Thermal fibers can be divided into two categories, passive thermal insulation materials, and active thermal insulation materials.
Passive Thermal Insulation Materials
It uses the low heat transfer characteristics of the material to prevent or reduce the spread of human body heat to the outside, thereby achieving the purpose of thermal insulation.
1. Natural Plant Fibers
Cotton fiber has good thermal insulation properties. However, during use, it has strong moisture absorption, is prone to matting, and its thermal insulation and compression elasticity deteriorate, leading to decreased comfort.
Kapok fiber is a lightweight, thin-walled, high-void fiber material. Its unique hollow structure is conducive to accommodating more stagnant air, while also having excellent moisture conductivity and thermal insulation functions. It is currently the natural thermal insulation material with the highest hollow rate. Due to the short length, low strength, poor cohesion, and difficult processing of kapok fiber, it is mostly used as filling thermal insulation material.
2. Natural Animal Fibers
Wool, cashmere, and camel hair are all high-end natural animal fiber thermal insulation materials. Due to their curly and fluffy characteristics, they have good thermal insulation properties.
Silk has good thermal insulation properties and contains 18 essential amino acids needed by the human body. It has a good affinity with the skin and has health benefits.
Down has unparalleled thermal insulation properties compared to other natural thermal insulation materials, due to its unique “branch-like” branching structure and moisture absorption and heat generation function. Down filling also has characteristics such as softness, warmth, and high elasticity.
3. Chemical Fibers
3.1 Ultrafine Fibers
The reason why ultrafine fibers have good thermal insulation performance is that, compared with conventional fibers, ultrafine fibers with a fineness of 1.0dtex have a higher specific surface area and a higher contact area with air. Under the action of high specific surface energy, they can adsorb more stagnant air, block airflow, reduce heat loss caused by natural airflow, and help improve the thermal insulation performance of ultrafine fiber aggregates.
In recent years, ultrafine fibers have been used not only to prepare high thermal insulation wadding but also as fiber raw materials for underwear fabrics. Fabrics processed with ultrafine fibers have many advantages, such as delicate texture, soft and skin-friendly, elegant appearance, natural shaping, not ease of deformation, thermal insulation, moisture absorption, and breathability.
3.2 Hollow Fibers and Shaped Fibers
Polyester hollow thermal insulation fibers have excellent thermal insulation effects, as well as superior moisture conductivity, light texture, softness, and comfort.
Shaped hollow fibers reduce the thermal conductivity of fibers by imitating the cavity structure of natural fibers to improve thermal insulation. For example, shaped hollow polyester functional thermal insulation fibers have the characteristics of being lighter and warmer, and having ultra-high voids. This type of fiber product has been widely used in thermal insulation textiles.
With the development of melt-blown plate manufacturing technology, shaped fibers have developed from simply shaped cross-sections such as triangles, clovers, and hollows to various complex-shaped fibers such as pentagons, crosses, and diamonds.
With the diversification of fibers, hollow fibers are developing towards shaped voids, porous structures, high voids, and three-dimensional curly structure fibers prepared based on composite spinning methods or asymmetric cooling principles.
3.3 Aerogel fibers
By using a unique spinning process, aerogel is perfectly combined with polyester fibers. Aerogel fibers have super strong thermal insulation, softness, comfort, and breathability. It is an ideal thermal insulation material for winter insulation clothing, with thermal insulation effects far exceeding traditional down and cotton fillings. Hubei Decon can supply Aerogel Polyester Chips.
Active Thermal Insulation Materials
In addition to isolating or reducing the loss of human body heat, active thermal insulation materials also have the ability to absorb and store external heat and transfer heat to the human body through additional heating effects. Therefore, they are also called energy collection and management materials, such as heat storage thermal insulation fibers, temperature-adaptive fibers, heating fibers, far-infrared thermal insulation fiber materials, etc.
1. Moisture-absorbing and Heating Fibers
The heating mechanism of moisture-absorbing and heating fibers is to absorb water vapor generated by the external environment or the human body, form hydrogen bonds, and release heat. Therefore, their moisture-absorbing and heating performance is closely related to the fiber’s regain rate. The higher the regain rate, the stronger the moisture-absorbing and heating performance. They are mostly used in underwear, bras, socks, and sportswear.
2. Solar Energy Heating Fibers
Solar energy heating fibers are materials that can absorb energy from different wavelengths of sunlight and convert it into heat energy, reflect human body heat radiation, and have thermal insulation functions. According to the range of spectra that fibers can absorb, they can be divided into two types of fibers: far-infrared solar energy heating fibers and visible light near-infrared solar energy heating fibers.
3. Electric Heating Fibers
Electric heating fibers use the heating effect of electric current. After the conductive material is electrified, the electric energy is converted into heat energy. Currently, polymer-based electric heating materials with excellent processing and stability are gradually replacing metal materials with high cost and strict application conditions. Usually, the heating effect is achieved by adding conductive fibers such as carbon fibers.
4. Chemical Reaction Heating Fibers
Chemical substances are added to the threads, and the exothermic chemical reaction is used to convert chemical energy into heat energy, thereby achieving the thermal insulation effect.
5. Phase Change Temperature-regulating Fibers
Phase change refers to the transformation of a substance from one phase to another. Phase change temperature-regulating fibers absorb or release heat through a phase change to achieve temperature regulation. In addition to space suits, phase change fibers are also used in sports clothing, such as ski suits, ski boots, gloves, and socks.