LBTZ-18 Low-Temperature Tensile Recovery Elasticity Testing Machine for Vulcanized Rubber (TR Test)
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Description
Product Introduction:
The specimen is stretched at room temperature, then cooled to a sufficiently low temperature at which no recovery occurs upon removal of the tensile force. The tensile force is released, and the temperature is raised at a uniform rate. The temperature corresponding to a specified degree of recovery is measured. This instrument is designed and developed in accordance with the national standard GB/T 7758, which specifies the temperature‑retraction method (TR) for determining the low‑temperature properties of vulcanized rubber, and incorporates a compressor‑based refrigeration system. The equipment employs cascade compression refrigeration technology, leveraging the principle of thermal equilibrium and a circulating stirring mechanism to achieve automatic, uniform cooling and stable temperature control of the specimen.
Technical Specifications:
| Project | Details |
| Temperature control range | Rt -70° |
| Temperature control error | ±2℃ |
| Temperature resolution | 0.1℃ |
| Cooling rate | About 2 hours or so |
| Displacement resolution | 0.01mm |
| Elongation | 0-175mm |
| Temperature fluctuation after reaching thermal equilibrium | Fluctuation within 3 minutes of the test is less than ±1°C. |
| Cold well dimensions | 200×140×400mm (Length × Height × Width) |
| Release fixture system | Automatic release |
| Cooling medium | Ethanol or other antifreeze |
| Stirring motor | 15W |
| Power supply | 220V~240V, 50Hz, 2kW |
| Heating rate | 1℃/min ± 0.2℃ |
| Number of sample holders | Group 1, Group 3, Group 6 (optional) |
| Usage Environment Instructions | Use at room temperature (23–25°C); during operation, the side door may be opened to ensure proper heat dissipation from the compressor. |
Specimen Requirements
The standard specimen is a strip with a broad, clamping‑friendly end, and its dimensions must meet the specified requirements. The initial length of the specimen shall be either 100 mm or 50 mm. A 100‑mm‑long specimen is suitable for testing materials with low elongation, whereas a 50‑mm‑long specimen is appropriate for materials with high elongation. Specimens are cut from flat test sheets having a thickness of 2.0 mm ± 0.2 mm using a sharp cutting blade; these test sheets may be prepared by molding or by cutting and grinding from finished products.
Test procedure:
1. The cooling tank shall be filled with an adequate amount of coolant to ensure that, during the test, the specimen is covered by at least 25 mm of liquid. In accordance with GB/T 9868, the coolant shall be cooled to −70 °C while being stirred.
2. While the liquid is cooling, place the specimen holder in the standard test temperature and stretch the initial length to the selected elongation value, then lock it in this position. Ensure that the specimen remains under tension at the standard laboratory temperature for the shortest possible duration.
3. The elongation may be selected according to the following principles:
1) Unless otherwise specified for technical reasons and to minimize the effects of crystallization, a concentration of 50% should be selected.
2) To investigate the combined effects of crystallization and low temperature, one of the following elongation values should be selected:
—250%;
— If 250% is not achieved, half of the elongation at break shall be used;
— If the elongation at break exceeds 600%, a value of 350% should be selected.
4. When the coolant reaches an equilibrium temperature between −70°C and −73°C, place the sample holder containing the specimen into the cooling bath and maintain it there for 10 ± 2 minutes at a temperature within the range of −70°C to −73°C. Release the locking mechanism of the upper clamp to allow the specimen to retract freely. Simultaneously, heat the liquid at a rate of 1°C/min, with a tolerance of 10°C ± 2°C over any 10‑minute interval. If the stretched specimen returns to its original length at −70°C, another cooling medium must be used to achieve a lower temperature.
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