PTT (polytrimethylene terephthalate) fibers are a type of thermoplastic polyester from the polyalkylene terephthalate family, which is obtained from the reaction of 1,3-propanediol (PDO) and terephthalic acid (TPA).

Chemical Background of PTT

•    Full Name: Polytrimethylene terephthalate (PTT)
•    Chemical Formula: (C₁₁H₁₂O₄)ₙ
•    Monomers:
o    Terephthalic acid (TPA)
o    1,3-Propanediol (PDO) — key to PTT's unique properties.
•    Synthesis Reaction:

PTT is a member of the polyester family, chemically between PET (polyethylene terephthalate) and PBT (polybutylene terephthalate), but it exhibits superior resilience and softness.

Manufacturing of PTT Fibers and Filament Yarns

•    Polymerization: Melt-phase polycondensation.
•    Spinning: Can be spun using conventional melt spinning lines (same as  PET).
•    Draw Ratio: Lower than PET (~3.0–4.0).
•    Crystallization: Moderate crystallization rate—more controllable than PET.
•    Producers:
o    DuPont: Under the brand Sorona^®
o    Shell (historically): Pioneered PDO production
o    Shenghong Group (China): Large-scale PTT filament production

Table1: Key Properties of PTT

Advantages of PTT over PET

•    Better stretch and recovery: Comparable to spandex, but without added elastomer.
•    Superior dyeability: Can be dyed under lower energy and cost.
•    Improved tactile properties: Silkier and softer.
•    Eco-friendly option: Bio-based PDO (from corn glucose) is used in Bio-PTT (e.g., DuPont Sorona® is ~37% bio-based).

Limitations

•    Cost: More expensive than PET due to costlier PDO monomer.
•    Lower tensile strength: Not ideal for high-tenacity applications.
•    Limited heat resistance: Slightly lower thermal stability than PET.

Applications

•    Textiles:
o    Stretch fabrics (sportswear, yoga wear)
o    Carpets (resilience stain resistance)
o    Automotive interiors
o    Lingerie and hosiery

•    Technical Textiles:
o    Nonwovens
o    Upholstery

•    Blends:
o    Cotton/PTT
o    PTT/PET
o    PTT/Nylon

Sustainability & Market Trends

•    Bio-PTT: DuPont Sorona uses bio-based PDO from corn sugar—reducing GHG emissions by up to 63% vs. petroleum-based polymers.
•    Circular Economy: PTT is recyclable using glycolysis or mechanical recycling.
•    Brands using PTT: Adidas, The North Face, and Patagonia (in certain garments).

Table 2: Comparison of PTT vs PET vs PBT

Compatibility with PET Melt Spinning Machines

•    Conventional PET melt spinning lines (extruders, spin packs, quenching zones, drawing units, and winding systems) can generally be used for PTT with minor modifications.
•    Equipment from companies such as Barmag, Oerlikon, TMT, and Jiangyin can handle both PET and PTT with appropriate parameter tuning.

Table 3: Thermal and Rheological Differences Between PET and PTT

Implication:

Because of the lower melting point and viscosity, PTT melts and flows more easily than PET. However, it also requires more precise temperature control to avoid thermal degradation.

Required Process Adjustments

A) Extruder Zone Temperatures

•    PET: 270–290 °C
•    PTT: 245–265 °C
→ Overheating PTT can lead to discoloration and degradation.

B) Cooling / Quenching

•    PTT requires more gentle cooling than PET due to its moderate crystallization speed.
•    Cross-flow or radial quenching air systems must be finely controlled to ensure consistent fiber solidification.

C) Drawing (Stretching)

•    Typical Draw Ratio:
o    PET: ~4.0–4.5
o    PTT: ~3.0–3.5

•    PTT has a higher elongation at break and lower modulus → needs lower draw tension.
•    Draw temperature: 55–90 °C

D) Winding Speed

•    PTT has lower orientation needs than PET.
•    Typical speeds:
o    PET: 3000–3500 m/min
o    PTT: 2000–3000 m/min (depending on yarn type)

Yarn Type Considerations

1. Fully Drawn Yarn (FDY)

•    Excellent elastic recovery, soft hand feel
•    Requires precise control of draw ratio and temperature to optimize properties.

