Technical textiles Protective clothing B Tech 7th sem Protective clothing • • • • • • • • • • • Protective clothing refers to garments and other fabric related items designed to protect the wearer from harsh environmental effects that may result in injury or death. They are used to protect the wearer from one or more of the following: Extreme heat and fire Extreme cold Harmful chemicals and gases Bacterial and viral environment Contamination Mechanical hazards Electrical hazards Radiation Vacuum and pressure fluctuations Protective clothing • • • • • • • • Flame resistant protective clothing Devastating burn injuries occur when a person’s clothing ignites. The greatest factor affecting whether a person survives a flash fire and how rapidly recovers, is the percentage of second and third degree burns on the person’s body. The lower percentage burn of the body increases the chance of survival. Wearing flame resistant protective apparel reduces burn injury and increase the chance of surviving a flash fire. Flame resistant fabrics are designed to resist ignition and self extinguish when ignited. A properly designed flame resistant fabric should prevent the spread of flames when subjected to intensive heat or flame. It should also self extinguish immediately as soon as the ignition source is removed. Protective clothing • • • • • • Resistance to both flame and associated heat transfer through the garments is defined as thermal protection. Primary and secondary protective clothing for flame resistance are defined by ASTM in standard F1002. Primary protective clothing is designed to be worn for work activities where significant exposure to molten substance splash, radiant heat, and flame etc are likely. Secondary protective clothing is designed for continuous protection from possible intermittent to molten substance splash, radiant heat and flame. Examples of primary protective clothing are fire fighter turnout gear and fire entry suits. Continuously worn flame resistant uniforms are considered as secondary protective clothing. Flame resistant in fabrics • • • • • • • • Flame resistance in fabrics can be achieved in two ways. 1. By using inherently flame resistant materials and fibres. 2. By using special treatments of fibres or fabrics. In first group, flame resistance is an essential or inherent characteristics of the fibre. In second case, chemical treatments or compounds are incorporated into or onto the fibre or fabric to achieve flame resistance. By mixing natural fibers such as cotton and wool with synthetic fibers, fabrics with high comfort and good aesthetic properties can be engineered to meet the specific thermal requirements. Flame Resistant Fibers and Fabrics Treated cotton is widely used in apparel for flame resistance. The most commonly used synthetic flame resistant fibers include aramids, PBI and PFR rayon. SEF acrylic is used in some chemical resistance requirements and in children's sleepwear. Flame resistant in fabrics • Table shows the commercially available flame resistant fibers for work apparel fabrics Flame Resistant (FR) Cotton • • • • • Various flame resistant treatments have been applied to cotton goods over the years. The two most widely used treatments for cotton today are: (1) A precondensate of tetrakis (hydroxymethyl) phosphonium chloride (THPC) reacted with urea and cured with gaseous ammonia to form a polymeric molecule, (2) A heat cured dialkylphosphonamide. Flame retardant finishes for cotton may be temporary or permanent. While FR treated cotton is suitable for foundries, flame cutting, welding, chemical environments, oil, gas and petrochemicals. it is not recommended for protection against molten white metals such as aluminum (molten metals will stick to the fabric) and in critical static control operations. Fabric weight is an important parameter for thermal insulation with FR cotton materials. It should be noted that the fabric itself, not the flame retardant treatment provides the insulative protection. Inherent flame retardant fibres • • • • • • Nomex is an inherently flame resistant material. It can be dyed in fiber or fabric form with various colors. it offers excellent thermal stability and does not melt, but decomposes at 700°F. it is recommended in petrochemicals, utilities and fire fighter uniforms but should not be used for protection against molten substances, welding operations and in critical static control applications. Modacrylic is an inherently flame resistant synthetic, acrylonitrile fiber. It is suitable for chemical plants, tire manufacturing plants, paint and varnish manufacturing plants. PBI (Polybenzimidazole) is an inherently flame resistant fiber. First used in manned spacecraft applications, PBI is mostly used for military and aerospace applications