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- 1. Fine Systems Technologies www.fine-systems.tech Russia 2020 Masks and respirators Materials and production techniques
- 2. 2 Types of masks In terms of certification and technology, masks are divided into the following groups Face masks They're not medical. Minimum requirements for functionality. It can be made industrially, on small manufactures, hand-made. Efficiency may vary, but by default, they are considered to be without protective functions in case of serious threats. Not recommended for use in medicine. Non-medical face masks, masks, common mask, etc. Different materials and technologies. A medical face mask (surgical mask or procedure mask) Medical masks are used to prevent breathing transmission of particles and droplets, including various infectious agents. They should cover the nose, mouth, and chin. Must be certified. Have different levels of protection. Affected by different standards. Only produced under industrial conditions. Covered by standard EN 14683:2014. Respirators, half face masks Apply to personal protective equipment (PPE). Should be able to trap both solid particles and liquid droplets, in some cases gaseous substances. May have additional elements such as filters, valves, etc. It is important to note that in many cases there is no filtration when exhaled. Respirators, half face masks, filtering face piece (FFP). Subject to EN 149:2001+A1:2009.
- 4. Masks
- 5. 5 Medical face mask There are several classifications of medical masks The masks are tested on the following parameters: - Test Method for Evaluating the Bacterial Filtration Efficiency (BFE) of Medical Face Mask Materials, Using a Biological Aerosol of Staphylococcus aureus; - Test method for determining the initial efficiency of materials used in medical face masks to penetration by particulates using latex spheres; - Test method for resistance of medical face masks to penetration by synthetic blood (horizontal projection of fixed volume at a known velocity); - Test method for resistance of materials used in protective clothing to penetration by blood-borne pathogens using Phi-X174 bacteriophage penetration as a test system Additionally, the safety of the used materials, flammability, etc. is tested. Classifications by: - EN 14683:2014. Medical face masks — Requirements and test Methods; - ASTM (American Society of Testing and Materials American Society of Testing and Materials (ASTM); - Numerous local standards https://www.beckershospitalreview.com/quality/the-4-fs-of-medical-mask-selection.html https://www.primed.ca/clinical-resources/astm-mask-protection-standards/ https://healthcentricadvisors.org/wp-content/uploads/2017/04/3_MaskEnomics_Poster_2012.pdf https://www.astm.org/standardization-news/?q=features/standards-medical-face-masks-and-protective- clothing-.html
- 8. 8 MEDICAL FACE MASK TESTS AND REQUIREMENTS https://www.nelsonlabs.com/wp-content/uploads/2020/03/Face-Mask-Testing-Requirements.pdf
- 9. 9 Multilayer construction Modern medical masks have a multi-layered design. 3-layer masks are found and manufactured, but there are masks from 4-5(7) layers Layer Description and properties Materials Importance Outer layer / Cover layer The outer layer is designed for rough filtering of large particles. Hydrophobic properties for rejecting liquids are required. Usually colored. Non-woven fabric: PP Spunbond (SBPP). Non-woven fabric: Melt-blown polypropylene. PP + PE. PET. Rayon. Need Additional layer / Support layer An additional layer. It can provide additional filtration, contain additional compounds to catch odors and liquids, oils, etc. It can be located outside for exterior applications. All listed filtering materials. In addition, various impregnations, activated carbon, graphene and other materials can be used. Optional or marketing Basic Filter Layer Basic filter layer. The finest filtration. Designed for basic filtration. Electrostatic properties are mandatory. Non-woven fabric: Melt-blown polypropylene. Micro spun fibers polypropylene + melt-blown polypropylene. PTFE. Need. Can be duplicated. Additional / Support layer An additional layer. It can provide additional filtration, contain additional compounds to catch odors and liquids, oils, etc. All listed filtering materials. In addition, various impregnations, activated carbon, graphene and other materials can be used. Optional or marketing Internal layer / Shell layer The inner layer is designed to filter exhaled and breathable air. It provides contact with the face. Hydrophilic properties for the absorption of liquids are required. Must be soft so as not to injure the skin. Non-woven fabric: PP Spunbond. PP + PE. PET. Rayon. Cotton. Thermal Bonded Polypropylene. Need
- 10. 10 Multilayer construction In addition to the basic layers, there are other parts of the masks The main parts: - Nose Wire (100% PE, alluminium); - Elastic Band (spandex and polyester) No threads are used in modern masks. The layers are joined mainly by ultrasonic welding. In rare cases, an adhesive joint is used. Also, different models use different strips and foams for liquid trapping (anti-fog), foam seals for the nose, etc. There are masks with different shields to protect the eyes, neck, etc. http://www.95mask.com/news/disposable-surgical-face-mask-material- details.html
- 11. 11 Multilayer construction The basic concept of building medical masks The design of medical masks is based on the concept of the multilayer. The number of layers can vary. But the basis is three-ply (3-ply) masks. 1. The outer layer has two functions. Rough pre-filtration and protection against liquid droplets. Rough filtration is needed to increase the operating time of the main filter layer. Hydrophobicity is needed to protect against liquid droplets; 2. The main or middle layer. Basic filter layer. Serves as the main filter against fine particles. The basis of the mechanism is electrostatic filtration; 3. The inner layer - has three functions. Exhalation filtration and additional filtration on inhalation, moisture absorption, facial skin protection from abrasion. All other outer or inner layers are used to obtain additional properties of the mask. https://www.georgetownpharmacy.com.my/pages/surgical-masks-which-side-out
- 12. 12 Basic parameters for the design of masks There is a large number of medical masks of different designs and constructions on the market. The basic standards specify only the functional parameters that medical masks must satisfy. This slide covers the "designer" for medical masks The class of masks can be changed by the following parameters: - Changing the number of layers. Adding layers with different characteristics can improve the performance of masks. However, increasing the number of layers will make it difficult to breathe and may not exceed a specific limit. - Changing the characteristics of individual layers. Nonwovens have properties such as thickness, density, porosity, and fibers thickness. By changing these properties, individual characteristics can be improved. But then again, if the thickness is too thick, it will make breathing difficult; - A change in the structure of the layers. That is, creating composite layers from different types of materials; - Modification of the layers by physical and physical-chemical methods; - Additional additives to the layers to give different properties; - Use of new materials In addition, the design of the masks may also be suitable to go beyond the current standards. For example, the design of masks with breathing disabilities for short periods of time. For example, shop visits, short trips on public transport. This can be the case for masks with a small number of layers and less demanding materials.
