rajesh mishra & jiri militky technical university of

Comfort of Clothing

Rajesh Mishra & Jiri MilitkyTechnical University of Liberec

Liberec, Czech Republic

Comfort

� Physical comfort - Mechanical

� Physiological comfort - Transmission

� Psychological comfort - Aesthetic

Issues associated with comfort

�Material characteristics�Thermal science�Environmental variants�Human body physiology�Mind and body interaction

Expectations from Fabric for Garment

� Aesthetic performance

� Intrinsic performance

� Utility performance

Aesthetic performance in terms of :

colour, design, texture and appearance in made-up form.

Aesthetic performance

Intrinsic performance comprising of : Mechanical comfort expressed in fabric hand

Thermo-physiological comfort associated with : transmission of heat, moisture and air.

Intrinsic performance

Utility performance associated with :

durability and serviceability of the garment measured in terms of :abrasion resistance, pilling resistance, fastness properties, wash and wear etc.Also includes Tailorability

Utility performance

Requirements in fabrics for Clothing

QUALITY OFFABRICS FORCLOTHING

INTRINSIC ANDESSENTIALPERFORMANCE

AESTHETICPERFORMANCE

UTILITYPERFORMANCE

ColorDesignTextureAppearance in garment form

Mechanical and TactileComfort as Judged by Hand

Environmental Comfortwhich depends on movementof heat, moisture, air

StrengthAbrasion resistancePilling resistanceWashing and Wear etc.

To appreciate their total effect, it is necessary to consider how the mind and body interact to maximize comfort for any human being.

Total effect on human being

� The way body and brain mechanisms achieve comfort for the attainment of thermal equilibrium

� Role of moisture in this process

� Extreme hot or cold environments can be prevented by using textiles

� Understanding choice of fibre type, construction factors and treatment mode in selecting a material to provide the optimum comfort level achievable.

Considerations for comfort

© Technical University of Liberec 2013

TEXTILE TESTING

Thermal Comfort definition

� According to ISO 7730 Thermal Comfort is

“ That condition of mind which expresses satisfaction with the thermal environment.”

� This is achieved when there is a balance between the energy produced by a human being and the energy lost to the environment

Functions of Clothing

� Protect the body against excessive heat loss

� Keep out detrimental environmental and weather effects

� Enhance the appearance

Role of Clothing

� Clothing is designed to maintain a hygienic and comfortable zone about the human body in which one feels well, even if inner or outer influences change rapidly

Clothing helps in achieving the thermal balance between the heat production by the body and heat transmission to the environment

Human-Clothing-Environment

Environment

Clothing system

Microclimate

Skin

Core

Radiative Heat Transfer

Convective Heat Transfer

Conductive Heat Transfer

COMFORT ZONE

� The zone in which the temperature, moisture and air circulation are properly matched so as to maintain the thermal and the moisture balance is called the “comfort zone”

� Moisture transfer from skin through clothing ideally in vapour form is necessary for comfort

Body Environment Interaction

Body Heat and Moisture

Vapour Production

EnvironmentClothing

Processes Involved

� Physical

� Physiological

� Neurophysiological

� Thermophysiological

� Psychological

The Processes Involved In Sensations And Attitudes On Comfort

Physical processes

Physiological processes

Psychological processes

Overall perception

Pressure stimuli – mechanical behaviorTactile stimuli – mechanical behavior

Neurophysiological processes:Sensory responses of nerve endings to stimuli– thermal, pressure, pain, …Thermophysiological processes:– sweating, blood flow control, shivering

Visual stimuli – color, light reflection, designPerception of sensation from thermal,pressure and pain and combination of varioussynthetic stimuli. Evaluate and weigh varioussensations.

