textile science

It’s the process of constructing sewing threads, the performance of textile fabrics and clothing is strongly influenced by the properties of the yarns from which they are made. Sewing threads require certain yarn properties.

Sewing thread-It’s a special kind of yarn that is designed/engineered to pass through a sewing machine rapidly. It’s used to form stitches without breaking or becoming distorted during production of the thread

PROPERTIES /CHARACTERISTICS USED IN THREADS

·         Tensile strength- This is the tension at which a thread breaks, expressed in g/kg. Yarn strength depends on the quality of the fibers, the yarn regularity and the twist. Folding increases the strength.

·         Tenacity – This is the relative strength obtained by twisting it’s tensile strength by the thickness of the structures

·         Loop strength- It’s the load required to break a length of thread of which is looped through another thread of the same

·         Elongation – It’s the amount by which a thread is extended at its break point

-          It’s expressed as a percentage of its original length

·         Elasticity –It’s that property of thread that enables it to recover to its original length after extension

·         Shrinkage –It’s the amount which a thread contracts after washing/heating

·         Moisture regain-It’s the weight of moisture in a fiber/Thread

-          It’s expressed as a percentage weight of completely dry material

·         Regularity - Smooth fabrics should be sewn only with very regular yarns. In spun yarns, this is achieved by repeated doubling and drafting, and by combing out the short fibers.

CHARACTERISTICS OF A GOOD SEWING THREAD (REQUIREMENTS)

• Good tensile strength to grip the seam firmly during wear and wash. The tensile strength should be higher than that of the fabric so that it won’t rupture during the stretch at the seams. Also, it would mean minimum thread breakage during sewing. 
• Higher initial modulus of thread guarantees the minimum of thread deformation during shock loading while sewing in the machine. The sewing thread should be moderately stiff to form the loops for stitch formation.
• Smooth surface without any abnormalities in the thread results in a minimum of friction between the needle and sewing thread while sewing at high speed.
• Uniform thickness of the sewing thread provides for smooth passage of the thread through the needle and the fabric. Also, it causes less movement of the thread while passing through the machine.
• Good elasticity facilitates the thread to recover its original length instantly after the tension has been released. It should be similar to that of the fabric being sewn, thus the requirement for woven and knitted fabric will be different. Also, it greatly influences the strength and quality of the stitched seam.
• Good color fastness of the thread makes it resistant to the various chemical and physical agents the thread is exposed to during manufacturing and during its useful life especially during washing, perspiration, sublimation, etc. This ensures no bleeding of the color into the garment. Also, it should be dyed evenly and uniformly.
• Lower shrinkage characteristics of the thread are very important as it can cause a critical defect in the garment in the form of puckering at the seams. Cotton thread usually undergoes washing shrinkage while synthetic thread suffers from thermal shrinkage during ironing.
• Resistance to chemicals as the sewing thread may be subjected to various chemicals during washing, bleaching, dry cleaning, etc.
• Higher abrasion resistance provides a good sewing performance and makes the thread more durable meaning it would return to its original shape after the tension is removed maintaining its physical properties. Nylon and polyester offer the best resistance to abrasion.

 

FACTORS AFFECTING THE FUNCTIONS OF SEWING THREAD

Factors affecting aesthetics
The appearance of the thread in terms of color, Lustre, fineness/thickness should be considered while selecting a thread. Apart from these hue and shade matching, color fastness, stitch selection and uniformity of stitch formation affects the aesthetics of the stitch.

Factors affecting the performance
Thread performance is measured by the ability of the thread to withstand physical and chemical effects on the seam or during stitching in the sewing machine. Thread performance in the garment can be evaluated from its

·         Seam Strength

·         Abrasion resistance

·         Elasticity

·         Chemical resistance

·         Flammability

·         Color fastness

 

CLASSIFICATION OF SEWING THREAD

Sewing thread can be classified in the following three ways:

·         Fiber type

·         Construction

·         Finish 

 

Classification based on fiber type:

·         Natural: the sewing thread is made from natural fibers. Mostly cotton is used for sewing thread but due to various disadvantages relating to the strength of the thread, it is mixed with polyester to make it stronger. Other natural fibers are very rarely used for manufacturing sewing thread.

·         Synthetic: the sewing thread is made up of synthetic man-made fibers. These have several advantageous characteristics compares to natural fibers as higher tenacity, better resistance to chemicals, and higher abrasion resistance. Also, it is resistant to rot, mildew, insect, bacteria, and moisture.

Classification based on thread construction

a. Spun threads

They can be made from both natural as well as synthetic fibers. Spun polyester is the most frequently used sewing thread in the garment. Due to its hairy yarn surface, it provides better lubrication properties and a much smoother hand. Also, its shrinkage is very low compared to a cotton thread. Its sewing performance is also very good but is lesser than the strength of continuous filament yarn. These are mostly used in seaming of shirts, trousers, knitwear, jackets, etc.

1. Cotton threads

·         Soft cotton threads

·         Glazed cotton thread: The glazed process gives the thread a hard finish that shields the thread from abrasion and improves ply security.

·         Gassed thread: Gassing process also known as singing process and it is used to burn off the protruding short fibers to give a lustrous finish. It is done by moving the cotton thread over a flame at a higher speed to reduce the hairy fibers on the surface of the thread.

