In long-term bending use, relative displacement between the insulation layer and conductor of silicone rubber cables is a critical issue affecting their reliability and lifespan. This displacement is usually caused by the combined effects of mechanical stress, thermal expansion and contraction, and material aging, and may lead to insulation cracking, conductor exposure, or even electrical failure. To effectively prevent such problems, a comprehensive approach is needed, encompassing material selection, structural design, process optimization, and usage and maintenance.
The properties of silicone rubber directly affect its resistance to displacement. High-quality silicone rubber should possess high elasticity, low compression set, and good tear resistance to withstand the dynamic stress generated by long-term bending. For example, adding reinforcing agents such as nano-silica can significantly improve the mechanical strength of silicone rubber and reduce material fatigue caused by repeated bending. Simultaneously, selecting conductor insulation materials with excellent compatibility with silicone rubber, such as cross-linked polyethylene (XLPE), can reduce the coefficient of friction between interfaces, thereby reducing the risk of relative displacement.
Structural design is the core element in preventing displacement between the insulation layer and conductor. For long-term bending scenarios, a layered structural design can be adopted, i.e., wrapping a low-friction buffer layer around the conductor before covering it with a silicone rubber insulation layer. This design disperses bending stress and absorbs some energy through the elastic deformation of the buffer layer, preventing stress from being directly transferred to the insulation layer. Furthermore, optimizing the conductor stranding process, employing tight stranding or a profiled structure, enhances the overall rigidity of the conductor and reduces insulation layer misalignment caused by conductor deformation.
The precision of the manufacturing process is crucial to preventing displacement. During insulation extrusion, temperature, speed, and pressure parameters must be strictly controlled to ensure the silicone rubber uniformly coats the conductor, avoiding defects such as uneven thickness or bubbles. For multi-core cables, symmetrical stranding technology should be used to ensure balanced stress on each core, preventing insulation layer cracking due to localized stress concentration. Additionally, at cable bends, the insulation layer can be locally thickened or reinforced to improve the deformation resistance of that area.
Controlling the bending radius is a direct means of preventing displacement. The minimum bending radius of silicone rubber cables is typically 6-10 times the cable's outer diameter. If the bending radius is too small, it will cause excessive stretching or compression of the insulation layer, leading to relative displacement between the insulation layer and the conductor. Therefore, during installation, the minimum bending radius requirement must be strictly followed according to the cable specifications and usage scenario to avoid forced bending or sharp-angle bends. For scenarios requiring frequent bending, such as robotic arms or mobile devices, silicone rubber cables specifically designed for dynamic applications can be selected, as they typically offer higher flexibility and fatigue resistance.
Environmental factors also significantly impact the displacement risk of silicone rubber cables. High temperatures accelerate the aging of silicone rubber, leading to decreased elasticity and reduced resistance to displacement; while low temperatures may make silicone rubber brittle, easily cracking during bending. Therefore, when used in extreme temperature environments, silicone rubber materials with matching temperature resistance ratings must be selected, and heat insulation or thermal insulation measures must be taken. Furthermore, environmental factors such as ultraviolet radiation and ozone also accelerate the aging of silicone rubber, requiring protection through the addition of anti-aging agents or the use of protective sheathing.
Regular maintenance and inspection are the last line of defense against displacement of the insulation layer and conductor. By using techniques such as infrared thermal imaging and partial discharge detection, abnormal heating or partial discharge phenomena in cables can be detected in a timely manner. These are often early signs of insulation damage or conductor displacement. At the same time, regularly inspecting the bent parts of the cable for signs of aging such as cracks and bulges, and promptly replacing severely aged cable sections can effectively prevent the expansion of faults caused by displacement.
