Terylene is the original British trade name for polyethylene terephthalate (PET) polyester fiber, one of the most widely produced synthetic textiles in the world. Developed in the early 1940s and commercialized by Imperial Chemical Industries (ICI), it is chemically identical to what Americans know as Dacron and what the rest of the global market simply calls polyester. The name “Terylene” has largely faded from everyday use outside the UK, but the fabric itself is everywhere, from dress shirts and bed sheets to surgical implants and industrial filters.
How Terylene Came to Exist
British chemists John Rex Whinfield and James Tennant Dickson synthesized the first polyethylene terephthalate fiber in 1941, building on earlier polymer research. ICI acquired the patent rights and branded the resulting textile fiber “Terylene.” DuPont independently licensed the technology for the American market and sold it under the name Dacron. By the 1950s, polyester was being mass-produced on both sides of the Atlantic, marketed as the miracle fabric that never needed ironing. The chemistry has not changed in any fundamental way since then: ethylene glycol reacts with terephthalic acid to form long polymer chains that are melted, extruded through tiny holes called spinnerets, and drawn into fibers.
What made polyester revolutionary was that it combined properties no natural fiber could match in a single package. It resists stretching, bounces back from creasing, dries quickly, does not rot or mildew, and holds its shape through repeated washing. Those qualities explain why, decades later, polyester still accounts for more than half of all fiber produced globally.
Why It Holds Its Shape So Well
Terylene’s stiffness and resilience trace to the molecular architecture of the polymer. Researchers have calculated the elastic modulus of the PET crystal along the chain axis using bond-stretching and angle-deformation force constants, confirming that the crystalline regions of the fiber are inherently rigid.1Polymer. Calculations of elastic moduli of polymer crystals: II. Terylene In practical terms, this means the fiber resists being pulled out of shape and returns to its original dimensions after stress is released. Compared to a natural fiber like cotton, which gradually relaxes and deforms when stretched or compressed, Terylene snaps back.
Heat setting enhances this dimensional stability further. When Terylene filament fabrics are exposed to dry heat at controlled temperatures during manufacturing, the internal structure reorganizes and locks in. That heat-set “memory” is what keeps a polyester garment from shrinking in the wash or sagging after a day of wear. The heat-setting step also influences how the fabric responds to wet creasing and dyeing, so manufacturers tune the temperature and duration carefully depending on the intended end use.
How It Compares to Nylon Under Stress
Nylon and Terylene are often mentioned in the same breath as competing synthetics, but they behave quite differently when held under tension. Stress relaxation experiments on nylon 66 and Terylene yarns found that Terylene’s behavior at room temperature could be described by a single composite relaxation curve across a wide range of strain levels, from half a percent to fifteen percent extension.2Journal of Polymer Science. Stress relaxation in nylon and terylene: Influence of strain, temperature, and humidity Nylon, by contrast, showed a more complicated picture: in moist conditions, two separate relaxation processes overlapped, one driven by thermal motion and the other by the fiber absorbing extra moisture as it stretched.
This difference matters for real-world use. Nylon absorbs considerably more water than Terylene and changes its mechanical behavior when wet. A nylon rope or garment under sustained load in humid conditions will gradually lose tension in a less predictable way than Terylene would. Terylene’s relative indifference to moisture is one reason it became the default choice for outdoor applications, sailcloth, and anywhere dimensional consistency in changing weather is important.
The Static Electricity and Soiling Problem
Terylene’s water-repelling nature is a double-edged sword. Because the fiber surface does not attract or hold moisture, it builds up static charge easily. That static cling is not just annoying when a shirt sticks to your skin; it also attracts airborne dust and grime, making polyester garments soil more quickly than cotton equivalents. Early research into this problem identified the hydrophobic fiber surface as the root cause and explored chemical treatments to modify it.3Journal of the Society of Dyers and Colourists. New Finishes for Terylene and Terylene Blend Fabrics
The first approach that worked involved treating the fiber with sodium polyglycollate, which made the surface more hydrophilic and reduced static buildup. But this proved impractical for large-scale commercial production. ICI eventually developed a finishing agent called Permalose T, which gave Terylene fabrics both antistatic and improved anti-soiling properties. Wearer trials confirmed that treated garments stayed cleaner and clung less than untreated ones.4Journal of the Society of Dyers and Colourists. New Finishes for Terylene and Terylene Blend Fabrics Modern fabric softeners and antistatic sprays work on a similar principle, depositing a thin hydrophilic or conductive layer on the fiber surface.