2. Partially Oriented Yarn (POY) Draw Texturing (DTY)

•    PTT is well-suited to DTY process due to its high stretch-recovery.
•    Draw texturing conditions must be optimized:
o    Lower heater temperature than PET
o    Higher false twist settings to achieve desired bulk

Material Handling and Storage

•    Drying is critical:

o    PTT is more hygroscopic than PET.
o    Pre-drying to <0.005% moisture content (50 ppm) is essential.
o    Recommended: Dry at 120–130 °C for 6–8 hours under vacuum or dry air.

Quality Control and Monitoring

•    Melt viscosity must be monitored during spinning to ensure consistent fiber properties.
•    Color monitoring: Thermal degradation or contamination can cause yellowing.
•    End-breakage: Can increase if PTT is processed with PET settings—requires fine-tuning of drawing zone tension and temperature.

Advantages of Using Existing PET Lines

•    Cost-effective: No need for new spinning infrastructure.
•    Flexible production: Same line can be used for PET and PTT with minimal downtime.
•    Adopted by major producers:
o    DuPont (Sorona®), Shenghong, and Toray use PET-compatible systems for PTT

Table 4:Challenges to Watch For in PTT Yarn Production

PTT can be successfully produced on conventional PET melt spinning machines, but:

•    You must reduce the temperature,
•    Adjust the drawing ratio,
•    Control moisture carefully,
•    And modify cooling and winding parameters.

Doing so enables the production of high-performance PTT yarns with superior elasticity, softness, and dye ability — without requiring major equipment investment.

Compatibility of FK6-1000 with PTT Yarns

The Barmag FK6-1000 is a false-twist texturizing machine widely used for polyester (PET), polyamide (PA6/PA66), and PBT. It is designed with modular, adjustable process zones (heaters, godets, tension control) — which allows it to be compatible with PTT filaments as well, provided that adjustments are made to accommodate PTT's distinct thermal and mechanical behavior.

Table 5: PTT, compared to PET and PBT

PTT requires:

•    Lower heater temperatures to avoid degradation
•    Specific yarn tensions due to its higher stretch and recovery
•    Optimized texturizing speed for proper crimp development and uniformity

Table 6: Recommended Settings for FK6-1000 to Texturize PTT

Note: Exact settings must be customized per denier, filament count, and application (e.g., apparel vs technical yarn). Below are typical starting ranges.

These parameters must be fine-tuned during sampling trials to avoid:

•    Yarn breakage
•    Inconsistent crimping
•    Excessive shrinkage or curling
•    Color variation in dyed yarn

Yarn Types Best for FK6-1000 PTT Texturizing

The FK6-1000 can be used for:

•    Apparel-grade PTT POY yarns (e.g., 75D/36F, 150D/48F)
•    Carpet face yarns or elastic fabrics
•    Fine denier filaments (microdenier down to 50D)

FK6-1000 offers:

•    Precision tension control (essential for PTT's elasticity)
•    Independent godet heating zones
•    Advanced crimp control mechanisms
•    Options for automatic doffing and multi-position drives

Table 7: Considerations Before Switching from PET to PTT on FK6-1000

Barmag FK6-1000 is suitable for texturizing PTT filament yarn, provided that:

•    Heater temperatures are lowered
•    Process speeds and tensions are optimized
•    Yarn breakage and shrinkage are carefully managed
•    Lubricants and heater cleaning are adapted for PTT

It is a proven and validated practice among producers of PTT DTY yarns, especially those using DuPont Sorona® or similar PTT grades.



keywords: PTT Fibers   PTT Yarn   PTT Polyester yarn   Bio PTT

♦ References

► https://www.sorona.com

►Textile Research Journal: Xu, W., et al. "Comparative Study of PTT, PET, and PBT Fibers." Textile Research Journal, 2004

►Journal of Applied Polymer Science: Man-Made Fiber Year Book (Japan, China, EU) – 2022–2024 editions.

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