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AS 11981973

Australian Standard

POLYTETRAFLUOROETHYLENE(PTFE)

EXTRUDED ROD AND TUBE

METRIC UNITS

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The following scientif ic, industrial and governmental organizations and departments

were officially represented on the committee entrusted with the preparation of t his

standard:

Australian Post Office

Australian Pump Manufacturers Association

Electronic Association of Australia

National Association of Australian State Road Authorities

Petroleum Refinery Engineers Advisory Committee

Plastics Institute of Australia

This standard, prepared by Committee PL/29, Polytetrafluoroethylene Materials, wasapproved on behalf of the Council of the S tandards Association of Australia on17 November 1972.

Review of Austr alia n Standa rds. To keep abreast of progress i n industry, Australian Standards are subjectto periodic review and are kept up t o date by the issue of amendments or new editions as necessary. It isimportant therefore that Standards users ensure that t hey are in possession of the latest edition, and anyamendments thereto.

Full details of all Australian Standards and related publications will be found in the Standards AustraliaCatalogue of Publications; this information is supplemented each month by the magazine The AustralianStandard, which subscribing m embers receive, and which gives details of new publications, new editi onsand amendments, and of withdrawn Standards.

Suggestions for improvements t o Australian S tandards, addressed to the head office of Standards A ustralia,are welcomed. N otification of any inaccuracy or ambiguity found in an Australian Standard should be madewithout delay in order that the matter may be investigated and appropriate action taken.

This standard was issued in draft form for public review as Doc. 1882.

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AS 11981973

Australian Standard

POLYTETRAFLUOROETHYLENE(PTFE)


First published . . . . . . . . . . . . . . . . . . . . . . . . 1973

PUBLISHED BY ST ANDARDS AUSTRALIA(STANDARDS ASSOCIATION OF AUSTRALIA)1 THE CRESCENT, HOMEBUSH, NSW 2140

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AS 11981973 2

PREFACE

This standard was prepared under the authority of the Plastics Industry StandardsCommittee and is one of a series of standards relating to PTFE products.

A preliminary draft was prepared by the N ational F luorocarbon Division of thePlastics Institute of Australia. In preparing the standard cognizance was taken of thefollowing publications:

BS 4271:1968 Polytetrafluoroethylene Rod

SPI FD 107 Polytetrafluoroethylene Rod

ASTM D1710 TFE-Fluorocarbon Rod

The standard specifies the classification and composition of the rod, finish, andphysical and electrical requirements.

This standard may require reference to the following standards:AS 1145 Method for the Determination of Tensile Properties of Plastics

Materials.

AS 1193 Method for the Determination of the Density and Relative Density(Specific Gravity) of P lastics excluding Cellular Plastics*.

AS 1255 Methods of Test for Electrical Characteristics of Solid PlasticsInsulating Materials*.

ASTM D1708 Method of Test for Tensile Properties of Plastics by use ofMicrotensile Specimens.

ASTM D1710 TFE-Fluorocarbon Rod.

* In course of publication.

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3 AS 11981973

STANDARDS ASSOCIATION OF AUSTRALIA

Australian Standard Specification

for

POLYTETRAFLUOROETHYLENE (PTFE)


1 SCOPE . This specification applies to extruded polytetrafluoroethylene (PTFE)

rod and t ube, for mechanical, electrical and chemical applications.

2 DEFINITION. For the purposes of this specification rod shall also includetube. Tube shall however refer only to tubing.

3 COMPOSITION. The extruded rod shall be manufactured from unpigmented,PTFE resin and shall be free from any foreign material.

4 CLASSIFICATION. PTFE extruded rod shall be classified as follows:

Grade A premium quality extruded rod of which the properties shallcomply with the Grade A requirements of Table 1.

Grade B general purpose extruded rod of which the properties shall complywith the Grade B requirements of Table 1.

Class 1 Grade A or B extruded rod conforming to the dimensionalstability requirements of Clause 13 and free from any internaldefects (see Clause 7).

Class 2 Grade A or B extruded rod conforming to the dimensionalstability requirements of C lause 13.

Class 3 Grade A or B extruded rod having similar dimensional stability asClass 2 and free from any internal defects (see Clause 7).

Class 4 Grade A or B extruded rod which if tested in accordance withClause 13, would not meet the requirements thereof.

NOTE: It is recommended that purchasing specifications should refer to the above classifications.

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AS 11981973 4

5 CONDITIONING. Samples for test shall be conditioned for 24 h at 23 2C.

NOTE:

1. PTFE extrusions do not absorb moisture so a humidity control requirement is not specified.

2. PTFE undergoes a transition during which there is a significant volume change in the material. Themajority of this change occurs between 19 and 20C.

