Prime Requirements and Classification of Sewing Threads

1.0 Introduction

Every creature on this earth wants to look beautiful including the human being. Since the development of various civilizations, considerable effort has been given for achieving this. Use of garment is one way to fulfill the long cherished need of human being. Various techniques of garment making were tried in the past but nothing has been successful as sewing. The sewing thread is one of the most important elements to produce neat firm and desirable seam, which gives garment necessary aesthetics and helps to make the quality product. High-speed sewing machines can stitch at the rate of 6000 stitches per minute. This sewing thread is subjected to heavy stresses and strain at the various points during the processes.

The needle is accelerated to over 180 kilometers per hour in the forwarded direction brought to rest and accelerated again backward before returning to the rest. The whole cycle is repeated approximately 120times per seconds. With lock stitches each length of thread is passed through the needle up to 40 times before being set in to the fabric. Sewing machine needle may reach a temperature up to 360 a C due to the frictional forces that are developed between the needle with thread and needle with fabric. This depends on the thickness of the fabric, number of piles and speed of the stitching.

2.0 Ideal sewing thread

The ideal sewing thread should confirm to a high standard of single thread strength and perfectly balanced twist. It should not have yarn defects like knots, cuts, snarling, twist subs etc. Thread should have color fastness and wash fastness. Length of the sewing thread should be within the specification. It should be smooth free from protruding fibres with exceptional good appearance .This same thread should perform plain stitch, button stitch, and button holding at various speeds.

3.0 Fibres for Sewing Threads

3.1 Glass and Asbestos

These are so unsatisfactory and only used when essential to provide complete homogenous sewn product.

3.2 Viscose Rayon

The low wet strength and poor abrasion resistance are main limitations as sewing thread.

3.3 Polyethylene and Polypropylene

Low melting point, inherent stiffness with tendency to slip in the seam, Poor fatigue resistance, poor creep and light fastness are the major limitations.

3.4 Linen and silk

Because of its low demand it has a limited usage.

3.5 Cotton

It has good strength and, low extension with resistance to shrinkage .It does not melt even at high sewing rate. Abrasion resistance also found appreciable. The negative aspects of the cotton could be due to its less durable nature, weaker then the synthetic fibre made yarns and poor mildew resistance.

3.6 Polyester

Polyester has good tensile, light and heat fastness. The wet abrasion resistance and Fatigue behavior are better then Nylon. The limitation might be the melting high-speed sewing.

3.7 Polyamides

The leather industry using the Ploy amides due to its different elastic properties and the heat setting properties .The limitations are due to 10-20% strength loss when exposed with the water and Kink formation after sudden retraction.

4.0 Classifications of sewing threads

4.1 Cotton Thread

It can withstand at a high temperature then the synthetic fibre yarns .it based on the end uses classified in to three types.

4.1.1 Soft thread

Most commonly used soft threads need no special treatment. Low friction lubricant only required

4.1.2 Polished Thread (Glaced)

Starch and lubricants are coated in the soft thread with high speed polishing performed by rotating brushes to give glazed appearance. Leather and heavy fabrics need such threads.

4.1.3 Mercerized Thread

For general stitching, button holding and embroidery purposes the mercerized threads are used. Improved luster and strength add value to the sewn fabrics.

4.2 Linen Thread

Before the synthetic threads invented this stiff thread from flax used in foot wear and tarpaulin. It is sensitive to bacterial action in wet condition. Hence it needed rot proof finish.

4.3 Silk Thread

It is used in short length for pick stitching the edges of mens jackets and is more expensive garments for stitching button holes .the main feature of this type threads are the extensibility with strength (about 20%). Cost is main restriction factor.

4.4 Polyester Stable Fibre Thread

It is considered one of the best and most satisfactory performing sewing thread dueto high strength at cyclic loading, good chemical and abrasion resistance properties with dye and light fastness properties with low cost. Comparative hairiness in the thread reduces thread friction and improves the Sewability.

4.5 Nylon Thread

It is having good fibre strength to fineness ratio. Puckering may results due to unfavorable extension characteristics.

4.6 Multi Filament Sewing Thread

Filaments often bonded with synthetic fibre copolymer that bonds the individual filaments and yarns together to give optimum sewing performance.

4.7 Intermingled thread

Continuos filament core surrounded by entangled filaments by an air jet. The core filaments contribute to tensile strength and the entangled surface filament increases the fullness and reduces the yarn friction textured yarns

4.7.1 False Twist Textured Thread

Textured threads are very soft and extensible; these threads are ideal knitted goods under wears

4.7.2 Air Jet Textured Continuos Filament Yarns

It provides discontinuous thread in the surface, which helps to reduce the danger of thread fusion at high sewing speeds .the soft handle fulfill the soft seam requirement.

4.8 Core-spun Sewing Threads

Extra ordinary strength and abrasion resistance of the polyester filament are provided strong and firm seams. Superior heat insulation of cotton cover makes seam totally a heat proof and excellent elastic recovery with no thread breakage at point of stress. Lubricant is retained well in the surface of the cotton to provide superior cooling to prevent thread burnout at the needle eye.

