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Polyester Thread Buying Guide

There are multiple factors to consider when selecting polyester thread. The most important consideration is the application in which the thread is going into. Other factors include choosing : the right thread size (or thickness), the correct amount you need, the stretchiness (elongation), left or right twist, and whether or not you need a bonding agent.
Given the following characteristics, polyester thread is preferred in items that will be bleached or have prolonged sunlight exposure.
• Effect of Bleaches and Solvents : Excellent resistance to oxidizing agents including bleach.
• Effects of Heat : Sticks at 440° to 445° Fahrenheit. Melts at 483° Fahrenheit.
• Effects of Aging, Mildew, Sunlight and Abrasion : Excellent resistance to aging and abrasion and is not weakened by mildew.
• Effects of Alkalis and Acids : Good resistance to most mineral acids and weak alkalis. Moderate resistance to strong alkalis at room temperature.

Thread Size

When thread size increases, the following characteristics increase as well :
• Needle Size
• Stitch Visibility
• Strength
• Sewing Machine Size
• Thread Diameter
• Sewing Heat and Friction
• Yard per Pound

Amount of Thread

Because the number of yards per pound decreases as thread thickness increases, polyester thread is sold by weight (ounces or pounds) and not yards. The stated weight can vary ± 10% from the normal stated weight.


Standard polyester thread will stretch approximately 25% before it will break. Stretchiness is desirable in most applications because it allows the seams to expand and contract with the material which allows for less puckering and breakage.


The most popular is the left twist, which is also referred to as a Z-Twist, because it is what most single-needle machines in the U.S. require. The right twist, or S-Twist, is used in double-needle machines.

Bonding Agent

Bonded polyester thread has a coating that reduces the needle heat and fraying. The agent causes the thread to be stiffer and about 5% thicker than standard polyester thread. Choosing a bonding agent greatly depends on the application in which the thread is to be used and the required thread thickness.


Choosing the right thread for your application is imperative to the products quality and performance. If you need assistance regarding the best type of thread for your application, please contact us today and we will be more than happy to guide you through the thread specifications.
2017-09-13T10:32:49+00:00May 17th, 2017|