As we mentioned in the previous post, bandages are made up of yarn, either a single type of yarn or several types of yarn. All of them are normally interwoven transversely and longitudinally to form the bandage fabric.

Yarns are usually divided into two main families. Thus we find natural yarns, those that come from plants or nature, and synthetic yarns, which are manufactured artificially and come from petroleum.

Natural yarns

Regarding natural yarns, the most commonly used in bandages are cotton and viscose. Cotton is a natural fiber and does not generate allergies. Some of its main characteristics are that it is biodegradable, its absorption capacity is low and it gives body to the bandage fabric. To achieve a higher absorption capacity, cotton must undergo a hydrophilization process.

Cotton is found in a wide range of bandages, among which are crepe bandages, cohesive bandages or compressive bandages. Its main disadvantage is that it has a higher price than synthetic or viscose yarns.

Viscose is noted for its ability to absorb liquids—superior to that of cotton—and it does not generate allergies. It is mainly used to retain those liquids and keep the covered area dry. It has elastic and resistant properties very similar to cotton but at a lower cost.

In recent years, other natural yarns are being experimented with such as bamboo yarn, which is antibacterial. Calvo Izquierdo has already developed a research project on this material and is looking into how to introduce it in bandages and socks.

Continuing with natural yarns, we have another group where the yarn itself has compressive properties due to its elasticity.  The most commonly used material is natural rubber. This yarn comes from latex and is very elastic. It is widely used in the manufacture of highly elastic bandages, although it has two disadvantages. The first is that it is a very thick yarn; the other is that it contains latex, which can cause allergies when in contact with the skin. For this reason it is a yarn that is no longer used in the healthcare sector.

Synthetic yarns

Synthetic yarns are usually derived from petroleum and there are different yarns for different uses.

Polyester is inelastic and is heavily used in common fabrics such as shirts, sheets, table linen, etc. due to its low cost. It is a continuous fiber that when extracted from petroleum is a very fine yarn, so it is not worked alone but grouped in a set of filaments (28 filaments or 120 filaments for example).

In addition, we have yarns that only provide elasticity to the bandage, such as polyamide and polybutylene terephthalate (known in the industry as PBT).

Polyamide is a synthetic yarn derived from petroleum, which is elastic and consists of many long and very fine fibers. It has a high elastic capacity and is present in many bandages such as support or cohesive bandages. An example of a synthetic polyamide is Nylon.

PBT is a variation of polyester that also provides elasticity to bandages but without endowing them with compressive properties on their own. PBT is now becoming popular because it has very similar properties to polyamide but is less expensive.

Elastane is used as a substitute for elastic or natural rubber yarn. In 1958, elastane yarn, developed by the DUPONT company, was introduced under the brand name Lycra. Elastane is known in the US as Spandex. This yarn, being a petroleum derivative, does not contain latex but has properties very similar to natural rubber, making it a very suitable substitute to avoid latex allergies. As a result, elastane is increasingly being marketed and used in sanitary bandages. This is what is commercially called technical yarn.

Non woven fabrics

Finally, and so as not to leave out any type of fabric used in the most common bandages, we have the nonwoven fabric bandages. These bandages consist of a mixture of synthetic materials (such as polyester and polyamide) and in some cases natural yarns. Non woven fabrics also have the property that they are thermoweldable, that is, at a certain temperature the synthetic fibers fuse and remain joined with each other. Natural fibers are not welded. The welding is done by taking fibers of between 1 and 3 cm long and other microscopic fibers that are sprinkled on the larger fibers. Once the two have been put together, pressure and heat are used to create the final fabric.

As we have been able to observe, there are a number of yarns with completely different properties, which serve to obtain a different final product based on the needs of the market. The following table shows a small summary of the yarns mentioned:

In future posts, when we talk about the properties of the different bandages, we will relate them to these materials since the composition of the bandage is closely related to its final properties and purpose.

Prepared by the technical department of Calvo Izquierdo S.L.

with the collaboration of Carmen Alba Moratilla

Bibliography

• https://www.lycra.com/en/consumers-discover/what-lycra-fiber
• Descrude y Blanqueado de Fibras de Algodón para obtención de Algodón Hidrófilo (M. R. Fernández, 2007)