Researchers also explored more exotic approaches. Exposing Terylene fabric to a glow discharge plasma in the presence of acrylic acid modified the surface enough that the fabric could be dyed with basic dyes to solid colors, something untreated Terylene resists because its surface chemistry does not bond well with that class of dye.5Journal of the Society of Dyers and Colourists. Prospects for Radiation Techniques in Dyeing and Finishing Plasma treatments remain a tool in textile research today, though they have not replaced conventional chemical finishing for most garments.
Breathability and the Reputation for Feeling Hot
Ask anyone who grew up wearing polyester dress shirts in the 1970s and they will tell you the fabric feels hot and clammy. That reputation is not undeserved. Terylene does not absorb moisture the way cotton does, so sweat stays on your skin rather than wicking into the fiber. In humid conditions, this creates a stuffy microclimate between the fabric and your body.
Modern sportswear engineering has tried to solve this with knit structures, microchannel weaves, and chemical finishes designed to transport moisture across the fabric surface even though the fiber itself does not absorb it. Research on functional sportswear textiles has achieved moisture-vapor transmission rates above 11,000 grams per square meter over 24 hours, with good elastic recovery and low friction, leading to measurably improved skin microclimate and reduced fatigue during athletic training.6Textile & Leather Review. Design of Functional Textile Fiber Materials for High-Performance Sportswear and Their Impact on Football Training Outcomes
Whether that engineering actually keeps you cooler at a systemic level is less clear. A study on runners exercising outdoors in heat found that a breathable functional T-shirt reduced intra-clothing humidity on the chest and back by a few percentage points and lowered upper-arm skin temperature by a fraction of a degree compared to a conventional shirt. But core body temperature, overall skin temperature, and whole-body sweat rate were not significantly different between the two shirts.7Fashion and Textiles. Does wearing a breathable T-shirt improve the microclimate and thermoregulatory responses during a hot outdoor running? In other words, a high-tech polyester shirt can make the space between fabric and skin slightly less humid, but your body’s overall thermoregulatory machinery does not notice the difference during hard exercise in the heat. If you run hot, managing your pace and hydration matters far more than your shirt’s fabric technology.
Blending with Cotton and What It Means for Flammability
Pure polyester has some drawbacks that pure cotton handles well, and vice versa. Cotton breathes and absorbs moisture but wrinkles and shrinks. Polyester holds its shape and dries quickly but feels slick and builds static. Blending the two fibers, typically in ratios like 65/35 or 50/50 polyester-to-cotton, gives a fabric that wrinkles less than pure cotton, dries faster, feels softer against the skin, and costs less than pure cotton of comparable weight. Polycotton blends dominate the market for work shirts, bedsheets, and uniforms for exactly this reason.
Blending introduces a fire-safety complication, though. When polyester burns, it melts and drips. When cotton burns, it chars and holds its shape as a scaffold. In a blend, the melting polyester clings to the charring cotton scaffold, creating a combined burning behavior that can be worse than either fiber alone. This so-called “scaffolding effect” is a known concern in textile flammability research. One approach to solving it treats each component of the blend independently with its own flame retardant. Research on this strategy found that treating the polyester and cotton components separately raised the limiting oxygen index of the blended fabric substantially and cut the peak heat release rate by more than half compared to untreated blended fabric.8Polymer Degradation and Stability. Flammability and combustion behavior of the polyester/cotton blended fabric via an independent flame-retardation for two components strategy The total heat release also dropped by about two-thirds, and the volume of combustible gases generated during burning fell significantly.
For everyday consumers, the practical takeaway is that polyester-cotton blends are not inherently more dangerous than pure cotton or pure polyester in normal use, but they do require careful flame-retardant treatment for applications like children’s sleepwear, industrial workwear, and military uniforms. Regulatory standards in most countries already require this, so garments sold for those purposes should meet the relevant fire codes. If you are sewing your own workwear from polycotton fabric, fire performance is worth checking before you assume the blend is safe near open flame or high heat.
Terylene in Medicine and the Dacron Graft Story
One of the most remarkable applications of PET polyester is inside the human body. Dacron, the American brand of the same polymer, has been used to make woven and knitted vascular grafts since the 1960s. These tube-shaped prostheses replace damaged sections of arteries, particularly the aorta, and are among the most commonly implanted synthetic devices in cardiovascular surgery. The body does not reject PET the way it might reject some other materials, and the fabric’s strength and dimensional stability make it well suited to withstanding arterial blood pressure for years.
Long-term performance is not perfect, however. A study examining 493 Dacron arterial grafts that had been implanted for three to more than fifteen years found that about three percent of the grafts showed fiber deterioration, with the rate reaching roughly five to six percent of patients across four different graft types.9PubMed Central. Late fiber deterioration in Dacron arterial grafts No defects appeared before three years of implantation. The deterioration involved thinning and breakage of yarn filaments, sometimes causing holes in the graft wall or dilation of the tube. Broken fiber ends showed patterns suggesting mechanical fatigue, and breakage tended to cluster at crimp ridges in the graft’s weave.
