ISO 3915:2022 プラスチック—導電性プラスチックの抵抗率の測定 | ページ 2

Foreword

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The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, 1. In particular, the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, 2 (see www.iso.org/directives ).

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This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 5, Physical-chemical properties,in collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/TC 249, Plastics,in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).

This second edition cancels and replaces the first edition (ISO 3915:1981), which has been technically revised.

The main changes compared to the previous edition are as follows:

• the apparatus specifications have been revised;
• the document has been editorially revised.

Introduction

0.1General

The method specified in this document is technically similar to that specified for rubber in ISO 1853.

However, it differs from that method in certain details, especially those associated with the greater stiffness of the plastic samples, and in particular in the limitation on specimen width. It takes into account two problems encountered in the measurement of resistivity of conductive plastics, namely the sensitivity of these materials to their temperature-history and strain-history, and the difficulty of making adequate electrical contact with them.

The prescribed width of the specimen is mandatory for reference purposes; however, a wider strip may be used, with correspondingly wider electrodes. There is a danger in using a wide strip, if the strip is slightly twisted and at the same time somewhat non-uniform in its resistivity. It is then possible to obtain erroneous results; the potential electrode nearer to the positive current electrode can even be found to be negative with respect to the other potential electrode.

0.2Effect of temperature changes and strain on conductive plastics

As mentioned, the resistance of these materials is sensitive to their temperature-history and strain-history. The relationships are complex and arise from the kinetic energy and structural configuration of the carbon particles in the polymer.

The resistivity may be increased by the effects of strain produced by (or subsequent to) removal from the mould, and a treatment is described for reducing specimens to a constant strain and temperature condition before measurements are carried out on them. Specimens are also cut in two perpendicular directions to assess anisotropy.

0.3Electrode systems (see 5.3)

Certain types of electrode, when applied to these polymers, have a contact resistance which can be many thousand times greater than the intrinsic resistance of the specimen. Dry contacts under light pressure or point contacts give very high resistances. However, the present test method eliminates the effects of contact resistances unless these are excessively high. (In such a case, no result, rather than a wrong one, is generally obtained.)

1 Scope

This document specifies the requirements for the laboratory testing of the resistivity of specially prepared specimens of plastics rendered conductive by the inclusion of conductive fillers or suitable modification of the structure. The test is applicable to materials of resistivity less than 10⁶ Ω⋅cm (10⁴ Ω⋅m).

The result is not strictly a volume resistivity, because of surface conduction, but the effects of the latter are generally negligible.

2 Normative references

There are no normative references in this document.

3 Terms and definitions

No terms and definitions are listed in this document.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

Bibliography