- 14. Respirators
- 15. 15 Mechanical filter respirator Respirators, respirator masks, half-face masks, mechanical filter respirator, FFP (filtering facepiece) mask. There are several classifications of such respirators Classifications by: - United States NIOSH-42CFR84; - Europe EN 149:2001+A1:2009 - China GB2626-2006; - Australia/New Zealand AS/NZA 1716:2012; - Korea 1st class (Korea KMOEL - 2017-64); - DS (Japan JMHLW-Notification 214, 2018) https://www.cdc.gov/niosh/npptl/topics/respirators/pt84abs2.html Europe EN 149:2001+A1:2009: Respiratory protective devices Filtering half masks to protect against particles. Requirements, testing, marking. FFP3, FFP2/N95 and analog respirators are used for work in biologically hazardous environments. They are not designed to protect against allergens (FFP3) for several reasons. In the case of pollen, it is meaninglessly expensive, although it will work. In the case of chemical compounds, it won't work without additional adsorbing layers.
- 16. 16 Mechanical filter respirator Example of a comparison of respirators meeting similar standards https://multimedia.3m.com/m ws/media/1791500O/comparis on-ffp2-kn95-n95-filtering- facepiece-respirator-classes- tb.pdf
- 18. 18 Mechanical filter respirator Mask respirators are designed for long-term work in contaminated environments. This imposes many restrictions on their construction, design, and testing The following features of respirator masks can be noted: - The edges of the respirator must fit tightly to the face; - Must have a "volume design" for a small amount of air between the mouth, noses, and respirator; - Must be tested for breathing quality; - Must be tested under working conditions; - Must be designed to absorb moisture; - Preferably reduced overheating of the face during prolonged work In general, they are designed to filter the air from solids and liquid droplets. https://multimedia.3m.com/mws/media/601738O/3m-disposable-respirators- brochure.pdf?&fn=MFR%2520Product%2520Catalogue.pdf https://multimedia.3m.com/mws/media/1829292O/3m-aura-particulate-respirator-9300- series-technical-datasheet.pdf https://www.cdc.gov/niosh/npptl/topics/respirators/factsheets/respsars.html
- 19. 19 Mechanical filter respirator There are several designs of respirators - Fold-flat respirators - folding respirators, folded to reduce volume. It can be folded horizontally or vertically. - Cone, cup or common respirators - have a rigid construction. It is not recommended to fold or wrinkle; - Valveless respirators - inhalation and exhalation pass through the respirator material and the air is cleaned both on inhalation and exhalation; - Respirators with a valve - an additional valve are used for exhalation. Usually, the air passing through it is not filtered. There may be several valves on the sides of the respirator or one in the center Reusable masks, similar to respirators, with changeable filters and valves, are not classified as respirators. Such products are intended for individual use only. The valve is set with two targets: - to improve the exhalation; - heat removal
- 20. 20 Multilayer construction Modern respirators have at least 4 layers in their design Layer Description and properties Materials Importance Outer layer / Cover layer The outer layer is designed for rough filtering of large particles. Hydrophobic properties for rejecting liquids are required. Non-woven fabric: PP. Non-woven fabric: Melt- blown polypropylene. Spunbond (SBPP). PP + PE. PET. Rayon. Need Basic Filter Layer Basic filter layer. The finest filtration. Designed for basic filtration. Electrostatic properties are mandatory. Non-woven fabric: Melt- blown polypropylene. Micro spun fibers polypropylene + melt- blown polypropylene. PTFE. Need Hydrophi lic layer / Frame support layer This layer is designed to collect moisture from breathing, to maintain the shape of the respirator and to provide additional filtration. Non-woven fabric: PP Spunbond. PP + PE. PET. Rayon. Cotton (PP or cotton). Thermal Bonded Polypropylene. Modacrylic. Need Internal layer / Shell layer The inner layer is designed to filter exhaled and breathable air. It provides contact with the face. Hydrophilic properties for the absorption of liquids are required. Must be soft so as not to injure the skin. Forming a frame. Non-woven fabric: PP Spunbond. PP + PE. PET. Rayon. Cotton (PP or cotton). Thermal Bonded Polypropylene. Need
- 21. 21 Multilayer construction General description of the functioning of the respirator When you inhale: - The air passes through the first filter layer. Large particles are rejected or filtered and liquid droplets are trapped; - The air passes through a fine filter layer. This is usually an electrostatic filter that traps the particles. Since the fine particles almost always have a charge on the surface, they stick to the filter fibers; - The air passes through a fourth layer. Here, additional filtration occurs; - The air passes through the last layer where additional filtration is provided. On exhalation: - The air passes through the fourth layer, providing basic rough filtration; - Air passes through the third layer. It also traps the liquid that emerges from breathing, accumulates saliva, perspiration, etc.; - The air passes through the second layer. Fine filtration takes place here; - The air passes through the last layer where additional filtration is provided.
- 22. 22 Multilayer construction Long operating time and moisture collection and removal Respirators are designed for continuous operation (up to 6 hours). During this time, a large amount of moisture accumulates when breathing, saliva, sweat. The third layer is used to accumulate this moisture. Which should accumulate moisture. In the case of respirators with a valve, it is assumed that some moisture can be removed without filtration. However, such respirators are not recommended for medicine. Interaction with the skin. The softest anti-abrasion materials are selected for the layer that comes into contact with the face when the respirator is worn for a long time. They only provide coarse filtration. Ideally, they should drain moisture into the layer to accumulate it.
- 23. 23 Multilayer construction Additional layers In addition to the 4 basic layers in modern respirators can be up to 10 layers. Usually 5-7 layers in most models. The additional layers may provide the following functions: - Additional rough filtration; - Additional fine filtration; - Oils hold; - Odor catching, such as the addition of activated carbon and graphene; - Additional shape support layers Basic limits on the number of layers: - The breathing ability of the respirator must be maintained. Too many layers will make it difficult to breathe; - It is necessary to maintain heat removal, increased sweating will lead to premature filling of the collecting fluid layer and loss of filtering functions by the respirator.
