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GB/T 1634.1-2025: Plastics - Determination of temperature of deflection under load - Part 1: General test method 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 1634.1: Historical versions
Similar standardsGB/T 1634.1-2025: Plastics - Determination of temperature of deflection under load - Part 1: General test method---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/GBT1634.1-2025 GB NATIONAL STANDARD OF THE PEOPLE’S REPUBLIC OF CHINA ICS 83.080.01 CCS G 31 Replacing GB/T 1634.1-2019 Plastics - Determination of Temperature of Deflection under Load - Part 1.General Test Method (ISO 75-1.2020, MOD) Issued on: JANUARY 24, 2025 Implemented on: AUGUST 1, 2025 Issued by. State Administration for Market Regulation; Standardization Administration of the People’s Republic of China. Table of ContentsForeword... 3 Introduction... 6 1 Scope... 7 2 Normative References... 7 3 Terms and Definitions... 7 4 Principle... 9 5 Instruments and Equipment... 9 6 Specimens... 12 7 Conditioning... 13 8 Operating Steps... 13 9 Result Expression... 15 10 Precision... 16 11 Test Report... 16 Plastics - Determination of Temperature of Deflection under Load - Part 1.General Test Method1 ScopeThis document describes the general method for determining the temperature of plastics deflection under load (flexural stress under three-point loading) to evaluate the relative properties of different types of plastic materials when heated to high temperatures at specified rates under specified loads. This document specifies the preferred dimensions of specimens.2 Normative ReferencesThe contents of the following documents constitute indispensable clauses of this document through the normative references in the text. In terms of references with a specified date, only versions with a specified date are applicable to this document. In terms of references without a specified date, the latest version (including all the modifications) is applicable to this document. GB/T 1634.2 Plastics - Determination of Temperature of Deflection under Load - Part 2. Plastics and Ebonite (GB/T 1634.2-2019, ISO 75-2.2013, MOD) GB/T 1634.3 Plastics - Determination of Temperature of Deflection under Load - Part 3.High- strength Thermosetting Laminates (GB/T 1634.3-2004, ISO 75-3.2003, IDT) GB/T 2918 Plastics - Standard Atmospheres for Conditioning and Testing (GB/T 2918-2018, ISO 291.2008, MOD) GB/T 16839.1 Thermocouples - Part 1.EMF Specifications and Tolerances (GB/T 16839.1- 2018, IEC 60584-1.2013, IDT) GB/T 30121 Industrial Platinum Resistance Thermometers and Platinum Temperature Sensors (GB/T 30121-2013, IEC 60751.2008, IDT) GB/T 44535 Plastics - Determination of Linear Dimensions of Test Specimens (GB/T 44535- 2024, ISO 16012.2015, MOD)3 Terms and DefinitionsThe following terms and definitions are applicable to this document. 3.1 flexural strain Tf As the test temperature increases, the temperature at which the specimen deflection reaches the standard deflection value. NOTE. it is expressed in degrees Celsius (C).4 PrincipleThe standard specimen is placed flat and subjected to a constant load of three-point bending, so that it generates one of the flexural stresses specified in the relevant parts of GB/T 1634.Under the condition of heating at a constant rate, measure the temperature when the standard deflection corresponding to the specified flexural strain increase is reached.5 Instruments and Equipment5.1 Device for Generating Flexural Stress The device consists of a rigid metal frame, and the basic structure is shown in Figure 1.There is a loading rod in the frame that can freely move in the vertical direction. One end of the rod is equipped with a weight bearing plate, and the other end is equipped with a loading head. The bottom plate of the frame is connected to the specimen support. These components and the vertical part of the frame are made of materials with the same linear expansion coefficient as the loading rod. The specimen support consists of two metal strips, whose contact surface with the specimen is a cylindrical surface, which is located on the same horizontal plane as the two contact lines of the specimen. The span size, that is, the distance between the two contact lines is specified by GB/T 1634.2 or GB/T 1634.3.The support is installed on the bottom plate of the frame, so that the vertical force applied to the specimen by the loading head is located at the midpoint of the two supports (1 mm). The edge line of the support contact head is parallel to the edge line of the loading head and is at right angles to the long axis direction of the specimen symmetrically placed on the support. The radius of curvature of the support contact head and the loading head is (3.0 0.2) mm, and the length of the edge line shall be greater than the width of the specimen. Unless the vertical components of the instrument have the same linear expansion coefficient, the different changes in the length direction of these components will cause errors in the apparent deflection readings of the specimen. A blank test shall be performed on each instrument using a standard specimen made of a