5.0 Treatments for Sewing Threads

5.1 Heat setting/Twist deadening

Setting of twist is made effective by steaming the yarns in an auto calve with steam pressure of 0.6 kg/cm2 for 30-60 minute. Temperature of the steam has to be maintained with 100-105 Centigrade. The steaming time is decided on the basis of twist level in the doubled yarn. The heat-setting leads to stabilization and equalization of the elongation properties of the thread and it prevent the snarling. Polyester and Nylon threads required high pressure steaming and the industrial sewing threads needed low pressure steaming.

5.2 Dyeing

High color fastness and precise shade matching are the key factor requirements for sewing threads normally to get uniformity cross wound packages with high pressure equipments used.

5.3 Hot Stretching

Hot stretching is a process of heating the thread to pre determined and controlled temperature in the range of 180-240 Centigrade with tension and length control. Heat setting operation causes a decrease in the modulus and increase in the extensibility of the thread. Consequently when high modulus thread requires subsequent stretches. This hot stretching improves the thermal stability and reduces the extensibility. The sewing thread length improved 4. -6%. The specific tenacity improved to 3-5%. This helps to get improvement in dyeing and kink free sewing thread.

5.4 Lubrication

Gliding and cooling effect on the needle could be done with effective lubricants good lubricant must not clog on the needle eye or causes stain. The lubricant must allow the thread to unwind evenly from the package. The friction between the abrading surfaces should be minimized with lubrications. Inexpensive lubricants will be preferred.

6.0 Seam Performance

The seam performance of sewing threads depends on Sewability, seam security and End use requirement

6.1 Sewability

The ability to produce a seam with a minimum amount of thread breakage and damage to the thread during the sewing operation.

6.2 Seam Security

In relation to its end use requirements, once the thread has been sewn in to a seam the performance characteristics of the seam in the garment.

6.3 End use Requirements

Seam strength, appearance (luster, size), abrasion resistance, stitch and impact.

7.0 Production of Sewing Threads

Sewing threads has to meet the above said quality requirements and the flow chart furnished below shows the typical sequence for the production. Care has to be taken from the selection of the raw material to the finishing so as to meet requirements. Figure1 shows a typical sewing thread flow chart.

8.0 Seam quality

It is the study and control over the seam strength, slippage, puckers, and seam appearance.

8.1 Seam failure

When seam is under transverse strain, the pulling force becomes more then fabric frictional resistance in stitch geometry then the stitch assembly permits the yarns being pulled to slip out which is termed as seam slippage. This slippage depends on fabric construction, raw material, type of seam-stitch density and sewing thread tension.

Higher inter yarn frictional force and high cover of the fabric will restrict the movement of the sewing thread. For slippery fabrics, high extensible thread would facilitate the slippage at much lower load.

Seam efficiency = {Seam tensile strength /fabric tensile thread} X100

Higher the seam efficiency better will be the quality. Generally it will be in the range of 85-90%. Type of stitch, type of seam, strength of sewing thread and wear of the sewing thread will affect Seam efficiency.

8.2 Seam pucker

It is defined as differential contraction occurring along a particular line of the fabric. Usually along the line of seam and it is caused due to tension variation and Fabric construction.

8.2.1 Causes for Seam Pucker

Different fabric layers causes unequal tension in the seam due to improper overfeed ratio. High sewing thread tension combined with highly elastic threads can cause buckling of the seam. Jamming of the fabric due to excessive number of sewing threads fabrics of different physical properties when combined in a seam, it shows these differences as pucker during the subsequent handling e.g. laundering. If different fabric length sewn as the part of the same seam, the excessive fabric being the source of pucker.

9.0 Summary

Selection of sewing threads is essential for shaping of valuable garments. The ideal sewing thread should confirm to a high standard of single thread strength and perfectly balanced twist. It should not have yarn defects like knots, cuts, snarling, twist subs etc. Thread should have color fastness and wash fastness. Length of the sewing thread should be within the specification. It should be smooth free from protruding fibres with exceptional good appearance .This same thread should perform plain stitch, button stitch, and button holding at various speeds.

10.0 References

1.Taylor MA Technology of Textile properties, Forbes, London, 1990,3rd editionP282

2.T.V.Ratnam, SebhanK.N., KPChellamani, S.Karthikeyan- Quality contol in spinning, SITRA- Coimbatore.

3.Chopra. K seam behavior of woven and apparel fabrics Ph.D. thesis IIT DELHI 1997

4. Galuszynskis- some aspects of Mechanism of seam slippage in weaving fabrics, Journal of textile institute 1985, No6, P425-433.

About the author:

Chidambaram Rameshkumar
Senior Lecturer,
Department of Textile Technology,
Bannari Amman Institute of Technology,
Sathyamangalam-638401
Erode District, India
crktex@gmail.com , crktex@yahoo.com
Tel: 04295-221289 , Fax- 04295-223775

Regarding my Research works

Currently I am doing my PhD in the Protective Fabrics. As a part of my study, I have planed to develop a cut resistance tester and cut resistance fabrics. The total estimated cost for this project is about Rs.15 lacks (Indian Rupees). In this connection I am looking for grant or suitable sponsors for my project work. If I get financial assistance through fibre 2 fashion.com business stars, it will be a timely help and booster for my research.

Area of Interest : Spinning, Technical Textiles, Fibres Characterization, Textile Mechanics, Process control in spinning and Textile marketing

Dr. N. Anbumani is working in PSG College of Technology,Coimbatore