15 December 2015
Specifics of Holofiber® non-woven heat insulating material performance in underlining at sub-zero temperatures
Maybe it is the most frequently asked question – why the heat insulator provides warmth.
Moreover, the least correct.
No heat insulator provides warmth itself.
The main function of the cloth heat insulating material is to retain heat. Significant target is also to maintain stable temperature and humidity level. These parameters mainly determine the efficiency of cold-protective clothing, which currently significantly differs both structurally and by the selection of materials from the specimen of say 10-15 years ago, when Russia saw the offset of new concept of cloth heat insulators development – synthetic, polyester insulators. Actually, they replaced cotton batting and wool. Replaced and surpassed those in properties, qualities, characteristics, features, and, above all, - in price, having become the cheapest and most available alternative.
Termopol plant of non-woven materials has played the most conspicuous part in the process of warmth-keeping synthetics development for clothing in the RF. The enterprise has developed and introduced in mass production dozens of Holofiber® insulator recipes. Year after year the new understanding, the new technology has been established and on the whole - the new quality clothing. Currently, Holofiber® stands for the most popular and efficient non-woven materials for winter and in-between-season clothing. Besides, it was Termopol plant that laid the basis for the ideology of high-quality synthetic heat insulators in the RF, after appearance of heat insulators produced there, the doubts in a possibility of polyester non-woven materials use instead of fly, feather, wool cotton batting, hugely expensive imported materials that existed among the experts in early 2000 were dispelled.
However, appearance of numerous sintepon analogs, falsifications, fake, Holofiber-like counterfeit, and heat insulator grades with holo-, hol-, thermo-, etc. prefixes with inferior properties critical for heat insulators significantly and, alas, negatively affected reputation of synthetic heat insulators on the whole (let’s mention replacement of heat insulators in new winter military uniform, nicknamed “uniform by Yudashkin”). However, it has set up the background for the top-quality products with their unique qualities projecting more prominently. One of such will be considered here in detail - Specifics of Holofiber® non-woven heat insulating material performance in underlining at sub-zero temperatures.
Heat transfer through clothes into ambient environment (heat exchange) takes place as follows: heat-transfer capacity (conductivity), convection (passage), radiation (emission), sweat evaporation. Usually heat transfer takes place in several ways. Correlation of different heat conductivity types is not constant and varies depending on the temperature and movement of environmental air, type of human activity, etc.
During elaboration of Holofiber® non-woven heat insulators for clothing, the following was proportionally considered and investigated
Since 2007 (completion of the first stage of comprehensive testing in TSNII (Central Research Institute) SHI, NII (Research Institute) of occupational medicine at RAMN (Russian Academy of Medical Sciences) and NII (Research Institute) of non-woven materials, and in European laboratories), the Termopol plant experts have been constantly supplementing this list, as an important factor, with qualities and properties of heat insulator used for clothes designing and fabrication. Physical and chemical data on heat transfer through the clothing material mainly via heat exchange are correspondingly corrected. The idea of heat transfer via convection and radiation taking place in the air interlayers and at the external surface of winterized clothing is also changing.
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Comparison of aggregate thermal resistance data for cotton batting & Holofiber® heat insulating material |
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Cotton batting unwoven stitched half-woolen 280 g/sq.m 3 layers |
Holofiber®-Soft 150 g/sq.m 3 layers |
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0.94 |
1.34 |
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to minus 30.7С |
to minus 61.5С |
Winterized clothing covers over 80% of the body surface. It is an efficient means of human body protection from adverse environmental impact and creates an artificially regulated microclimate around the human body. The specifics of such blanket differ depending on the heat insulator used during clothes manufacturing.
Thermal scanning of a dog's head (nose, a wetted area, is apparently visible on the thermogram)
The human body thermogram shows surface wetted areas with an apparently lower temperature. Wet clothes at sub-zero temperatures increase the heat transfer capacity many times!
The main parameters of the underclothing air microclimate that influence the man’s well-being include three interrelated indicators: 1) temperature, 2) relative humidity и 3) carbon dioxide content.
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difference with ambient environment - 87 С (-50С outside, +37С body)
b) temperature difference should not exceed 10С: body +37С, in the clothes package +27С)
Reducing heat loss, the clothes winterized with Holofiber® contribute to constant skin temperature maintaining and comfort. Whatisitdueto? How does it work as exemplified by certain properties of non-woven materials?
Multiple tests performed in various laboratories prove that Holofiber® heat insulators having high air permeability indicators show the best performance in terms of aggregate thermal resistance and heat insulation. It is mainly obtained due to a combination of zero hygroscopy and air-exchange function. The “breathing” capacity is realized inside the heat insulator. Holofiber materials developers have proved that the heat insulator should not steam off.
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t has become possible due to selection and particular type of multidirectional positioning and thermal binding of a fiber mix with hollow components that do not interfere with air flows movement inside the insulating layer (including the top cloth and backing).
Heavy moisture-retentive cotton batting, foreign heat insulators with microfiber, secondary sintepons of plastic bottles and packages have significantly lower air permeability indicators, and higher hygroscopy indicators (cotton batting, in particular), which significantly reduces heat insulating functions of clothing in time with performance of physical work making it less convenient and comfortable.
Heat insulator should not be an unbreathing layer. It can be easily checked: a hand placed into a cellophane package will fist become hot, it will sweat, but then it will soon feel cold as the moisture heat transfer will “start comparing” the environmental and body temperatures.
