testing of protective outdoor garments

1

© 2006 W. L. Gor e & Associates GmbH. GORE®, GORE-TEX®, WINDSTOPPER®, CROSSTECH®, GORE CHEMPAK®, and designs are trademar ks of W. L. Gore & Associates | Gore C ompany Confidenti al

Testing of Protective Outdoor Garments

Charlie ThwaitesW. L. Gore & Associates Inc., Livingston, Scotland

Uli SpindlerW. L. Gore & Associates GmbH, Putzbrunn, Germany


Content

1. General testing approach: from fabrics to garments in the field

2. Lab tests• protection against rain• protection against wind

3. Methods to predict the protection from• cold strain• heat strain

4. Tests that differentiate good and bad base-layers


Content






Level One: Physical analysis of fabrics using the Sweatinghot plate, Base layers - sensorial tests

Level Two: Biophysical analysis of clothingsystems using moving thermal manikin

Ventilation measurements

Level Four: Controlledand limited Field test

Predictive CalculationsPhysiological / empirical

models

Predictive Calculationsclothing models

General testing approachFrom fabrics in the lab to garments in the field for comfort

According to:

Level Three: Controlled wearer testswith subjects in a Climatic Chamber


Fabrics are tested on the Skin ModelRct and Ret Measurements (ISO 11 092) “ Physiological effects”

RctThermal Resistance to conductiveheat transfer (textile)The larger the value,the more insulating the fabric

RetThermal Resistance to evaporativeheat transfer (textile)The smaller the value,the more water vapour permeable the fabric

>20Unsatisfactory

13 to 20Satisfactory

6 to 13Highly Breathable

<6Extremely Breathable

Ret [m2 . Pa / W]Rating

Regarding shell fabric


Level 2Manikin evaluation of clothing for evaporative and thermal resistance

Manikin withsweating skin

• heated

• articulated

• measurement of thermalinsulation

• calculation or measurement ofevaporative resistance

Dressed manikin

2


0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

Dry Rain - good DWR Rain - no DWR

Man

ikin

Rc

Tors

oin

cl. a

ir b

ound

ary

laye

r [m

²*s/

W]

Influence of Water Repellency on Heat Loss in the RainEffect Decreases with Increasing Insulation

Gore internal study on manikin at Cord2-Layer unlined jacket + long sleeved t-shirt


RainWet Clothing loses its Thermal Insulation

SourceFour Inns walk - G Pugh study on Clothing insulation and accidental hypothermia 1966

Thermal insulation [m²*K/W]

0

0.02

0.04

0.06

0.08

0.1

0.12

Typical clothing + plastic over anorak[=DRY]Four Inns walk: typical clothing anorak +hood, cotton garments =[WET]

Insulation value of wet clothing is reducedby about 70% over a wide range ofwater content

• Heat loss in wet clothing is about 3times higher than in dry clothing

• Wind speed 14 kph

• Thermal insulationmeasured on movingsubjects

• Values are of the clothingalone, omitting theboundary air layer


Level 2Ventilation can be measured on manikins or more naturally on humans


0

20

40

60

80

100

120

WIN

DS

TOP

PE

R®

stan

ding

ven

tscl

osed

WIN

DS

TOP

PE

R®

wal

king

ven

tscl

osed

WIN

DS

TOP

PE

R®

wal

king

ven

tsop

en

air p

erm

flee

cest

andi

ng v

ents

clos

ed

air p

erm

flee

cew

alki

ng v

ents

clos

ed

air p

erm

flee

cew

alki

ng v

ents

open

Vent

ilatio

n ra

te [

L / m

in ]

Ventilation rate of standard fleece and air impermeable fleeceNo change if worn under rain suit

• Ventilation rate of GORE-TEX® suitworn with either windproof or air permeable fleece underneath

• no difference in ventilation rates under these conditions

Vents open = Pit zips, cuffs neck


Thermal insulation vs. ventilation rate

0.000

0.025

0.050

0.075

0.100

0.125

0.150

0.175

0.200

0.225

0.250

0 5 10 15 20 25

Ventilation rate L / min

Tota

l the

rmal

Insu

latio

nm

2 K /

W

See Withey, Relationship between clothingventilation and thermal insulationAIHA 2002 63 ; 262-268

Correlation of ventilation rate and thermal insulationMeasured simultaneously on a thermal manikin


• Measurement of physiological effectof clothing

– thermal strain• core body temperature

– skin temp– microclimate temperature and

relative humidity– work rate– perceived exertion– tolerance time etc.

