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GB/T 2941-2025: Rubber - General procedures for preparing and conditioning test pieces for physical test methods Delivery: 9 seconds. True-PDF full-copy in English & invoice will be downloaded + auto-delivered via email. See step-by-step procedure Status: Valid GB/T 2941: Historical versions
Similar standardsGB/T 2941-2025: Rubber - General procedures for preparing and conditioning test pieces for physical test methods---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GBT2941-2025 GB NATIONAL STANDARD OF THE PEOPLE’S REPUBLIC OF CHINA ICS 83.060 CCS G 40 GB/T 2941-2025 / ISO 23529.2016 Replacing GB/T 2941-2006 Rubber – General Procedures for Preparing and Conditioning Test Pieces for Physical Test Methods (ISO 23529.2016, IDT) Issued on: APRIL 25, 2025 Implemented on: NOVEMBER 1, 2025 Issued by. State Administration for Market Regulation; Standardization Administration of the People’s Republic of China. Table of ContentsForeword... 3 1 Scope... 5 2 Normative References... 5 3 Terms and Definitions... 6 4 Specimen Identification and Record Keeping... 6 5 Standard Laboratory Conditions... 6 6 Storage of Samples and Specimens... 7 7 Preparation of Specimen... 7 8 Conditioning... 13 9 Measurement of the Dimensions of Specimens... 13 10 Conditions of Test... 15 11 Test Chambers... 17 12 Test Report... 19 Annex A (Normative) Conditioning Time of Rubber Specimen... 20 Annex NA (Informative) Maintenance of Cutter... 24 Bibliography... 26 Rubber – General Procedures for Preparing and Conditioning Test Pieces for Physical Test Methods WARNING 1.Persons using this document shall have the practical experience working in formal laboratory. 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 shall be made to appropriate documentation on safe handling and disposal after use of the waste.1 ScopeThis Document specifies general procedures for the preparation, measurement, marking, storage, and conditioning of rubber test pieces for use in physical tests, 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 ReferencesThe provisions in following documents become the essential provisions of this Document through reference in this Document. For the dated documents, only the versions with the dates indicated are applicable to this Document; for the undated documents, only the latest version (including all the amendments) is applicable to this Document. 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) When controlled temperature and humidity are not required or when standard laboratory conditions are difficult to achieve, prevailing ambient temperature and humidity can be used.6 Storage of Samples and Specimens6.1 Samples of specimen to be prepared and specimens before conditioning shall be stored in an environment that is least susceptible to aging, such as avoiding light, heat and contamination (such as cross-contamination from other samples). 6.2 For all tests, the minimum time interval between sample formation and testing shall be 16 h. If the specimens are cut from finished products or the entire finished product (such as bridge bearings) for testing, the time interval between sample formation and testing may be much longer than 16 h. In this case, the minimum time interval shall be as specified in the product instructions or relevant test methods. 6.3 For unfinished product tests, the maximum time interval between sample formation and testing shall be 4 weeks. In order to make the tests comparable, they shall be carried out within the same time interval as much as possible. 6.4 For finished product tests, the time interval between finished product formation and testing shall not exceed 3 months whenever possible. In other cases, the test shall be carried out within 2 months of the date of receipt of the product by the customer. 6.5 These requirements only relate to initial rubber material testing and finished product testing during the initial and delivery stages. Special tests for other purposes may be carried out at any time, such as process control or evaluation of the effects of abnormal storage conditions on the product. Such reasons shall be clearly stated in the test report. 6.6 If it is an unvulcanized rubber compound, it shall be conditioned at a standard laboratory temperature specified in 5.1 for 2 h to 24 h; preferably in a sealed container to prevent moisture in the air, or placed in a room with a relative humidity controlled at 50% ± 5%.7 Preparation of Specimen7.1 Specimen thickness The specimen thickness shall comply with the provisions of the relevant test method. The preferred specimen thickness is shown in Table 2.If it is necessary to retain the original surface of the sample, a specimen thickness other than that shown in Table 2 may be used. 7.2.3.1 Rotary cutting equipment This equipment refers to a slicer. It consists of a motor-driven or manual disc-shaped cutter of appropriate diameter and a movable cutting table that can transport the sample to the edge of the knife. The cutting table is equipped with an adjustable slow feed mechanism to transport the rubber in the cutting direction and control the thickness of the slice. The equipment shall also have a clamping device to fix the rubber. The blade is preferably lubricated with a diluted aqueous detergent solution to facilitate the cutting operation. 