How to Test the Elasticity of Silicone Rubber?
Testing the elasticity of silicone rubber requires designing test methods based on material properties (such as hardness, rebound rate, and tensile performance) and actual application scenarios. Below are common testing steps and considerations:
1. Define the Testing Objective
Type of Elasticity: Is it compressive elasticity (e.g., silicone pads), tensile elasticity (e.g., silicone straps), or bending elasticity (e.g., silicone tubes)?
Key Parameters: Rebound rate, compression set, tensile strength, fatigue life, etc.
2. Common Testing Methods
(1) Rebound Rate Test (Compression/Tension)
Tools: Durometer, tensile testing machine, thickness gauge.
Procedure:
Compress or stretch the sample to a fixed deformation (e.g., 50% of original length).
Hold for a set duration (e.g., 10 seconds).
Release and measure the recovered size.
Calculation:
Rebound Rate=(1−Initial Thickness−Recovered ThicknessDeformation Amount)×100%\text{Rebound Rate} = \left(1 - \frac{\text{Initial Thickness} - \text{Recovered Thickness}}{\text{Deformation Amount}}\right) \times 100\%Rebound Rate=(1−Deformation AmountInitial Thickness−Recovered Thickness)×100%
Standard Reference: ASTM D395 (Compression Set Test).
(2) Tensile Performance Test
Tools: Universal testing machine.
Procedure:
Mount the silicone sample (e.g., dumbbell-shaped specimen) in the grips.
Stretch at a constant speed until break.
Record the stress-strain curve to calculate elastic modulus and elongation at break.
Standard Reference: ISO 37 (Rubber Tensile Testing).
(3) Dynamic Mechanical Analysis (DMA)
Used to test the dynamic modulus and damping performance of silicone under varying frequencies and temperatures.
(4) Fatigue Test
Repeatedly compress/stretch the sample (e.g., thousands of cycles) and observe elastic degradation and permanent deformation.
3. Simplified Testing Methods (Without Professional Equipment)
Drop Ball Test: Drop a steel ball from a fixed height onto the silicone surface and measure the rebound height.
Tactile Evaluation: Press the silicone with fingers and observe rebound speed and residual dents (qualitative comparison).
Bending Test: Repeatedly bend a silicone strip and check if it returns to its original shape.
4. Key Considerations
Environmental Conditions: Temperature and humidity may affect results (silicone is temperature-sensitive).
Sample Consistency: Samples from the same batch should have the same size and shape.
Preconditioning: Some silicones require aging or pre-compression before testing.
5. Application of Results
Quality Control: Compare results to industry standards or customer specifications.
R&D Optimization: Adjust silicone formulations (e.g., crosslinking agent ratio) to improve elasticity.