The summer season causes discomfort to people in many ways. Therefore, comfortable clothing forms an integral part of a summer season wardrobe. An interaction of the clothing with the natural surroundings or environment plays an important role in the feeling of comfort. Clothing may have several physical and aesthetic characteristics that may affect the feeling of comfort in various degrees such as heaviness, thickness, thermal transmission or heat transfer, air permeability, moisture absorbency and moisture diffusion, handle and texture, ease of movement (flexibility), drape, etc. It may have aesthetic aspects such as colour, lustre, fashion, style, and fit along with the user’s geographical, social, religious and other beliefs or requirements that affect the use of certain kinds of clothing.

When summers are approaching, fashion designers and producers get busy developing products using the two most important summers fibres—cotton and linen. Cotton and linen are the two cellulosic based natural fibres that find great use and adaptability during summers worldwide. These fibres are naturally cool, extremely soft and comfortable for the wearer. So, which are the important properties that make these textile fibres summer friendly?

Cotton (genus Gossypium)

Cotton fibres grow naturally as fluffy balls of fibres around a cotton seed. These account for the largest bulk of the short-staple spun yarn market. India is the largest producer of conventional cotton fibre in the world accounting for about 22 per cent of the world cotton production. Indian cotton is known as Gossypium Arboreum. Cotton can also be grown organically, i.e., without the use of pesticides or harmful chemicals. Such cotton can be used for making clean clothing. India is the largest source of organic cotton fibre production, and it accounts for about 51 per cent of global organic cotton production.

To understand what makes cotton very desirable for summers, some of its physical and chemical properties are discussed below.

Physical Properties of Cotton

  • Staple length – Staple length is the minimum length of fibre that can be spun into a yarn. Indian cotton has a staple length of 2-2.5cm. The Egyptian cotton is the best variety of cotton with a staple length of around 3.8 cm to 4.4 cm. A higher staple length produces a more uniform yarn with great lustre, strength and durability.

  • Porosity – Cotton fibres are porous and exhibit capillary effects due to the hollow lumen present at its core. Due to this property cotton absorbs a great amount of moisture, perspiration and water.

  • Lustre – Cotton fibres have less lustre due to their convoluted shapes and short staple lengths. Therefore, they are treated with sodium hydroxide solution, also known as mercerisation, to have a good lustre. Mercerisation results in removal of twists in the fibre and attaining an almost circular cross-section. This helps the fibre to reflect light better and develop more lustre. It also enhances the fibre strength, absorbency and smoothness.

  • Moisture Regain Capacity – Due to its fibre imperfections, cotton fibres have good moisture regain (MR) capacity and absorbency. The moisture pick-up depends on the atmospheric temperature and relative humidity (RH) in the atmosphere. Cotton has 8.3 per cent MR at 220C and 65 per cent RH.

  • Strength – It is the load required to break the fibre. Tensile strength of cotton fibres varies widely and depends on the fibre maturity and thickness, atmospheric humidity and MR capacity. Average strength of fine and intermediate types of fibres varies from 4 gm to 9 gm per fibre.

  • Elongation – When load is applied, cotton fibres have the ability to increase in length up to around 6-8 per cent with respect to its original length. This is very low as compared to wool fibres. Cotton has less elongation and poor elasticity property.

Chemical Properties of Cotton

Cotton is primarily a cellulosic fibre consisting of small amounts of moisture, fatty acids, minerals, proteins, pectin, oils and waxes and natural colouring substances. Therefore, its chemical properties are affected by the chemical composition and cellulose content in the fibres.

  • Heat – Cotton catches fire easily and burns at around 2100C with a smell of burning paper. The fibre continues to burn even after removing it from the source of fire. After the flame is extinguished, it continues to smoulder and smoke. It is a very typical test for cellulosic fibres.

  • Scorching – Prolonged exposure of cotton to heat or fire above 1500C leads to a brown colouration in the fabric. This causes tendering due to the formation of oxycellulose. It affects the bleaching effect on the fabric. The fabric loses strength and durability.

  • Light – Light in presence of atmospheric air causes tendering when cotton is over exposed due to formation of oxy-cellulose. Colour fading of dyed cotton fabrics may occur under certain light conditions.

  • Water – It is very difficult to wet un-scoured cotton fibre due to the presence of wax on it. After scouring cotton fibres can easily become wet. Cold water can help to remove twists/convolutions in cotton fibres.

  • Micro-organisms – Many micro-organisms and fungi cause mildew that leads to discolouration and weakening of cotton fibres.

  • Acids – Cold dilute acids have no effect on cotton. However, if the acid solution is not completely washed out before drying, then it can lead to tendering in the cellulose material. Cold concentrated sulphuric acid dissolves cellulose completely and forms cellulose hydrate. This technique is used to make parchment paper to give it a transparent effect. Hydrochloric acid affects cotton much more severely than sulphuric acid.

  • Alkalis – Cotton is resistance to alkali solutions. Dilute solution of strong alkalis like sodium hydroxide (2-7 per cent) can be used for scouring process (removal of oil and wax) of cotton fibres. This helps the fibres to absorb water and other solutions well. It improves the dye uptake capability of cotton. Strong alkalis with higher concentration (7-15 per cent)like sodium hydroxide are used for inducing structural and physical changes in the cotton fibres like de-convolution of cotton fibres. The fibre swells and appears more round, thereby reflecting more light in a uniform manner. Cotton is severely attacked and degraded by strong hot alkalis in the presence of atmospheric oxygen/air.

