Synthetic Fibre Spinning Methods – Part 2: Drawing and Texturizing Explained

Introduction: Why Post-Spinning Processes Matter

If you’ve read Part 1: Synthetic Fibre Spinning Methods, you already understand how synthetic polymers are converted into continuous filaments using melt, dry, or wet spinning. However, producing filaments is just the beginning. The real functionality and performance of synthetic fibres are developed only after spinning — through carefully controlled post-spinning operations.

Draw-texturizing process in synthetic fibre manufacturing using industrial textile machinery

fig: Texturizing ( just for demonstration )

This second part of the series focuses on two crucial post-spinning processes:

Drawing – which aligns polymer chains to improve strength and durability
Texturizing – which modifies the yarn’s structure for bulk, stretch, and aesthetic feel

Together, these processes convert raw filaments into usable textile-grade yarns, suitable for applications ranging from technical textiles to everyday apparel.

Drawing – Aligning Molecules for Fibre Strength

What Is Drawing in Synthetic Fibre Manufacturing?

Drawing is a controlled stretching process performed after the filaments emerge from the spinneret. It aligns the disordered polymer chains within the fibre along the axis of the filament, improving mechanical strength, dimensional stability, and moisture resistance.

This is essential because freshly spun synthetic fibres are:

Amorphous (low molecular orientation)
Weak and low in tenacity
Prone to deformation and shrinkage
Drawing transforms these fragile filaments into high-strength, high-performance yarns.

Technical Parameters of Drawing

Draw Ratio: Usually 3:1 to 6:1 depending on polymer type
Draw Temperature Ranges:

Nylon 6: 150–180°C
Polyester (PET): 80–120°C

Drawing can be done in cold conditions (cold drawing) or with heat (hot drawing), depending on the required orientation and polymer properties.

What Does Drawing Achieve?

Increases Tensile Strength – drawn yarns can be 4–5× stronger
Improves Crystallinity – better resistance to chemicals and heat
Enhances Dimensional Stability – reduced shrinkage and elongation
Improves Dye Affinity – due to increased orientation

Industrial Insight

In technical textiles like tyre cords, airbags, or industrial belts, multi-stage drawing is used to achieve highly consistent orientation and tensile behaviour.
On the other hand, fast-fashion brands often skip or minimise drawing to reduce production time and cost — leading to yarns that pill easily, stretch out with use, or degrade after minimal washes.

Risks of Improper Drawing

Underdrawing: Results in soft, weak yarns prone to deformation
Overdrawing: Makes yarn brittle, causing breakage during weaving or knitting
Uneven Drawing: Leads to inconsistent denier and poor fabric uniformity

What Is Texturizing in Synthetic Fibre Processing?

A very important post-spinning process is texturizing which gives flat synthetic filaments a three dimensional structure. Although drawn yarns are strong and firm it lacks softness, bulk and elasticity. Texturizing takes care of these gaps by physically changing the physical structure of the yarn permanently which makes the synthetic fibres more comfortable and functional.

Texturizing is particularly relevant in fields of use, such as activewear, lingerie, sportswear, home textiles, carpets, and winter clothes, where performing properties and hand feel are equally important.

Objectives of Texturizing

To create bulk and loft
To add elasticity and stretch recovery
To simulate the natural appearance of cotton or wool
To improve thermal insulation in cold-weather fabrics
To modify fabric drape and hand feel

Key Texturizing Methods in Use

Let’s break down the three most commonly used techniques:

1. False Twist Texturizing

Process Summary:

The yarn is twisted, heated above the glass transition temperature (Tg), cooled to set the shape, and then untwisted. Despite untwisting, the thermoplastic memory retains a crimped structure.

Typical Setup:

Draw Texturizing Machines (DTM) are used in high-speed production (500–900 m/min).

Result:

Yarn gains a springy, elastic nature and improved thermal bulk.

Used In:

Leggings, swimwear, activewear, elastic garments

Why It Works:

Above Tg, polymer chains become mobile. When twisted and then cooled, the structure locks in the new shape — permanently modifying fibre geometry.

2. Air Jet Texturizing

Process Summary:

Compressed air is blasted onto continuous filaments, causing random entanglements and loops. No heat is used — it is a purely mechanical process.

Result:

The yarn mimics cotton in feel and texture. It remains soft, bulky, and has limited stretch.

Used In:

Innerwear, home textiles, soft outerwear

Key Advantage:

Because no heat is applied, this method is energy-efficient and suitable for recycled yarns or blends that degrade under heat.

