Another popular synthetic fiber in the textile world is PBT fiber. These fibers, which are part of the polyester family, offer a combination of good elasticity, high crystallization rate, favorable chemical resistance, and ease of production. These fibers are known as a cost-effective alternative to spandex in some applications, especially in sports and technical clothing. They are also widely used in the production of technical and industrial fabrics due to their dimensional stability and high abrasion resistance. In this article, we will learn more about this group of synthetic fibers.

Introduction to PBT Fibers

PBT (Polybutylene Terephthalate) is a semi-crystalline thermoplastic polyester, chemically related to PET (Polyethylene Terephthalate), but made by polycondensation of terephthalic acid (or DMT) with 1,4-butanediol.

•    Chemical Formula: (C₁₂H₁₂O₄)ₙ
•    Polymer Type: Aliphatic-aromatic polyester
•    Fiber Form: Staple fibers, filament yarns, textured yarns

Production of PBT Fibers

PBT fibers are produced using melt spinning, followed by drawing and thermal setting. Due to their lower melting point (ca. 223°C) compared to PET (ca. 255–260°C), PBT can be processed at lower temperatures, making it energy-efficient.

•    Polymerization: Transesterification or direct esterification
•    Melt Spinning: Preferred due to PBT's thermal properties
•    Draw Ratio: Typically 3–4x depending on final use
•    Crystallization: Fast, leading to excellent dimensional stability

Table 1. Key Properties of PBT Fibers

Table 2. Advantages of PBT Over PET

Applications of PBT Fibers

 
1. Apparel & Fashion

•    Stretch fabrics (as an alternative to spandex/Elastane)
•    Swimwear, sportswear, lingerie
•    Blends with cotton or PET for elastic knits and wovens

2. Technical Textiles

•    Automotive seat covers and interior fabrics (due to dimensional stability and UV resistance)
•    Home textiles: Curtains, upholstery

3. Industrial Applications

•    Filter fabrics, conveyor belts, 3D spacer fabrics

Table 3. PBT vs. PTT vs. PET

Note: PTT is derived partly from bio-based 1,3-propanediol (PDO), giving it more sustainability appeal compared to PBT and PET.

Environmental Considerations

•    Not biodegradable
•    Recyclable (thermoplastic nature)
•    Often recycled in blends with PET
•    PBT's fast crystallization and lower energy consumption during processing may offer lower carbon footprint than PET in some applications

Commercial Producers of PBT Fiber/Resin

•    BASF (Ultradur^®)
•    Celanese
•    Sabic
•    Toray
•    Chang Chun Group
•    Lanxess

Table 4. Comparison with Other Fibers

Key Performance Advantages

1. Elasticity and Stretch Recovery

•    Excellent elastic recovery (similar to spandex).
•    Retains shape over long-term use.

2.Chlorine Resistance

•    Superior to spandex and nylon; ideal for swimwear.

3.Quick-Drying & Low Water Absorption

•    Low moisture regain (<0.2%) → dries quickly.

4.Chemical & UV Resistance

•    High resistance to alkalis, acids, sweat, and UV degradation.

5. Thermal Stability

•    Better than polyamide 6 and elastane; compatible with heat-setting processes in warp knitting and weaving.

key words

PBT   Polyester fibers  

♦ References and Sources

1.    K. O. Kessler, 'Polyesters and Their Applications', in Handbook of Textile Fibres, Woodhead Publishing, 2017.

2.    BASF Technical Datasheets, Ultradur^® PBT: https://www.basf.com

3.    J. R. Aspland, 'Dyeing of Synthetic Fibers', AATCC, 1993.

4.    A. R. Horrocks & S. C. Anand, 'Handbook of Technical Textiles', Elsevier, 2016.

5.    G. O. Shonaike & G. P. Simon (Eds.), “'Polymeric Materials for Industrial Applications', CRC Press, 1999.

6.    M. Lewin, 'Handbook of Fiber Chemistry', 3rd Ed., CRC Press, 2007.

7.    Toray Industries - PBT fibers in technical fabrics: https://www.toray.com

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