ISO 75-1:2020 pdf free download.Plastics — Determination of temperature of deflection under load — Part 1: General test method.
I Scope
1.1 ISO 75-1 gives a general test method for the determination of the temperature of deflection under load (flexural stress under three-point loading) of plastics. DilTerent types of test specimen and different constant loads are defined to suit different types of material
1.2 ISO 75-2 gives specific requirements for plastics (Including filled plastics and fibre-reinforced plastics in which the fibre length, prior to processing. is up to 7,5 mm) and ebonite, while ISO 75-3 gIves specific requirements for high-strength thermosetting laminates and long-fibre-reinforced plastics In which the fibre length, prior to processing, is greater than 7.5 mnt
1,3 The methods specified are suitable for assessing the relative behaviour of different types of material at elevated temperature under load at a specified rate of temperature increase. The results obtained do not necessarily represent maximum applicable temperatures because, In practice, essential factors, such as time, loading conditions and nominal surface stress, can differ from the test conditions. True comparability of data can only be achieved for materials having the same room-temperature flexural modulus.
1.4 The methods speci& preferred dimensions for the test specimens.
1,5 Data obtained using the test methods described are not intended to be used to predict actual end-use performance. The data are not intended for design analysis or prediction of the endurance of materials at elevated temperatures.
1.6 This method is commonly known as the heat deflection temperature nr heat distortion temperature (HOT) test, although there Is no official document using this designation.
2 Normative references
The following documents are referred Co 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 75-2. Plastics — Determination of temperature of deflection under load — Part 2: Plastics and ebonite
ISO 75-3. Plastics — Determination of temperature of deflection under load — Part 3: Hi,qh-strength thermosetting laminates and long-fibre-reinforced plastics
ISO 291. Plastics — Standard atmospheres for conditioning and testing
ISO 16012, Plastics — Determination of linear dimensions of test specimens
IEC 60584-1. Thermocouples — Part 1: EMFspeclfications and tolerances
IEC 60751. Industrial platinum resistance thermometers and platinum temperature sensors
4 Principle
A standard test specimen is subjected to three-point bending under a constant load in the ulatwise position to produce one of the flexural stresses given in the relevant part of ISO 75. The temperature is raised at a uniform rate, and the temperature at which the standard deflection, corresponding to the specified increase in flexural strain, occurs is measured.
5 Apparatus
5.1 Means ofproduclnga flexural stress
The apparatus shall be constructed essentially as shown in Eigur1. It consists of a rigid metal frame In which a rod shall move freely in the vertical direction. One end of the rod is fitted with a weight- carrying plate and the other end is equipped with a loading edge. The base of the frame is fitted with test-specimen supports. These supports and the vertical members of the frame are made of a material having the same coefficient of linear expansion as the rod.
The test-specimen supports consist of metal pieces that are cylindrical In the contact area and with their lines of contact with the specimen in a horizontal plane. The size of the span. i.e. of the distance between the contact lines, is given in ISO 75-2 or ISO 75-3. The supports are fitted to the base of the frame in such a way that the vertical force applied to the test specimen by the loading edge is midway (±1 mm) between them. The contact edges of the supports are parallel to the loading edge and at right angles to the length direction of the test specimen placed symmetrically across them. The Contact edges of the supports and loading edge have a radius of (3,0 ± 0,2) mm and shall be longer than the width of the test specimen.
Unless vertical parts of the apparatus have the same coefficient of linear thermal expansion, the difference in change of length of these parts introduces an error in the reading olthe apparent deflection of the test specimen. A bbnk test shall be made on each apparatus using a test specimen made of rigid material having a low coefficient of expansion and a thickness comparable to that of tile specimen under test. The blank test shall cover the temperature ranges to be used in the actual determination. and a correction term shall be determined (or each temperature. If the correction term is 0,01 mm or greater, its value and algebraic sign shall be recorded, and the term applied to each test result by adding it algebraically to the reading olthe apparent deflection of the test specimen.
NOTE Invar and borosilicate glass have been found suitable as materials tor the test specimen in the bLank test.
The heating rate shall be verified periodically either by
— checking the automatic temperature reading, or
— manually checking the temperature at least every 6 miii.
The requirement tar the heating rate shall be considered satisfied if, over every 6 mm interval during the test. the temperature change is (12± 1)C.
NOTE 1 The apparatus can be designed to stop heating automatically when the standard deflection has been reached.
NOTE 2 Liquid paraffin, transformer oil, glycerol and silicone oils are suitable liquids, but others can be used. For fluldized beds, aluminium oxide powder has been round suitable.
5.3 WeIghts
A set ci weights shall be provided so that the test specimen can be loaded to the required flexural stress, calculated as specilied in Li.
5.4 Temperature-measuring instrument
Use a suitable temperature-measuring instrument of appropriate range and maximum error limit oh 1 °C.
Temperature-measuring Instruments shall be calibrated at the depth of immersion particular to the apparatus in use. The temperature-sensing part of the instrument shall be located not farther than 12,5 mm from the point where the loading edge contacts the specimen. The temperature-sensing part of the instrument shall not touch the specimen or be in contact with any part of the frame.
Thermocouples shall comply with the requirements of IEC 60584-1. Resistance thermometers shall comply with the requirements of IEC 60751,
It Is recommended that the heating bath is eqepped with a separate temperature-measuring instrument at each test station. if there are several.
5.5 Deflection-measuring instrument
Use a calibrated dial gauge or any other indicating or recording device, including electric displacement sensing apparatus, to measure the deflection of the specimen at the point where the loading edge contacts the specimen. The deflection measuring device shall be readable to 0.01 mm.
In certain types of apparatus. the force. F. exerted by the dial gauge spring acts upwards and therefore reduces the downward force exerted by the weighted rod. while in other types. F, acts downwards and augments those exerted by the weighted rod. In such cases, it is necessary to determine the magnitude and direction of F so as to be able to compensate for it as specified in Li. Since, in certain dial gauges, F1 varies considerably over the measurement range of the Instrument. It shall be measured in that part of the range in which the Instrument is to be used.
5.6 Micrometers and gauges
These are used to measure the width and thickness of the test specimens. They shall be accurate to 0,01 mm and conform to ISO 16012.