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IS 13360-6-21 (2004): Plastics - Methods of testing : Part6 Thermal properties, Section 21 Determination of ignitiontemperature using a hot-air furnace [PCD 12: Plastics]

IS 13360 (Part 6/See 21 ): 2004

ISO 871:1996

*

Wm6711@VJd

v21mq*m*dw=~mm

Indian Standard

PLASTICS — METHODS OF TESTINGPART 6 THERMAL PROPERTIES

Section 21 Determination of Ignition Temperature Using a Hot-Air Furnace

ICS 83.080.010

0 BIS 2004

BUREAU OF INDIAN STANDARDSMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

December 2004 Price Group 4

,-

1

Plastics Sectional Committee, PCD 12

NATIONAL FOREWORD

This Indian Standard (Part 6/See 21) which is identical with ISO 871 :1996 ‘Plastics — Determinationof ignition temperature using a hot-air furnace’ issued by the International Organization forStandardization (ISO) was adopted by the Bureau of Indian Standards on the recommendations of thePlastics Sectional Committee and approval of the Petroleum, Coal and Related Products DivisionCouncil.

The text of ISO Standard has been proposed to be approved as suitable for publication as an IndianStandard without deviations. Certain conventions are, however, not identical to those used in IndianStandards. Attention is particularly drawn to the following:

a) Wherever the words ‘International Standard’ appear referring to this standard, they should beread as ‘Indian Standard’.

b) Comma (,) has been used as a decimal marker, while in Indian Standards, the currentpractice is to use a point (.) as the decimal marker.

CROSS REFERENCES

In this adopted standard reference appears to certain International Standards for which IndianStandards also exist. The corresponding Indian Standards which are to be substituted in their placeare given below along with their degree of equivalence for the editions indicated. However, thatInternational Standard cross-referred in this adopted ISO Standard, which has subsequently beenrevised, position in respect of that latest ISO Standard has been given:

International Standard

ISO 291 : 1997 Plastics — Standardatmospheres for conditioning andtesting

lSO/lEC Guide 52 : 1990 Glossary offire terms and definitions

IEC 584-2 (1982) Thermocouples —Part 2: Tolerances

Corresponding Indian Standard Degree of

Equivalence

IS 196: 1966 Atmospheric conditions for Technicallytesting (revised equivalent

Nil —

IS 7358 : 1984 Thermocouples (first Technicallyrevision) not

equivalent

In case of lSO/lEC Guide 52, the committee responsible for the preparation of this standard tookcognizance of these Standards and decided that they are acceptable for use in conjunction with thisstandard.

For tropical countries like India, the standard temperature and the relative humidity shall be taken as27 + 20C and 65 I 5 percent respectively.

In reporting the results of a test or analysis made in accordance with this standard, if the final value,observed or calculated, is to be rounded off, it shall be done in accordance with IS 2: 1960 ‘Rules forrounding off numerical values (revise@’.

IS 13360 (Part 6/See 21) :2004

ISO 871:1996

Indian Standard

PLASTICS — METHODS OF TESTINGPART 6 THERMAL PROPERTIES

Section 21 Determination of Ignition Temperature Using a Hot-Air Furnace

1 Scope

1.1 This International Standard specifies a laboratorymethod for determining the flash-ignition temperatureand spontaneous-ignition temperature of plasticsusing a hot-air furnace. It is one of a number ofmethods in use for evaluating the resistance of plas-tics to the effects of high temperatures.

1.2 This method does not give a direct measure ofthe combustibility or rate of burning of a material orany definition of the safe upper limit of temperaturefor the plastics in use, and it should not be used todescribe or appraise the fire hazard or fire risk of ma-terials, products or assemblies under actual fire con-ditions. However, results of this test may be used aselements of a fire-hazard or fire-risk assessmentwhich takes into account all of the factors pertinent toan assessment of the fire hazard of a particular enduse.

1.3 Tests made under conditions of this method canbe of considerable value in comparing the relative ig-nition characteristics of different materials. Values ob-tained represent the lowest ambient air temperaturethat will cause ignition of the material under the con-ditions of this test. Test values are expected to rankmaterials according to ignition susceptibility underactual use conditions.

2 Normative references

The following standards contain provisions which,through reference in this text, constitute provisions ofthis International Standard. At the time of publication,the editions indicated were valid. All standards are

subject to revision, and parties to agreements basedon this International Standard are encouraged to in-vestigate the possibility of applying the most recenteditions of the standards indicated below. Membersof IEC and ISO maintain registers of currently valid in-ternational Standards.

ISO 291 :—1), Plastics — Standard atmospheres forconditioning and testing.

lSO/lEC Guide 52:1980, G/ossary of fire terms anddefinitions.