Level 3Human subject testing in climatic chambers

3


Disadvantages of chamber testingChamber tests should be done only if strictly needed

• Can involve considerable discomfort(see pictures)

• Human subject tests– time consuming (at least 4 to 8

weeks)– costly (£ 40 to 80,000)– minimum of 8 subjects needed

• To avoid them, enormous amounts oftime and effort were invested to relatemanikin data with wear trials

• Human subject tests will always beneeded, but with predictive modelsthey can be minimised


Content






TestsWaterproofness and durability of waterproofness

• Hydrostatic head test

• Dry flex followed by suter testing• Wet flex followed by suter testing

• Shower tests• Field testing


FabricHydrostatic head test ISO 811 – destructive


WaterproofnessDifferent requirements of hydrostatic head pressure

1.1 1.9

30.0

25.0

2.9

0

5

10

15

20

25

EN 343class 1,2

EN343class 3

EN 469class 2

NFPA 1971(2007 ed)

Fire hoseSDF

EuropeanMilitary

common

US Military

Hyd

rost

ativ

hea

d M

etre

s w

ater

hea

d

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

P.S.

I.


Durability of waterproofness of laminatesFlex testing followed by constant pressure suter testing

• Dry Flexing –followed by Sutertesting

• Wet Flexing –followed by Sutertesting

4


Test for waterprofness of garmentsRain tower testing depending on end use

• Vertical “rain” is equivalent to a violent shower– 76 mm / hr

• Side nozzle flow is 4 L/min through each


European standard for shower tests (EN 14360 – 2004)Overhead rain only – for some applications not severe enough


Field Tests for durability of waterproofness

• Need– Sufficient number of

garments (>40) for statistics– Reference fabric of known

durability• Half and half garments

ensure equal use andreduce number ofsamples


Effect of wind on thermal insulationMeasured with a heated cylinder or preferably a thermal manikin

Tore manikin, SwedenHeated cylinder test


Wind reduces the total insulation value of clothingInsulation of air permeable clothing drops drastically in the wind


Content





5


Protection from the ColdRequired insulation levels can be estimated

• ISO 11079 (pub. 2005):Determination of Required ClothingInsulation (IREQ)

• Calculation applet at:wwwold.eat.lth.se/Research/Thermal/IREQ2002alfa.htm

• Input– clothing thermal insulation– activity– environmental conditions

• Output– prediction of the exposure time– Required basic insulation value


Clothing insulation dataValues for typical clothing ensembles from ISO 11079


Metabolic rate estimationExamples for general activities from ISO 11079 – use with care


How much protection from the cold is needed?Example calculation with the IREQ-software

• IREQver4 ISO 11079 Oct 2008


Required minimal insulation (ISO 11079)Influence of work rate and temperature


Protection against heat strain Influencing Factors on Body CoreTemperature and PerformanceReducing heat strain requires lowest possible evaporative resistance

Clothing• Thermal Insulation (Rc)• Waterproofness• Windproofness• evaporative Resistance (Re)• Ventilation

Ambient• Temperature• Humidity• Precipitation• Wind• Radiation

Activity• Physical power• Duration

Body temperature / Sweat rate

Person• Sex • Fitness • Age • Size • Weight

Comfort / Performance

6


Level One: Physical analysis of fabrics using the Sweatinghot plate, Base layers - sensorial tests

Level Two: Biophysical analysis of clothingsystems using moving thermal manikin

Ventilation measurements

Level Four: Controlledand limited Field test

Predictive CalculationsPhysiological / empirical

models

Predictive Calculationsclothing models

General testing approachFrom fabrics in the lab to garments in the field for comfort

According to:

Level Three: Controlled wearer testswith subjects in a Climatic Chamber


Fabric 1 Fabric 2Ret [m2*Pa/W] 5 10

skin modelFabrics• Vapour permeability (Ret)• Insulation (Rct)

Typical jacket Fabric 1 Fabric 2

Re [m2*Pa/W] 9.7 16.7

calculationsGarment pieces• Vapour permeability (Re)• Insulation (Rc)

Wearing scenario• Ambient Conditions• Activity Levels

physiology model Prediction of body temperature, heart rate,skin wettedness comfort and performance

According to NATO AC PP1

• Design, Construction• Pockets, Doublings, Linings, Tape...