- 24. 24 Multilayer construction Other parts of the respirator The main parts: - Nose Wire (aluminum or100% PE). Required for fixation on the face and nose. When using a respirator, bend hands to the shape of the nose; - Elastic Band or strap (spandex and polyester, polyisoprene); - Staples (steel or aluminium); - Nose foam (polyurethane). Used to reduce nose abrasion. To fit tightly to the face, the edge of the respirator must be flat. No threads are used in modern respirators. The layers are joined mainly by ultrasonic welding. In rare cases, an adhesive joint is used. Also, different models use different strips and foams for liquid trapping (anti-fog), foam seals for the nose, etc. There are masks with different shields to protect the eyes, neck, etc.
- 25. 25 Multilayer construction Other parts of the respirator Some models use an additional exhalation valve. Usually, it does not filter out the exhaled air. It is designed to remove heat and liquid. Valve materials: - Valve (polyproylene); - Valve diaphragm (polyisoprene)
- 26. 26 Multilayer construction The basic concept of building respirators The design of respirators is based on the concept of the multilayer. The number of layers can vary. There are at least four basic layers in modern respirators. 1. The outer layer should provide rough filtration, push away liquid droplets, i.e. have hydrophobic properties. Particle holding is necessary to extend the life of the fine filter; 2. The fine filter is used to trap fine particles. It is due to electrostatic filtration. 3. The layer of moisture accumulation. It is used to remove moisture that occurs during breathing, saliva, sweat. Also, this layer supports the shape of the respirator; 4. A layer to prevent abrasion of the face. It provides rough filtration; 5. The respirator should fit tightly to the face. The edges of the respirator should be flat. All other outer or inner layers are used to obtain additional properties of the respirators.
- 27. 27 Basic parameters for the design of respirators There are a few major respirator manufacturers on the market. They produce many different models. This slide covers the "designer" for respirators The design of the respirators is not directly mentioned in existing standards. Respirators are tested for performance only. The following principles can be proposed for the design of respirators: - Change in the number of layers. Adding new layers. Changing the functions of the layers, etc.; - Changing the characteristics of individual layers. It can be the use of different materials, change the density of layers, thickness, porosity, etc.; - Changing the shape of the respirator. There are hard-fitting and folding respirators on the market; - Introduction of additional materials into the layers of the respirators; - Changing the design of individual layers. For example, using layers of the same material or using composite layers. For example, SS, SMS, SM and similar; - Shortening the working time of the respirators for use in niches where several hours of work are not necessary. In any case, the respirators are designed. There are no uniform designs beyond the basic principles.
- 30. 30 Masks and respirators hybrid Due to the epidemic of the new virus, medical professionals are now in many cases required to use N95(99) or FFP2(3) respirators Medical masks do not provide the necessary protection when dealing with virus diseases. They don't fit tightly to the face. They do not provide the necessary filtering. For this reason, medical professionals are now using respirators in routine procedures that previously did not require this level of protection. But mass-use respirators are expensive, difficult to produce and so on. https://www.cdc.gov/coronavirus/2019-ncov/hcp/checklist-n95-strategy.html https://www.businessinsider.com/types-of-masks-used-for-coronavirus-outbreak-n95- surgical-2020-3 https://www.vox.com/2020/4/8/21209895/coronavirus-face-masks-n95-covid-19-ppe- shortage A possible solution to the problem may be an intermediate solution. Special masks similar to respirators are available on the market. https://www.amazon.com/Medline-Surgical-Style-Non27381-Pound/dp/B00B973OYM https://www.walgreens.com/store/c/walgreens-face-mask,-cone- style/ID=prod6172910-product https://products.halyardhealth.com/infection-prevention/facial-respiratory- protection/masks-respirators/standard-cone-mask-with-headband-blue.html
- 31. 31 Masks and respirators hybrid Designing masks to meet the standards for respirators will require considerable effort. However, they may conform to current standards for medical masks, but have additional features that make them suitable for wider use It's necessary for the right match: - Provide the necessary protection against drops and splashes; - Provide a fitting to the face; - Provide the right time to work; - Provide a fixed form to preserve breathing air volume; - Provide the necessary moisture-absorbing properties This can be achieved in the following ways: - Define specific performance characteristics for the medical niche (reduce respirator running time); - Using new materials (e.g. membrane waterproof materials); - Use of additional constructions to maintain the shape
- 32. Filters
- 33. 33 Filters Masks and respirators are by nature filters There are several filtering mechanisms: - Rough mechanical filtration. In this case, the filter pores are smaller than the particles. The most effective method, but the smaller the pore size, the harder it is to breathe through such a filter. In the case of masks and respirators, it is used only for large particles; - Mechanical filtration. There are a few mechanisms. It is the reflection, slowing down the particles by filter fibers. Catching of particles by filter fibers (direct impact). Grabbing the particles in the boundary layers of air near the fibers (stopping their movement). Limiting the diffusion of the particles by reducing the Brownian motion at the surface of the fibers; - Electrostatic filtration. If the fibers of the filter material are charged, they attract or reject the charged particles. Particles with positive charge are rejected by such filter, particles with negative charge stick to the filter fibers. This mechanism makes it possible to create filters to trap particles smaller than the filter pores. Without this mechanism, particles would pass through pores of similar material without resistance. The basic material for such filters is molten blown polypropylene https://www.ncbi.nlm.nih.gov/pubmed/10957816 https://multimedia.3m.com/mws/media/99824O/spurious-research-on-electrostatic- filter-performance-2001.pdf https://journals.sagepub.com/doi/pdf/10.1177/155892501300800307 https://blogs.cdc.gov/niosh-science-blog/2009/10/14/n95/
- 35. 35 Commercial secrets Production of respirators, masks, and other personal protective equipment (PPE) is a big market. Manufacturers are interested in keeping confidential detailed information about the materials and technologies used Manufacturers provide information about materials used from a chemical point of view for safety assessment. Sometimes reference is made to single-layer technology. But most of the technical information is usually not mentioned. This information includes: - Characteristics of individual layers such as density, thickness, porosity, etc..; - Materials used for individual layers. For example, single-layer fabrics (S or M), multi-layer fabrics (SS, SM, SMS, and others); - Precise characteristics of each layer; - General mask or respirator design On the one hand, it complicates the development of new protection equipment, by studying the advantages and disadvantages of separate solutions, on the other hand, it allows us to create essentially new designs.