as well as professional fire fighters. P84 (Lenzing) is an inherently flame resistant long chain polyimide fiber. It is usually blended with other fibers. Flame retardant clothing • • • • • • Requirements for FR Textiles Important parameters for flame resistant apparel are, ergonomical design for wearer comfort, durability, easy maintenance, and aesthetics. Comfortable, lightweight garments, moisture vapor transport ability of the fabric are critical for the effectiveness of a fire fighter. Chemical or molten substance resistance depending on the workplace. Garments should have color fastness, appearance or physical properties. Dimensional stability is important after repeated washings. Chemical protective clothing (cpc) • • • • • The purpose of chemical protective clothing is to isolate parts of the body from direct contact with a hazardous chemical. Application of chemical protective clothing: e.g., to protect farmers from insecticides, truck drivers from toxic/flammable materials during loading/unloading, and fire fighters from chemical substances, etc. Chemical protective clothing should be considered as the last line of defense. Fabrics used in CPC can protect against only a limited number of specific hazards for certain chemicals. No matter how effective the protective clothing, the worker's exposure to the hazardous chemicals should be minimized through engineering controls (isolation) or administrative controls (avoidance). Chemical protective clothing (cpc) • • • • • The Environmental Protection Agency (EPA) has defined four levels of protection: (1) Level A offers the highest protection from skin and respiratory exposure to chemical hazards. Level A protection must be gas and vapor tight and prevent any external contaminant from reaching the wearer. Level A ensembles include a self-contained breathing apparatus (SCBA). (2) Level B protection must prevent the passage of any liquid into the ensemble, but may not prevent the penetration of gases or vapors. SCBA is used for respiratory protection. (3) Level C is the same clothing as Level B, but with an air-purity respirator. Level C systems provide limited protection from minor contamination. Level C protection is not usually used by emergency-response personnel. (4) Level D is the normal work clothing to keep off dirt, grease, limited spill protection, etc., and is not considered protective clothing by emergency-response personnel. Chemical protective clothing (cpc) • • • • • • Chemical protective clothing may be categorized as encapsulating and non-encapsulating. Encapsulating ensemble covers the whole body including the respiratory protection equipment. The non-encapsulating system is assembled from separate components and the respiratory apparatus may be worn outside the suit. Encapsulating garments usually provide better chemical protection. All Level A and Level B protective clothing is encapsulating. Non-encapsulating systems usually apply to Level B or below Chemical protective clothing (cpc) • Chemical Protective Materials • Porous fabrics are used for particulate protection and coated/laminated fabrics are used for liquid and gas protection. Some of the currently used materials for chemical protection. Chemical protective clothing (cpc) • • • • • • • • Particulate Protective Textiles Textile materials for particulate protection are spunbonded olefins, hydroentangled spun lace, cellulosic materials and spunbondmeltblown- spunbond composites. Spunbonded polyethylene material has high strength, low permeability and meets the federal flammability requirements. It is formed by a continuous process from very fine 0.5-10 micrometer fibers. These non-directional fibers are first spun and then bonded together by heat and pressure, without binders or fillers. Spun laced Nomex offers fair barrier protection, however, FR properties are identical to Nomex. Spunbonded polypropylene is a lightweight, breathable fabric. Meltblown polypropylene is heat bonded between two layers of spunbonded polypropylene: the outside layer gives strength and durability while the inner layer provides barrier protection. Chemical protective clothing (cpc) • • • • • • • • • Liquid and Gas Protection Fabrics which are coated or laminated with special films are suitable for chemical protection involving liquids and gases. They are used in hazardous or toxic material handling. A multilayer structure that consists of low density polyethylene (outside layer), film (second layer), ethylene vinyl acetate copolymer (third layer) are used. The EVA acts as an adhesive. It is very suitable for garment manufacturing with various seam types. By laminating 1.25 mil of polyethylene, a tough fabric with good barrier properties is produced that is suitable for garment manufacturing with