Sewing thread construction explained: types, properties and applications
Intro
Next to the choice of raw material, the properties of a sewing thread are determined by the following parameters:
- construction type
- twist
- ply
- cord
While the construction of the yarns individually determines the type of sewing thread, twist, ply, and cord define general construction parameters for all sewing threads. The same applies to embroidery threads.
Sewing thread construction
The type of construction is defined by the different processing methods used for the fibres and filaments (staple fibres, smooth multifilaments, monofilaments, textured filaments) and their combination in the fibre composite.
It is important to understand that the construction types are described based on the structure of a single yarn. However, the finished sewing thread usually consists of two or more single yarns that are twisted together.
The following wiki subpages provide a more detailed overview of various types of thread construction.
Twist
Yarns and threads are twisted by turning them around their own longitudinal axis, thereby tightly binding the fibres or filaments together. This compact twist increases strength and thus determines sewing performance.
There are two directions of rotation, which can be easily distinguished by the letters S and Z. Depending on the direction of rotation, the course of the centre bar of the respective letter corresponds to the diagonal of rotation of the yarn or thread.
Single yarns are usually twisted in the S direction, while twisted yarns are twisted in the Z direction. To stabilise the sewing thread and ensure flawless sewing performance, it is important that the yarn and twisted yarn have opposite directions of twist. The determination of the twist direction ‘Z’ for twisted yarns and ‘S’ for single yarns is due to the sewing process on standard double lockstitch machines, for which Z-twisted yarns are better suited. Due to the position of the needle and hook and the associated pull-off direction of the needle thread from the needle eye on double lockstitch machines, Z-twisted sewing threads undergo additional twisting during the sewing process, which does not have a negative effect on the sewing process. S-twisted threads, on the other hand, exhibit the so-called untwisting effect, which can lead to an unattractive seam appearance and sewing problems.
The number of twists is very important for optimum sewability and high performance. Sewing threads with too few twists have a low twist count, i.e. they are ‘open’. This has a negative effect on sewing performance. During the stitch formation process, e.g. on double lockstitch machines, the hook can ‘hit’ the open twist, causing the thread to break. Sewing threads with too high a twist tend to curl and have too much ‘liveliness’. Knots and loops can form, leading to sewing problems and even thread breakage.
Coarser yarns or threads have fewer twists than fine ones. The number of twists is adjusted to the respective fineness and the requirements of the sewing process. AMANN sewing threads therefore have a precisely coordinated number of twists with tight tolerances, which is regularly checked as part of quality assurance.
Ply
The ply is another characteristic of sewing thread construction and indicates how many single yarns a twisted thread consists of. Most sewing threads are 2-ply or 3-ply, i.e. they consist of 2 or 3 single yarns. Single-ply and multiple-ply twisted threads are rare.
The use of different plies is illustrated in the AMANN range by the example of the polyester/polyester core spun thread Saba:
| Product | Plies (number of single yarns) |
|---|---|
| Saba 8 | 12 |
| Saba 12 | 8 |
| Saba 18 | 6 |
| Saba 30 | 3 |
| Saba 35 | 2 |
| Saba 50 | 3 |
| Saba 80 | 2 |
| Saba 100 | 2 |
| Saba 120 | 2 |
| Saba 150 | 2 |
The ply has an influence on the sewing performance and the appearance of thread. For decorative seams, 3-ply threads are preferred in the coarse thickness range, as their thread cross-section has an approximately round shape. 2-ply threads, on the other hand, usually have a higher twist and are therefore suitable for demanding sewing operations, e.g. multidirectional sewing machines. For this reason, and due to their flat character, 2-ply threads are preferred for machine embroidery.
Comparison of sewing thread cross-sections
When specifying the sewing thread thickness, the ply can also be included, in the Nm system by adding a slash to the ply number, and in the Tex system by adding a multiplication sign to the number.
Cord
All standard sewing threads are usually single-twist or direct-twist threads. This means that the thread consists of two, three or, in rare cases, four yarns and was produced ‘directly’ from them. In contrast, multi-level or corded threads are made from several yarns. This requires several production steps: from yarn to thread, from thread to corded thread. These yarns are very rare today and are used exclusively in the coarse ticket range when the desired fineness cannot be achieved with the yarn finenesses available on the market.
Spun thread
Intro
In this type of sewing thread, the single yarns consist of individual, short fibres that are twisted together. The raw materials most commonly used for this type of construction are cotton, polyester and aramid.
While natural fibres are available as staple fibres (limited length), synthetic raw materials can be used to produce cut staple fibres and staple fibres (schappe). In the case of staple fibres, the filaments are stretched lengthwise and break at their weak points. This results in fibres of varying lengths (20 to 70 mm) with tapered fibre ends. Spun threads have a relatively smooth thread surface. In the case of cut staple fibres, the filaments are cut into pieces of equal length (e.g. approx. 40 mm, based on the model of high-quality cotton).
