1. Overview
With the rapid development of information and communication technology, optical fiber cables, as critical carriers of modern data transmission, face increasing requirements for material performance and product reliability. During long-term operation, optical cables must withstand mechanical stress, environmental changes, and temperature fluctuations, which demands high stability, durability, and processability from structural materials.
Polybutylene Terephthalate (PBT) is a semi-crystalline thermoplastic engineering polymer, synthesized through esterification and polycondensation of dimethyl terephthalate (DMT) or terephthalic acid (TPA) with butanediol. PBT is a relatively late commercialized general-purpose engineering plastic, industrialized in the 1970s with development led by GE Company, but it quickly gained wide application. PBT, along with PPO, POM, PC, and PA, is considered one of the five major general-purpose engineering plastics.
PBT typically appears as a milky translucent to opaque material with high heat resistance and excellent mechanical properties. It is resistant to many organic solvents but not to strong acids or bases; it is flammable and decomposes at high temperatures. Its molecular structure includes two additional methylene groups compared to PET, forming a helical backbone that gives the material good toughness and processing performance.
Thanks to its excellent physical properties, chemical stability, and processability, PBT has been widely used in electrical, automotive, communication, home appliance, and transportation industries. In the optical fiber cable industry, PBT is primarily used for the production of fiber optic loose tubes and related structural components.
2. Material Properties of PBT
In practice, PBT resin is mostly processed as compound blends, with various additives or blended with other resins to further enhance heat resistance, flame retardancy, electrical insulation, and processing stability.
Physical Properties
PBT exhibits high mechanical strength, toughness, and wear resistance, effectively protecting the optical fibers inside cables and reducing the impact of external mechanical stress.
Chemical Stability
PBT is resistant to a variety of chemical agents, suitable for use in complex environments, and helps ensure long-term operational stability of optical cables.
Processability
PBT is easy to process via extrusion, injection molding, and other techniques, meeting dimensional and consistency requirements for optical cable components.
Thermal Stability
PBT maintains stable physical properties across a wide temperature range, making it suitable for optical cables operating under different climates and environmental conditions.
3. Typical Applications of PBT in Optical Cables
Fiber Optic Loose Tubes
PBT is widely used in the manufacture of loose tubes. Its high strength and toughness provide stable support for optical fibers, reducing damage from bending or tensile forces. PBT loose tubes also offer excellent heat resistance and aging performance, ensuring structural stability over long-term use.
Cable Structural Components
In certain cable designs, PBT is used for specific structural parts or functional outer layers to enhance overall mechanical performance and environmental adaptability.
Fiber Optic Splice Boxes and Related Components
PBT is also used in splice boxes and internal structural parts, which require sealing, weather resistance, and mechanical stability. The molecular structure and physical properties of PBT make it an ideal choice for these components.
Processing Considerations
Before molding, PBT should be thoroughly dried, typically at 110–120°C for around 3 hours. Injection molding temperatures should be maintained at 250–270°C, with mold temperatures of 50–75°C.
Due to PBT’s low glass transition temperature, it crystallizes quickly once cooled, resulting in short cooling times. If the nozzle temperature is too low, the flow channel may solidify and block. Exceeding 275°C or prolonged residence of molten material in the barrel may lead to degradation. Proper mold venting and “high-speed, medium-pressure, medium-temperature” processing conditions are recommended. Hot runner systems are not advised for fire-retardant or glass-filled PBT, and barrels should be cleaned promptly with PE or PP after shutdown to prevent carbonization.
4. Advantages of PBT in Optical Cable Applications
Enhanced Cable Performance: PBT’s strength and toughness improve mechanical performance and fatigue resistance, extending cable lifespan.
Improved Manufacturing Efficiency: Excellent processability enhances production stability and reduces costs.
Increased Operational Reliability: Aging resistance and chemical stability ensure long-term cable reliability in harsh environments.
5. Conclusion and Outlook
With the continuous expansion of communication networks and applications, demands for material performance and stability in optical cables will continue to rise. As a mature and well-balanced engineering plastic, PBT demonstrates clear advantages in loose tubes and related components.
Future development of PBT materials will focus on performance optimization, improved processing stability, and environmental sustainability. Through continuous technological innovation and product upgrades, PBT is expected to play an increasingly important role in the optical fiber cable industry.
Post time: Feb-14-2026