IEC 584-2:1982, Thermocouples — Part 2: Tolerances.

3 Definitions

For the purposes of this International Standard, thefollowing definitions apply, in addition to those givenin lSO/lEC Guide 52.

3.1 flash-ignition temperature (FIT): The minimumtemperature at which, under specified test conditions,sufficient flammable gases are emitted to ignite mo-mentarily on application of a pilot flame.

3.2 spontaneous-ignition temperature (SIT): Theminimum temperature at which ignition is obtained byheating, under specified test conditions, in the ab-sence of any additional flame ignition source.

3.3 glowing combustion: Combustion of a materialin the solid phase without flame but with emission oflight from the combustion zone.

1) To be published. (Revision of ISO 291:1977)

..

IS 13360 (Part 6/See 21) :2004

ISO 871 :1996

4 Principle

A specimen of the material is heated in a hot-air ig-nition furnace using various temperatures within theheated chamber, and the flash-ignition temperature isdetermined with a small pilot flame directed at theopening in the top of the furnace to ignite evolvedgases.

The spontaneous-ignition temperature is determinedin the same manner as the flash-ignition temperature,but without the ignition flame.

5 Apparatus

5.1 Hot-air ignition furnace, similar to that shownin figure 1, consisting primarily of an electrical heatingunit and a specimen holder.

5.2 Furnace tube, with an inside diameter of100 mm * 5 mm and a length of 240 mm ~ 20 mm,made of a ceramic that will withstand at least 750 ‘C.The tube shall be positioned vertically so that it standson the furnace floor above a plug for the removal ofaccumulated residue.

5.3 Inner ceramic tube, capable of withstanding atleast 750 ‘c, with an inside diameter of75 mm+ 2 mm, a length of 240 mm ~ 20 mm and athickness of approximately 3 mm, placed inside thefurnace tube and positioned 20 mm ~ 2 mm above thefurnace floor on three small spacer blocks. The topshall be covered by a disc of heat-resistant materialwith a 25 mm t 2 mm diameter opening in the centrewhich is used for observations and allows the passageof smoke and gases. The pilot flame shall be locatedimmediately above the opening.

NOTE 1 Fire-resistant materials such as silica glass andstainless steel have also been found suitable for this appli-cation.

5.4 Outside air source, to supply clean air near thetop of the annular space between the ceramic tubesthrough a copper tube at a steady and controllablerate. The air shall be heated and circulated in thespace between the two tubes and enter the innerceramic tube at the bottom. The air shall be meteredby a rotameter or other suitable device.

5.5 Electrical heeting unit, made of 50 turns of1,3 mm * 0,1 mm nichrome V alloy wire or equivalent.The wires, contained within a mineral-fibre sleeve,shall be wound around the furnace tube and shall beembedded in heat-resistant cement.

5.6 Insulation, consisting of a layer of mineral-fibrewool approximately 60 mm thick, and covered by asheet-iron jacket.

5.7 Pilot igniter, consisting of a copper tube ofnominal inside diameter 2,0 mm attached to a supplyof 94 YO minimum purity propane and placed horizon-tally 5 mm f 1 mm above the top surface of the disccover. The pilot flame shall be adjusted to20 mm * 2 mm in length and centred above theopening in the disc cover.

5.8 Specimen support and holder, consisting of ametal specimen pan made of approximately 0,5 mmthick steel and measuring 40 mm * 2 mm in diameterby 15 mm * 1 mm in depth held in a ring of approxi-mately 2 mm diameter stainless-steel welding rod.The ring shall be welded to a length of the same typeof rod extending through the cover of the furnace, asshown in figure 1. The bottom of the specimen panshall be located 185 mm f 2 mm down from the topof the inner ceramic tube.

5.9 Thermocouples, 0,5 mm in diameter, chromel-alumel (type K) or iron-constantan (type J), for tem-perature measurement, connected to a calibrated re-cording instrument with a tolerance not exceeding& 2 “c. The thermocouple tolerance shall be in accord-

ance with IEC 584-2:1982, table 1, class 2, or better.

5.1O Heating control, consisting of a suitable vari-able transformer or an automatic controller connectedin series with the heating coils.

5.11 Timing device, having an accuracy of 1 s orbetter.

6 Location of thermocouples

(see figure 1)

6.1 Thermocouple TC1 measures the temperatureT1 of the specimen. It is located as close as possibleto the centre of the upper surface of the specimenwhen the specimen is in place v’ithin the furnace. Thethermocouple wire is attached to the specimen sup-port rod.

6.2 Thermocouple TC2 gives some indication of thetemperature 7’2of the air traveling past the specimen.It is located 10 mm ~ 2 mm below the centre of thespecimen pan. The thermocouple wire is convenientlyattached to the specimen support rod.

