GB/T 2941-2025 Rubber - General procedures for preparing and conditioning test pieces for physical test methods
WARNING 1——Persons using this document should be familiar with normal laboratory practice. This document does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user to establish appropriate safety and health practices and to ensure compliance with any national regulatory conditions.
WARNING 2——Certain procedures specified in this document might involve the use or generation of substances, or the generation of waste, that could constitute a local environmental hazard. Reference should be made to appropriate documentation on safe handling and disposal after use.
1 Scope
This document specifies general procedures for the preparation, measurement, marking, storage, and conditioning of rubber test pieces for use in physical tests specified in other International Standards, and the preferred conditions to be used during the tests. Special conditions, applicable to a particular test or material or simulating a particular climatic environment, are not included, nor are special requirements for testing whole products.
This document also specifies the requirements for the time interval to be observed between forming and testing of rubber test pieces and products. Such requirements are necessary to obtain reproducible test results and to minimize disagreements between customer and supplier.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 1795, Rubber, raw natural and raw synthetic - Sampling and further preparative procedures
Note: GB/T 15340-2025, Rubber, raw natural and raw synthetic - Sampling and further preparative procedures (ISO 1795:2017, IDT)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 1382 apply.
4 Identification and record keeping
Records shall be kept of the identity of each test piece so that it is identifiable with the sample supplied and such that all the relevant details of preparation, storage, conditioning and measurement are traceable to each individual test piece.
Each sample or test piece shall be individually identifiable by marking or segregation at each stage of its preparation and testing. Where marking is used as the method of identification, the markings shall be sufficiently durable to ensure that the test piece or sample remains identifiable until discarded. Where grain effects can be significant, the direction of the grain shall be identified on each sample or test piece.
The method of marking shall not affect the properties of the sample or test piece and shall avoid significant surfaces, i.e. surfaces which are to be directly tested (e.g. in abrasion tests) or surfaces at which a fracture terminates in the test (e.g. tear or tensile tests).
5 Standard laboratory conditions
5.1 Standard laboratory temperature
The standard laboratory temperature shall be either (23 ± 2) °C or (27 ± 2) °C in accordance with national practice. If a closer tolerance is required, it shall be ±1 °C.
Note: The temperature 23 °C is normally the standard laboratory temperature in temperate countries and 27 °C is normally the standard laboratory temperature in tropical and subtropical countries.
5.2 Standard laboratory humidity
If control of both temperature and humidity is necessary, they shall be selected from Table 1.
Table 1 Preferred relative humidity
Temperature
°C Relative humidity
% Tolerance on humidity
%
23 50 ±10a
27 65
a If a tighter tolerance is needed, ±5 % can be specified.
5.3 Other conditions
When control of temperature and humidity is not necessary, the prevailing ambient temperature and humidity can be used. The latter conditions shall be used where standard laboratory conditions cannot easily be achieved.
6 Storage of samples and test pieces
6.1 Samples awaiting the preparation of test pieces and test pieces prior to conditioning shall be stored under conditions which minimize the possibility of degradation by ambient conditions, such as heat or light, or of contamination, e.g. cross-contamination from other samples.
6.2 For all tests, the minimum time between forming the material and testing shall be 16 h. When test pieces are cut from a product or where a whole product, e.g. bridge bearings, is tested, considerably more time than 16 h between forming the material and testing can be necessary. In these cases, the minimum time shall be as given in the product specification or relevant test method.
6.3 For non-product tests, the maximum time between forming the material and testing shall be 4 weeks and, for evaluations intended to be comparable, the tests shall be carried out, as far as possible, after the same time interval.
6.4 For product tests, whenever possible, the time between forming the product and testing shall not exceed 3 months. In other cases, tests shall be made within 2 months of the date of receipt of the product by the customer.
6.5 These requirements relate only to initial rubber material tests and to product tests at both the initial and delivery stage. Special tests for other purposes can be carried out at any time, e.g. for the purposes of process control or to evaluate the influence of abnormal storage conditions on a product. Such reasons shall be clearly stated in the test report.
6.6 In the case of unvulcanized compound, batches shall be conditioned for between 2 h and 24 h at one of the standard laboratory temperatures specified in 5.1, preferably in a closed container to prevent absorption of moisture from the air, or in a room in which the relative humidity is controlled at (50 ± 5) %.
7 Preparation of test pieces
7.1 Test piece thickness
The test piece thickness shall be as specified in the relevant test method. However, the test piece thicknesses other than those in Table 2 may be specified where it is necessary to retain the original surface of the sample.
Contents
Foreword I
1 Scope
2 Normative references
3 Terms and definitions
4 Identification and record keeping
5 Standard laboratory conditions
6 Storage of samples and test pieces
7 Preparation of test pieces
8 Conditioning
9 Measurement of the dimensions of test pieces
10 Conditions of test
11 Test chambers
12 Test report
Annex A (Normative) Conditioning times for rubber test pieces
Annex NA (Informative) Maintenance and Care of Cutting Blades
Bibliography