- 36. 36 Commercial secrets There are many ways to obtain information Basic ways to find information: - Searching by patents. The main intellectual property of companies is collected in patents. Studying of patents will help to avoid overlapping by patents. However, having a patent does not mean that the information described there is used in reality; For example, this link lists quite a lot of patents: https://docs.google.com/spreadsheets/d/1SCCCKsGBNC8NmbsydtJfag3wwBl384Fc6hvFMntQfT 0/edit#gid=0 - Analysis of suppliers' offers. Since PPE manufacturers often purchase materials from third parties, these materials are available for free sale; http://www.ppnonwoven-fabric.com/sale-10683492-n95-30gsm-meltblown-nonwoven-fabric- antibacterial-for-face-mask-purifier-filters.html https://cihengnonwoven.en.made-in-china.com/product/TNyJfvWdZmhc/China-Custom- Medical-Respirator-80GSM-N99-N95-Filter-Material-for-Making-Dust-Mask.html https://www.alibaba.com/showroom/n95-fabric.html - A direct study of the purchased samples. Including device analysis, comparison with created samples
- 37. Materials
- 38. 38 Some parameters For some types of fabrics, there are marks It's possible to highlight: S - spunbonded non-woven M - meltblown non-woven fabric S, SS, SMS, SMMS http://www.ritschelastic.com/En_NewsInfo-77.html Since nonwovens have a porosity that is difficult to determine directly, the following two main parameters are used to evaluate their functionality: - GSM (Grams per Square Meter); - Thickness; - Diameter of elementary fibres; - Porosity Other important quality parameters: - Tensile strength and elongation. - Tear resistance; - Bursting strength https://www.technicaltextile.net/articles/influence-of-gsm-6502 Main parameters
- 39. Main parameters 39 Some parameters Other required parameters may be listed as necessary: - Filtering properties of layers; - Hydrophobic properties of layers; - Hydrophilic properties of layers; - Ability to hold moisture; - Applicability for skin contact (skin friendly); - Construction properties of layers; - Antibacterial protection In addition, additives of various materials, such as activated carbon and graphene, also provide additional properties. Those that can give additional hydrophilic properties, trapping odors, etc. Antibacterial properties of masks and respirators belong more likely to marketing parameters. Since in the case of medical masks, the time of use does not play a significant role in bacterial growth, in the case of respirators, bacteria reproduce in any case in the water held by the respirator. In addition, the filtering properties of masks and respirators work against bacteria. As the size of bacteria is always more than 0.2 microns. In other words, the filters must be able to catch the bacteria in any case. The use of bactericidal materials for respiratory protection is subject to safety tests and in most cases is questionable either in terms of effectiveness or safety.
- 40. Basic properties of filter layers 40 Filtering properties of layers Filtering properties are affected: - Layer thickness; The thicker the layer, the more likely it is to trap droplets or particles. But too much individual layer thickness starts to interfere with air flow, which makes breathing difficult. - The density of the layer; For filter media, the important parameter is the density of the layer. The denser the layer, the better it filters, but the air flow decreases similarly. - Layer homogeneity; In production it is possible to obtain fabrics with different densities at different areas. This hurts the quality of the products in the series. - Distribution of pores by size; An important parameter is the distribution of pores by size. If the density and thickness of the layer are the same, if there are a large number of large pores, the filtering properties will drop.
- 41. Spun bond filters 41 Filtering properties of layers The basic characteristics of SP filters: - Random arrangement of the fibers; - Have a layered structure or cups; - GSM 5-800, typical production 10-20; - The diameter of the fibers is 1-50 microns, typical production is 15-35 microns; - Good moisture holding due to large internal volume Characteristics may vary from manufacturer to manufacturer. From process features. Melt blown filters The basic characteristics of MB filters: - Random arrangement of the fibers; - Have a layered structure or cups; - GSM 8-350, typical production 20-200; - The diameter of the fibers is 0.5-30 microns, typical 2-7 microns produced; - Due to the smaller diameter of the fibers, it has a developed internal volume and a larger surface area. - Good moisture holding due to high internal volume Characteristics may vary from manufacturer to manufacturer. From process features.
- 42. Electrostatic properties 42 Filtering properties of layers The main mechanism of fine filtration in medical masks and respirators is electrostatic. The following parameters influence the electrostatic properties of filters: - The ability of a material to obtain electrostatic properties; - How it has been treated, as electrostatic properties are given during processing; - Surface area. Since the total charge and the number of particles caught depend on it The table shows an example of the difference in filtering properties of a material before and after electrostatic properties.
- 43. The general approach to the selection of filter media for the layer 43 Filtering properties of layers Basic parameters: - Spun bond filter media have a larger fiber diameter than melt blown filters. In other words, it is better to use melt-blown technology to increase the filter surface area; - Electrostatic properties depend on processing. They are not basic for any material and strongly influence the filtration mechanism; - Within a single process, characteristics such as fiber diameter, density, and thickness of the filter may vary from manufacturer to manufacturer; - As the filter surface area grows as the fiber diameter decreases, the structural properties of this material may decrease, limiting the use of smaller diameter filtration technologies without interfacing with materials created by other technologies. Thus, the melt-blown technology is better suited for the fine filtration layer due to the possibility of making filters with a large surface area. Both technologies are suitable for mechanical filtration. For rough filtration, the spun bond technology is better suited as it allows for larger filtration diameters. Also, materials with larger fiber diameters have better design characteristics, which may be important for maintaining the shape of the product and preventing crushing.