different seam types. A multi-layer film laminated to a substrate of polypropylene offers good barrier properties. For better protection, total encapsulation suits made of special coated fabrics such as Teflon onto Nomex or fiberglass fabrics may be needed. Various nylon, cotton, or polyester fabrics coated with butyl, PVC and neoprene also offer good barrier properties. Chemical protective clothing (cpc) • • • • • • • • • Applications Simple chemical protective clothing is gloves, boots, face shields, and aprons. Hoods, coveralls and splash protective suits provide additional body protection. Highly sophisticated systems such as totally encapsulating suits provide a ''gas-tight" envelope around the wearer. Chemical protective clothing is customarily classified as durable, disposable or ''limited use.'' Durable protective clothing may need costly decontamination treatments between uses. Durable protective clothing is usually made of woven or knit fabrics and is coated. Laminated nonwovens are also used. Disposable protective clothing is made of nonwovens and can be used only once. It is typically used in the medical field. Limited use garments may be used several times depending on the degree of contamination. Chemical protective clothing (cpc) • • • • • • • • • Protective garment manufacturing requires careful attention to fiber and fabric selection, cutting, sewing, and inspection. The seams may be especially critical with seam types like glued seams, serged, single needle seams and bound seams. Sealed and bound seams and sealed and taped seams are also used. The sealed seams can be ultrasonic, thermal or RF sealed. Sealed seams provide the greatest resistance to toxic material penetration. Hazardous material response, toxic waste dump cleanup and manufacture of some chemicals require complete encapsulation of workers. A typical totally encapsulating chemical protective (TECP) suit is made up of several components: self-contained breathing apparatus, lens, suit closure, vent valves, suit membranes, seams, gloves and boots. Factors to consider when selecting a protective garment include type of application, level of protection and type of chemicals, productivity, cost, acceptance and durability (decontamination versus reuse). Different garments provide different degrees of protection, have different sealing properties, etc. Their selection also depends on whether respiratory equipment is used or not. The goal is to provide just the right amount of protection in order to minimize cost and maximize production by acceptability. Electromagnetic Protection • • • • • Utility workers who work close to power lines and electrical equipment may be exposed to electric shocks and acute flammability hazards. To protect the workers in these situations, rubber gloves, dielectric hard hats and boots, sleeve protectors, conductive Faraday Cage garments, rubber blankets, nonconductive hot sticks, and live line buckets are used. Conductive protective clothing is necessary for people who work in the vicinity of very high-voltage electrical equipment. These garments must be flame resistant, wear resistant and comfortable. Humans are sensitive to electrical energy because of their sophisticated nervous system. • Conductive protective materials are made by closely weaving metal and natural or synthetic fibers. These garments are called "Live Line" garments • A typical protective fabric is woven from spun yams containing a mixture of fire retardant textile fibers and stainless steel fibers (8- 12 micron diameters). It was proved that "Faraday suits" made of fabrics with 25% stainless steel fiber/75% wool blend or 25% stainless steel fiber/75% aramid fiber can be effective at voltages up to 400 kV. This Garment protects the wearer from the effects of electromagnetic field generated by high voltage in the vicinity of the power line, i.e., The garment cannot protect the individual if there is direct contact with the high voltage line. More protection is obtained by using two or more fabric layers. • • • Thermal protective clothing • • • • • • There is a need for personal thermal protection for workers in selected sectors such as energy (oil and gas), electrical, other industry sectors, and both structural and wildland firefighting. Clothing issues such as fit, comfort, and other ergonomic factors are important for safety and better performance. Materials specifically developed for protection against heat and flames have been available for many years. For single layer garments, two approaches primarily have been used: fabrics incorporating inherently flame resistant fibres and their blends and cotton fabrics and blends treated with flame retardant finishes. Garments made from these materials still predominate in the PPE marketplace. Much