Comfort/Discomfort

clothing & environment

&body skin

brain

Running: 9.5 Met

Teaching: 1.6 Met

Metabolic Heat Production

1 Met = 58.15 W /m2 of body surface

Sleeping: 0.8 Met

Environmental Factors

� Air Temperature� Mean Body Temperature� Mean Relative Air Velocity� Ambient Humidity

Effect of Wind

� It has been observed that wind induces a reduction in thermal insulation of fabrics

� In cold temperature, wind causes rapid cooling of skin temperature which is known as the “Wind Chill Effect”

Ia=ambient insulation

Ic=clothing insulation

Wind Chill Effect

W = the wind chill index, based on the Celsius W = the wind chill index, based on the Celsius

temperature scale temperature scale

TTair = the air temperature in degrees Celsius (air = the air temperature in degrees Celsius (°°C) C)

VV1010mm = the wind speed at 10 metres (standard = the wind speed at 10 metres (standard

anemometer height), in kilometres per hour anemometer height), in kilometres per hour

(km/h) (km/h)

Thermal Comfort

� The actual combination of skin temperature and the body’s core temperature provide a sensation of thermal neutrality

� The fulfillment of the body’s energy balance: the heat produced by the metabolism should be equal to the amount of heat lost from the body

Human Body Temperature

� Normal body temperature in humans is

35.5–37.5 °C (98–100 °F).

� Hypothermia is defined as any body temperature below 35.0 °C (95.0 °F).

� Heat stroke is defined as a temperature of greater than 42 °C (107 °F) due to environmental heat exposure with lack of thermoregulations

Thermal Comfort

Body Core

37o C

HypothermiaHypothermia Heat StrokeHeat Stroke

Skin Temperature 33Skin Temperature 33ooCC

Tolerance Tolerance �� (20-30 (20-30ooC)C)

Thermal Management Mechanism of Human Body

� When body becomes too warm� Vasodilation of blood vessels� Increased blood flow through the skin and subsequent sweating

� When the body becomes too cold� Vasoconstriction of blood vessels� Stimulating the muscles, which causes shivering

Factors Affecting Heat Transfer from Skin

� The Fit of The Garment

� Proportion of Body Surface Area Covered

� Geometry of Human Body

� Body Movements

Heat Transfer Mechanism

�� Dry Heat TransferDry Heat Transfer

�� ConductionConduction

�� Convection Convection

�� Radiation Radiation

�� Evaporative Heat TransferEvaporative Heat Transfer

�� Moisture TransmissionMoisture Transmission

�� Vapour Transmission Vapour Transmission

Heat Transfer Mechanism

Heat flows through materials depend on their thermal conductivity but this is not the case in textile structure.

Most textile fibres have similar value of thermal conductivity and the more important one is the nature of textile structures

What is important in textile structures for heat flow

Insulation is governed by the bulk structure of a fabric, rather than by any of its individual parts, and air has a much higher insulation value than fibres.

Thus, the thermal insulation is governed exclusively by the amount of entrapped air within a structure.

Which structural parameters are important for better insulation in Textiles

Fibre : which have an irregular surface, a non-circular cross-section, high levels of unevenness or a convoluted form will produce materials with better insulation

Yarns : which are loosely twisted, irregular, hairy and fancy will be better insulators

Fabrics : which are loose in structure, soft, thick, porous or textured will generally insulate better than those which are flat, boardy, thin or level-surfaced

Cloth : clothing system consists of many garments layered over each other than if it is a single-layer garment of the same total thickness and weight

Which structural parameters are important for minimum heat retention in Textiles

Fibre : straight, uniform, even fibres

Yarns : straight, uniform, even, tightly twisted yarns to make thin, flat, open fabrics

Fabric : thin, flat, open fabrics

Garment : single thin layer garment to allow heat to escape efficiently

Garment design : design which provides ample ventilation to permit the free movement of air over the surface of the body will allow convection currents to flow over the skin, removing heat more rapidly.

