29 Apr Engineer Spotlight: Cortland Biomedical’s Wesley Conger Discusses the Advantages of Heat and Cold Stretching Techniques for Braided Textiles
Cortland Biomedical’s Engineering Director explains why heat and cold stretching can be important post-processing capabilities that benefit medical device OEMs.
What are heat and cold stretching techniques used for?
These techniques are designed to use during post-processing to improve the mechanical properties of textiles used in medical devices by eliminating constructional elongation, increasing the precision and performance for critical medical applications.
How does it work?
When braids are initially created, they contain a natural looseness due to air spaces between the filaments and strands. This causes the braids to stretch at a higher rate when exposed to initial tension, which can negatively impact mechanical performance. The introduction of heat and cold stretching techniques help remove this initial elongation, ensuring a more stable, compact structure for improved efficiency in medical devices. During these processes, tension is applied to braided products by passing them over successive rollers that travel at varying speeds and are set to specified temperatures that enhance the properties of the braid. These techniques work with a variety of materials, including Ultra High Molecular Weight Polyethylene (UHMWPE), which responds particularly well due to its low processing temperature.
Can you tell us more about the benefits of these processes?
The cold stretching process makes the braids less pliable by compacting the fibers, while heat stretching adds further stability, creating a permanent change. Heat stretching, depending on the material and parameters, can even affect the polymer structure at a microscopic level, making it comparable to “yarn drawing” in some cases. Both techniques also reduce the braid’s diameter due to the compaction, while heat stretching may slightly increase tensile strength.
By removing constructional elongation, the axial stiffness of the braid increases, allowing for more direct force transfer with less mechanical latency. This is particularly beneficial in applications where mechanical responsiveness is critical, such as when braids are used as actuator cables. A stretched braid performs more efficiently, ensuring quicker response times and better overall performance.
Does Cortland Biomedical offer heat and cold stretching?
Yes, as part of our continued commitment to investing in a range of state-of-the-art equipment, heat and cold stretching are now part of a comprehensive suite of post-processing services and technologies offered by Cortland Biomedical. This vertical integration enables Cortland Biomedical to provide our medical device OEM customers with products that can achieve improved performance in their medical devices.