- 44. Links 44 Filtering properties of layers https://www.researchgate.net/figure/Filtration-performances-of-PP-melt-blown-nonwovens- fabricated-at-various-DCD-a_fig3_323269037 https://m.ciop.pl/CIOPPortalWAR/file/72491/2013121295630&R1999-V5-N3-str361-379.pdf https://www.sciencedirect.com/topics/engineering/nonwoven-filter https://www.ncbi.nlm.nih.gov/pubmed/10602654 https://medcraveonline.com/JTEFT/multilayer-nonwoven-fabrics-for-filtration-of-micron-and- submicron-particles.html https://www.textiletoday.com.bd/nonwoven-for-filtration/ https://www.ncbi.nlm.nih.gov/pubmed/32033314 https://www.textileebook.com/2019/07/composite-nonwoven-materials-structure.html https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7152121/ https://en.scribd.com/book/282656214/Handbook-of-Medical-Textiles https://www.ncbi.nlm.nih.gov/pubmed/32033314 https://link.springer.com/article/10.1007/s10965-011-9812-2 https://www.filtercloths.org/technology/select-filter-cloth.html https://www.tandfonline.com/doi/full/10.1080/02786826.2015.1061649 https://pubs.acs.org/doi/10.1021/acsami.9b13162 https://pubs.rsc.org/en/content/articlehtml/2018/ra/c7ra10916d https://www.sciencedirect.com/topics/engineering/melt-blown-process https://www.handanhy.com/item/polypropylene-melt-blown-filter-media/ https://www.scientific.net/AMR.1048.493 https://content.sciendo.com/view/journals/aut/ahead-of-print/article-10.2478-aut-2019- 0067/article-10.2478-aut-2019-0067.xml https://aip.scitation.org/doi/full/10.1063/1.5116336 http://www.welcron.com/_ENG/html/material01.asp
- 45. Basic functions of hydrophobic layers 45 Hydrophobic properties of layers Medical filters and masks require hydrophobic layers for the following reasons: - Many viruses and bacteria spread in droplets; - Most biological contaminants have a water base (e.g. blood); - Water clogging pores and obstructing breathing; - Water is a media for bacteria to reproduce; - In the case of an electrostatic filtration mechanism, water harms the effectiveness of this mechanism. In filters and masks, hydrophobic layers are required in the following layers: - Outer protective layer. Protects the filter or mask from water penetration. Also, it protects the electrostatically filtered layer against wetting. Protects the fluid accumulation layer from premature filling; - Intermediate hydrophobic layers protect the electrostatic filter against wetting; - It is possible to place an additional hydrophobic layer between the electrostatic layer and the water accumulation layer; - Perhaps the edges of the filter should be hydrophobic to prevent moisture from entering between the filter and the face.
- 46. Materials 46 Hydrophobic properties of layers Of the polymers used for nonwoven materials, polypropylene is one of the most hydrophobic and penetration resistant liquids. The performance of non-woven polypropylene filter media can be affected: - The impurities in the material itself can increase wettability; - Too large pores can cause the liquid to enter the filter; - The insufficient or excessive surface roughness of the layer; - Contamination leads to loss of hydrophobic properties; - Filtered material accumulation leads to loss of hydrophobic properties; - Fine charged droplets may also adhere to hydrophobic electrostatic layers; - Mechanical damage may increase the wettability of the filter Two or more electrostatic layers can be used, external or internal electrostatic layers are used to capture small charged air droplets. The hydrophobic properties of polypropylene can be enhanced by additives or coatings.
- 47. Links 47 Hydrophobic properties of layers http://syntechfibres.com/polypropylene/properties-of-polypropylen-fibres/ https://rilonfibers.com/blog/polypropylene-fiber/ https://www.alibaba.com/showroom/hydrophobic-nonwoven-fabric.html https://www.nonwovenproductsupplier.com/news/What-is-water-repellent-non-woven- fabric.html https://patents.google.com/patent/EP2473660A1 http://www.freepatentsonline.com/6632385.html https://www.intechopen.com/books/non-woven-fabrics/fiber-selection-for-the-production-of- nonwovens https://www.textileebook.com/2019/11/nonwovens-process-structure-properties.html https://www.iso.org/obp/ui/#iso:std:iso:9073:-5:ed-1:v1:en https://journals.sagepub.com/doi/abs/10.1177/0887302X9501300103?journalCode=ctra https://www.researchgate.net/publication/330975233_A_new_approach_to_measure_the_resi stance_of_fabric_to_liquid_and_viral_penetration
- 48. Basic functions of hydrophilic layers 48 Hydrophilic properties of layers Hydrophilic layers in masks and filters are needed for the following reasons: - The exhaled air contains water vapor, liquid droplets, saliva, and sweat. They must be captured and drained from the face surface; - For complete protection against exhalation (e.g. medical applications), the exhaled air must be filtered through a medical mask or respirator and the electrostatic filter must be protected against fluid clogging Thus, the following layers should have hydrophobic properties: - A layer that stores moisture; - The inner layer that comes into contact with the face; - Additional layers are available to protect the base filter layer from inhalation and exhalation. The hydrophilic layers can be made of different materials. For the inner layer, it is sufficient to drain the fluid into the moisture- retaining layer. Moisture retention layers must have good absorbency.
- 49. Materials 49 Hydrophilic properties of layers Different materials have different hydrophilic properties. These can be either their basic properties or obtained through various additives to the basic material or by creating coatings. As hydrophilic materials, both with additives and based on basic properties are usually used: - Polyester; - Rayon; - Cotton; - Polypropylene Beyond hydrophobicity, some materials may accumulate moisture in the fibers themselves. These are usually natural materials or special synthetic materials. For the inner layer adjacent to the face, it is not recommended to use materials that can accumulate moisture in the fibers. They should draw moisture away into the accumulation layer but do not retain it. The inner layers may have large pores to improve moisture exchange with the storage layer.
