is shown in table 5.

 

Tab．5 The different trial production of head-face parts’crafts

Tab．6 The contrast between new protective clothing＆traditional one

2.3 Clinical try-on study

The comparative results of subjective and objective tests for three groups of clinical wear and tear off and long-term wear are shown in Table 6. The results show that the new protective clothing designed in this study takes significantly less time to wear and take off than traditional protective clothing; After continuously wearing protective equipment and working for a period of time, the facial exposure rates of the two groups of participants wearing traditional protective clothing were 100.0% and 71.88%, respectively. The three groups of participants wearing new protective clothing did not show any facial exposure; The proportion of fogging in the window area of the two groups wearing traditional protective clothing was 100.00% and 28.13% respectively, and there was no fogging in the window area when wearing new protective clothing; After the third group tried on the new protective clothing, the particle filtration efficiency of each test site was>94.00%, which was better than the national standard of "no less than 70%". The hydrostatic pressure of penetration in each test site was>14.00 kPa, which was better than the national standard of ≥ 1.67 kPa. The surface moisture resistance of each test site reached level 3 or above.

3 Conclusion

1 ) The head and face of medical protective clothing using PP-PET can simultaneously obtain a higher moisture permeability of more than 8 000 g / ( m2 · d ) and a higher filtration efficiency of more than 98 %, which can take into account both wearing comfort and protective safety, and can be firmly combined with multi-layer materials in the nose and mouth.

2 ) Thermoplastic elastomer rubber ( TPE ) is used in the eye mask part, which can be combined with the grafting agent in PP-PET non-woven fabric. The strength of the spliced sheet is better than that of traditional frame materials PVC, TPO, TPU, etc.    

3 ) Adding ' dotted hot melt ' process in the injection molding process of head and face piece can solve the problems of uneven penetration and poor adhesion of the sandwich layer, and greatly improve the breaking strength of the head and face integration part, so as to improve the quality stability of the product.

 

FAQ 1: What is head and face integrated design in medical protective clothing?

Answer: Head and face integrated design in medical protective clothing refers to the incorporation of a protective hood or face shield directly into the garment. This design approach ensures comprehensive protection for healthcare professionals by covering their head, face, and neck areas along with the body. The integrated design minimizes potential exposure to infectious agents, aerosols, and other contaminants during medical procedures, enhancing the overall safety and efficiency of the protective clothing.

FAQ 2: How does head and face integrated design improve the functionality of medical protective clothing?

Answer: The integration of head and face protection in medical clothing offers several key benefits:

• Seamless Coverage: The unified design eliminates potential gaps between separate headwear and bodywear, ensuring complete coverage and reducing the risk of exposure.
• Enhanced Comfort: Integrated designs often prioritize comfort and ease of movement, allowing healthcare workers to perform their tasks with greater flexibility and comfort.
• Simplified Donning and Doffing: The one-piece design streamlines the process of putting on and taking off the protective clothing, optimizing workflow and saving time.
• Reduced Contamination Risk: By minimizing the need for additional accessories like goggles and face shields, the integrated design helps minimize the risk of self-contamination.

FAQ 3: What are the potential applications of medical protective clothing with head and face integrated design?

Answer: The application of head and face integrated design in medical protective clothing has diverse potential uses:

• Infection Control: Medical professionals can wear such clothing during high-risk procedures, such as surgeries, where the risk of exposure to bodily fluids and pathogens is heightened.
• Epidemic Outbreaks: During infectious disease outbreaks, the integrated design provides an added layer of protection for healthcare workers attending to infected patients.
• Containment Units: The clothing can be utilized in isolation and containment units, where a high level of protection is necessary to prevent the spread of contagious agents.

How to Contact Us:

• Visit our website: https://www.nbyichou.com/
• Email us: [email protected]
• Call us/whatsapp: +86 13355741031
• Chat with us: Live chat support available on our website