Technical Information

Inherently Flame Resistant Fibers
Flame Retardant Treated Fibers | Comparison of Fiber Properties
Sewing Thread Construction | CRAQ-SPUN® Sewing Threads

Inherently Flame Resistant Fibers

Among these are a number of fibers which are known either by their generic fiber designation or a branded trademark. These include:

Generic Fiber Trademarks Producer
E.I. Du Pont de Nemours and Company
Teijin Limited
E.I. Du Pont de Nemours and Company
Teijin Aramid BV
Polybenzimidazole Pbi® Pbi Performance Products, Inc.
FR Viscose Lenzing Viscose Lenzing
Carbon Fibers   Toray
Stainless Steel   Baekaert

Flame Retardant (FR) Treated Fibers

These fibers, usually natural fibers, e.g. cotton, wool, and flax, can be chemically treated to provide a greater level of resistance to flame impingement than the untreated fiber would provide.

These two groups of FR fibers demonstrate a range of performance characteristics. However, the common link for both types is to provide protection. For a manufacturer to produce finished garments, FR fabrics must first be cut into component parts which are then sewn together with FR sewing thread to produce shirts, trousers, coveralls, etc. The sewing threads most commonly used to manufacture FR protective clothing are made of aramid fibers.

Comparison of Fiber Properties

Generic Fiber Meta-Aramid Para-Aramid
Trademarks NOMEX®
*Decomposition Temperature 750°F - 800°F
(399°C - 427°C)
800°F -850°F
(427°C - 454°C)
*Effect of Direct Flame Chars1 Carbonizes2
*Resistance to Dry Heat Shrinkage Fair Good
*Chemical Resistance Good Fair
*Resistance to Ultraviolet Light Fair Fair
*Moisture Regain Good Fair

1 Charring of meta-aramids is comparable to the phenomenon that occurs when a log is put into a fire. The heat energy causes the wood to become embrittled as it dries out, shrinks in size, and will break apart when any force or pressure is applied.

2 Carbonizing of para-aramids can be compared to a charcoal briquette. Heat is absorbed until a limit is reached. At this point a breakdown occurs which turns the superheated item into a powder.

Sewing Thread Construction

Sewing threads made of aramid fibers are available in three types:

  • Continuous Filament (CFF) (multiple plies or monocord)
  • Variegated Length Long Staple (VLLS)
  • long staple (wool system spun yarn)
  • short staple (cotton system spun yarn)

Each type of sewing thread has distinct characteristics that you need to consider when selecting the type of thread to use for each particular application.

What are CRAQ-SPUN® sewing threads?

CRAQ-SPUNŽ is the Atlantic Thread trademark for Variegated Length Long Staple (VLLS) sewing threads.

This spinning system is able to produce a superior sewing thread with essentially the best characteristics of the other two types:

  1. Sewing threads that demonstrate break strength that is the nearest in strength performance to that of continuous filament sewing thread; and
  2. Sewing threads which are able to match the sewing performance and ease of processability of short staple sewing threads.

Please contact Atlantic Thread & Supply Company by phone, fax, or e-mail if you would like additional technical information.