Cutting the fibres results in smooth fibre ends of uniform thickness. Spun threads acquire a textile thread surface. Cotton spun threads are mainly used in the clothing industry for special applications. AMANN cotton sewing threads include Mercifil and MercifilGD. Spun threads made from para- or meta-aramid are used for technical applications.
Core spun thread
Intro
In case of core spun threads, the single yarns consist of a core of multifilaments and a sheath of fine fibres. In sewing thread production, this finished strand is called core yarn. The ratio of core to sheath is usually about two-thirds to one-third (the sheath envelops the core but does not cover it completely). This can vary depending on the application of the sewing thread.
The multifilaments in the core are usually made of polyester. Other raw materials are rarely used for this purpose. Polyester or cotton fibres are used for the fibre coating. A distinction is therefore made between polyester/polyester core spun thread and polyester/cotton core spun thread. Polyester/polyester core spun threads can be covered with cut staple or staple fibres. The latter are rather rare today. Almost all polyester/polyester core spun threads are covered with polyester cut staple fibres modelled on high-quality cotton with a length of approx. 40 mm.
Like spun threads, core spun threads have a smooth and textile surface. The combination of a multifilament core and fibre covering makes core spun threads particularly high-performance. Their tear resistance and abrasion resistance are significantly higher than those of spun threads. The sewability of core spun threads is excellent and enables flawless processing even for difficult tasks, such as multidirectional sewing operations and laundry buttonholes. This is why core spun threads have a very wide range of applications.
The polyester/polyester core spun thread Saba is one of the most important products in the AMANN range. An example of a polyester/cotton core spun thread is AMANN's Rasant.
Continuous filament
Intro
In continuous filament threads, the single yarns are made from continuous fibres (filaments). In some cases, up to 200 individual filaments are combined to form a yarn (multifilament). The raw materials are mainly polyester and polyamide, but aramids, polyethylene, polytrimethylene terephthalate, polypropylene and polyether ether ketone are also used for technical applications. While the coarser thicknesses are usually 3-ply constructions, the finer qualities are predominantly 2-ply constructions.
Due to their construction, continuous filaments have a smooth, shiny surface and a uniform twisted character. They are also characterised by very high tear resistance and abrasion resistance. Continuous filament yarns are mainly used for shoes and accessories, home interiors and technical textiles.
Well-known AMANN products include Serafil (polyester continuous filament) and Onyx (polyamide continuous filament), as well as Nc-tech, Kc-tech, C-tech, I-tech and Zyex in the Techtex range.
In the clothing sector, only the finest thicknesses are generally used. The main areas of application are overlock seams for cut edges and blindstitch seams.
In the field of embroidery threads in particular, the classic construction type is continuous filament made from trilobal polyester. The trilobal filament shape increases the light-reflecting surface area of the material and ensures the impressive, important shine of embroidery.
Continuous filament, texturised
Intro
To produce this type of construction, continuous filaments are permanently crimped using a process known as false twisting. These textured continuous filaments are usually made of polyester or polyamide and are bulky and voluminous. Colloquially, they are also referred to as bulky yarns.
The crimping of the continuous filaments also ensures a soft feel, a matt appearance and high elasticity.
Due to its special properties, typical areas of application include serging and flatlock seams in the lingerie and clothing sector, as well as edge covering on carpets.
Continuous filament, braided
Intro
To produce a braided continuous filament, 12 to 16 filament yarns (continuous filament bundles) – depending on the thickness of the finished thread – are wound together on so-called clappers in a circular weaving process. This means that the production time for a ‘braided thread’ is significantly longer (18 times longer than the production of a comparable continuous filament yarn).
The most commonly used raw material for braided continuous filaments is polyester. Due to their construction and the continuous filaments used, braided threads have a smooth and decorative surface. Their tear resistance and abrasion resistance are very good.
Braided threads are used for decorative seams on shoes, upholstery and leather. Their special construction really shows off the seam to its best advantage.
AMANN's braided polyester continuous filament is Serabraid. Unlike all other sewing threads and embroidery threads, the ticket numbers are based on the optical diameter. Serabraid 800 has an optical diameter of 0.8 mm, etc.
Serabraid is available in three different finishes:
- T60 suitable for machine sewing
- T90 (waxed) for hand sewing
WRe (water-repellent, eco-friendly) suitable for machine sewing
Microfilament, texturised
Intro
A textured polyester microfilament is recommended for particularly soft seams. The high number of fine microfilaments makes the sewing thread extremely soft and supple, and the seams are barely noticeable.
Wrapped yarn
Intro
This is the classic construction for metallic embroidery and sewing threads. A continuous filament core (polyester, polyamide) is wrapped with a band of metallic foil made of metallised polyester to create the characteristic sheen. In the embroidery thread sector, single yarns are used to create a filigree look.