- 50. Links 50 Hydrophilic properties of layers https://rajshreefabrics.com/hydrophilic-non-woven/ http://www.ppnonwoven.com/news/what-is-hydrophilic-nonwoven-fabric-6761144.html https://www.nonwovenproductsupplier.com/news/Talking-About-Polypropylene-Hydrophilic- Nonwovens.html https://www.nonwovenproductsupplier.com/products/Water-Absorbent-PP-Spunbonded-Non- Woven-Fabric.html#.Wk8k1o9L-Uk https://www.wptnonwovens.com/blog/hydrophobic-material-vs-hydrophilic/ https://patents.google.com/patent/WO2005045114A1/en https://www.tandfonline.com/doi/abs/10.1080/02670844.2018.1429205 https://iopscience.iop.org/article/10.1088/1757-899X/659/1/012044/pdf http://www.haomingjz.com/en/prod_66.html https://www.go4worldbusiness.com/find?searchText=15-gsm-hydrophilic-spun-bond-non- woven- fabrics&BuyersOrSuppliers=Suppliers®ion=worldwide&_format=html&matchToCatgListOnly= false https://www.wptnonwovens.com/hydrophilic-material/
- 51. Main parameters 51 Ability to hold moisture Moisture holding layers are used to hold the moisture generated by breathing, saliva, sweat in masks, and respirators. The best moisture holding properties are found in cotton. This is up to 30g per 1g of fabric. Of modern fabrics the nearest to cotton by these functions of viscose based fabrics. Most synthetic fabrics are unable to store large amounts of moisture. Cotton wool and viscose can be used for the moisture-retaining layer. On the other hand, the liquid is difficult to remove from cotton, this creates a heat barrier even after a certain period. After a certain amount of moisture in the layer, it may stop breathing and begin to interfere with ventilation. In some cases, polypropylene-based moisture absorbent materials are used. The strategy for choosing the material for the basic moisture-holding layer can be structured as follows: - Choosing a material that holds moisture; - Ensuring the evaporation of moisture from this layer Also, moisture-holding layers can be added to protect the main filter layer. In some cases this layer is perforated.
- 52. Links 52 Ability to hold moisture https://www.researchgate.net/publication/249776964_Water_Absorbency_of_Jute- Polypropylene_Blended_Needle-punched_Nonwoven https://www.alibaba.com/product-detail/medical-grade-water-absorbent-pads- n99_62311816954.html?spm=a2700.7724857.normalList.32.6a835731cD5BJD https://www.alibaba.com/product-detail/100-pp-air-n95-n99- bfe99_62365128402.html?spm=a2700.details.deiletai6.6.4fae3d6bzpvDU1 https://www.alibaba.com/product-detail/China-Factory-SS-Non-Woven- Fabric_60717689223.html?spm=a2700.7724857.normalList.167.221b44f9tDTf0O https://www.indiamart.com/proddetail/white-melt-blown-absorbents-11242495697.html https://www.aliexpress.com/item/32463222040.html https://sciencing.com/commercial-uses-sodium-polyacrylate-6462516.html https://blog.transferexpress.com/advantages-and-disadvantages-of-cotton-and-polyester- fabrics/ https://home.howstuffworks.com/home-improvement/household-hints-tips/cleaning- organizing/question547.htm https://www.undershirts.co.uk/blogs/research/moisture-absorbing-vs-moisture-wicking-fabrics https://link.springer.com/article/10.1007/s12221-016-6347-5 https://www.rei.com/blog/hike/what-does-moisture-wicking-mean https://www.ejisinc.com/blogs/news/what-is-the-best-moisture-wicking-fabric https://www.barnhardtcotton.net/technology/cotton-properties/ https://www.sciencedirect.com/topics/engineering/cotton-fibre https://www.nonwovenproductsupplier.com/news/Test-Process-of-Water-Absorption-Rate-of- Non-Woven-Fabric.html https://omnexus.specialchem.com/polymer-properties/properties/water-absorption-24-hours
- 53. Main parameters 53 Applicability for skin contact (skin friendly) Skin contact requires materials that do not cause damage to the face. There are two approaches to creating nonwoven materials for skin contact: - Use of nonwoven materials based on natural materials such as cotton or viscose derivatives; - Additional processing of nonwoven synthetic materials In many aspects, tissue comfort is a subjective parameter, but there are common approaches. The use of hydrophobic or hydrophilic materials is debatable. But in general, moisture in masks and respirators should be removed from the face skin. The following finishing methods are used to treat nonwoven synthetic materials: - Smoothing the surface; - Softening Softening is necessary because nonwovens have a rough structure. Softening is either achieved by using special additives or by machining to partially destroy the fabric. - Perforation. Necessary for better moisture removal and air exchange. Perforate such fabrics with either a needle press or hot air jets.
- 54. Links 54 Applicability for skin contact (skin friendly) https://www.sciencedirect.com/book/9781855739215/textiles-for-protection https://textilelearner.blogspot.com/2012/01/finishing-process-of-nonwoven-fabrics.html https://www.researchgate.net/publication/295839299_Finishing_of_nonwoven_bonded_fabrics https://www.sciencedirect.com/topics/engineering/nonwoven-fabric https://www.sciencedirect.com/science/article/pii/B9780081006184000042 https://www.sciencedirect.com/topics/engineering/fabric-softness https://www.sciencedirect.com/topics/engineering/textile-surface https://www.sciencedirect.com/science/article/pii/B9780081006467000060 https://patents.google.com/patent/US5413811A/en https://www.andritz.com/products-en/group/nonwoven-textile/spunlaid/finishing-systems- nonwoven-and-textile https://www.goulston.com/fiber-nonwovens.php
- 55. The materials for masks and respirators are also required in terms of design 55 Construction properties of layers The following requirements can be highlighted: - Mask and filter materials must not break during normal use; - Respiratory materials should be kept in shape to maintain volume for mouth and nose air; - Respirators must be able to restore their shape under normal use. Compression of filters can lead to loss of filtering properties; - The materials of masks and respirators must not be destroyed during use; - The outer surfaces of masks and respirators must not lose their filtering and hydrophobic properties when touched. This is achieved by using materials with the necessary characteristics, creating supporting layers of the right shape, making structures for bending in the case of folding respirators.
