Major requirements for a good quality sewing thread
The amount of strength required to break a thread. It varies according to temperature, humidity, rate of applied force, moisture etc. It is expresses in gm, kg, lb, CN etc.
Tensile strength of the thread should be high enough to hold the stitched seam securely during wash and wear.
For coarser thread, Tensile strength is higher and vice-versa.
Tenacity is the relative thickness of thread expressed in gm/denier, gm/tex etc.
Tenacity = (Thread tensile strength/Thread count or thickness).
Sewing threads’ tensile strength depends on count but tenacity is not dependent on count because it is the strength per unit thickness.
Loop strength is the load required to break a length of thread which is looped through another thread of same length same fibre.
As strength is less at the loop portion, so if thread breakage occurs in other place than loop portion that is not accepted.
Loop strength is closely related with stitch strength.
Loop strength ratio:
Loop strength ratio = (Single thread breaking strength/Loop strength).
The highest value should be 2
Loop Strength Ratio is used to determine the efficiency of thread strength in stitch.
Elongation at break:
The extension of thread under the load which causes break called elongation at break. It is important for seam extensibility.
Elongation at break = (Extension/Original length) x 100%
Stress – strain curve:
Tenacity is plotted against elongation or strain. If the elongation property is more, then the curve will be bigger and vice versa.
If thread returns to its original length after deformation/ extension is called elastic. If thread cannot return to its original length is called plastic. Most of the threads are between elastic and plastic.
The elasticity of sewing thread affects the strength and finished quality of a stitched/finished seam.
The dimensional change of thread after washing with water or heat is called shrinkage. Thread shrinkage should always be as low as possible, otherwise seam pucker will occur.
It is the friction resistance of one thread to another thread. This is most important to determine the sewing performance of threads.
To become abrasion resistant, the threads should be –
- Well lubricated.
- Should have a smooth surface.
- Should be free from faults.
The thread must retain its original color and shade till the life time of the garments. Threads should be color fast to wash and light. staining of color from thread to fabric is completely unacceptable.
Should be uniform to pass the thread smoothly.
Resistance to chemical attack:
The garments which may undergo washing, bleaching or dry cleaning, the sewing thread used should have good resistance to chemical attacks to avoid any damage.
These are the most important properties that a high quality sewing thread must possess.