Frost won't be a problem: PNIUP experts revealed which materials in down jackets will keep you warm and prevent freezing.

The Most Popular Upper Material is Polyester

“The production of polyester involves various types of polyesters in fiber form, such as polyethylene terephthalate (PET). Its raw components are derived from oil or gas,” explains Sergey Kotelnikov, Associate Professor of Polymer Materials Technology and Explosives at PNIPU, PhD in Technical Sciences. The process of producing polyester fibers based on PET begins with the pre-treatment of ethylene glycol and terephthalic acid.

These substances are purified and chemically transformed into polyethylene terephthalate through a polycondensation reaction. The resulting melted polymer is then extruded through special openings to form fibers. Once they solidify, they are wound onto spools. The threads are washed, bleached, dyed, and treated to enhance softness, strength, and a sliding effect.

Why is Polyester Used in Down Jackets?

This synthetic fiber is relatively inexpensive and widely available, making it a common choice. Its properties are especially advantageous for winter clothing. Firstly, polyester is treated with special water-repellent coatings. This is crucial for outerwear, as the insulation loses its thermal properties when wet.

Another benefit is its lightweight nature. Polyester is a light material, which makes down jackets comfortable to wear. Additionally, it boasts high strength and durability, extending the lifespan of the garment. It nearly does not fade in sunlight, maintaining the color and appearance of clothing for longer. Snow effectively reflects ultraviolet rays, so it’s important not to forget about sun exposure even in freezing temperatures.

“Pure polyester is rarely used. More often, it is combined with polyamide—a synthetic fabric resembling silk. It is also utilized for jackets and raincoats due to its resistance to temperature fluctuations and UV rays. Another option is elastane, which serves as an excellent base for tights, sports suits, windbreakers, and gloves,” notes the scientist from Perm Polytechnic.

Is Nylon Better than Polyester?

Nylon is a family of synthetic polyamides commonly used for fiber production. There are two main types: anid (or nylon-66) and capron. Both of these polymers are derived from petroleum products through a polycondensation reaction. The polymer granules are then melted and formed into threads using a sieve.

“Unlike natural fabrics, synthetic materials are difficult to tear. They are elastic, resistant to chemicals, and repel water. However, there are still differences. Nylon feels smooth to the touch, while polyester fibers are rougher, resulting in a less dense fabric that allows for better air circulation,” explains Sergey Kotelnikov.

Nylon fabric is lighter than polyester material, providing an additional advantage. It is also waterproof and does not require further treatment. However, it does not allow air to pass through, making it suitable for outerwear that does not come into contact with the skin, such as the outer part of down jackets. Light autumn jackets and windbreakers are better made from polyester to allow the skin to breathe and avoid a greenhouse effect.

“Nylon polymer gradually degrades under the influence of UV radiation present in sunlight. This weakens the intermolecular bonds between macromolecules and, consequently, in the fabric fibers,” adds the expert from PNIPU.

When and Which Material to Choose?

When deciding between polyester and nylon for the outer fabric of a down jacket, specific needs and preferences should be considered.

“Nylon is lighter and softer, more durable and stronger, and can repel moisture and dry quickly when wet. However, it has limited thermal insulation and lower resistance to ultraviolet rays. In contrast, polyester retains heat well, making it an ideal choice for cold weather. Thus, the former material is better suited for humid conditions and outdoor sports, while polyester is preferable for freezing temperatures,” believes Sergey Kotelnikov.

Sintepon, Isosoft, Holofiber, Synthetic Down — Which Filler is Better?

Artificial materials are currently used as fillers for down jackets. Sintepon, for example, is made from polyester fibers that are interconnected. This creates a uniform insulating layer. It is cheaper than alternatives, retains heat well, is lightweight, moisture-resistant, and dries quickly. However, over time it clumps together, losing its ability to retain heat.

Modified insulators have replaced sintepon. Isosoft consists of siliconized fibers evenly distributed throughout the material. It has good thermal insulation properties, is lightweight, does not clump, retains its shape well, and allows air to pass through. Holofiber is made from hollow fibers, enabling it to retain more air and heat. Synthetic down is a group of several types of insulation that mimic natural materials. For instance, Tinsulate is referred to as artificial swan down. It usually consists of fine polymer fibers. The most expensive types are often used in high-quality clothing.

“In fact, these are all different types of polyester that vary in the size of the air layer between the fibers. Air is the main thermal insulator in down jackets. Among those listed, synthetic down and isosoft are considered the 'warmest',” notes the scientist.

Down Jacket or Natural Fur Coat — Which is Warmer?

Modern high-quality insulators outperform natural furs in thermal insulation properties. Tinsulate, for example, was originally used as a filler for astronaut suits. This material has unique thermal-retaining properties and can keep warm at extremely low temperatures down to -70 °C.

“If we consider not only fur but also other natural insulators, the best is bird down, such as duck or swan down, due to its microstructure that traps more air,” explains Sergey Kotelnikov.

Additional Insulation

Besides outerwear, it is worth considering insulation through thermal underwear. Its purpose is to provide thermoregulation directly at the body by wicking moisture away. Cotton is a natural, "breathable" material but easily absorbs moisture. Polyester, on the other hand, is denser, retains heat better, and repels moisture, but it provides poorer air exchange, which can lead to sweating. And wet synthetic materials lose their ability to provide warmth. Wool retains heat even when damp due to its structure. However, in slightly below-freezing temperatures, it can be too warm.

It is important to understand that thermal underwear will not work effectively without additional outerwear to protect against cold: jackets and down jackets with an "air" structure.

“Each material has its own advantages. Therefore, it makes sense to choose a blended fabric. For example, when it says '70 percent cotton, 30 percent polyester', the aim is to achieve properties that are not inherent in them separately. This way, the durability of natural fabrics can be improved, while maintaining their attractive appearance, color brightness, and ability to repel dirt, among other benefits. Unlike purely synthetic fabrics, blends acquire better air permeability,” comments the expert.