Cannabis is an annual woody plant belonging to the Cannabinaceae family, close to the nettles. This plant, whose homeland is Asia, has spread all over the world by following various paths. Two subspecies exist today. These; cannabis sativa and cannabis indica.
The genus Cannabis sativa, which is used for fiber production and has industrial importance. Apart from the textile industry, hemp is also used in other fields. Its seeds are used in oil production and animal feed production, and its fibers are also used in paper making. Cannabis is one of the first cultivated plants in human history. As a result of archaeological researches, remains of fabric made from hemp dating back to 8000 BC were found. B.C. It is known that cannabis was produced in Anatolia in the 1500s.
Hemp fibers have held a very important place in textile production throughout history and have shaped the economies of the countries. In fact, until the end of the 19th century, hemp fiber was the raw material of 80% of all textile products in the world. With the use of cotton fiber with the developing technology in the early 20th century, finer yarns could be produced and it became possible to obtain lighter clothes. With the laws against cannabis enacted in the 1930s, hemp farming was severely interrupted, in addition, hemp textiles began to lose their former importance with the synthetic fibers developed in parallel with the war industry. Today, it is seen that the demand for textile products produced from hemp fibers is increasing rapidly.
The high level of environmental concerns is the main reason for this interest. Compared to cotton, which is the most used natural fiber in the world, and petroleum-derived synthetic fibers, hemp fibers attract attention with their superior ecological (environmental) properties and organic textile production potential. Another reason why hemp textiles have come to the fore lately is that they provide superior usage properties. These properties result from the physical and chemical structure of the fiber.
PHYSICAL AND CHEMICAL STRUCTURE OF HEMP FIBER
The hemp fibers used in the textile industry are obtained from the male sexual individuals of the cannabis sativa type of hemp. The plant has a long stem containing knuckles. There are different categories of fibers in the sac section (the secondary cell bundle is absent in the flax sac, which is a distinctive feature). Fibers suitable for textile use are primary fibers. Primary and secondary fibers are shown below.
Primary fibers are composed of apical shoot tissue. The number of primary fibers between the nodes does not change with the growth stages of the plant, but the fibers are elongated. Fiber length and yield depend on the distance between the nodes. The said fibers are in bundles in the shell part and there are 30-50 fiber cells in the fiber bundles. Each fiber cell is 20-35 microns, and the fiber thickness changes, increasing towards the lower parts. The fibers are shiny and their color is yellow-brown.
The cross section of the hemp fiber is polygonal as can be seen below. The iodine-sulfuric acid mixture can be used to differentiate hemp fiber. When treated with this mixture, the lumen is colored yellow, the cellulosic wall is colored blue, the other parts are dyed yellowish green.
Obtaining Fiber from Hemp Stalks Maturity is an important parameter for fibers to be used in industrial applications. The maturity of a single fiber occurs from outside to inside with the development of the secondary wall. In mature sac, the cell walls are thin and the lumen occupies a small volume. The development of the secondary wall begins during the growth phase of the plant and continues after flowering. The fiber characteristic varies according to the harvesting period of the plant, so the right harvest period should be selected according to the fiber quality desired to be obtained. Below is a cannabis field in the harvest season.
According to the desired fiber maturity, harvesting can be done by the following methods:
1. After the flowering of the male plants, the male plants are harvested.
2. After pollination, male and female plants are harvested so that the fiber of female plants can also be utilized.
3. After seed formation, male and female plants are harvested. In this method, fiber production is secondary and the main purpose is to obtain seeds.
The process of separating the fibers from the stems after the harvest is similar to the flax fibers, for this process methods such as mechanical method, dew-holding, pooling method, chemical method and enzyme treatment method are used. The aim here is to obtain fibers by removing the woody parts.
Chemical Structure of Hemp Fiber Hemp, which is a natural cellulose fiber, contains impurities such as hemicellulose, lignin and pectin as well as cellulose. The chemical components of hemp fibers along with some other natural cellulose fibers are shown in the table below.
It is important to examine the non-cellulose materials contained in the fibers in order to better understand the physical and chemical properties of the fibers and to choose the processes to be applied in production efficiently. Hemp fibers are formed by the combination of many elementary fibers.
Elementary fibers come together thanks to pectin gum. Pectic substances are structural polysaccharides and have high water holding capacity. In hemp fiber, pectin is found in the primary wall and middle lamella. In the middle lamella, pectin is coated with lignin. Lignin is the second most abundant biopolymer in the world after cellulose. Unlike cellulose, it has aromatic and aliphatic groups. Its main component can be considered as 4-Alkylcatechol. The structure of the lignin molecule is shown below.
Lignin is a difficult molecule to decompose and is resistant to enzymes. The survival of plants that grow above the soil level is provided by lignin. Lignin increases the reactivity of the fibers but also gives the fibers a hard handle.
