1、GM DAEWOO Auto & Technology EDS Engineering, GM DAEWOO Auto & Technology Standards STANDARD TEST METHOD FOR LINEAR THERMAL EXPANSION OF PLASTICS BY THERMOMECHANICAL ANALYSIS EDS-T-7541 ISSUED DATE: 1999. 08. 30 REVISED DATE: 2006. 06. 19 VERSION: 2 EDS-T-7541STANDARD TEST METHOD FOR LINEAR THERMAL E
2、XPANSION OF PLASTICS BY THERMOMECHANICAL ANALYSIS PAGE: 1/3 ISSUED DATE: 1999. 08. 30 REVISED DATE: 2006. 06. 19 VERSION: 2 GM DAEWOO Auto & Technology 1. PURPOSE This standard aims at specifying the method of evaluating linear thermal expansion of the plastic standard test piece using TMA (ThermoMe
3、chanical Analysis). 2. SCOPE This standard applies to the method of getting the coefficient of linear thermal expansion of plastic materials used for vehicle interior and exterior parts by measuring change of length of the plastic test piece according to temperature rise using TMA. 3. TEST PIECE 3.1
4、. The dimensions of the test piece shall be 210mm for a side (a) and not larger than 10mm for other sides (b, c). The dimensions shall be recorded on the test report. 3.2. Each plane of the test piece shall be flat with a deviation not exceeding 25W to enhance accuracy of the test result. 3.3. Unles
5、s specified otherwise, at least 5 test pieces shall be provided. 4. PRE-TREATMENT 4.1. Pretreatment conditions specified in the drawing or material spec shall be followed. Unless specified otherwise, the test piece shall be exposed to a temperature of 232 and relative humidity of 505% for a minimum
6、of 40 hours prior to test. 4.2. Moisture-absorbing materials, such as nylon, shall be kept isolated from moisture as long as possible until arrangement for the test is completed. 5. TEST EQUIPMENT 5.1. Thermomechanical Analyzer EDS-T-7541STANDARD TEST METHOD FOR LINEAR THERMAL EXPANSION OF PLASTICS
7、BY THERMOMECHANICAL ANALYSIS PAGE: 2/3 ISSUED DATE: 1999. 08. 30 REVISED DATE: 2006. 06. 19 VERSION: 2 GM DAEWOO Auto & Technology 5.1.1. Test piece support and probe : The probe has a flat circular tip with a diameter of 25mm and supports the test piece being in direct contact with it. Once the tes
8、t piece is placed on the support, it measures the length of the test piece and sends the result to the transducer. The tip of the probe shall not protrude into the test piece within the test temperature range. 5.1.2. Transducer : It perceives the moved distance of the probe according to dimensional
9、changes of the test piece to have it recorded by the recorder. 5.1.3. Furnace : It heats the test piece uniformly at the pre-determined rate 5.1.4. Temperature-Sensing Element : It measures the test piece temperature. 5.1.5. It injects the inert gas, such as nitrogen and helium, around the test piec
10、e during test. 5.1.6. Recorder : It records the length change of the test piece according to temperature in the form of a X-Y graph. 6. TEST PROCEDURES 6.1. Place the test piece onto the test piece support below the probe and position the temperature sensor as close to the test piece as possible. 6.
11、2. In the normal temperature, measure the initial length of the test piece in the desired measuring direction of the coefficient of linear thermal expansion. 6.3. Move the furnace to the test piece support. When the temperature is to be lowered below the normal temperature, adjust the temperature in
12、 a way that the refrigerant is not in direct contact with the test piece. 6.4. While the normal temperature measuring range is -30 to 80, it may be changed upon necessity. 6.5. Once the lowest point of the desired measuring range is reached, raise the temperature at a constant rate of 5/min. 7. EVAL
13、UATION 7.1. From the graph acquired with the recorder, get the coefficient of linear thermal expansion (W /m) in the following range: = (Lsp X k)/(L X T), : Coefficient of linear thermal expansion, W /m Lsp : Change of specimen length, W k : Calibration coefficient L : Specimen length at room temper
14、ature, m T : Temperature difference over which the change in specimen length is measured EDS-T-7541STANDARD TEST METHOD FOR LINEAR THERMAL EXPANSION OF PLASTICS BY THERMOMECHANICAL ANALYSIS PAGE: 3/3 ISSUED DATE: 1999. 08. 30 REVISED DATE: 2006. 06. 19 VERSION: 2 GM DAEWOO Auto & Technology 7.1.1. C
15、ode A : Get the coefficient of linear thermal expansion from the inclination of the tangent line of the graph at the room temperature(23). 7.1.2. Code B : After dividing the portion of the graph around the inflection point into 23 temperature sections, get the coefficient of linear thermal expansion
16、 in the temperature range (t2-t1) of each section. Each section will have a different coefficient of linear thermal expansion. 7.1.3. Code C : Get the coefficient of linear thermal expansion in each of the -300, 030, 3060 and 6080 sections. 7.1.4. Code D : Get the coefficient of linear thermal expan
17、sion in the temperature range other than the above that has been designated by the requester or tester. 8. CODING SYSTEM The coefficient of linear thermal expansion shall be called up on drawings, material spec, etc. as follows: Coefficient of linear thermal expansion TO EDS-T-7541 A 3060 5x10-5W /m measurement test Requirements Test temperature Test code Test method Test item 9. REFERENCE ASTM E 831 Standard test method for linear thermal expansion of solid materials by thermomechanical analysis
