Requirements of optical fiber cables for PBT

PBT used in optical fiber cables must provide mechanical protection, thermal stability, hydrolysis resistance, chemical resistance, and processability to ensure long-term reliability and performance. Mechanical PropertiesPBT loose tubes and secondary coatings must have high flexural modulus and excellent bending resistance to protect the delicate optical fibers from external forces such as stretching, bending, and flattening during installation and operation. High elongation at break (>50%) and tensile strength retention after aging are critical to prevent brittle failure and ensure flexibility under long-term stress, including microbending and impact resistance.

Creep resistance is also important to maintain the stable excess length of optical fibers over time. Thermal and Environmental StabilityPBT must exhibit low thermal expansion and minimal water absorption to maintain dimensional stability and long-term reliability under varying temperatures and humidity conditions. Thermal stability ensures that the material does not degrade, discolor, or react adversely with cable pastes during high-speed extrusion and processing.

For outdoor or buried applications, hydrolysis-resistant PBT compounds are required, with a low hydrolysis rate (