7.2.3.2 Skiving machines This equipment is based on commercial leather-slitting machinery, and convenient types are available for cutting strips about 50 mm wide with thicknesses up to about 12 mm. Adjustment shall be possible to vary the thickness of cut, and feed rollers shall be provided to transport the material past the knife. Provision shall be made for maintaining the cutting edge in a sharp condition. Attachments are available for splitting and cutting sections from cable sheathing. 7.2.3.3 Abrasive wheels The abrading apparatus shall consist of an abrader with a motor-driven abrasive wheel. It is important that the wheel runs true without vibration, and that the abrasive surface, of aluminum oxide or silicon carbide, is true and sharp. The abrader can be equipped with a slow-feed mechanism so that very light cuts can be made to avoid overheating of the rubber. Suitable means shall be provided for securing the rubber to prevent excessive deformation and for controlled traversing of the rubber against the abrasive wheel. NOTE. Wheels of diameter 150 mm operating at a surface speed in the range of 10 m/s to 12 m/s, designated C-30-P-4-V for roughing and designated C-60-P-4-V for finishing (see ISO 525), have been found suitable. C-30-P-4-V means. the abrasive is black silicon carbide, the particle size is 30, the hardness code is P, the abrasive structure number is 4, and the ceramic bond. C-60-P-4-V means. the particle size is 60, and the rest is the same as C-30-P-4-V. The depth of cut produced in the first pass shall not exceed 0.2 mm. Successive cuts shall be progressively less deep to avoid overheating of the rubber. Buffing shall not be carried out beyond the point where unevenness in the thickness has been eliminated. For removal of greater thicknesses of rubber, cutting equipment as specified in 7.2.3.1 or 7.2.3.2 shall be used. 7.2.3.4 Flexible abrasive belts The apparatus shall consist of either a motor-driven drum on which a helical strip of the abrasive belt is secured, or of two pulleys, one motor-driven and the other adjustable, to tension and align the belt. The abrasive belt shall be of textile or paper or a combination of the two, with the abrasive, of aluminum oxide or silicon carbide, bonded to the surface with a resin which is unaffected by water. Equipment shall be provided for slow feeding device of the material to the abrasive belt and for securing the material without excessive deformation. NOTE. A linear speed of the abrasive belt of (20 ± 5) m/s has been found suitable. With this apparatus, cuts removing several tenths of a millimeter of rubber are practicable as much less heat is produced than with the equipment specified in 7.2.3.3.Abrasion can be carried out against the drum, against one of the pulleys or against the taut belt between the pulleys. 7.3 Specimen cutters 7.3.1 General requirements The structure and type of cutter or die employed depends on the thickness and hardness of the material under test. In the case of thin materials, punching or rotary cutting tools shall be used as specified in 7.3.2, 7.3.3 or 7.3.4.For thicker materials, usually above 4 mm, a rotary cutting tool as specified in 7.3.4 is desirable to reduce the degree of dishing of the cut edge resulting from compression of the rubber during cutting. 7.3.2 Fixed-blade cutters For cutters which do not have replaceable blades, an example of a suitable cutting edge is shown in Figure 1.These shall be made from high-quality tool steel and can be of either one-piece or two-piece construction. They can be designed to punch out single or multiple specimens. It is essential that the design ensures sufficient rigidity to prevent distortion of the cutting shape, and the cutter shall preferably be fitted with an ejection system to release the specimen. If fitted, such a system shall be designed to accommodate material up to the maximum thickness to be cut, normally 4.2 mm. If an ejection system is not fitted, access shall be available from the rear to permit release of the specimen by the operator without damaging the cutting edge. The cutting edge shall be kept sharp and free from nicks, as specified in 7.4, to prevent the formation of ragged edges on the specimens. to release the specimen. If fitted, such a system shall be designed to accommodate sample up to the maximum thickness to be cut, normally 2.2 mm. If an ejection system is not fitted, access shall be available from the rear to permit release of the specimen by the operator without damaging the cutting edge. Checks shall be made to ensure that the blade is not significantly deformed during the cutting operation, particularly with rubbers of high hardness. 