Physical and Chemical Properties of Linen

Last updated on October 17th, 2023 at 11:56 pm

Linen or Flax is a bast fibre taken from the stalk of the plant linen usilatissimum. Fibre processed into yarn or fabric is known as linen.

Physical Properties of Linen

Length: Flax is a long fibre running from 6-40” but averages 15-25”. Due to its length it is not essential to spin the fibres, although they can be spun lightly to hold the ends in. Flax is a very strong fibre due to its very crystalline polymer system allows its very long polymers to form more hydrogen bonds than cotton polymers. It is one of the few fibres which gains strength when wet. This is due to the temporary improvements in polymer alignment in the amorphous regions of the polymer system. The improved alignment brings about an increased hydrogen bonds and consequent tenacity.

Elastic plastic nature: The inelastic nature of flax is because of its great crystalline structure. Its polymers get locked into position by the hydrogen bonds which are formed between the polymers. Hence the polymers cannot yield and resist displacement. This crystalline polymer system gives the flax stiffness. Flax creases and wrinkles easily since when folded the polymer tends to break.

Hydroscopic nature: Flax is very absorbent because of innumerable polar OH groups in its polymers. These attract water molecules which are also polar. The water can only enter the polymer system in its amorphous regions, as the inter polymer spaces in the crystalline regions are too small for the water molecules. The hydroscopic nature prohibits the development of static electricity.

Thermal properties: Flax with its very long polymers has the best heat resistance and conductivity of all the commonly used textile fibres. It is not thermoplastic and burns without melting.

Chemical Properties of Linen

Effects of alkalis: Resistant to alkalis and comparatively unaffected by normal laundering. The resistance is because of the lack of attraction between the flax polymers and alkalis.

Effect of Acids: Weakened and destroyed by acids. Acids hydrolyze the flax polymer at the glycosidic oxygen atom which connects the two glucose units to form the cellobiose unit. Mineral acids being stronger than organic acids will hydrolyse the flax polymer more quickly.

Effect of Bleaches: The most common bleaches used on linen textile materials are sodium hypochlorite and sodium perborate. They are: oxidizing bleaches and bleach because of the oxygen liberated from them.

Effect of Sunlight and weather: The ultra-violet rays of sunlight provide photo chemical energy whilst the infra-red rays provide heat energy essential to degrade the linen polymers in the pressure of atmospheric oxygen, moisture and air pollutants. The breakdown of polymers takes place through diverse hydrolysis reactions. The beginning degradation is noticed as a slight fibre discoloration. Fading of colored flax textile is partially because the breakdown of the dye molecules in the fibre’s polymer system.

Color Fastness: Flax is easy to dye and print. The classes of dye which may be used to color flax are azoic, direct, reactive, sulphur and vat dyes. The polar polymer system easily attracts any polar dye molecules into the polar system. Therefore, dye molecules which can be dispersed in water will be absorbed by the polymer system of flax.

However, the dye molecules can enter solely the amorphous regions of the polymer system of flax. The small inter polymer spaces in the crystalline regions of the polymer system prohibit the entry of the crystalline molecules.

Mildew: Flax is damaged by fungi. Heat and dampness support the growth of mildew. The fungi produce a chemical compound which has the power of changing cellulose to glucose. The fungi feed on the molecules of sugar: Flax treated with acrylo nitrite is resistant to mildew.

Insects: Moths and beetles do not change flax. Silver fish will eat flax cellulose especially if heavily starched.