ISO 2285:2013 download free.Rubber, vulcanized or thermoplastic — Determination of tension set under constant eIongation and of tension set, elongation and creep under constant tensile load.
ISO 2285 specifies a number of methods of determining the dimensional changes in test pieces of vulcanized or thermoplastic rubber during and after tensile loading For relatively short periods under constant elongation or constant loading.
Theconstant-elongation Lest is intended to measuretheabilityofrubbersto retain theirelastic properties after extension, at a standard laboratory temperature, to a specified strain which is maintained for a specified time at the same or at a specified higher temperature and then released at the test temperature or at the standard laboratory temperature.
The constant-load test specifies a method for the determination of elongation, creep and tension Set of rubbers subected to a constant load at standard Laboratory temperature.
The test methods are intended to measure the elastic properties of rubber in the hardness range 20 IRHD to 94 IRIID.
The creep measurement is not recommended for product design or the evaluation of low-creep materials. For these, reference should be made to ISO 8013. Nv agreement between the results of this test and those of ISO 8013 should be inferred.
NOTE The constant-load test Is primarily intended [or the measurement of state of cure and the quality control of thin-walled productL An Increase In the state of cure or degree of crosslinking is usually reflected in a decrease In set, creep or elongation.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited ipplies. For undated references, the Latest edition of the referenced document (Including any amendments) applies.
ISO 188, Rubber, vulcanized or thermoplastic — Accelerated ogeing and heat resistance tests
ISO 8013, Rubbe,r vulcanized— Determination of creep in compression or shear
ISO 18899:2004, Rubber — Guide to the calibration of test equipment
ISO 23529:2010, Rubber — General procedures for preparing and conditioning test pieces for physical test methods
3 Terms and definitions
For the purposes of ISO 2285, the following terms and definitions apply (see also the definitions of creep functions given in ISO 8013).
tension set at constant load
elongation remaining in a test piece in the unloaded condition after it has been subjected to a constant load during a specified time, expressed as a percentage of the original length in the unloaded condition
tension set at constant elongation
elongation remaining In a test piece in the relaxed condition after It has been subjected to a constant elongation during a specified time, expressed as a percentage of the elongation
3.3
creep
Increase In elongation of a test piece at constant load during a specified time, expressed as a percentage of the elongation at the beginning of that time
4 Apparatus
4.1 Constant-elongation measurements
4.1.1 StraIning device, consistingofa metal rod or other suitable guide fitted with pairs of holders, one fixed and one moveable. for the ends of the test piece. The holders shall be In the form of self-tightening damps for strip test pieces. In the form of jaws to hold tab (enlarged) ends, and In the form of flat pulleys of about 5 mm width and 10 mm diameter for ring test pieces.
liso desired, a means of operating the movIng holder other than by hand may be provided, for example a threaded rod. Suitable stops or graduations may also be provided to avoid over-extension In the Initial straining of the test piece.
The straining device shall be so designed that, when used at high temperatures in an oven, it can be placed with the reference length of the test piece perpendicular to the direction of the air flow. It shall also be of minimum mass In order to avoid excessive lag in the attainment of temperature equilibrium alter its introduction into the oven.
A multiple-unit straining device may be used, provided that the foregoing requirements are met.
4.1.2 Oven, conforming to the requirements of ISO 188 (If the test Is to be carried out at a emperature above the standard laboratory temperature). For short heating times, controlled air flow Is not necessary.
4.1.3 Length-measuring device, capable of measuring the reference length of the test piece to the nearest 0,1 mm.
For strip test pieces, a marker shall be provided to mark the length used as the reference length.
For ring test pieces, the reference length may be the Inner diameter of the rIng. In which case a graduated cone allowing measurements to be made to the nearestfl,1 mm shall be used. Alternatively, lfmeasurements are to be made on a straight reference length, a rigid channel. 3,5 mm deep and 20 mm wide for brge ring test pieces and 1.75mm deep and 10mm wide forsmalLring test pieces, shall be provided forstraightening portions of such test pieces during marking and measuring of the reference length.
Samples and test pieces shall he protected from light as completely as possible during the interval between forming and testing.
6.7 ConditionIng
Prepared test pieces shall be conditioned immediately before testing for a minimum period of 3 Ii at one of the standard laboratury temperatures defined In ISO 23529, the same temperature being used throughout any one test or series of tests intended to be comparable.
7 Procedure
7.1 Testing under constant elongation
7.1.1 Measurement of the test pieces
Measure the unstrained reference length (Li) of each test piece to the nearest 0,1 mm at standard laboratory temperature. Insert the test pieces in the tralnlng device in the appropriate way.
7.1.2 Stretching the test pieces
Extend the test pieces to the required strain. When testing ring test pieces, rotate the pulleys slightly by hand to equalize the strain In the two halves of the ring Ensure that the reference length remains centralized between the two pulleys.
Between 10 mm and 20 mm after the specified strain has been reached, measure the strained reference length (L2) to the nearest 0.1 mm. When the inner diameter of ring test pieces is used as the reference length, it can be calculated from the diameter of the pulleys and the distance between them, measured to the nearest 0,1 mm. If the strain, calculated as specified in 7.Ltl, does not conform to the appropriate standard value, taking into account tolerances, discard the test piece and prepare and test a replacement test piece with a modified applied strain.
7.1.3 Exposure at the test temperature
7.1.3.1 Tests at standard laboratory temperature
Maintain the strained test pieces at the standard laboratory temperature.
Immediately following the end of the test period, release the strain, remove the test pieces from the clamps or pulleys and lay them free on a flat non-sticky wooden surface. After (301) mm. measure the reference length to the nearest 0.1 mm (L%).
7.1.32 Tests at temperatures other than standard laboratory temperature
Between 20 miii and 30 mm after the specified strain has been reached, place the strained test pieces in an oven operating at the test temperature and leave them there for the specified period.
There are three methods ofcoollngthe test pieces and releasing the strain, of which method A is preferred. Method A
At the end of the test period, remove the straining device from the oven, immediately release the strain, remove the test pieces from the clamps or pulleys and lay them on a flat non-sticky wooden surface. After (301) mm, measure the reference length to the nearest 0,1 mm.
Method B.