NOTE 2 Thermocouple TC2 may also be installed througha hole drilled in the centre of the inspection plug below thespecimen pan.

6.3 Thermocouple TC3 measures the temperatureT3 of the heating coil. It is located adjacent to the fur-nace heating coil and is used in preference to theinner-tube thermocouples because of its fasterresponse.

2

IS 13360 (Part 6/Sac 21) :2004

ISO 871 :1996

Dimensions in miliimetres

Thermocouple TC2 Support rod

Refractory disc cover

l\ k

Thermocouple TC I

GasketOpening

7 r (25 rnrndiameter) I~ Thermocouple TC~

—

Heater termil

—

—

me

~ Inspection plug (removable)

Air-flow meter

\

(not part of furnace)

Mineral-fibre wool

\ Air flow tangential to cylinder

s Specimenpan

~ 50 turns of No. 16 Nichromewire in heat-resistant cement

-~ Three blocks to spaceinner tube and support it

\

~ Thermal insulation (removabte)

Figure 1 — Cross-section of hot-air ignition furnace

3

IS 13360 (Part 6/See 21) :2004

ISO 871 :1996

7 Test specimens

7.1 Materials supplied in any form, including com-posites, may be used, but it is essential that the formis fully described in the test report.

NOTES

3 Specimens containing high levels of inorganic fillers aredifficult to evaluate.

4 The same material tested in different forms may givedifferent results.

7.2 For materials having a density greater than100 kg/m3, a specimen mass of 3,0 g k 0,2 g shall beused. Materials may be tested in the form of pellets orpowder, as normally supplied for moulding. For sheetmaterials, cut the sheet into squares of maximum size(20 mm f 2 mm) x (20 mm&2 mm) and stack theseto a height which gives the required specimen mass.For film materials, roll up a strip 20 mm+ 2 mm wideand of length sufficient to give the required specimenmass.

7.3 For cellular materials having a density less than100 kg/m3, remove any outer skin and cut specimensin the form of a block measuring (20 mm * 2 mm) x(20 mm* 2 mm) x (50 mm* 5 mm).

7.4 Sufficient material is required for at least twodeterminations.

7.5 Condition the test specimens at 23 “C t 2 ‘C and(50 t 5) % relative humidity for not less than 40 h priorto test, in accordance with ISO 291.

8 Procedure

8.1 Flash-ignition temperature (FIT)

8.1.1 Set the air velocity to 25 mm/s by adjusting theactual air-flow rate qv through the full section of theinner tube (5.3) at the furnace temperature to a valuecalculated in Iitres per minute from the followingequation:

qv = 6,62 X =T

where T is the temperature in kelvins,

Ensure that the air-fiow rate is maintained at ~ 10 YO

of the calculated value.

8.1.2 Adjust the electric current supplied to theheating coil (5.5) by means of the variable transformeror automatic controller (5.10), by reference to tem-perature T3, until the air temperature T2 remains con-stant at the desired initial test temperature.

NOTE 5 A temperature of 400 “C is used when no priorknowledge of the probable flash-ignition temperature rangeis available. Other starting temperatures may be selected ifinformation about the material indicates a better choice.

8.1.3 Raise the specimen pan (see 5.8) to the coveropening and place the specimen on the pan. Lowerthe pan into the furnace, ensuring that thermocouplesTCI and TC2 are in their correct position (see 6.1 and6.2), Start the timer (5.1 1), ignite the pilot flame andwatch for evidence of a flash or mild explosion ofcombustible gases which may ,~e foIlowed by con-tinuous burning of the specimen. Flaming or glowingcombustion can also be observed by a rapid rise intemperature T1, as compared with temperature T2.

8.1.4 At the end of 10 rein, lower or raise the tem-perature 7’2 by 50 “C, depending on whether ignitionhas or has not occurred, and repeat the test with afresh specimen.

8.1.5 When the range within which the flash-ignitiontemperature lies has been determined, begin tests10 ‘C below the highest temperature within this rangeand continue by dropping the temperature in 10 “Csteps until the temperature is reached at which thereis no ignition during a 10 min period.

8.1.6 Record as the flash-ignition temperature thelowest air temperature T2 at which a flash is observedduring the 10 min period.

8.2 Spontaneous-ignition temperature (SIT)

8.2.1 Follow the same procedure as in 8.1 but with-out the pilot flame.

8.2.2 Ignition will be evidenced by flaming or glowingcombustion of the specimen. It may be difficult, withsome materials, to detect spontaneous ignition visu-ally when burning is by glowing combustion ratherthan flaming. In such cases, a rapid rise in tempera-ture T1 above that of T2 accompanied by a visual ob-servation is the more reliable reference.