The researchers pointed to manufacturing variations that likely reduced individual fibers’ resistance to the constant pulsing stress of blood flow. Storage conditions, sterilization methods, handling during surgery, and the slow degradative action of tissue fluids and enzymes may have contributed as well.10PubMed Central. Late fiber deterioration in Dacron arterial grafts Modern graft manufacturing has improved quality control since these early findings, but the lesson is a useful one for understanding PET in general: the polymer is extremely durable, but not indestructible, and the way it is processed and handled has a meaningful impact on its long-term performance.
Recycling Polyester and Why It Is Harder Than It Sounds
Polyester’s durability, one of its greatest selling points, becomes a liability at the end of a garment’s life. PET does not biodegrade in any meaningful timeframe, so polyester clothing that goes to landfill stays there. The scale of the problem is enormous: polyester dominates global fiber production, and fast fashion has shortened garment lifespans dramatically.
Three recycling routes exist for polyester textiles, each with trade-offs. Mechanical recycling involves shredding the fabric and pulling it apart into shorter fibers that can be respun. It is cheap, but the shredding process significantly shortens fiber length, which limits the quality of the recycled material and how many times it can be recycled. Chemical recycling breaks PET back down into its chemical building blocks, which can then be reassembled into virgin-quality polymer. The quality is excellent, but the process is expensive and requires auxiliary chemicals. Thermo-mechanical recycling, which melts the polyester and re-extrudes it, offers a middle ground: it is cheaper than chemical recycling, does not require additional chemicals, and can use existing manufacturing equipment.11PubMed Central. Impact of Chemicals and Processing Treatments on Thermo-Mechanical Recycling of Polyester Textiles
In practice, the biggest barrier to textile-to-textile recycling is not the recycling technology itself but what is in the fabric. Dyes, flame retardants, antistatic finishes, elastane blended in for stretch, and even the sewing thread (which may be a different polymer) all complicate the process. Sorting mixed-fiber garments at scale remains a massive logistical challenge. The polyester bottle-to-fiber recycling pipeline, where clean PET bottles are melted and spun into fiber, is much more developed than the garment-to-garment loop, partly because bottles are a cleaner and more uniform feedstock than old clothing.
Dyeing Challenges Specific to Polyester
Terylene’s tightly packed, hydrophobic molecular structure makes it resistant to dyeing under normal conditions. Most textile dyes are dissolved in water, and because PET does not absorb water readily, getting color into the fiber requires either high temperatures, high pressures, or chemical carriers that swell the fiber and open up its structure to let dye molecules penetrate.
The standard industrial approach for polyester uses disperse dyes, a class of water-insoluble colorants that are finely ground and suspended in the dye bath. At temperatures above 100°C, usually around 130°C in a pressurized vessel, the PET fiber’s amorphous regions soften just enough for dye molecules to migrate inside. Once the fabric cools, the polymer chains tighten again and trap the dye, producing colors that are remarkably resistant to washing and light exposure. This is why polyester garments tend to hold their color far longer than cotton ones.
The downside is that this high-temperature process uses significant energy and water. It also means that printing polyester with complex patterns requires different equipment and chemistry than printing cotton. Sublimation printing, where heat converts solid dye directly to gas that bonds with the polyester surface, has become the dominant method for custom-printed polyester sportswear and flags. If you have ever ordered a custom-printed jersey, it was almost certainly made this way.
UV Degradation and Outdoor Longevity
Polyester is often described as resistant to sunlight, and compared to nylon, it is. But PET does degrade under prolonged ultraviolet exposure. The polymer chains absorb UV radiation and gradually break down, causing the fabric to lose tensile strength, become brittle, and sometimes yellow. For garments, this process takes years of heavy sun exposure. For outdoor applications like awnings, boat covers, and flags, it can become a real problem within a few seasons.
Manufacturers address this by adding UV-stabilizing agents to the polymer melt before spinning, or by applying UV-absorbing finishes to the fabric surface after weaving. These treatments extend outdoor life considerably but do not eliminate degradation entirely. If you are choosing a fabric for a permanently sun-exposed application, look for specifications that mention UV stabilization. Untreated commodity polyester will fade and weaken much faster than treated grades.
The same UV sensitivity creates an ironic situation for recycled polyester. Each recycling cycle subjects the polymer to heat and mechanical stress that, like UV exposure, can shorten chains and reduce material quality. Combined with any UV history the fiber accumulated during its first life, recycled polyester may start its second life with slightly diminished mechanical properties. This does not matter much for low-stress applications like stuffing or insulation, but it becomes relevant for performance fabrics where tensile strength and elasticity are critical.