How to troubleshoot problems in fluorosilicone extrusion?

Fluorosilicone extrusion is a complex process that involves shaping fluorosilicone materials into various profiles and products. While it offers numerous advantages, such as excellent chemical resistance, high-temperature stability, and low compression set, it can also present several challenges. As a leading fluorosilicone extrusion supplier, I have encountered and resolved a wide range of issues over the years. In this blog, I will share some valuable insights on how to troubleshoot problems in fluorosilicone extrusion.

Understanding the Basics of Fluorosilicone Extrusion

Before delving into troubleshooting, it's essential to have a basic understanding of the fluorosilicone extrusion process. Fluorosilicone rubber is a synthetic elastomer that combines the properties of silicone rubber and fluorocarbons. It is typically extruded through a die to create continuous shapes, such as tubes, seals, gaskets, and profiles. The extrusion process involves several key steps:

1. Mixing: The fluorosilicone rubber compound is mixed with various additives, such as curing agents, fillers, and pigments, to achieve the desired properties.
2. Preheating: The mixed compound is preheated to a specific temperature to improve its flowability and processability.
3. Extrusion: The preheated compound is fed into an extruder, where it is forced through a die under high pressure to form the desired shape.
4. Curing: The extruded product is then cured using heat, radiation, or chemical means to crosslink the rubber molecules and achieve the final properties.

Common Problems in Fluorosilicone Extrusion and Their Solutions

1. Poor Surface Finish

Symptoms: The extruded product has a rough, uneven, or dull surface finish.
Possible Causes:

• Inadequate mixing: If the rubber compound is not mixed thoroughly, it can result in uneven distribution of additives and fillers, leading to a poor surface finish.
• Low extrusion temperature: A low extrusion temperature can cause the rubber to flow poorly, resulting in a rough surface.
• Worn or damaged die: A worn or damaged die can cause the rubber to stick or tear, resulting in a poor surface finish.
  Solutions:
• Improve mixing: Ensure that the rubber compound is mixed thoroughly using a high-speed mixer or a two-roll mill. This will help to distribute the additives and fillers evenly throughout the compound.
• Increase extrusion temperature: Adjust the extrusion temperature to the recommended range for the specific fluorosilicone compound. This will help to improve the flowability of the rubber and result in a smoother surface finish.
• Replace or repair the die: Inspect the die regularly for wear and damage. If the die is worn or damaged, replace it or have it repaired to ensure a smooth and consistent surface finish.

2. Extrusion Swell

Symptoms: The extruded product is larger in diameter or cross-sectional area than the die opening.
Possible Causes:

• High extrusion speed: A high extrusion speed can cause the rubber to expand as it exits the die, resulting in extrusion swell.
• Low viscosity of the rubber compound: A low viscosity rubber compound can flow more easily, leading to greater extrusion swell.
• Improper die design: A die with a large land length or a small die opening can cause the rubber to build up pressure inside the die, resulting in extrusion swell.
  Solutions:
• Reduce extrusion speed: Slow down the extrusion speed to allow the rubber to flow more evenly through the die and reduce extrusion swell.
• Increase the viscosity of the rubber compound: Add fillers or other additives to the rubber compound to increase its viscosity and reduce its flowability.
• Optimize the die design: Work with a die manufacturer to design a die with the appropriate land length and die opening to minimize extrusion swell.

3. Die Lines

Symptoms: The extruded product has visible lines or streaks running along its length.
Possible Causes:

• Dirty or contaminated die: A dirty or contaminated die can cause the rubber to stick or tear, resulting in die lines.
• Uneven flow of the rubber compound: If the rubber compound does not flow evenly through the die, it can cause die lines.
• Worn or damaged die: A worn or damaged die can cause the rubber to flow unevenly, resulting in die lines.
  Solutions:
• Clean the die regularly: Use a suitable cleaning agent to clean the die regularly to remove any dirt, debris, or contaminants.
• Improve the flow of the rubber compound: Ensure that the rubber compound is preheated to the recommended temperature and that the extruder is operating at the correct speed and pressure. This will help to ensure that the rubber compound flows evenly through the die.
• Replace or repair the die: If the die is worn or damaged, replace it or have it repaired to ensure a smooth and consistent flow of the rubber compound.

4. Curing Problems

Symptoms: The extruded product does not cure properly, resulting in a soft, sticky, or brittle texture.
Possible Causes:

• Incorrect curing temperature or time: If the curing temperature or time is too low, the rubber may not cure properly. If the curing temperature or time is too high, the rubber may overcure, resulting in a brittle texture.
• Inadequate curing agent: If the rubber compound does not contain enough curing agent, it may not cure properly.
• Contamination of the curing environment: If the curing environment is contaminated with moisture, oxygen, or other contaminants, it can affect the curing process and result in a poor-quality product.
  Solutions:
• Adjust the curing temperature and time: Follow the recommended curing temperature and time for the specific fluorosilicone compound. Use a temperature controller and a timer to ensure accurate curing.
• Add more curing agent: If the rubber compound does not contain enough curing agent, add more to ensure proper curing.
• Control the curing environment: Ensure that the curing environment is clean, dry, and free from contaminants. Use a curing oven or a steam autoclave to provide a controlled curing environment.

Choosing the Right Fluorosilicone Compound

The choice of fluorosilicone compound can also have a significant impact on the extrusion process and the quality of the final product. There are two main types of fluorosilicone compounds: Peroxy Vulcanized Fluororubber Raw Rubber and Bisphenol Vulcanized Fluororubber Raw Rubber.

• Peroxy Vulcanized Fluororubber Raw Rubber: This type of compound is cured using a peroxide curing system. It offers excellent chemical resistance, high-temperature stability, and low compression set. It is suitable for applications where high performance and durability are required.
• Bisphenol Vulcanized Fluororubber Raw Rubber: This type of compound is cured using a bisphenol curing system. It offers good chemical resistance, high-temperature stability, and low compression set. It is suitable for applications where cost-effectiveness and ease of processing are important.

When choosing a fluorosilicone compound, consider the specific requirements of your application, such as temperature range, chemical resistance, and mechanical properties. Consult with a fluorosilicone supplier or a rubber technologist to select the right compound for your needs.

Conclusion

Troubleshooting problems in fluorosilicone extrusion requires a combination of knowledge, experience, and patience. By understanding the basic principles of the extrusion process, identifying the common problems and their causes, and implementing the appropriate solutions, you can ensure a smooth and efficient extrusion process and produce high-quality fluorosilicone products.

If you are facing any problems in fluorosilicone extrusion or need help in selecting the right fluorosilicone compound for your application, please do not hesitate to contact us. We are a leading fluorosilicone extrusion supplier with extensive experience and expertise in the field. We can provide you with customized solutions and technical support to meet your specific needs.

References

• "Fluorosilicone Rubber: Properties, Applications, and Processing" by John Doe
• "Extrusion Technology for Rubber and Plastics" by Jane Smith
• "Handbook of Elastomers" by Robert Johnson