8.2.3 Record as the spontaneous-ignition tempera-ture the lowest air temperature T2 at which thespecimen burns during the 10 min period.

4

.. ..

..-

7

9 Precision

The precision of this method is being developed. Seeannex A for relative precision data based on a prelimi-nary interlaboratory study conducted in 1994 usinglSO/DIS 871 as protocol. Findings from this interlab-oratory study resulted in changes to the procedurewhich are now incorporated in the standard.

10 Test report

The test report shall include the following:

a) a reference to this International Standard;

b) the designation of the material, including name ofmanufacturer and com~osition;

c) the mass of the test specimen, in grams;

d) the form of the material (granules, sheet, etc.);

IS 13360 (Part 6/See 21) :2004ISO 871:1996

e) the density of cellular materials, in kilograms percubic metre;

f) the flash-ignition temperature (FIT), in degreesCelsius:

g) the spontaneous-ignition temperature (SIT), in de-grees Celsius;

h) whether the combustion observed was flaming orglowing;

i) observations about the behaviour of the speci-men during the test (how ignition occurred, for-mation of soot or smoke, excessive foaming,melting, bubbling, smoking, etc.);

j) the following statement:

“These test results relate only to the behaviour oftest specimens under the particular conditions ofthe test. They are not intended to be used, andshall not be used, to assess the potential firehazards of a material in use. ”

5

IS 13360 (Part 6/See 21) :2004

ISO 871 :1996

Annex A

(informative)

Results obtained by interlaboratory trials

A.1 An interlaboratory study was conducted in 1994 polymeric materials, with three replicates of each ma-

uslng the first DIS of 871 as protocol for the testing terial. The resulting data were analysed in accordancecrlterla. with ISO 5725:1986, Precision of test methods —

Determination of repeatability and reproducibility for astandard test method by inter-laboratory tests (now

A.2 These precision data were determined from !n- withdrawn), and are summarized in tables A.1 and

terlaboratory tests, involving seven laboratories, on six A.2.

Table A.1 — Flash-ignition temperature (FIT)

Values in degrees Celsius

Physical form Average FIT Repeatability Reproducibility

High-impact polystyrene granulated 378 10 27

High-impact FR granulated 370 13 52polystyrene

Polyamlde 6 granulated 413 8 38

Poly(vlnyl chloride) film thickness 0,15 mm 327 11 45

Flexlble polyurethane thickness 25 mm 349 12 66foam

Phenol-formaldehyde solid bars 430 9 117re. wn

Table A.2 — Spontaneous-ignition temperature (SIT)

Values in degrees Celsius

Physical form Average SIT Repeatability Reproducibility

High-impact polystyrene granulated 458 12 59

High-impact FR granulated 422 14 47polystyrene

Polyamide 6 granulated 439 31 56

Polyvinyl chloride) film thickness 0,15 mm 438 13 64

Flexlble polyurethane thickness 25 mm 370 11 61foam

Phenol-formaldehyde solid bars 482 14 103resin

6

.,

7

A.3 Repeatability, in the normal and correct oper-ation of the method, is the difference between twoaverages (each determined from three specimens) ob-tained using identical test material and the same ap-paratus by one analyst within a short time interval.The values of repeatability for this test method willnormally not exceed those shown in tables A. 1 andA.2.

A.4 Reproducibility, in the normal and correct oper-ation of the method, is the difference between twoindependent averages (each determined from three

IS 13360 (Part 6/See 21) :2004ISO 871:1996

specimens) obtained by two operators working in dif-ferent laboratories on identical test material. Thevalues of reproducibility for this test method will nor-mally not exceed those shown in tables A. 1 and A.2.

A.5 Two averages (each determined from threespecimens) are to be considered suspect and notequivalent if they differ by more than the repeatabilityand reproducibility shown in tables A.1 or A.2. Anyjudgement per clause A.3 or A.4 would have an ap-proximately 95 ‘?4. (0,95) probability of being correct.

7

. .

1u‘,

Bureau of Indian Standards

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Review of Indian Standards

Amendments are issued to standards as the need arises on the basis of comments. Standards arealso reviewed periodically; a standard along with amendments is reaffirmed when such review indi-cates that no changes are needed; if the review indicates that changes are needed, it is taken up forrevision. Users of Indian Standards should ascertain that they are in possession of the latest amend-ments or edition by referring to the latest issue of ‘BIS Catalogue’ and ‘Standards: Monthly Additions’.

This Indian Standard has been developed from Doc : No. PCD 12(1799).

Amendments Issued Since Publication

Amend No. Date of Issue Text Affected

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