·         Mercerized cotton thread: The cotton yarn is treated with caustic soda with 16%-18% concentration under pressure to improve the strength and luster.

·         Cotton threads are mostly used for sewing cotton threads that are to be post dyed.

1.      Linen thread

2.      Silk thread

3.      Spun synthetic –fiber threads

4.      Spun blended sewing threads

 

a.       Core Spun Threads: 

It is a mixture of both staple fibers and filaments. The most commonly used core spun sewing thread has a multiple-ply structure, with each ply comprising a core polyester filament wrapped by the cotton or polyester staple fibers. The strength of the thread is provided by the filament and sew ability through cotton or polyester fiber wrap. It is mostly used in topstitch of shirts, blouses, trousers etc.

b.      Filament threads

These are stronger than spun threads. They are same fiber and size

·         They are of various types such as:

Ø  Continuous filament thread: 

It is produced by extruding the filaments from the synthetic polymer and is given a twist to improve the strength. The strength of these threads is stronger than spun threads for the same thread size.

Ø  Monofilament threads: 

Monofilament sewing thread is produced from a single continuous fiber with a specific fineness. They are strong, uniform, and cheap but its use is very limited due to their low flexibility and rough feel. These are mostly used in the sewing of hems, draperies, and upholstered furniture.

Ø  Multifilament thread: 

These are mostly produced from nylon or polyester and are used where there is a requirement of higher strength. It comprises two or more continuous filaments twisted together to give more strength. It is mostly used in leather garments, shoes, and industrial products. These are again can be classified in lubricated, bonded, and braided threads.

Ø  Smooth multifilament

Usually made from nylon or polyester and where high strength is a primary requirement. It consists of two or more continuous filaments which are twisted together. It’s commonly used to sew shoes, leather garments and industrial products

c.       Textured thread: 

Textures are given to continuous filament yarn to provide softness and bulk. These are then slightly twisted and heat set to make it permanent. These threads give high seam coverage, high extensibility but they are subjected to snagging. The types of textured sewing threads are

§  False twist textured filament threads

§  Air textured filament threads

§  Air-jet intermingled filament threads. These are mostly used in seams that are in contact with the body like that in underwear, swimwear, etc.
 

d.      Embroidery threads: 

These are mainly required for decorative purposes and thus color and luster are the two main requirements for embroidery thread. These are mostly made from mercerized cotton, silk, viscose rayon, and polyester fiber. Threads for machine embroidery are usually of polyester or rayon less often cotton or silk.

e.       Technical threads: 

These are specially developed for technical/industrial uses to be used in adverse climatic, industrial conditions, and also for heavy-duty applications. These are generally made from aramids, glass, ceramics etc.

Classification base on the finishes

The classification is done based on the type of finish applied over the thread. These are being done for mainly two purposes:

Ø  To enhance the sew ability of the thread – Certain finishes improve the thread strength, lubrication property, and abrasion resistance.

Ø  To accomplish a specific functional requirement – these are special finishes such as fire retardant, water repellent, anti-fungal, anti-static, etc. which are coated over the sewing thread.

Thus, sewing thread is one of the most important accessories in a garment, and to make it properly a total compatibility check should be performed. Even a small thread failure can fail the garment in a quality check thus making a total loss in investment for making the garment.

 

Factors in thread Selection:

      Garment design, type, quality, end use, and life expectancy.

      Desired strength and durability.

      Fabric weight and type.

      Stitch and seam type, number of stitches/inch, machine speed, and needle size.

      Cost

                        Terms used in thread construction

a.      Twist

The number of turns per unit length, too little twist will cause the thread to be loose and break and too much twist can cause looing and snarling

A good sewing thread must be moderately twisted

b.      Twist direction

Twist can be impacted in S or Z direction. The direction of the twist does not affect the thread but it can affect its performance when it’s used on a machine when it’s not sorted

c.       Ply

Yarns with many components are twisted together to form ply thread, the most commonly used are 2, 3 and 4 ply threads

d.      Cord

Threads that are twisted together to give corded thread, the most commonly use are 4,6 cord thread

e.       Size

The overall thickness of the thread is referred to as ‘Gist’ or Ticker’ Number or Count’ Depending on the required strength of seam, thread should be as fine as possible

Thicker threads have more strength, finer threads are to be blended into the fabric surface and less subjected to abrasion than seams with heavier threads. Finer threads perform better with finer needles and distort the fabric less than heavier

f.       Needles

A sewing needle, used for hand-sewing, is a long slender tool with a pointed tip at one end and a hole (or eye) to hold the sewing thread. The earliest needles were made of bone or wood; modern needles are manufactured from high carbon steel wire and are nickel- or 18K gold-plated for corrosion resistance. High quality embroidery needles are plated with two-thirds platinum and one-third titanium alloy. Traditionally, needles have been kept in needle books or needle cases which have become objects of adornment. Sewing needles may also be kept in an étui, a small box that held needles and other items such as scissors, pencils and tweezers.

 

 

Uses of different threads

·         Used in leather industry

·         In apparel industry

·         For firemen clothing

·         Hot metal industry

·         Defense and police

·         Used in hospitals for surgical purposes

·         Used in stitching