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OTT RubberTech is a professional solution provider of rubber process formula, material, machinery with Mixer, Rubber Mixer, Mixing Mill, Precision Performer, Vulcanizing Press, Calender, batch-off Cooling unit, rubber Extruder, and other support plastic machines.
Features and Performance
The performance of a tensile tester for rubber is characterized by its "long-travel" capability and high resolution. Since rubber can often stretch up to 800-1000 percent of its original length, the machine must have a tall frame and an extensometer designed for high-elongation materials.
| Technical Feature | Performance Standard |
|---|---|
| Load Cell Capacity | Range from 1 kN to 10 kN for rubber |
| Testing Stroke | Up to 1000mm or more for high-stretch elastomers |
| Extensometer | Long-travel contact or non-contact (Video) types |
| Crosshead Speed | Constant speed (e.g., 500 mm/min per ASTM D412) |
| Grips / Fixtures | Pneumatic or eccentric roller grips for rubber |
| Data Rate | High-speed sampling (up to 1000 Hz) |
Key features include the use of pneumatic grips, which provide a constant clamping force as the rubber thins during the test, preventing sample slippage. The software allows for the automatic detection of the "break point" and calculates the energy absorbed (toughness). Advanced versions can be equipped with an environmental chamber to test rubber properties at extreme temperatures, simulating conditions like engine compartments or arctic environments.
Usage Tips and Techniques
Accurate tensile results depend heavily on the quality of the sample preparation. Use a high-quality die and a hydraulic press to cut samples from a vulcanized sheet; any nicks or rough edges on the dumbbell will cause a premature break and give falsely low strength readings. Always measure the thickness of each specimen at three points and use the median value for stress calculations.
| Operation Phase | Optimization Technique |
|---|---|
| Sample Cutting | Sharpen the cutting die frequently to avoid nicks |
| Specimen Loading | Ensure the dumbbell is perfectly vertical in the grips |
| Extensometer Use | Clip the extensometer only on the "gauge length" section |
| Testing Speed | Follow ASTM/ISO standards exactly (usually 500mm/min) |
| Waste Control | Cut samples in the grain direction (unless otherwise specified) |
A useful technique for high-stretch rubber is to use a video extensometer. This uses a camera to track marks on the sample, eliminating the physical weight and potential damage caused by traditional clip-on extensometers. When testing recycled or low-grade rubber, be prepared for high variability in results; testing at least five specimens and averaging the results is standard practice to ensure statistical reliability.
Maintenance Skills
Maintenance for tensile testers involves the calibration of the load cell and the lubrication of the drive screws. The load cell is a sensitive electronic component that can be damaged by overload; always ensure the machine's software limits are set correctly. The ball screws that move the crosshead should be kept clean of rubber dust and lubricated with the manufacturer-recommended grease to ensure smooth, constant-speed movement.
| Maintenance Area | Procedure | Frequency |
|---|---|---|
| Load Cell | Calibration by certified third party | Annually |
| Drive Screws | Clean old grease and re-apply fresh lubricant | Quarterly |
| Pneumatic Grips | Inspect air lines and grip faces for wear | Weekly |
| Extensometer | Verify displacement against a standard scale | Monthly |
| Crosshead Alignment | Check for verticality and parallelism | Annually |
Maintenance staff should check the "grip faces" regularly. For rubber, these faces are usually serrated or covered with a high-friction material; if they become worn or clogged with rubber residue, the sample will slip, ruining the test. It is also important to check the grounding of the machine to prevent electrical noise from affecting the sensitive load cell signals. If the machine is equipped with a video extensometer, the lens and lighting system must be kept clean to ensure accurate tracking.
Application Scenarios
Tensile testers are the primary tool for verifying the mechanical performance of a rubber compound. They are used for long-term aging studies, checking the quality of incoming batches, and benchmarking competitor products. They are vital for manufacturers of tires, seals, conveyor belts, and any rubber product that is subjected to mechanical stress during its life.
| Industry Sector | Typical Property Tested |
|---|---|
| Tire Industry | Tensile strength and abrasion resistance correlation |
| Automotive Seals | Modulus at 100 percent and compression set |
| Consumer Goods | Elongation at break and tear resistance |
| Medical / PPE | Puncture resistance and tensile strength for gloves |
| Material Research | Evaluating the effect of new fillers or polymers |
In the manufacture of rubber gloves, the tensile tester ensures that the material is strong enough to resist tearing during use while remaining flexible. For bridge bearing manufacturers, the machine is used to test the shear modulus of the rubber, ensuring the bearing can handle the weight and movement of the structure. The machine can also be used for "tear testing" by using a different sample shape (Die C), providing a comprehensive view of the rubber's physical durability.