6 APPEARANCE AND FINISH. The colour of the rod may vary from white tomottled grey and the rod shall be free from obvious surface defects and inclusions thatcould affect its serviceability.

7 INTERNAL DEFECTS. The rod shall be substantially homogeneous and freefrom internal defects likely to affect its serviceability. Methods of test and acceptablelimits shall be agreed between purchaser and supplier.

8 DIMENSIONS AND TOLERANCES. The length of rod shall be as agreedbetween purchaser and supplier.

The diameter of the rod when measured at any point shall not differ from thenominal diameter by more than the appropriate amount shown in Table 2.

NOTE: Where closer tolerances on outer diameter are required by the purchaser a ground f inishshould be specified.

9 TENSILE STRENGTH AND ELONGATION AT BREAK. When tested inaccordance with AS 1145* at a speed of 50 mm/min 10 per cent using theappropriate test specimen specified in Appendix A, the t ensile strength at break andelongation at break shall conform to the requirements of Table 1. The elongationmeasurement shall be made on the sample length between grips.

10 DIELECTRIC STRENGTH. When tested in accordance with Method 3 of

AS 1255, the dielectric strength of the rod shall conform to the requirements ofTable 1.

11 RELATIVE DENSITY. When tested in accordance with Method A ofAS 1193, the relative density of the rod shall conform to the requirements ofTable 1. Alternatively Method D of AS 1193 may be used as a quality control method.

*AS 1145 Method for the Determination of Tensile Properties of Plastics M aterials.

AS 1255 Methods of Test for Electrical Characteristics of Solid Plastics Insulating Materials.

AS 1193 Method for the Determination of t he Density ( Specific Gravity) of Plastics excluding CellularPlastics.

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5 AS 11981973

12 HEAT RESISTANCE. When tested by the method described in Appendix B,

the rod shall show no signs of melting and the loss in mass shall not exceed 0.5 percent.

13 DIMENSIONAL STABILITY (Class 1 and Class 3 only). When tested by themethod described in Appendix C, the rod shall not change in length by more than1.5 per cent nor in diameter by more than 0.5 per cent.

14 IDENTIFICATION AND MARKING. Each package shall be indelibly andlegibly marked with the following information:

(i) Manufacturers name and/or registered trademark.

(ii) Grade and class of extruded rod (e.g. AS/B/4).

NOTE: The Standards Association of Australia is the owner of a registered certification trade mark. Thisis shown below, enclosed in the words Approved to Australian Standard. This mark can be used only bymanufacturers l icensed under t he certification mark scheme operated by the SAA. The presence of this mark

on a product is an assurance that the goods have been produced to comply with the requirements of theAustralian standard under a system of supervision, control and testing operated during manufacture andincluding periodical inspection at the manufacturers works in accordance with the certification mark schemeof the SAA.

Further particulars of the terms of l icence may be obtained from the Dir ector, Standards Association ofAustralia, 1 The Crescent, Homebush, N.S.W. 2140.

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AS 11981973 6

TABLE 1

PHYSICAL AND ELECTRICAL PROPERTIES

Property

Grade A Grade B

Rod dia., mm Rod dia., mm

Under10

Over 10to 25

Over25

Under10

Over 10to 25

Over25

Relative density,min.

2.14 2.15 2.15 2.12 2.13 2.14

Tensile strengthat break, MPamin.

12.4 13.1 13.8 11.0 11.7 12.4

Elongation atbreak, per centmin.

135 160 180 90 110 135

Dielectricstrength (0.5 mmsection), V/0.025 mmmin.

700 750 800 600 650 700

TABLE 2

DIMENSIONS AND TOLERANCES

Nominal diametermm

OD Tol.mm

ID Tol.mm

Up to and incl. 10 + 0.50 0

0.50+ 0

Above 10 and up to 25 + 0.75

0

0.75+ 0

Above 25 + 2.50 0

2.50+ 0

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7 AS 11981973

APPENDIX A

TEST SPECIMENS FOR TENSILE TESTS

A1 ROD EXCLUDING TUBE.

A1.1 Rod of diameter greater than 38.1 mm. A disc of thickness 0.75 mmshall be parted from the end of the rod and a specimen conforming to the dimensionsof Fig. A1 shall be prepared for testing.

A1.2 Rod of diameter greater th an 6.4 mm but less than 38.1 mm. Wherepracticable a skiving of thickness 0.75 mm shall be taken from the rod and alongitudinal specimen conforming to the dimensions of Fig. A1 should be prepared fortesting. If impracticable to skive, a specimen shall be machined conforming to thedimensions shown i n Fig. A2 and Table A1 using a lathe fitt ed with a follower andcutter of the dimensions shown in Figs A3, A4 and A5.