7.3.4 Rotary cutters Either annular or arc-shaped knives or razor blades, held in a suitable adapter permitting them to be fitted in a drilling machine, shall be used. Means shall be provided for holding the rubber in place during the cutting operation. This can consist of a combination of a plunger with a presser foot incorporated in the adapter to secure the central portion of the rubber and a metal pressure plate having a central hole larger than the size of the specimen to be cut out, or it can consist of a vacuum-type holder which applies suction to the lower surface of the rubber. Means can be provided for lubricating the surface of the rubber during the cutting operation. Using two inner and outer ring cutters to cut simultaneously helps to obtain a ring specimen with a vertical cross section. The size of the blades and the movement of the drill head shall be sufficient to accommodate the thickness of rubber to be cut. The leading edge of an arc-shaped blade shall be angled and sharpened to facilitate entry into the rubber. It is important that the cutting area be adequately guarded with a transparent shield permitting examination of the cutting operation. Other techniques in which the rubber is rotated against a stationary knife or razor blade can also be used. 7.4 Maintenance of cutters Care shall be exercised at all times to protect and maintain the cutting edges of cutting equipment, as any dulling, nicking or bending of the cutting edge can lead to defective specimen which give atypical results. During storage, cutters shall be placed either in such a way that the cutting edge is resting on a soft surface such as foamed rubber or, preferably, that the cutting edge does not contact any surface. See Annex NA for the relevant maintenance of cutter. 7.5 Preparation of specimens by molding 7.5.1 Test sheets When test sheets are prepared by mold cure, vulcanize them to reproduce as closely as possible the state of vulcanization of the product. First, press-cure the sheets to the thickness specified in the relevant test method, then cut out specimens using cutters. NOTE. Suitable methods for the preparation of vulcanized test piece of compression-molded dumbbell- shaped specimens and vulcanized test piece of circular ring-shaped test specimens are specified in ISO 2393. 7.5.2 Specimen When specimens, e.g. in the form of discs, are prepared directly by mold cure, vulcanize them to reproduce as closely as possible the state of vulcanization of the product. 7.5.3 Thermoplastic materials Samples of thermoplastic materials shall be molded in accordance with the manufacturer’s instructions for the material, application and type and size of molding. 7.6 Preparation of nonvulcanized specimens The specimens of nonvulcanized rubbers or compounds shall be prepared in accordance with ISO 1795.8 Conditioning8.1 General requirements When both temperature and humidity are specified, the conditioning time of the specimen shall be a period of not less than 16 h, immediately before testing. When a standard laboratory temperature is specified without the need to control the humidity, the conditioning time of the specimen shall be a period of no less than 3 h, immediately before testing. When a temperature other than a standard laboratory temperature is specified without the need to control the humidity, the conditioning time shall be a period sufficient for the specimen to reach temperature equilibrium with the environment or the period required by the specification covering the material or product being tested. Specimens prepared from buffed samples shall be conditioned before testing. 8.2 Conditioning times for subnormal or elevated temperatures Annex A gives calculated times for the center of a specimen to reach a temperature within 1 °C of a set conditioning temperature, starting from an initial temperature of 20 °C. The time depends on the geometry and size of specimen, the material and the type of used heat-transfer medium.9 Measurement of the Dimensions of SpecimensNOTE. For the measurement of the dimensions of products for control purposes, see ISO 3302-1. 9.1 Method A. For dimensions less than 30 mm This method is applicable to the measurement where the dimension to be measured is less than The caliper shall be adjusted so that the faces which contact the surfaces of the specimen or product do not compress them. NOTE. Suitable calipers are specified in ISO 13385-1. At least three measurements shall be made of each dimension to be determined, and the median value of each dimension shall be taken. 9.3 Method C. For dimensions over 100mm The measurement shall be made by means of a graduated ruler or tape with an error of no more than 1 mm. Each measurement shall be made along a line perpendicular to the opposite faces of the specimen or product defining the dimension to be measured. At least three measurements shall be made of each dimension to be determined, and the median value of each dimension shall be taken. 