Factors Influencing Thermal Resistance of Fabrics

� The most important factor which influences the dry thermal resistance of a fabric is the Thickness

� Cover factor, surface roughness, finishing or coating materials used on the fabric may also have some effect

Thermal Resistance of Clothing

� Clothing consists of a number of fabric layers

� Thermal resistance of a combination of garments is more than the sum of the thermal resistance of individual items

� Additional layers of air are trapped between fabrics

� Boundary layer of still air over outer surface of clothing

Water vapour Permeability� Water vapour is constantly being released by the skin

� For comfort, this vapour should be able to easily escape from within the clothing microclimate to outside through the fabric

� Vapour transmission takes place by diffusiondiffusion

� In general, fabrics having high vapour permeability have low resistance to air flow and rain water

� Breathable fabrics have solved the problem

Moisture and Clothing

Perspiration

Insensible Sensible

� Insensible: under normal atmospheric conditions and at rest, human body continuously produces perspirations which evaporates within skin layers and is emitted in the form of water vapour

� Sensible: Liquid sweat

Moisture and Clothing

� Vapour permeability and air permeability are not equivalent in case of hygroscopic textile materials

� The rate at which water vapour passes through a fibre depends on the nature of the fibre

� Hydrophilicity of the fibre becomes an important criterion in case of dense fabric construction

� Wicking behaviour of fabric is also important in the moisture management of the clothing

Which cloths are important from MVTR point of view

� Sportswear

� casual wear

� Protective textiles from comfort point of view

� Surgical gown, Masks etc.

Liquid moisture flow through textile materials

Liquid moisture flow through textile materials is controlled by two processes:

� wetting

� wicking

Wetting is the initial process, involved in fluid spreading and it is controlled by the surface energies of the involved solid and liquid

As water wets the fibre, the water enters the inter fibre capillary channel and is dragged along by capillary pressure.

Capillary pressure through textile material

The magnitude of the capillary pressure is given by the Laplace equation:

P is the pressure developed in the capillary channel

is the radius of the capillary formed in the fibrous structure

represents the surface tension at the interface between the various

combinations of fibre(S), liquid (L) and air (V)

is the contact angle between the liquid drop and fibre surface

is the resultant surface tension between fibre and liquid interface

2 c o sL V

c

PR

γ θ=

cRγ

θcosLVγ θ

Perspiration and thermal balance

Perspiration of human body should be transferred to the atmosphere in order to maintain the thermal balance of the human body.

Factors of vapor transmission that maintain Thermo-physiological comfort index

Parameters of vapor transmission that maintain the thermo-physiological comfort index :

� Absorption-desorption

� Diffusion and convection of vapour perspiration

� Wetting and wicking of liquid perspiration

Moisture Vapour Transmission Rate (MVTR) through any clothing

The moisture vapor transmission rate (MVTR) through any clothing item depends on :

� Moisture content of the fabric

� Type of material used

� Perspiration rate

� Atmospheric stimuli like temperature, wind speed

and relative humidity.

Air Transmission

� Fabric interstices,pore size and their distribution are prime factors for air transfer. Factors which influence air flow are:

� Yarn crimp

� Yarn flattening

� Yarn twist

� Fibre fineness

� Cross-sectional shape of the fibre

Comfort Measurement

Method for predicting thermal comfort of fabric comprises of a provision of

� a perspiring hot plate to simulate the skin hermoregulatory responses of a human

� fluid flow through the fluid input source and a power flux through the thermal input source to correspond to human perspiring and thermal output level

� placing a fabric on top of the perspiring hot plate

Comfort Measurement

� temperature of the top surface of the plate as the temperature changes to simulate the skin surface

� thermoregulatory responses can be observed. The temperature profile is analyzed and the comfort level of the fabric from the results is determined

Research in Comfort

� Functional clothing

� Advanced Materials

� Fibre Engineering

Concluding Remarks

� Clothing protects from cold or heat to maintain body thermal comfort throughout the full range of human activities

� Comfort can be affected by any variation of the following parameters beyond certain tolerances:

�� PersonPerson

�� ClothingClothing

�� EnvironmentEnvironment

�� ActivityActivity

Concluding Remarks

Concluding Remarks

� The design of the clothing, the tactile and thermal insulation behaviour of the fabric assembly and the moisture management capabilities of the clothing affect the comfort.

rajesh mishra & jiri militky technical university of

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