rigid material with a low linear expansion coefficient (such as Invar and borosilicate glass) and with a thickness comparable to that of the specimen under test. The blank test shall include the various temperature ranges used in the actual determination, and the correction value shall be determined for each temperature. When the correction value is not less than 0.01 mm, it shall be recorded. For each test, it shall be added to the apparent deflection reading of each specimen. temperature range and has no effect on the material under test, for example, does not lead to swelling or cracking. In case of dispute or contradiction, if the temperature is within the feasible range, the method of using liquid heat transfer medium shall be used as the arbitration method. The heating device shall be equipped with control elements, so that the temperature can rise at a constant rate of (120 10) C/h. The heating rate shall be regularly calibrated by checking the automatic temperature reading or manually checking the temperature at least every 6 minutes. At every 6-min time interval during the test, if the temperature change is (12 1) C, then, the heating rate requirement is considered to be met. The instrument can be designed to automatically stop heating when the standard deflection is reached. NOTE. liquid paraffin, transformer oil, glycerine and silicone oil are suitable liquid heat transfer media, and other liquids may also be used. For fluidized beds, aluminum oxide powder is suitable. 5.3 Weights A set of weights that can be adjusted in 1 g increments shall be available to load the specimen to the required flexural stress calculated in accordance with 8.1. 5.4 Temperature Measurement Device Use a temperature measurement device with an appropriate measuring range and an accuracy of 1 °C. The temperature measurement device shall be calibrated at immersion depth. The temperature sensing part shall be located no more than 12.5 mm from the point of contact between the loading head and the specimen and shall not contact any part of the specimen or the frame. The thermocouples shall comply with the requirements of GB/T 16839.1.Resistance thermometers shall comply with the requirements of GB/T 30121. If there are multiple test stations, each test station should be equipped with a separate temperature measurement device. 5.5 Deflection Measurement Device The deflection of the specimen at the point of contact between the loading head and the specimen can be measured using a micrometer or any other indicating or recording device, including an electric displacement sensor. The deflection measurement device shall be accurate to 0.01 mm. For some types of instruments, the force Fs generated by the micrometer spring acts upward, reducing the downward load applied by the loading rod; in other cases, Fs acts downward, increasing the load applied by the loading rod. For such instruments, the magnitude and direction of the force Fs shall be determined, so that it can be compensated (see 8.1). Since the Fs of some micrometers considerably varies over the entire measurement range, the calibration shall be carried out over the part of the range in which the instrument is to be used. 5.6 Dimension Measurement Device It shall comply with the provisions of GB/T 44535 and be used to measure the width and thickness of the specimen, with a division value of 0.01 mm.6 Specimens6.1 General Requirements All specimens shall not have warpage caused by asymmetric thickness. For example, different cooling conditions or asymmetric structures during specimen molding may cause the specimen to warp during heating. In other words, it is already bent when there is no load, and correction shall be made by applying loads to two opposite surfaces of the specimen. 6.2 Shape and Dimensions The specimen shall be prepared in accordance with the relevant provisions of GB/T 1634.2 or GB/T 1634.3. The specimen shall be a spline with a rectangular cross section (length l > width b > thickness h). The dimensions of the specimen shall comply with the provisions of GB/T 1634.2 or GB/T 1634.3. The thickness and width of any part of the middle 1/3 length of the specimen shall not deviate from the average value by more than 2%. 6.3 Inspection of Specimen The specimen shall be free of distortion and its adjacent surfaces shall be perpendicular to each other. All surfaces and edges shall be free of scratches, pits, dents and trimming, etc. NOTE. the demolding angle of injection molded specimens is usually between 1° ~ 2° to facilitate demolding, and the sides of the specimens are usually unparallel. It is difficult for injection molded specimens to be absolutely free of dents. Due to differences in cooling, the thickness of the center of the specimen is usually less than that of the edge. It shall be ensured that all cutting surfaces of the specimen are as smooth as possible, and any unavoidable machining marks are in the longitudinal direction. In order to ensure that the specimen meets these requirements, it shall be placed close to a straight ruler, triangle ruler or flat plate, and the specimen shall be measured and inspected by visual observation or with