Another non-cellulose component in hemp fibers is hemicellulose. Hemicelluloses are heterogeneous polymers of pentose, hexose and sugar acids. Unlike cellulose, they do not have a homogeneous chemical structure. These compounds give the fiber important properties such as breathability and heat insulation.
Effect of Chemicals on Hemp Fiber
Due to the cellulosic nature of the fibers, they are damaged by concentrated inorganic acids. Weak acids cause strength loss with temperature rise. If treatment with acids is required, it is useful to choose organic acids. Hemp fibers are highly resistant to alkalis. Especially cottonized hemp fibers are very resistant to basic processes. The fibers melt in hot dense bases, and with the use of cold dense bases, the fibers swell and a mercerized effect is created. Organic solvents, including dry cleaning solutions, do not damage hemp fibers. It is very resistant to microorganisms.
Physical Structure of Hemp Fiber The physical properties of the fibers significantly determine the fabric structure to be produced and the usage properties of the fabric. The table below shows the important physical properties of hemp fiber.
Again, as can be seen in the table below, hemp fibers are superior to other cellulose fibers in terms of some physical properties. Hemp fibers are natural fibers that provide very good strength, durability and absorbency. Due to the long fibers, there is no pilling or pilling problem in fabrics produced from hemp fiber.
At 20 oC, it absorbs 65% under 12% RH and 95% under 30% RH. These values are higher than cotton and linen. In addition to these features, other important usage advantages of hemp are that it shows very good electrostatic properties, provides UV protection and does not cause allergic reactions.
ECOLOGICAL PROPERTIES OF HEMP FIBER
Organic agriculture is a production system with a high degree of controllability, aiming to protect the environment and human health, and aiming at sustainable production without destroying natural resources and ecological system. The use of organic products is gradually becoming a way of life. Organic products, which were previously preferred for health reasons, are now also demanded in order to protect the environment and to be transferred to future generations in an undisturbed way. According to the data of the relevant institutions, 10-12% of the greenhouse gas emissions in the world are directly caused by the agriculture sector, and indirect emissions are not included in this rate. The use of synthetic fertilizers, pesticides and genetically modified organisms is prohibited in organic farming. In this way, it is aimed to minimize the pollution of air, water and soil and to protect resources.
Despite the high water, pesticide and fertilizer needs of cotton, which is the most used natural fiber in the textile industry, and flax, which is widely used, and the relationship of synthetic fibers with fossil fuel sources, it is important that hemp can be grown without the need for fertilizers and pesticides, in terms of protecting the soil and the environment. In addition, the fiber yield of hemp is much higher. This situation reveals the suitability of hemp for the production of organic products. Cannabis is a crop suitable for crop rotation. Especially the wheat planting in September and the cannabis harvest in September create a very suitable ground for rotation. However, the cannabis plant kills weeds and can grow in a rich soil type for the next crop.
HEMP-SYS
HEMP-SYS is a project supported by the European Union within the framework of the program 'Quality of Life and Management of Living Resources'. The project started on November 1, 2002 and was implemented within a 3-year plan. The main aim of the program is to develop an innovative, competitive and sustainable hemp-based textile industry and to produce products with high added value. Within the framework of the project, it is aimed to carry out the following steps by working with scientific and industrial partners:
a) Establishing an ecologically sustainable production chain developed for high quality hemp fibers and extending this phenomenon to all processing steps from fiber production to the final product
b) Establishing an effective and widespread hemp textile market and economic infrastructure
c) The dissemination of information on the subject through advanced communication resources, even this project itself shows the importance that developed countries attach to hemp textiles.
USAGE AREAS OF HEMP FIBER
Hemp fiber is used in the use of products with high added value due to its superior properties such as high strength properties, high moisture absorption and breathability, no pilling, organic products, antibacterial properties, UV protection, and good electrostatic properties. There is a wide variety of products made from hemp fibers.
Shirt,
pants,
jacket,
T shirts,
outerwear products such as skirts,
underwear products,
towel,
loses,
mop,
bags and many textile products such as these can be produced from hemp fibers.
In these products, 100% hemp fibers can be used, as well as fabrics consisting of hemp and other fiber mixtures. In order for hemp fibers to be mixed with short staple fibers, they must be subjected to a cotonization process. In the cotonization process, hemp fibers are converted into short staple fibers by chemical or biological processes such as flax fibers.
Hemp fibers are also used in the production of composite materials as well as clothing and home textile products. Hemp fiber has managed to attract the attention of automotive manufacturers, especially in recent years. In 2002, 2200 tons of hemp fiber was used in the automotive industry of Germany and Austria. The car's body parts, spoiler, door panels and seats are made of composite material obtained from hemp fiber. Hemp fibers are also used as insulation material for the construction industry. However, the woody substance outside the fiber obtained from the hemp plant is also used in the construction sector.
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