Clothing heat insulator should feature “breathing” capacity
Air permeability of Holofiber® non-woven heat insulators should be considered through a prism of carbon dioxide content in the underclothing space. This issue has become urgent after appearance of cheap non-breathing sintepons, fibers in spunbond and dense cotton battings (RF, regenerated or garnetting), preventing air convection. Water, carbon dioxide, salts, fat are released through the skin cover. Skin cover emits about 4.5 l of carbon dioxide and receives 1.9 l of oxygen a day. Rising of air temperature and heavy physical work increase gas exchange via skin several times to reach up to 10 % of pulmonary gas exchange.
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he works of physiologists showed that at carbon dioxide content in the underclothing space of over 0.07 %, gas exchange via skin and, consequently, a man’s well-being significantly worsen. Carbon dioxide content over 0.1 % results in a fainting fit. In case the nitrogen partial pressure under the clothes exceed environmental, it is absorbed by the blood, which is unsafe for an organism. Hence, underclothing space ventilation should be provided for in the clothes.
Light air heat insulators Holofiber® promote retaining of dry warmth and air exchange inside the insulating layer. Therefore, a man’s skin in the insulating package is continuously emitting carbon dioxide and absorbing oxygen, which enables speaking of Holofiber® insulating materials influence on a scarcely investigated in the textile context “skin breathing”.
At high ambient air temperatures, and while performing hard physical work outdoors at sub-zero temperatures, heat transfer via evaporation increases significantly. Moisture is continuously evaporating from a man’s skin surface to the environment. This evaporation takes place according to well-known physical laws, due to the difference between the moisture vapors pressure in the man’s skin and in the environment.
Take a good look, in all cases moisture-retentive fibers transfer moisture, consequently, cold. “Heat insulator in the insulating layer should be dry,” say the developers of Holofiber® materials.
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At rest at a relatively low ambient air temperature (10-18 °С) about 1/5 of heat produced by the body is emitted via evaporation of water vapors through the skin. Children, for example, spend most time in motion, and their heat production increases 2-4 times, hence, the amount of evaporating moisture is rather significant.
At a high ambient air temperature, active sweating starts, and almost all excess heat is emitted via moisture evaporation from the body surface. That’s why we consider the issue of heat transfer (heat conductivity) in the insulating layer in view of insulator specifics: its composition, way of manufacturing, size (thickness), weight. All these factors determine the qualities expressed by a consumer as the elementary notions of “warm and comfortable clothes” while evaluating the entire item, actually meaning the significant parameters of heat insulating material, which is an invisible, but the most important basis of winterized clothing – “the primary hidden”.
Microscopic moisture is the transferred substance carrying the temperature (providing conductivity). Thermal conductivity ratio of water is 0.6, of air - 0.025! What is Holofiber® heat insulator? It is the air volume retained within the hollow fibers not absorbing moisture. It passes between those and is removed outside through the top cloth or backing.
Sweating (wet) parts of the body cool down faster. With removal of moisture from the skin surface, the thermal transfer process slows down. The same pattern applies to “wet” and “dry” heat insulators.
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herefore, moisture in the heat insulator performs adverse heat transfer function in general. Water “takes” too much heat! Even its minimal content in heat insulator and insulating layer results in the cloth thermal protection reduction down to 30% (!). Sure, we speak not about the wet clothes, but about the clothes, which heat insulator has a hygroscopy of more than 1%. In plain language, moisture transfers “minus”, primitively cools down the insulating layer. It can be illustrated by hoarfrost and ice covering the winterized clothing. On the one hand, micromoisture brings out heat. On the other hand, moisture on the top clothing layer results ina significant reduction of thermal protection.
Northern peoples still have a custom to freeze out fur or woolen clothes. It is done exclusively to get rid of moisture inside the clothes, make it dry, as to retain heat, the heat insulator should be dry. By the way, recall animals trying to immediately get rid of moisture in the fur, both as an additional weight, and as a heat conductor (cold – in cold season, heat – when it is hot).
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Hoarfrost on natural fibers of animal or plant origin is a crystallized moisture retained by these fibers. Polyesterfibersin Holofiber® heat insulator are moisture-repellant |
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Natural fiber of plant origin |
Natural fiber of animal (biological) origin |
Polyester fibersin Holofiber® heat insulator |
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Natural fibers of animal or plant origin are moisture-retentive. They absorb and retain moisture. Synthetic polyester fibers in Holofiber® heat insulating material do not absorb and retain moisture. This unique feature is revealed by means of macroscopic recording having become symbolic for the entire Holofiber® project (see below).
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t’s also worth mentioning that in a wet condition (in case of wetting) the strength of polyester fiber in Holofiber® does not change. This property is directly related to the entire item durability, preservation of stable aggregate data during the entire period of clothes use implying washing, cleaning and wetting of clothes when worn, worked in and even stockpiled and stored.
In case of 5-6% elongation, elongation of polyester fiber in Holofiber® material is fully reversible. It explains high resistance of polyester fibers to creasing in normal temperature and humidity conditions. However, polyester Holofiber® heat insulators are high-elastic at low temperatures, too (-61.5С).
Holofiber TM heat insulator with a plastic bottle filled with water placed between its layers prevented water from freezing at a temperature of (!) minus 18 С during several hours
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t very low sub-zero temperatures (below minus 60 С) fiber in Holofiber® heat insulator does not break, remains dry and fully functional as an insulating layer (unlike heat insulators of some natural, artificial and synthetic fibers, and of reprocessed material with a disturbed and deformed molecular structure). Such type of polymers is defined as “extra strong at low density”. In terms of physical and chemical properties, the Holofiber® heat insulator fiber is arigid-chain polymer, which molecular chain is a rigid stem.
equipment
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