Understanding and Improving Elongation at Break for TPE Materials
Time of issue:2024-11-26
### Concept and Expression of Elongation at Break
**Definition:**
Elongation at break is a measure of a material's ability to stretch under tensile stress before breaking. It is typically expressed as a percentage. For example, if a material with an original length of 100mm stretches to 300mm before breaking, the elongation at break would be:
\[ \text{Elongation at Break} = \left( \frac{300 \text{mm} - 100 \text{mm}}{100 \text{mm}} \right) \times 100\% = 200\% \]
### Related Testing Factors
#### A. Tensile Speed
Plastics are viscoelastic materials, and their stress relaxation process is closely related to the deformation rate. Stress relaxation requires a certain amount of time:
- **Low Tensile Speed:** At low speeds, the molecular chains have enough time to reposition and realign, resulting in ductile behavior. This leads to a decrease in tensile strength and an increase in elongation at break.
- **High Tensile Speed:** At high speeds, the molecular segments cannot keep up with the applied force, resulting in brittle behavior. This leads to an increase in tensile strength and a decrease in elongation at break.
Different types of plastics have varying sensitivities to tensile speed. Hard and brittle plastics are more sensitive to tensile speed and typically use lower tensile speeds, while more ductile materials can use faster tensile speeds.
#### B. Minor Defects in the Product
Even with the same material, the elongation at break can vary between different samples due to internal defects, stress concentration points, and microcracks, which cause localized deformation within the material.
### Tips for Improving Elongation at Break in TPE Formulations
To achieve higher elongation at break, the following points should be considered in TPE formulations:
1. **Choose PP Copolymers:**
- PP (polypropylene) copolymers can enhance the toughness of TPE, contributing to increased elongation at break.
2. **Select High Molecular Weight SEBS and SBS:**
- Higher molecular weight means longer molecular chains, which can improve the elasticity and toughness of the material, thus increasing elongation at break.
3. **Use Relatively More White Oil:**
- White oil acts as a plasticizer, increasing the flexibility and flowability of the material, which helps to improve elongation at break.
4. **Partially Combine with Polyolefin Elastomers (e.g., POE, POP):**
- Polyolefin elastomers can improve the elasticity and toughness of TPE, contributing to higher elongation at break.
5. **Choose Appropriate Compatibilizers:**
- Compatibilizers can improve the compatibility between different components, ensuring uniformity and consistency in the material, which helps to increase elongation at break.
6. **Increase the Proportion of Lubricants, Recommend Silicone-Based Lubricants with Some Polarity:**
- Lubricants can reduce friction during processing, improving the flowability and processability of the material, which helps to increase elongation at break. Silicone-based lubricants with some polarity offer good lubrication and can enhance the overall performance of the material.
7. **Relatively Reduce the Amount of Fillers:**
- Excessive fillers can reduce the elasticity and toughness of the material, thereby affecting elongation at break. Reducing the amount of fillers can help to increase elongation at break.
By optimizing the TPE formulation with these considerations, the elongation at break of the material can be significantly improved, enhancing its performance in various applications.
TEL: +86-0752-6768128 FAX: +86-0752-6768088 MAIL: sales@tpe-sp.com WEB: en.tpe-sp.com
ADD: Huangxi Industrial Park, Shiwan Town, Boluo County, Huizhou City, Guangdong Province，China