- 56. Links 56 Construction properties of layers https://journals.sagepub.com/doi/pdf/10.1177/1558925001OS-01000209 http://oa.upm.es/6671/1/ALVARO_RIDRUEJO_RODRIGUEZ.pdf http://www.fibtex.lodz.pl/51_15_50.pdf https://austinpublishinggroup.com/textile-engineering/fulltext/arte-v4-id1039.php https://www.researchgate.net/publication/311869914_Experimental_Investigation_Of_Properti es_Of_Polypropylene_And_Non-Woven_Spunbond_Fabric http://blog.fdinonwovens.com/the-benefits-of-polypropylene-nonwoven-fabric https://medcraveonline.com/JTEFT/spun-bonding-technology-and-fabric-properties-a- review.html https://www.iosrjournals.org/iosr-jpte/papers/Vol3-Issue5/B03050814.pdf https://news.ncsu.edu/2020/04/a-necessary-filter/
- 57. Main parameters 57 Antibacterial protection In the case of bacteria, masks and respirators work like mechanical filters. The size of bacteria is always greater than 0.2 µm. Bacteria can multiply under a mask and a moisture-holding layer. As water accumulates there. For this reason, the accumulation of moisture on the skin is avoided and the operating time of the mask or respirator is limited. Various antibacterial agents in the case of masks and respirators are controversial. Because some of these methods do not work in real conditions. Some working methods may be dangerous when used in respiratory protection equipment. The ability of masks and respirators to filter out bacteria is a basic standard. Testing for this parameter is mandatory.
- 58. Nonwoven materials for medical masks and respirators. Processes and technologies
- 59. General description 59 Spunbond Spunbond (spunlaid) is one of the processes for producing nonwovens. In general, it has four stages: - Filament spinning; - Drawing; - lay down; - bonding For use in medical masks and filters, the process can be described as follows: - The melt is extruded through small holes and fibers are formed; - By air, the fibers are knocked into bundles; - The bundles are randomly laid out on a moving surface to form a fabric web; - The fabric is then strengthened in some way. In the case of nonwoven materials for filter applications, thermal and/or pressurized sealing is best. Sealing with needles and flows of water or air can impair the filtering properties of the material. Although there are methods to supply heat with special solvents In some cases, the fabric is perforated (for the inner layer).
- 61. General description 61 Melt blown The Melt blown process has been specially developed for the production of nonwovens with thin fibers. The principle of forming individual threads is similar to the spun bond process. But because the fibers are additionally stretched by hot airflow, it is possible to produce fibers with a very small diameter. After forming the fibers, they are randomly laid out to form the fabric. Beyond the possibility of producing fibers with smaller diameters for the fabrics produced with this technology, reinforcement is not required in many cases. With smaller fibers diameters, the fabric can hold the shape. Also, fibers with a diameter comparable to that of Spunbond can be produced using this process. This technology can be used as a replacement for filtering and adsorbing materials. The diameter of melt-blown fibers is usually 2-7 µm but can be larger - up to 15 µm, or smaller - up to 0.1 µm. Thus, in filtration applications, melt-blown fabrics can also replace Spunbond fabrics if rough filtration is required. Both technologies are similar in basic processes and can be easily integrated into the same process chain.
- 63. General description 63 Electrospinning When solutions or melts in polymers are squeezed out in the electric field due to the presence of moving charges in the polymer electrostatic repulsion of the polymer molecules from each other occurs. If the repulsion force is less than the keeping forces of the polymer molecules in the melt or solution, no rupture of the medium occurs. In this case, these forces counteract the surface tension. This causes the polymer jet to lengthen - a fiber is formed. As the fiber solidifies, the charge migrates to the surface of the fiber and the individual fibers are pushed away from each other, which allows for uniform spreading without forming too dense stretches. Electrospinning will produce fibers with diameters of 0.1-0.3 µm and a homogeneous fiber. One of the possible applications of nonwoven materials developed with the help of electrospinning is filtration. However, this technology has not yet become widespread in medical filters (masks and respirators) for several reasons. On the one hand, the process is more complex than described and it is difficult to design equipment based on it, on the other hand, there are limitations on the use of this type of nonwoven material in practice.
- 64. General description 64 Electrospinning Nonwovens based on electrospinning for filtration. Advantages: - Small pore size - provides better fine filtration; - Fabric homogeneity; - Slipping of airflow or liquid in thin filtration threads reduces pressure drop on filter sides; - Fabric properties begin to approach those of solid material, allowing it to hold its shape. The high density of the fibers is implied; - Electrostatic filtration mechanism can be used Disadvantages: - Pre-filtration is required. Particles larger than pore diameter quickly fill the top layer of the filter and the process stops; - The most suitable materials for the filter require spraying from the melt, not the solution, due to the absence of suitable solvents; - Lose the flexibility of woven materials, in thin layers they are particularly brittle, which imposes restrictions on their use in wearable materials; - Quickly filled with moisture due to the best capillary effects in the absence of through-flows; - Support structures are required to maintain form and integrity under physical effects
- 65. General description 65 Electrospinning Possible use in surgical masks and respirators. Although the manufacturers of electrospinning (E) equipment have announced that it is possible to use surgical masks and respirators as a filter media, there is no real application yet. How it is possible to use it: - Adding a layer of fine filtration. For example, an improvement when filtering viruses. For example, layer contracts SMES, SMEMS, ME, MEM and similar; - Due to the peculiarities of the technology, it is possible to apply pointwise on individual sections of products or on products with complex shapes. For example, on cups of respirators; - Drainage of moisture from respirators. Due to good capillary effects, such fabrics can drain moisture to the surface from the layer of moisture accumulation if there is no airflow through them (no clogging particles);Perhaps best suited for general applications where there are no requirements for long filter life in heavily contaminated environments and fluids. Electrospinning technology should be taken into account for the potential development of new filter devices. But in general, because filters are complex multi-layer structures where layers have different functions, this technology will not completely replace them, but it is promising to create layers with new characteristics.
- 67. 67 Spunbond, melt blown, electrospinning Technology Spunbond Meltblown Electrospinning Fiber diameter, µm 15-35 до 15 До 1 2-7 До 0.1 0.05-0.4 Filtering level Rough Fine and ultrafine by electrostatics Ultrafine due to mechanical filtration and electrostatics Extra hardening of fabrics In most cases, it is required It's not always necessary No need. Tissue behavior Behaving like fabric is flexible enough It behaves like fabric in thin layers. In thick layers it loses flexibility (at high density) It behaves like fabric only in very thin layers. In thick layers, it begins to show the properties of a solid material (at high density) Materials based on the meltblown process are well suited for creating different layers in modern filters (with different characteristics of the source material). However, building filters based on materials created with different technologies is more productive. Both from individual material layers and composite layers.