Ensemble (long underwear + rain suit)

Fabric 1 Fabric 2Re [m2*Pa/W] 24.3 33

manikinClothing ensemble• Vapour permeability (Re)• Insulation (Rc)

• Underwear, Mid layers, Socks, Shoes...• Air layers, ventilation

• Wearer, Activity, Weather

Lab Testing and Prediction MethodsEffect of shell fabric Ret moistute vapour permeability) on ensembleperformance


37.0

37.2

37.4

37.6

37.8

38.0

38.2

38.4

38.6

38.8

39.0

20 40 60 80 100 120 140 160 Time[min]

Body temperature [Tr in °C]

tolerance limit for trained

tolerance limit for untrained

decrease of psychomotoricabilities (e.g. tracking)

Ret 5 Ret 13 Ret 20 Ret 40

Source: GORE simulation based on

Hohenstein physiology model

Influence of shell Ret only on heat strainGarments with lower shell Ret ( higher MVP) reduce heat strain

Ret 10

• varying fabric Ret

• Long Underwear+ Rain suit

• Ambient10°C / 80%

• Activity level450 W

Predicted Core Temperatures for different ShellFabric Ret for same activity


Heat Stress affects performance e.g. diminishes vigilance

Study• Analysis of literature on vigilance and thermal

stress– Goal

understand the influence of thermal stresson vigilance

– Conductionauditory signal detection while walking ona treadmill in different temperatureconditions

– FindingIncreasing body temperature impairsattention and vigilance

Missed signals perminute of exposure

0

10

20

30

40

50

37 38 39 40

body temperature [°C](0.64 Tr + 0.36 Ts)

Missed signals [%]

Source: Hancock, Sustained Attention under Thermal Stress, Psych. Bul. 1986, Vol.99, No 2, p 263ff, data from Benor and Shvartz, 1971


Heat stressed helicopter pilots more likely to crash

Study• Severe helicopter pilot errors in Israel

– GoalFind out why there are many morecrashes in summer

– ConductionInvestigation of temperaturedistribution of days with andwithout accidents and near missoccurrences

– FindingHigher heat stress on hot daysincreases significantly the chanceof severe pilot errors

odds for a day with severe pilot errorsdepending on ambient temperature

0

1

2

3

4

5

6

7

24°Cand

lower

25 to29°C

30 to34°C

35°Cand

higher

Source: Froom et al, J. o. Occ. Med., Vol. 35, No 7, 1993, p 271 ff


Content





7


Differentiation between good and bad base-layers

Opinion of professional field testers (KLETS)

• Comments from a report of a test field comparing base-layers includingCapilene® and Cotton

• “The Capilene® vest is previously nominated here as among the bestbase-layers available

• In low activity all testers had no complaint until the Cotton vest becamedamp and adhered against the skin.

• In high activity the Cotton vests became saturated and a chill effect wasexperienced during short stops. It retained this accumulated wetnessand clung to the skin and was very uncomfortable”


Measurement of thermal absorptivity with Alambeta TesterCorrelates well with “coldness to touch” feeling

Fabric

Bottomplatecontaining heatfluxsensor

10

Metal plates with heat fluxsensors- The upper plate is

10ºC warmer than the lower plateFabric


Coolness to touch of wet fabricsThermal absorbtivity vs. water content of Cotton and Capilene®

0

200

400

600

800

1000

1200

0 1 2 3 4 5 6Water content [g m-2 *100]

Th. A

bsor

ptiv

ity [W

s0.

5m

- ² K-1]

Capilene®

Cotton

Warmer to touch

Cooler to touch


Coolness to touch of wet fabricsCotton much colder than Capilene ® inner

0

200

400

600

800

1000

1200

0 1 2 3 4 5 6Water content [g m-2 *100]

Th. A

bsor

ptiv

ity [W

s0.

5m

- ² K-1]

Cotton

Capilene® inner

Capilene® outer

Cooler to touch

Warmer to touch


Thermal resistance (insulation) of wet base-layersComparison of Rct of wet cotton and Capilene®

0

5

10

15

20

25

30

35

0 1 2 3 4 5 6

Water content [g m-2 *100]

Ther

mal

Res

ista

nce

m2 K

/ W *

10-3

Cotton

Capilene®

Warmer


Moisture Management TesterThe movement of sweat on either side of a fabric

Measures electrical resistance between theupper and lower sets of pins and alsoconcentric circles of pins.

8


Moisture Management TesterExample: “Water penetration fabric”

Properties• Small spreading area• Excellent one-way

transport

Changed !


Moisture Management TesterExample: “Moisture management fabric”

Properties• Medium to fast wetting• Medium to fast absorption• Large spread area at bottom

surface• Fast spreading at bottom

surface• Good to Excellent one-way

transport


Dry and wet clingForce to pull a fabric over a smooth dry and wet surface

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

UK Mil Cottondry

UK Mil Cottonwet

Capeline®Yellow dry

Capilene®Yellow wet

Pulli

ng fo

rce

[N]


Conclusions

• Testing all aspects of protective clothing performance and comfort isrelatively complex,and takes much effort.

• For comfort, the use of thermal manikins and physiological modellingcuts the evaluation cost considerably, whilst at the same time enablingmore questions to be answered.

• Testing for product integrity, performance, and durability is a severe costfactor e.g.

Garment Shower Testing

Factory support for seam sealing etc.

testing of protective outdoor garments

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