DIFFERENCES BETWEEN HEMP AND FLAX IN A CHEMICAL AND DYEING TESTS

Olha Sumska,
PhD (Engin.), Associate Professor
Yuliia Feshchuk,
Postgraduate student
Kherson National Technical University, Ukraine, Kherson

Differentiating hemp and flax is a long-time analytical problem, which is becoming more relevant with the wider loading of bast fibers. Hemp and flax are very similar fibres in all aspects, and their differentiation is often controversial. Vegetable fibers were often not morphologically specific to species [1-2].
In this work, chemical and dyeing methods were analyzed. Under the influence of chlorzinciod, flax fibers are painted in a pinkish-violet color, and hemp is uneven in yellow-violet. Fluoroglycine stains flaxen fibers in a lilac color, and hemp stains in light pink. When exposed to the test samples with a chromium mixture (Hanaucek reaction), flax fibers swell quickly, forming segments, into which they gradually disintegrate.
When flax dissolves in Schweizer's reagent along the entire length of the fiber, constrictions located parallel to each other form on both sides of the fiber, which, as they swell, are compressed to the center and separated in the form of segments. The narrow channel takes on a tortuous shape. Hemp fibers under the influence of Schweizer's reagent, on the contrary, swell unevenly along the entire length, forming swellings and constrictions, acquire wave-like folding and become like beads. In this case, the transverse lamination (strips of bright colors) is preserved. The ends of the fibers swell, expand, align and take the form of a bouquet.
Linen is immersed in a 1% solution of fuchsine in alcohol to give red rose color. Later they are washed and immersed into ammonia, linen retains the red coloration [3].
The tested methods of differentiating flax and hemp based on the orientation of fibril bundles  are reliable and fast. Their basis does not depend on the degree of fibre treatment. These methods also have minimal demands on the laboratory equipment and staff.

The work investigated 5 unidentified textile samples. The results of the action of chlorzinciod on the samples are shown in the figure.

By the methods of chemical analysis (color reactions) it was established: the raw material composition of samples 1, 3, 4, 5 - hemp fiber. Sample 2: warp yarn - hemp fiber, weft yarn - flax fiber (under the microscope, clear polygonal fragments were not identified in the lumbar section; under the influence of chlorzinciod, the fibers were colored pink-violet, which is typical for flax fiber, when stained with a dye, it was directly pure the blue color is less intense than hemp fiber and there is no staining.
The tested methods of differentiating hemp and flax based on the chemical and dyeing tests have minimal demands on the laboratory equipment and staff.
1. Jakub Wiener, Vladimír Kovačič, Petra Dejlová. Differences between flax and hemp// AUTEX Research Journal Vol. 3, No2. URL: http://www.autexrj.org/No2-2003/0053.pdf/ (Last accessed: 23.03.2020) [in Ukraine]
2. Martha Goodway. Fiber identification in practice. URL: https://repository.si.edu/bitstream/handle/10088/42791/mci19684.pdf?sequence=1&is  (Last accessed: 26.03.2020) [in Ukraine]
3. Site of journal «Identification of textile fibers». Chemical test. URL: https://www.slideshare.net/huzaifa95/identificationoftextilefibers140826074254phpapp01-1-2  (Last accessed: 26.03.2020) [in Ukraine]