- 68. General description 68 SMS concept Fabrics based on melt-blown polypropylene are formed by thin fibers, which on the one hand provide good filtration ability, and on the other hand, reduces the strength of such materials at the density required for good airflow. Also, fine filters can quickly clog with large particles and lose their filtering properties. Fabrics based on spun-bonded polypropylene are formed by thin fibers but with a larger diameter than melt-blown fabrics. On the one hand, this gives better construction characteristics, on the other hand, it allows the production of materials for the filtration of large particles. To combine material properties, a composite material concept has been developed based on these technologies. Since both types of fabrics are based on the same thermoplastic polymer, these fabrics can be easily welded into one fabric. There are many options. These are composites based on the same fabric type, for example, SS or SSS (spun-bonded + spun-bonded). But the most popular composites are SMS (spun-bonded + melt-blown + spun-bonded) and more complex ones.
- 69. 69 SMS concept In SMS composites, layers can perform the following functions: - S layers are designed for rough filtering; - S hydrophobic layers are designed to protect M layers from wetting with water; - S hydrophilic layers are designed to remove moisture from the body; - S perforated layers are designed to remove heat and water vapor; - M layers are designed for fine filtration There are many options for such composites. SMS, SSMS, SM, SMMMS, and others. In addition, polyethylene and/or hydrophilic additives are often added to S layers to give additional properties. The disadvantages of such fabrics are: - Difficulty in producing multilayer structures; - Introduction into layers of materials without thermoplastic properties; - Difficulty in introducing some additives. For example, activated carbon; - Difficulty in modifying M layers to give them electrostatic properties. The last disadvantage is the main one. Since the electrostatic properties of M layers provide better filtration of fine particles. For this reason, separate M layers are common in various products.
- 71. General description 71 Charging In the case of catching fine charged particles due to electrostatic effects, it is necessary to give appropriate properties to the fabric. This is applicable for technologies to produce small diameter fibers. For this purpose, the surface of the fibers is "charged" in some way. The effect can occur in a strong electric field. But the best efficiency is provided by corona discharge systems. In the production of electret non-woven fibers, no "charging" is possible anywhere in the process. The process of changing electrostatic properties is not very suitable for molten polymers and after cooling. Optimal placement of corona discharge units at the points where the polymer solidifies but is not cooled to room temperature. Other options are possible. Active search for various additives to the basic materials to enhance the effect. "Charging" polypropylene works better on individual layers. When creating SMS constructions, it is difficult. Used for the main filter layer. Several layers are possible. Managing these characteristics may allow you to create new types of filters.
- 73. General description 73 Additives There are many different additives for nonwovens. You can list them: - Additives to give hydrophilic properties to polypropylene; - To reduce or increase electrostatic properties; - Additives for changing mechanical properties; - Other polymers for changing properties; - Additives to protect the polymer from UV; - Additives for giving bactericidal properties; - Various coatings There may be a lot of options. https://www.researchgate.net/publication/287080124_Surface_modification_of_polypro pylene_films_using_hydrophilic_additives https://patents.google.com/patent/EP2411061A1/en https://www.sciencedirect.com/science/article/pii/S030438941730763X https://www.adeka.co.jp/en/chemical/products/plastic/knowledge_04.html https://www.plastic-additives.com/product/break-thru/downloads/additives-post- treatment-modification-pigments_fillers.pdf http://oil.vcdcenter.com/wp-content/uploads/2018/10/Additives-for-PolyolefinsGetting- the-Most-out-of-Polypropylene-Polyethylene-and-TPO-2015.pdf
- 74. General description 74 Ultrasonic welding Ultrasonic welding is one way of joining nonwoven materials. It is used for: - Hardening of nonwoven fabrics (fusion of individual fibers on the whole area or along contours; - Joining individual layers of nonwoven materials in a single piece. Usually along a contour or at individual points; - Cutting the fabric; - Cutting individual items. It is used to replace cords, adhesives, joining at increased temperatures. The principle of operation is based on the partial melting of thermoplastic polymers on the surface, at the point of contact, etc. This ensures the connection of individual layers. Now it is actively applied at the manufacture of medical masks, respirators, and other products from nonwoven materials.
- 76. New materials
- 77. 77 New materials One of the directions for creating new and competitive constructions is the use of new materials and technologies One of the promising materials for PPE is membrane materials based on fluoropolymers. These materials have hydrophobic properties, are thermoplastic - that allows to create on their basis nonwoven materials from thin fibers and to combine with other materials. They are already used in clothing and are mass produced. Limitations of their use are the price (higher by about 5 times than other materials) and the inability to create electrostatic filters on the damage of modern technology. Filtration in such materials can be done only mechanically. For respirators and other means of respiratory protection, the use of thin mechanical filters is difficult due to their reduced breathing air permeability. However, as additional hydrophobic and filtering layers, they can be used. https://www.dhafilter.com/face-masks/ https://www.teflexgasket.com/ptfe-membrane.html https://www.sukopolymer.com/ptfe-nano-masks-a-new-trend-of-future-masks/ https://www.cleanroomtechnology.com/news/article_page/Air_filtration_Advantages_of_PTFE_ materials/153455
- 78. 78 New materials Modern production technologies The possibility of making reusable metal filters using additive manufacturing methods has recently been demonstrated. Similar ideas were offered for the creation of filtering materials on the basis of 3D printing polymeric materials, however, it is unprofitable from the economic point of view. However, in the case of printing by metals, it is possible to create reusable filters. Suitable for clearing, sterilization, etc. Such products can be established as additional filters, filters on valves. Although the main niche for such technologies is cartridge filters for other types of respirators. https://3dprintingindustry.com/news/exone-and-university-of-pittsburgh-produce-promising- reusable-respirators-using-3d-printed-metal-filters-171117/
- 79. 79 Contact us: Fine Systems Technologies, LLC Russia Vladislav Troshin (CEO) troshin@fine-systems.tech info@fine-systems.tech www.fine-systems.tech +7 929 509 44 89 (RU)