Protective Clothing Dr. V. K. Kothari Department of Textile Technology, IIT, Delhi
Materials & Technologies • Processing technologies for specific protective clothing are different, the main processes generally include: • Material manufacturing or selection; • Producing fabrics and other related items; • Finishing, and • Clothing engineering.
Schematic of materials and technologies for manufacturing protective textiles
Steps in selection of protective clothing materials Step 1: Assess hazards • Type of hazard(s) • Severity of the hazard Step 2: Identify relevant standards, specifications, or guidelines • With well defined performance requirements • Not well defined performance requirements
Steps in selection of protective clothing materials Step 3 Screen materials based on protection performance of fabrics, e.g. • Cold climate protection performance • Chemical protection performance • Biological protection performance • Flame and thermal protection performance • Mechanical protection performance Step 4 Select materials based on other major factors • Job performance • Comfort • Cost • Durability • Use, care & maintenance
AGENDA • Look at some aspects related to: • Extreme old protection • Chemical & Biological protection • Radiation protection • Electrical protection • Heat & Flame protection • Mechanical protection • High visibility Protection
Hazards of Extreme Cold Climate • Increased incidence of Arthritis, Rheumatism and Bronchitis • Cold metal injury • Hypothermia - one of the serious hazards of cold exposure • Frostbite
Comfort & Survival Factors in Cold Protective Clothing 1.Physiological Factors • Metabolic heat output • Perspiration rate 2. Environmental Factors • “Wind Chill” • Relative Humidity or Dampness of the Environment
3. Fabric Factors • Thermal insulation • Air permeability • Moisture vapour permeability 4. Design of the Fabric Assembly
The human heat balance equation • Appropriate protection against cold is provided when the human body is in heat • balance at acceptable levels of body temperatures (for example skin and core • temperatures). • This implies that heat losses are equal to metabolic heat production. • The following equation describes the heat balance. • where S is the rate of change in body heat content, • M is the metabolic heat production, • C is the convective heat exchange, • R is the radiative heat exchange, • E is the evaporative heat exchange, • and RES is the respirative/airway heat loss, all in W/m2.
Measurements of clothing performance • Thermal insulation • Evaporative resistance • Wind resistance • Water resistance
Category of Fibres which provides Thermal Insulation A. Heat Insulating -to entrap as much air as possible. - Low compressibility and high resilience - Conventional fibres, hollow fibres & high bulk fibres
B. Heat Absorbing -to maintain the microclimate inside the clothing - Solar radiation absorbing fibre and fibres containing ceramic particles to absorb IR radiation C. Heat Storing - Phase change materials
Types of Layer- Combination • Outer layer should provide adequate resistance to wind penetration & should be water vapour permeable • Next-to-skin layer of the garment should wick the liquid sweat away from the body rapidly • Middle layer(s) should provide the main insulation. Body heat should be reflected back using a inner reflective layer.
Structural Model of a Cold Weather Protective Clothing
Engineered Fibres • An unique polyester fibre such as Primaloft • Air pockets increases the thermal resistance and help it to resist the passage of water while allowing body moisture in form of water vapour to escape
Insulation through Incorporation of Integrated Heating Panels • Light weight, washable heating panels powered by batteries are laminated in the fabric
Smart Polymeric Membranes • Laminated fabrics made from monolithic breathable membrane which react to build up of heat and moisture • As the microclimate temperature rises, the openings between the polymer molecules in the membrane expand, thereby increasing the fabric moisture permeability. As the temperature drops the pores in the fabric close, thereby trapping heat.