3. Stuffer Box Texturizing

Process Summary:

Yarn is mechanically pushed into a heated chamber or box. The confined space causes it to fold, bend, and crimp. The heat sets this crimp permanently.

Result:

High bulk and resilience — perfect for floor coverings and heavy-duty fabrics.

Used In:

Carpets, mats, automotive seat fabrics

Considerations:

Crimp variability may lead to irregular dye uptake or difficulties in recycling due to complex geometry.

When and Why Texturizing Is Essential

Texturizing is more than just a cosmetic process. Without it, synthetic yarns:

Lack stretch and form recovery
Feel rough or plasticky
Offer poor thermal insulation
Do not drape well in garments

Properly texturized yarns are also easier to knit or weave, and improve fabric aesthetics significantly.

Fibre Properties and Identification after Drawing and Texturizing

Post-spinning processes like drawing and texturizing do not just change the physical appearance of yarns — they also alter key thermal, mechanical, and structural properties. Understanding these changes helps in:

Quality control
Material selection for specific applications
Identification during testing and research
Answering exam and viva questions confidently

1. Glass Transition Temperature (Tg)

What is Tg?

Tg is the temperature at which a polymer changes from a hard, glassy state to a soft, rubbery state. Above Tg, polymer chains gain mobility.

Relevance in Texturizing:

For a texture to be set permanently, the process must be done above Tg. Otherwise, the crimp or loop may disappear after washing or use.

Fibre Type Approx. Tg

Nylon 6 ~50°C

Nylon 66 ~70°C

Polyester ~80°C

If texturizing is done below Tg, the structural memory is not retained, resulting in yarns that lose elasticity and bulk over time.

2. Tensile Behaviour After Drawing

Drawing increases tenacity (strength per denier) and modulus (stiffness). A drawn fibre is:

Less extensible
More dimensionally stable
Stronger in both dry and wet states

A poorly drawn fibre may show:

Excessive elongation
Fibre distortion during spinning or weaving
Low strength or early breakage

3. Crimp and Bulk Retention

After texturizing, two factors are evaluated:

Crimp Stability: The ability of crimps or coils to retain their shape after repeated stretching
Bulk Retention: The volume maintained after compression or laundering
These are especially important in knitted fabrics, carpets, and performance wear.

4. Moisture and Dye Uptake

Well-drawn fibres have more oriented crystalline regions, which may reduce moisture absorption slightly but improve uniformity in dye penetration.

However, texturizing increases surface area and capillarity, improving:

Moisture transport
Comfort
Dye spread

5. Identification and Testing Techniques

A. Burn Test

Drawn polyester: Melts cleanly, shrinks away from flame, sweet smell
Improperly drawn yarn: May sputter or give inconsistent melting
Drawn nylon: Melts, drips, slight celery-like odour

B. Snap Test

Gently stretch a yarn and release:

Well-drawn and texturized: Controlled stretch with full recovery
Weak yarn: Irregular break or no recovery

C. Microscopic View

Texturized yarns show loops, crimps, and irregular filament paths
Drawn yarns show parallel, smooth filaments with consistent diameter

Final Summary

Post spinning process such as drawing and texturising plays an important role in the manufacture of synthetic fibres. Whilst spinning would result in filaments, drawing would enhance their strength and stability and, texturizing would make it comfortable, elastic and attractive to the eyes.

Whether you are a textile professional or a textile student, probability of success in this highly competitive world is based on having insight on how to adjust draw ratio, control texturizing parameters, and comprehend the effects on fibre structure, - in manufacturing or Research and Development, or in competitive exam preparation.

Whether it is sports wear, home textile, each man made yarn is influenced by these unseen magic processes. Learning them would translate into learning the science of contemporary textiles.

Frequently Asked Questions (FAQ)

Q1: Why is drawing important in synthetic fibre processing?

A: Drawing aligns polymer chains, increasing strength, crystallinity, and dimensional stability. Undrawn yarns are weak and not fit for textile use.

Q2: Which texturizing method is best for stretch recovery?

A: False twist texturizing produces yarns with excellent elasticity and stretch recovery, making it ideal for leggings and activewear.

Q3: Can texturizing be done below glass transition temperature (Tg)?

A: No. Effective texturizing requires temperatures above Tg to enable permanent shape setting.

Q4: What’s the difference between drawn and undrawn yarns?

A: Drawn yarns have high orientation and strength. Undrawn yarns are soft, unstable, and prone to deformation during use.

Q5: How can I identify a poorly drawn or texturized yarn?

A: Poorly processed yarns show irregular stretch, low recovery, and inconsistent burn or snap test behaviour.