a micrometer caliper. When applying the test force F, the impact of the mass of the loading rod mr shall be considered, and it shall be considered as part of the test force. If a spring loading instrument, for example, a dial micrometer, is used, the impact of the magnitude and direction of the force Fs applied by the spring on the total force F (either positive or negative, see 5.5) shall also be considered. An additional weight with a mass of mw shall be placed on the loading rod to generate the required total force F as specified in Formula (2). Hence Where, mW---the mass of the additional weight, expressed in kilograms (kg); F---the total force applied to the specimen, expressed in Newtons (N); Fs---the force generated by the spring loading instrument used, expressed in Newtons (N); mr---the mass of the loading rod that applies the test force, expressed in kilograms (kg). If the spring presses down against the specimen, then, the force is positive; if the spring pushes in the opposite direction to the downward movement of the loading rod, then, the force is negative; if no such instrument is used, then, the force is zero. The error in the actual applied force shall be 2.5%F. NOTE. all formulas involving flexural properties are correct only when the stress / strain relation is linear. Therefore, for most plastics, these formulas are only relatively accurate for small deflections, but they can be used to compare materials. 8.2 Initial Temperature of Heating Device At the beginning of each test, the temperature of the heating device shall be below 27 °C, unless previous tests have shown that starting the test at a relatively high temperature will not cause errors for the specific material under test. 8.3 Measurement Tests on specimens of different dimensions or prepared under different conditions may produce different results. Therefore, when reproducible data are required, the sample preparation conditions and test conditions shall be the same. Check the span between the specimen supports, and if necessary, adjust it to the appropriate value. Measure and record this value to an accuracy of 0.5 mm for the calculation in 8.1. Place the specimens on the support and make the longitudinal axis of the specimens perpendicular to the support. To compensate for asymmetric effects, for example, warping of the specimens, the specimens shall be tested in pairs with opposite faces facing the loading head, unless the involved parties agree to test the specimens on only one side. Place the loading device in the heating tank. In accordance with the provisions of GB/T 1634.2 or GB/T 1634.3, apply the force calculated in 8.1 to generate flexural stress in the specimens. 5 minutes after the first application of force, record the reading of the deflection measurement device or return it to zero. NOTE. a waiting time of 5 minutes is maintained to partially compensate for the creep shown by some materials when subjected to the specified flexural stress at room temperature. Creep that occurs within the first 5 minutes usually accounts for most of the creep that occurs within the first 30 minutes. If the material under test has no obvious creep within the first 5 minutes of the initial temperature, then, ignore this waiting period. At a constant rate of (120 10) C/h, raise the temperature of the hot bath, and record the temperature when the net increase in the initial deflection of the spline reaches the standard deflection, which is the temperature of deflection under load under the flexural stress specified in GB/T 1634.2 or GB/T 1634.3.The standard deflection is a function of the thickness h, the span used, and the flexural strain increase specified in GB/T 1634.2 or GB/T 1634.3.Calculate in accordance with Formula (4). Where, s---the standard deflection, expressed in millimeters (mm); L---the span, i.e., the distance between the contact lines of the specimen support and the specimen, expressed in millimeters (mm); f---the flexural strain increase, expressed in (%); h---the specimen thickness, expressed in millimeters (mm). If the specimen deflection - temperature curve is obtained, then, it is usually conducive to the interpretation of the test results. Therefore, it is advisable to continuously monitor the specimen deflection during the waiting and heating period.9 Result ExpressionUnless otherwise specified in GB/T 1634.2 or GB/T 1634.3, the temperature of deflection under load of the specimen is expressed as the arithmetic mean of each test result, and the result is retained as an integer. If the difference between the results in different loading directions ......Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al. Tips & Frequently Asked Questions:Question 1: How long will the true-PDF of English version of GB/T 1634.1-2025 be delivered?Answer: The full copy PDF of English version of GB/T 1634.1-2025 can be downloaded in 9 seconds, and it will also be emailed to you in 9 seconds (double mechanisms to ensure the delivery reliably), with PDF-invoice.Question 2: Can I share the purchased PDF of GB/T 1634.1-2025_English with my colleagues?Answer: Yes. 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