Flax & Hemp:
Flax (in fibre form) is practically undifferentiated from hemp, which threatens possible confusion with the latter, which is considerably different in price. Flax and hemp are cellulose fibres produced from stocks of row material. Their properties are similar and they are scarcely differentiated at the fibre form. Analytical differentiation is complicated by strong interventions into these fibres during the textile treatment, which is similar in both flax and hemp: the fibres are separated, blanched, and undesirable additions are removed.
These operations are connected with the change of average chemical composition of fibre material, e.g. the concentration of lignin decreases, the portion of low molecular celluloses decreases and the macromolecules of cellulose are abbreviated. There is also a wide variance in fiber characteristics at wide intervals, e.g. the specific strength of fibres and the length of fibre fluctuations.
Difference Between Flax and Hemp
Differentiating flax and hemp is a long-time analytical problem, which is becoming more and more relevant with the wider loading of bast fibres. Flax and hemp are very similar fibres in all aspects, and their differentiation is often controversial. In this work, the literature is researched for the classic methods of differentiating these two types of fibres. Additionally, a further to twist discrimination methods (the twist test method and the method using polarised light) were analysed. The method most suitable for practical use was tested on a wide spectrum of fibres and compared with the usual methods.Review of analytical methods resulting of literature research .
Microscopic differentiation
The morphological characteristics mentioned in Table 1 can be used for microscopic differentiation of flax and hemp. The observation is mostly oriented towards the observation of the shapes of the fibre’s cross-sections and fibre ends at the longitudinal view. This method is time-consuming (requiring preparations to be prepared), the appreciation of the characteristics observed is rather subjective, and it also requires considerable experience. An advantage is the fact that the shape of the elementary fibres does not change during the processing.
Swelling test
Various morphological structures of flax and hemp are exhibited by the diverse extents of the swelling property of the fibres. in the cuoxam solution. The flax swells uniformly and relatively rapidly, the tube in the non-blanched fibre contracts in a serpentine fashion, and it resists the solvent. The hemp swells slowly; during this process the tube in the raw fibre often obtains a typical periodic-shape. The swelling of the flax and the hemp has been photographically documented by Koch [8] and Felix [9]. For observing fibres it is necessary to use the microscopic technique.
Dyeing tests
Hemp contains more lignin and non-cellulose portions than flax. On this basis, a group of tests has been prepared in which the dyestuff of the agent is e.g. sorbed only by the lignin part of the fibre, for example, or when the agent reacts with the non-cellulose parts of the fibre depending on the colour compound applied. Dyeing tests are especially applicable to raw fibres before eliminating non-cellulose substances from fibres (preliminary finish or otherwise); after their elimination, the fibres will not colour. The methods are easily executed, and their results are apparent by visual evaluation even without microscopic equipment.
Twist tests
Indirect method of determination of fibril slope in the flax and the hemp .
Flax and hemp have different orientations of fibril bundles in the fibre. Indirectly, this fact is verified by the opposing behaviour of flax and hemp in polarised light (as directed from above), and by the possibility of distinguishing the fibres by X-ray diffraction.
From the analytical aspect, the orientation of the fibrils at the hydration and dehydration of lamellas is important. During these processes, changes to the geometry characteristics of the fibril bundles occur. These changes are macroscopically expressed by the fibre’s effort to turn, and so eliminate the internal stress at the sorption (or desorption) of water. Sonntag used this method for the analytical distinction of flax and hemp.
The so-called ‘Twist test’ method for differentiating flax and hemp is founded on this basis, , the merit of which is the observation of the spontaneous twisting of the fibre as it dries. If a wet flax is held by one end and dried, then its free end, which is oriented towards the observer, will turn clockwise. Under the same conditions, hemp will turn round in the opposite direction. The direction of twisting is characteristic for both flax and hemp, whereas cotton fibres twist in various directions during this test. Ramie twists as flax. This process described in literature was modified according to the possibilities of our laboratory and is presented below.
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| Flax Hemp |
Difference Between Flax and Hemp
Differentiating flax and hemp is a long-time analytical problem, which is becoming more and more relevant with the wider loading of bast fibres. Flax and hemp are very similar fibres in all aspects, and their differentiation is often controversial. In this work, the literature is researched for the classic methods of differentiating these two types of fibres. Additionally, a further to twist discrimination methods (the twist test method and the method using polarised light) were analysed. The method most suitable for practical use was tested on a wide spectrum of fibres and compared with the usual methods.Review of analytical methods resulting of literature research .
Microscopic differentiation
The morphological characteristics mentioned in Table 1 can be used for microscopic differentiation of flax and hemp. The observation is mostly oriented towards the observation of the shapes of the fibre’s cross-sections and fibre ends at the longitudinal view. This method is time-consuming (requiring preparations to be prepared), the appreciation of the characteristics observed is rather subjective, and it also requires considerable experience. An advantage is the fact that the shape of the elementary fibres does not change during the processing.
Swelling test
Various morphological structures of flax and hemp are exhibited by the diverse extents of the swelling property of the fibres. in the cuoxam solution. The flax swells uniformly and relatively rapidly, the tube in the non-blanched fibre contracts in a serpentine fashion, and it resists the solvent. The hemp swells slowly; during this process the tube in the raw fibre often obtains a typical periodic-shape. The swelling of the flax and the hemp has been photographically documented by Koch [8] and Felix [9]. For observing fibres it is necessary to use the microscopic technique.
Dyeing tests
Hemp contains more lignin and non-cellulose portions than flax. On this basis, a group of tests has been prepared in which the dyestuff of the agent is e.g. sorbed only by the lignin part of the fibre, for example, or when the agent reacts with the non-cellulose parts of the fibre depending on the colour compound applied. Dyeing tests are especially applicable to raw fibres before eliminating non-cellulose substances from fibres (preliminary finish or otherwise); after their elimination, the fibres will not colour. The methods are easily executed, and their results are apparent by visual evaluation even without microscopic equipment.
Twist tests
Indirect method of determination of fibril slope in the flax and the hemp .
Flax and hemp have different orientations of fibril bundles in the fibre. Indirectly, this fact is verified by the opposing behaviour of flax and hemp in polarised light (as directed from above), and by the possibility of distinguishing the fibres by X-ray diffraction.
From the analytical aspect, the orientation of the fibrils at the hydration and dehydration of lamellas is important. During these processes, changes to the geometry characteristics of the fibril bundles occur. These changes are macroscopically expressed by the fibre’s effort to turn, and so eliminate the internal stress at the sorption (or desorption) of water. Sonntag used this method for the analytical distinction of flax and hemp.
The so-called ‘Twist test’ method for differentiating flax and hemp is founded on this basis, , the merit of which is the observation of the spontaneous twisting of the fibre as it dries. If a wet flax is held by one end and dried, then its free end, which is oriented towards the observer, will turn clockwise. Under the same conditions, hemp will turn round in the opposite direction. The direction of twisting is characteristic for both flax and hemp, whereas cotton fibres twist in various directions during this test. Ramie twists as flax. This process described in literature was modified according to the possibilities of our laboratory and is presented below.
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