of the development is driven by the desire to improve the comfort properties of the materials without sacrificing the wearer’s protection (e.g. lighter, more vapour permeable, more flexible, etc.). High visibility is also achieved in blends with fibres that accept fluorescent dyes. Thermal protective clothing • • • • Fibre choices for thermal protective clothing include inherently flame resistant (FR) fibres such as the meta- and para-aramids, polyamideimide, polybenzimidazole, modacrylic and chemically modified fibres such as viscose and modal, polyester, and nylon, as well as FR treated or finished cotton and wool. The suitability and selection of the fibres are dictated by the workplace hazards (molten metal splash, hot surface contact, pressurised steam, arc flash, flash fire, etc.). The preference is to use fibre blends that take advantage of the beneficial properties of several fibre types. Apart from use of appropriate fibres in single fabric constructions, fabric layers with specific functions are used in fabric systems to provide liquid repellency and thermal insulation for workers requiring such protection. Typical three-component system (FR outer shell, moisture barrier, and thermal liner) are used for structural firefighters’ protective clothing. Thermal protective clothing • • • • Methods and materials for protection from high pressure steam and hot water also indicates the need for layered fabric systems that can provide water repellency and greater thermal insulation than single layered garments. Water repellency required for protection from certain thermal hazards (steam, hot water) has been achieved with the use of laminated fabrics that incorporate water repellent, vapour permeable membranes, and liquid impermeable coatings. These membranes or coatings are applied to suitable FR shell fabrics and in the case of coatings may form the outermost surface of the material (e.g. FR neoprene rainwear). Finishes to repel oil and water are also used on protective clothing materials to repel liquid and soil during use and improve soil removal in cleaning. Pesticides Protective clothing • • • • • • Dermal and respiratory pesticide exposure of agricultural workers involved in spray operations may be significant. Spray operations include field or row crop spraying, orchard (air blast) spraying, spraying in greenhouses, aircraft spraying and mixing and handling. Pesticides can move through the fabric (wicking), wet inner layers of fabric and skin, and be dermally absorbed. Farm workers are involved in other tasks such as cultivation, harvesting, irrigation, scouting and fruit thinning. Protective clothing is used to reduce exposure to workers that are directly or indirectly involved in pesticide applications. The risk factor (R) of personal exposure to pesticide spraying and handling depends on the possible routes of exposure and toxic characteristics of pesticide. This factor is defined as, Pesticides Protective clothing • The risk factor (R) is defined as, • Wearing of protective clothing such as rubber aprons, waterproof outer garments and face masks for a long period is difficult especially in hot climates. Therefore, selection of protective clothing materials is extremely important. The major requirements of the materials are: • protection against a range of pesticide formulations; aqueous organic solvent, or oil based • lightweight • low price • readily washable without losing protective properties • durable • good air exchange to maintain wearer comfort • acceptable to wearer Pesticides Protective clothing • • • • • • • • • • The penetration of pesticide through the fabric is influenced by capillary forces. Pesticide protective clothing can be made of traditional textiles such as cotton, polyester (or their blend) and treated with repellent finishes. Special woven and nonwoven protective materials offer better protection. Protective clothing should not cause heat stress or impair the worker's movement. The effectiveness of protective clothing is influenced by garment properties (fiber content, yarn and fabric geometry, and textile finish), environmental conditions and pesticide characteristics. Fluorocarbon finishes provide better protection against pesticide penetration than non-fluorocarbon-finished fabrics and reduce wicking. Hydrophobic fluorocarbon soil-repellent (SR) finishes may cause redeposition of soil in laundering. The presence of fluorocarbon finish increased the resistance to aerosol penetration. It was found that water-repellent and soil release finishes increase the fabric effectiveness for protection. The USDA, EPA and NIOSH (National Institute for Occupational Safety and Health) recommend the use of protective apparel during handling and application of most pesticides.