9.4 Method D. Non-contact method This method, which does not involve any contact with the rubber, can be required when the specimen or product has a special shape (e.g. O-rings or specimen taken from hoses). Various types of optical apparatus can be used, e.g. a travelling microscope, projection microscope or shadowgraph. The gauge shall be capable of measuring the thickness with an error of no more than 1 % or 0.01 mm, whichever is the smaller. At least three measurements shall be made of each dimension to be determined, and the median value of each dimension shall be taken.10 Conditions of Test10.1 Duration of test The period required to obtain any given degree of change in a specimen (e.g. during ageing) depends largely upon the type of rubber, its composition and state of cure, and the nature and severity of the test environment. When an extensive investigation is required, changes are usually monitored by testing at set time intervals. For control purposes, such a procedure is not usually necessary and a single test period can be sufficient. In both cases, it is recommended that the test period(s) be selected from Table 4. The gaseous medium shall be heated by means of suitable electric heating elements, a fan or blower being provided to ensure adequate circulation of the gas. The heating elements shall be shielded to avoid thermal radiation falling directly onto the specimens. To obtain the necessary precision of temperature control, the heating system shall. a) use a recirculating gas system; b) be designed so that most of the heat required is supplied continuously and the remainder intermittently for temperature control or with proportionating devices in the heat supply that prevent large cyclic variations in temperature. 11.2.2 Liquid heat-transfer media Such chambers shall preferably follow the same principles as in 11.2.1, using an immersion heater instead of the heating elements used in 11.2.1, and a stirrer or pump instead of the fan or blower. 11.2.3 Fluidized beds Such chambers shall preferably utilize a bed of inert material which can be “fluidized” by passing a suitable gas through the bed at a suitable speed. 11.3 Chambers operating at subnormal temperatures 11.3.1 Mechanically refrigerated units In general, mechanically refrigerated low-temperature chambers have a multi-stage compressor and suitable cooling coils which surround the test chamber. 11.3.2 Cooling by solid carbon dioxide (direct-cooling type) In the direct-cooling type of solid carbon dioxide cooled low-temperature chamber, a suitable fan or blower, located in the solid carbon dioxide compartment, circulates the carbon dioxide vapor from the solid carbon dioxide compartment into the specimen compartment and back. 11.3.3 Cooling by solid carbon dioxide (indirect-cooling type) In the indirect-cooling type of solid carbon dioxide cooled low-temperature chamber, air is used as the heat-transfer medium and no carbon dioxide vapor comes into contact with the specimens. 11.3.4 Packaged refrigeration units It is frequently desirable to house the test equipment in the test chamber and circulate temperature regulated cold air or carbon dioxide vapor from a separate refrigeration unit to the test chamber and back through insulated ducts or pipes. 11.3.5 Cooling by liquid nitrogen Annex NA (Informative) Maintenance of Cutter NA.1 Maintenance of the cutter NA.1.1 The maintenance of the cutting edge of the cutter is very important. The cutting edge can be gently ground and trimmed with a grindstone frequently, and the condition of the cutting edge can be evaluated by checking the fracture position of the specimen after the test. Remove the broken specimen from the holder and check whether the specimen always breaks at the same position or close to the same position. If there is such a trend, it indicates that the cutting edge may be blunt, notched or rolled at this particular position. NA.1.2 The cutter shall be stored in a dry environment and coated with protective oil to prevent corrosion of the cutter. NA.1.3 Pay attention to protecting the cutting edge during use. Place a high-quality cardboard or a pad of appropriate material with appropriate hardness under the sample to protect the cutting edge from damage. The cutting edge needs to be ground regularly to keep it sharp. NA.1.4 When larger grinding is required, first grind with a silicon carbide grindstone with a diameter of 12.5 mm installed on a universal grinder. a) Four types of grindstones are required. 1) Type A. has a flat surface perpendicular to the grindstone axis, used to grind the cutting edge parallel to the bottom of the cutter; 2) Type B. has a diameter small enough to be installed inside the cutting edge of the cutter, so that the inside surface is perpendicular to the plane determined by the end point of the cutting edge; 3) Type C. has a tapered end with an angle of 36°~44°, which can produce an angle of 18°~22° on the cutting edge; 4) Type D. has a tapered end with an angle of 60°~70°, which can produce an angle of 30°~35° on the cutting edge. b) Install each grindstone on the machine and grind it with a grinding wheel to shape the grindstone. c) Move the cutter along the machine processing table and contact each rotating grindstone in turn to resharpen the cutter. ......Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al. 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