ASTM D1329-16(R2021) pdf free download

ASTM D1329-16(R2021) pdf free download.Standard Test Method for Evaluating Rubber Property—Retraction at Lower Temperatures (TR Test)
1. Scope
1.1 This test method describes a temperature-retraction procedure for rapid evaluation of crystallization effects and for comparing viscoelastic properties of rubber and rubber-like materials at low temperatures. This test method is useful when employed in conjunction with other low-temperature tests for selection of materials suitable for low-temperature service. 1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.4 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
3. Summary of Test Method
3.1 This test method is carried out by (1) elongating the specimen, (2) locking it in the elongated condition, (3) freezing it to a state of reduced elasticity, (4) releasing the frozen specimen and allowing it to retract freely while raising the temperature at a uniform rate, (5) measuring the length of the specimen at regular temperature intervals while it is retracting, and (6) computing the percentage retraction at these tempera- tures from the data obtained. In practice, the temperatures corresponding to 10 % and 70 % retraction are of particular importance, and are designated as TR10 and TR70, respec- tively.
4. Significance and Use
4.1 The difference between the temperature at which a vulcanizate retracts 10 % (TR10) and the temperature at which a vulcanizate retracts 70 % (TR70) increases as the tendency to crystallize increases. 4.2 TR70 correlates with low-temperature compression set. 4.3 TR10 has been found to correlate with brittle points in vulcanizates based on polymers of similar type. 4.4 In general, the retraction rate is believed to correlate with low-temperature flexibility of both crystallizable and noncrystallizable rubbers.
5. Apparatus
5.1 Specimen Rack, designed to maintain a slight tension on the specimen of 7 to 21 kPa (1 to 3 psi), and to permit it to be stretched and anchored at any elongation desired up to a maximum to 350 %. Means of measuring the length of the specimen at any time during the test within an accuracy of 61 mm (60.04 in.) shall be provided. The rack may be designed to hold a number of specimens at the same time. 5.2 Insulated Cooling Bath, equipped with stirrer, thermometer, and an immersion heater. A rheostat shall be included in the heater circuit. A suitable thermocouple- potentiometer measuring system may be substituted for the thermometer. 5.4 Liquid Coolant, which does not attack the test specimen under the conditions of the test. Methanol cooled with dry ice is satisfactory for most samples. Where methanol-dry ice combination is not appropriate, other cooling media may be used to achieve the prescribed test temperatures. Gaseous media may be employed as the coolant when the design of the apparatus is such that tests using it will duplicate those obtained with the standard liquid media. 5.5 An apparatus specially designed for the TR test 3,4 is schematically illustrated in Fig. 1. The sample rack is shown on the left, and the overall assembly on the right. The bath consists of an unsilvered Dewar flask that is contained in an insulating wooden frame, 0. The frame contains a wide slot in front, through which the test can be observed and the temperatures read. Other details of the apparatus are given in Section 8.
6. Test Specimens
6.1 The test specimens may be prepared by dieing out with a die of the design shown in Fig. 2. The choice of die length is governed by the elongation required and the limitations of the specimen racks. For most work a 38 mm (1.50 in.) die is suitable. Thickness of the specimens shall be 2.0 6 0.2 mm (0.08 6 0.01 in.). Any other method of obtaining test speci- mens of uniform cross section is satisfactory, provided that a suitable clamp is used on the rack. 6.2 Three specimens per material shall be tested.