Hygroscopicity is ... Hygroscopicity of fibers, clothes

Surely many have heard this word many times and even, perhaps, wondered exactly how it is written and what it means. But not everyone is aware that knowledge about this physical property of materials can be useful in everyday life. That's why we'll get to know him better.

Definition

Hygroscopicity is the property of a material to absorb and retain moisture from the air. Some may be confused by the letter "g" in the first part of the word, because we all know that complex terms associated with water usually begin with the prefix "hydro". But here it is a little bit of another. Hygroscopicity takes into account the absorption of materials only by the water that is sprayed in the air in the form of steam, which means that the prefix needs a completely different one. "Hygro" means that the word has to do with humidity. It's simple.

We have made out the definition, and now it's time to find out what the word really means. The air around us has a certain humidity - this is even said in the weather forecast. Some fibers are able to absorb this water, often changing their properties. It is thanks to hygroscopicity that clothes and shoes can get wet even without rain. In which cases this is good, and in which cases it is bad, we find out below.

What materials have hygroscopicity?

In this article, we will mainly talk about tissues. But not only they are able to absorb moisture from the air. The indicator of the hygroscopicity of a material is often necessary for the builders, furniture makers, manufacturers of complex equipment and many others.

For example, we all know that wood has a porous structure, this increases its hygroscopic properties. Water, penetrating into the structure of the tree, deforms it. That is why furniture from wood is practically not installed in rooms with high humidity. To reduce hygroscopicity, special impregnations can be used.

No less important are the hygroscopic properties of heaters used in construction. The air in the pores of the material keeps the heat in the room. But if the insulation gets wet, it instantly loses its basic properties. Therefore, the materials used for these purposes must have minimal hygroscopicity. The ideal score is 0%.

Hygienic properties of tissue

All materials have different physical characteristics, such as density, strength, etc. But for tissues, which must later turn into wardrobe items, other properties are also important - hygienic. They determine how comfortable clothes from this or that material will be.

• Breathability . The name speaks for itself. Fabrics with a high breathability rate are able to "breathe", and with a low - protect from the wind.
• Water vapor permeability . The ability of the fabric to pass moisture to remove sweat and other fluids from the body.
• Waterproof . Protects the body from liquids. This property of the fabric is increased by various impregnations and polymer coatings.
• Dust extraction . This property allows the tissue to hold small particles on its surface. The stronger the material is loose, the higher the index of the dust content.

• Electricity is the ability of a fabric to store static electricity.

Do not forget about the heat-shielding properties of the fabric. This is the ability to maintain normal body temperature at a time when it's cold outside. And the last property will be discussed in more detail.

Hygroscopicity of tissue

This indicator refers to the hygienic properties of textiles, which, in turn, determine the comfort of a material when worn. And the requirements for clothing largely depend on its purpose.

Hygroscopicity is the most important property of a sports uniform or summer clothes. The increased temperature of air and body leads to profuse sweating, which, in turn, creates considerable discomfort for a person. To get rid of excessive moisture allows exactly high hygroscopicity of the fabric. This property is an important indicator for manufacturers of everyday underwear.

What determines the ability of the fabric to absorb moisture from the environment? First of all - from the fibers from which it is made. In addition, the importance of the presence of protective coatings and impregnations.

Types and hygroscopicity of fibers

The materials from which the fabrics are made can have different origins. There are natural fibers and synthetic ones. First, let's talk about the first. They are created by nature itself, though not without the participation of man.

Wool, shorn from various animals, is most often used for the production of warm clothes. It is one of the leaders among natural fabrics for the ability to absorb moisture. The hygroscopicity of the fibers of the wool is approximately 15-17%. But here the rate of moisture absorption is relatively small.

This figure is much higher in many other tissues. For example, the hygroscopicity of cotton is only 8-9%, but it is able to absorb moisture much faster than wool. Another natural material is flax, obtained from bast fiber. Its ability to absorb moisture can range from 12 to 30%.

Artificial and synthetic fibers

The first type includes materials obtained from natural compounds. A vivid example is viscose. It is created using natural cellulose. Viscose fibers are characterized by strength, heat resistance, and high hygroscopicity, which is almost 40%.

Synthetic fibers are created from products of oil and coal processing. These include polyamides. Nylon, capron and anide are created from these fibers. Hygroscopicity of such materials is rather low, only 3-4%, but they retain their tensile strength and are very durable. Polyester fibers, from which lavsan fabric is created, have a high index of heat resistance and resistance to light. But their hygroscopicity is minimal - only 0.4%.

Polyurethane fibers, which are the basis for lycra and spandex, also do not differ in ability to absorb moisture from the environment. From the above, it can be concluded that the hygroscopicity of clothes made from synthetic materials is much lower than those of natural fabrics. But is it really a flaw?

Hygroscopicity - is it good or bad?

Everything in the world is relative. The same can be said about the topic that we raised. It can not be unequivocally said that hygroscopicity is good. Yes, it allows people to easily survive the heat, and athletes - to perform exercises in more comfortable conditions. But to some tissues the excessive humidity can only do much harm.

On the example of insulation we have already found out that water reduces the heat-insulating properties of materials. In addition, some tissues are deformed by the action of moisture - we all know how stretchable after washing the knitwear. The same fate, only on a smaller scale, can comprehend some materials at very high relative humidity. Therefore, it is not always possible to say with certainty that tissue hygroscopicity is a plus. The question is the purpose of this or that material.

How is this indicator determined?

In the 80 years of the XX century in the USSR GOST 3816-81 was created. It contains a detailed description of methods for determining certain properties of textiles, including hygroscopicity. Here's how it works.

Experts take samples of a cloth measuring 5x20 cm and each is placed in a separate glass for weighing. The main task of the experiment is to find out how much water will absorb the material under certain conditions. For this, a sample cup is placed in a desiccator, in which the air humidity is 97-99%. After 4 hours, the sample is weighed, and then, at a temperature of 105-109 ° C, the material is dried and its new weight is determined.

The hygroscopicity index (H) in percent is determined using the formula: H = (Мв - Мс) / Мс х 100, where for Мв and Мс, respectively, the mass of wet and dry tissue.