As one of the leading producers of industrial polyester yarn, Hailide America works with customers industries ranging from a variety of industries that produce products used with automobiles, public services, construction projects, and more. We are asked by prospective customers about the raw materials used to make industrial polyester yarn from time to time, so we decided to address that in this article.

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What Is the Primary Raw Material Found in Polyester Yarn?

The primary raw material found in industrial polyester yarn is the polyester polymer itself, which compromises around 98.5-99.5% of the yarn. Within the polymer there could be additives such as colorants and functional polymer additives providing long lasting beneficial properties to the yarn. These additives, often known as “melt additives” are added into the polyester polymer during the extrusion process and are therefore locked inside the polymer.

On the surface of the yarn, chemicals known as “spin finishes” are applied. These spin finishes are normally 0.5 to 1.5% of the yarn composition. Spin finishes are either basic processing aids which are needed in the production process of the polyester yarn itself but can also play an important role in downstream processing such as knitting or weaving by providing needed lubrication. Or the spin finishes can also provide “functionality” or “performance” such as low wick, adhesive activation, abrasion resistance (marine rope applications), etc.

What Are Polyester Polymers Made Of?

The polyester polymer is comprised of two ingredients.

Purified Terephthalic Acid (PTA):  This is the primary raw material in the production of polyester.  It is a powder that is primarily used in the production of polyester. 

Mono Ethylene Glycol (MEG):  This is the second component of polyester polymer.  MEG is essentially anti-freeze.  Its applications are very widespread and diverse.  Polyester production is just one market in a sea of many for this petrochemical.

To produce polyester chip (or polymer), you need approximately 86% PTA and 35% MEG by weight.  Obviously, these figures do not add up to 100%.  An excess of MEG is required to facilitate the chemical reaction.  At the end of the polyester polymer production process, the manufacturer ends up with Spent Ethylene Glycol.  This can be refined and recycled back into the EG markets for other end uses.

Melt additives; Color masterbatch.

Color masterbatches, in its basic form, is a blend of dye or pigment with a polymer which is the carrier for the color. The masterbatch is produced by first mixing the components in the correct ratio and then melting, extruding, cooling, and cutting into pellets. These pellets are the masterbatch which will be used to color the polyester during the yarn production process.

The masterbatch is added at a controlled and consistent level into the front end of the extruder which is used to melt the polyester polymer. The masterbatch melts along with the polyester and is mixed homogenously throughout the molten polyester so that the filaments emerging from the spinneret are all the same color. A wide range of colors can be offered from black to pastel shades. Masterbatches are designed to give the yarn good color fastness, good consistency, and repeatability of color from batch to batch and within the batch.

Melt additives for functionality.

Using a similar production process as is used to make color masterbatches, flame retardant (FR), UV stabilizer (UV), anti-microbial and other types of additives can be made which are added into the extruder and melted and mixed into the polyester. The functionality or performance that the additive brings to the polyester yarn is locked into the polymer structure and can give much longer lasting performance to the yarn and final knitted or woven product than a surface applied product (spin finish) which could be removed by washing or abrasion.

Spin finish as a process aid.

Spin finishes typically contain a blend of lubricants, emulsifiers, anti-stats and wetting and spreading agents. Applying a spin finish to a yarn in a high-speed process is not easy. It was once described to me as like trying to paint a car as it passes by at 70 mph on the highway. Getting the finish onto the individual filaments in the yarn bundle, wetting and spreading evenly, is critical.

Protecting the filaments during the heating and drawing process so they do not break is vital to yarn quality. Once the yarn is drawn to the correct linear density and tenacity then it must be wound onto cardboard tubes in the winding process which could be between 4000 and 6000 m/m. The role of the spin finish does not end there.

Most industrial polyester yarn is produced in Asia and is shipped around the world. The stability of the yarn package needs to be good so that the yarn can be used when it arrives at the customer. Spin finish helps with this. Finally, the customer will use the yarn in their own process, whether that is knitting, weaving, braiding or other uses. The lubrication that the spin finish provides can also help in these processes.

Spin finish for functionality.

It is quite common to apply a spin finish that is more than just a process aid. Some level of “functionality” can be applied to the yarn either with the basic spin finish or at a secondary finish application point before winding. It is also possible to apply these functional finishes during a secondary operation such as beaming.

Functional finishes are ones that provide beneficial properties to the yarn that will be carried through further processing into the final product. As an example, polyester yarn which is to be used in a tire, hose or belt (Mechanical Rubber Goods, MRG) will typically have an adhesive active finish applied to it. During the process of producing the MRG, the polyester will be coated with a rubber compound. Forming a good bond between the polyester and the rubber compound is key for the performance of the MRG over its lifetime. The adhesive active chemistry applied to the polyester helps with this process.

Other functional finishes can include low wick finishes which prevent moisture from moving along the length of the polyester yarn in a knitted or woven fabric. These low wick finishes are often used on yarns that will be woven and then coated and will often be found as architectural fabrics such as in stadium roofs.

Abrasion resistant finishes are often applied to polyester yarns that will form ropes that are used in marine applications such as mooring of oil platforms. These ropes are under tension and constant motion due to the ocean currents. As the ropes move the yarns rub against each other and can abrade and lose strength. The finishes applied to these yarns have been designed to reduce abrasion under these conditions giving longer life to the rope.

Final Thoughts

By doing the research to better understand how polyester yarn is constructed, you’ve taken an important step in ensuring the product you use is of the highest standards. We hope the transparency offered here assists you in this, but should you have further questions, reach out to us. We would be happy to answer any additional questions regarding the construction of polyester industrial yarn or the applications that use it.