Chemical Protection Chemical Hazard • Affects human based on its characteristics and mode of entry • Chemicals present a variety of hazards such as toxicity, corrosiveness, flammability, reactivity, and oxygen deficiency • Routes of chemical entry into the human body are oral, respiratory, and dermal • Dermal exposure considered primary mechanism of chemical entry through human body
Chemical Resistant Clothing • It provides an effective barrier between the chemicals used & area of the body to be protected • No single material will protect against all chemicals • Appropriate chemical resistant clothing must demonstrate: No penetration No significant degradation Low permeation rate
Chemical and biological protection • Chemical/Biological (CB) warfare agents and their effects • To design and to fabricate effective CB protective clothing, it is necessary to • have an understanding of the hazardous threats that must be prevented from • reaching the wearer. • CWAs are defined as natural or synthesized chemical substances, whether • gaseous, liquid or solid, which might be employed because of their direct toxic • effects on man, animals and plants. • BWAs are microorganisms (viruses and bacteria) or toxins derived from • living organisms. • They are used to produce death, or incapacitation in humans, animals, or • plants. Typical effects of selected CWAs are listed in Table given in the • next slide.
Different types of protective materials There are basically four different types of CB Protective Materials. Figure illustrates the differences in their protective capabilities.
Examples of Chemical Protective Clothing • Three layers outer fabric, sorptive layer and inner layer Layers of Protective Clothing • Outer shell is water repellent layer protecting from liquid chemicals • Sorptive layer is soul of protective clothing absorbing liquid & • air borne chemicals • Inner layer provides comfort to the wearer
Development of Chemical Protective Clothing Polyester fabric Cotton Nonwoven Activated carbon Cotton Nonwoven Cotton fabric • Formed by five layers • Outer shell made of polyester as it has low absorption of 2% & provides good strength to the fabric and polyester has a good resistance to lab grade chemicals • Inner layer is made up of cotton fabric as it gives good absorbency and comfort • Middle layer comprises of activated carbon sandwiched in cotton nonwoven
CPC Garment materials • Textiles • Unsupported rubber or plastics • Microporous film basics • Adsorbent-based fabrics • Coated fabrics • Plastic laminates • Combinations
Clothing system designs • The use of excellent protective materials, effective closures, and ergonomic survival equipment for an individual will be meaningless and unproductive without proper garment designs. • There are different garment designs given as follows: • Coverall or one-piece garments • Two-piece garments • Undergarments • Multilayered garments • Closure system, components, and systems
UV exposure and human skin Effect of UV rays on different types of skin
Radiation Protection Radiation Protection Ultraviolet radiation band UVA (320 to 400 nm) UVB (290 to 320 nm) UVC (200 to 290 nm) Causes little visible reaction on skin but decrease immunological response of skin cells Responsible for development of skin cancers Totally absorbed by atmosphere & doesn’t reach the earth
Textiles as protection from ultraviolet radiation Fabric's ability to block UVR dependent on several parameters: Principal Parameters Fiber Chemistry Fabric Construction Moisture content Wet Processing History Porosity Thickness Weight Dye Concentration Fluorescent Whitening Agents UV-absorbers
Electrostatic Protection The term `electrostatic' or `static electricity' refers to the phenomenon associated with the build up of electrical charges generated, for example, by contact and/or rubbing of two objects. Static electricity is generated by unbalancing the molecular configuration of relatively non-conductive materials.
Discharge of static electricity • In principle, there are three methods for neutralizing charges on insulators: • conductance through the bulk of the material • conductance along the surface of the material • the attraction of oppositely charged ions from the air
Measurement techniques • There have been two main approaches to assessing the electrostatic propensity of textile materials. • One is to measure the charge built up on a clothed person or the electrical capacitance of a body (human-body model) • The second is to measure some electrostatic characteristics of textiles (e.g., surface resistivity, charge decay rate, peak potential, etc.) in small-scale tests.
The most common way to confer anti-static properties on a fabric is to incorporate conductive fibres/yarns. • Common conductive elements used in fabrics include carbon, copper, silver, stainless steel or metallic salts. • The choice of conductive product will partly depend on the end use and the required level of static protection.
Modern ESD-textiles • Many ESD-garments are made of heterogenous composite fabrics where a grid or stripes of conductive threads are present inside an insulating matrix of cotton, polyester or mixtures of these materials. • The conductive threads are more and more frequently made by composites, i.e. by a mixture of conductive and insulating fibres. • There are several variations in both fabric and thread structures.
Gore-tex: Antistatic Source: AVANTEX 2000