NOTE: This specimen is based on that in ASTM D1710, TFEFluorocarbon Rod.

A1.3 Rod of diameter less than 6.4 mm. A sample of the rod 38.1 mm inlength shall be used as the test specimen.

A2 T UBE .

A2.1 Tube of outside diameter greater than 6.4 mm. Where practicable, askiving of thickness 0.75 mm shall be skived from the tube and a longitudinalspecimen conforming to the dimensions of Fig. A1 shall be prepared for testing. Ifimpractical to skive, a specimen shall be machined conforming to t he dimensionsshown in Fig. A2 and Table A1 using a lathe fitted with a follower and cutter of thedimensions shown in Figs A3, A4 and A5. The two ends of the specimen shall besuitably plugged with metal inserts, t he inserts having a length equal to the full jawlength to avoid crushing.

A2.2 Tube of outside diameter less than 6.4 mm. A sample of the tubesuitably plugged as detailed in Paragraph A2.1 shall be used as the test specimen.

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AS 11981973 8

Dimensions are in millimetres.

A Ov er al l l en gt h . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 .1 m i n.B Wi dt h at en ds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 m in.C W id th of n arr o w p ar al le l po rt i on . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. 75 0.125D Di st an ce b et we en g ri p s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 m i n.E Ra di us . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 7 to 3 .7F Th ic kn ess . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0. 75 0.05

NOTE: This basically conforms to the microtensile test specimen of ASTM D1708 and test specimens madefrom cutters conforming to A STM D1708 may be used.

Fig. A1. TENSILE TEST S PECIMEN

d = 60 per cent nominal D 0.13 mm.

Fig. A2. TENSILE TEST S PECIMEN

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9 AS 11981973

Fig. A3. FOLLOWER Fig. A4. DETAIL OFEND OF BOSS OF FOLLOWER

TABLE A1

PREFERRED FOLLOWER DIMENS IONS

(See Fig. A4)

Dimension A (Bore)mm

Dimension Bmm

1012.51416

344.55

All dimensions are in millimetres.

Fig. A5. FOLLOWER ASSEMBLY AND CUTTER

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AS 11981973 10

APPENDIX B

METHOD OF THE DETERMINATIONOF HEAT RESISTANCE

Approximately 1 g of the material cut from the rod shall be weighed to an accuracyof 1 mg. T he weighed t est portion shall be heated for 6 h in an oven at 300 5C, andthen cooled in a desiccator to room temperature and re-weighed. Any loss in mass shallbe expressed as a percentage of the original mass.

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11 AS 11981973

APPENDIX C

METHOD FOR DETERMINATION OFDIMENSIONAL STABILITY

The ends of a length of rod, of minimum length 100 mm, shall be machined flat andat ri ght angles to the axis. The specimen shall be conditioned in accordance withClause 5 and t he length and diameter measured to t he nearest 0.025 mm whilstmaintained at that temperature.

The specimen shall be transferred to an oven maintained at 300 5C for the timespecified in Table C1.

TABLE C1

HEATING TIME

Radius or thicknessmm

Heating timemin.

Less than 6Over 6 up to and incl. 12Over 12 up to and incl. 18Over 18 up to and incl. 24Over 24

3090

150180210

At the end of the appropriate t ime the specimen shall be allowed to cool to23 2C at a rate not greater than 30C/h. The specimen shall be re-conditioned forat least 24 h at 23 2C and its length and diameter re-measured at this temperatureto the nearest 0.025 mm.

Since the heat treatment may distort the specimen, giving dished or bulged end

sections, the axial distances between end sections at a number of places shall bemeasured to establish the maximum change in length.

The maximum change in length shall be expressed and the change in diameter asa percentage of t he original dimension.

NOTE: Extruded Rod from PTFE fluorocarbon resins as normally processed will contain internal stresses.The magnitude of these stresses wil l vary with the thickness. These stresses may result in dimensionalchanges when parts cut therefrom are heated or machined. Annealing the extruded rod may relieve someof t he stresses and may distort t he surface and flatness of the extruded rod. However, this stress relieftreatment is only partially effective. The magnitude of the residual stresses is not uniform throughout andvaries with the size. It is clear that no amount of annealing will insure complete stability in the finalproducts. The best dimensional stabilit y in a finished product can only be accomplished by carrying outa stress relief procedure on a finished part after all cutting operations are complete. For close toleranceson a finished part, the best procedure i s to fabricate to approximate dimensions, str ess relieve and thenfinish to specified dimensions.

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