  • Mercerisation – Fibre properties of cotton can be enhanced by the process of mercerisation where cotton—at any stage of fibres/ yarns/ fabrics—is treated with caustic soda (sodium hydroxide) or caustic potash (potassium hydroxide) at about 7-15 per cent concentration. It improves the evenness (even diameter) of the fibre throughout its length. It leads to shrinkage in yarn due to the swelling. It improves lustre (due to better light reflection), tensile strength, dye-ability and uniform dyeing properties, dimensional stability, better fabric cover, elasticity and stretch ability, smoothness and even texture.

Desirable Properties of Cotton Fibres

•   Cotton fabrics have a soft handle, light weight, and good drape. They are strong and durable, inexpensive, and easily biodegradable.

•   Cotton absorbs body sweat effectively due to its porosity and absorption capacity.

•   It does not cause any skin irritation or inflammation due to wear.

•   It does not heat up rapidly during wear and keeps the wearer cool.

•   It is breathable and therefore allows the body heat to pass through making the wearer feel cool and comfortable.

•   It is hypoallergenic, non-toxic and skin-friendly.

•   It does not produce static electricity due to its moisture regain capacity.

•   It does not have pilling problems.

•   Low maintenance cost.

•   It has high wet modulus (stronger when wet).

•   Due to its lumen, it has high wicking properties.

•   Easy perspiration absorption property.

•   Comfortable to wear in all seasons.

•   Cotton can be blended with other fibres like rayon, silk, polyester, etc to manufacture fabrics for different purposes.

•   Due to its non-toxicity and high absorbency, it has greater use as a medical textile as well.

Therefore, due to the above desirable properties cotton is mostly preferred during summers. However, colour fading, wrinkle formation, bacteria or mildew formation, poor elasticity and resiliency, less lustre, scorching effect, and dust acquiring properties are some of the undesirable properties of cotton. Proper care, regular washing and use of better-quality dye materials, anti-crease finish and anti-bacteria finish can reduce these properties in cotton. It is most desirable for making jerseys or T-shirts, kids’ clothes, innerwear, medical textiles, kitchen apparels and accessories, industrial usage, home furnishings, etc.

Linen

Linen or flax fibre is found in the stem or stalk of the flax plant. It is a cellulose based bast fibre. It grows in moist and cold conditions. It is older than cotton fibres. The flax fibre is extracted through the method of retting. The longer fibres are used to make apparels while shorter fibres are used to make ropes, twines and rug backings. Fibre length varies between 2 inches to 36 inches. Belgian linen from Europe is considered as gold standard. It is much stronger than cotton and can withstand more wear.

Desirable Properties of Flax Fibres

•   Linen is one of the strongest natural fibres that retains its shape, size and looks for a very long period.

•   It has good strength and natural shine.

•   It has very delicate and soft textures.

•   Moisture regain capacity is 12 per cent under normal atmospheric conditions.

•   It is hydrophilic in nature and gains about 8-10 per cent strength when wet.

•   It has good lustre and is stronger and more durable than cotton.

•   It is anti-static in nature due to its moisture regain capacity and better wicking property.

•   It has temperature regulating properties and provides greater comfort. It feels cooler in summers and warm in winters.

•   Gives a light airy feeling.

•   It has quick drying capacity and is easy to wash and dry clean.

•   It has no pilling issues and does not gain dust easily.

•   It is ultra-hygienic and odour resistant.

•   It is breathable and soft.

•   It gets softer and shinier over time.

•   It is antibacterial and odour resistant.

•   It is hypoallergenic and skin friendly.

•   It is eco-friendly and has lower carbon footprint compared with cotton.

•   It is completely bio-degradable and eco-friendly.

These properties make linen an ideal material for use during summers. However, the fibre has a few undesirable properties like lesser durability than cotton, poor drape, poor elasticity and resiliency; expensive and higher maintenance cost; scorches easily under sunlight; wrinkles easily and severely; colour frosting happens on the edges; repeated creasing at the same place weakens the fibres and damages the fabric. But it still has a great demand and is used in multiple products like fashion apparel, sleepwear, undergarments, bath and beach towels, table clothes, napkins and runners, upholstery, curtains, bed linens and many soft furnishing items. In fact, linen fabric is very much in trend today.

Other Fibres

There are many other commonly used textile fibres like the naturally available protein-based fibres, regenerated fibres and synthetic fibres.

Silk and wool are two important protein-based fibres. Silk is obtained from silkworms and wool is obtained from sheep. Mulberry silk is the most commonly used silk for commercial purposes, while Merino wool is one of the best varieties of wool.

Silk is a long length filament fibre with a protein-based structure. It is the thinnest natural fibre and has good strength, high lustre, luxurious drape and hand and generates rich colours on dyeing. Therefore, it is a very expensive fibre. Silk is hydrophilic in nature, does not pill on wear, moisture regain is 9 per cent (degummed silk). It is a poor conductor of heat and electricity and provides great warmth to the wearer by trapping the body heat inside. So, silk cannot be worn in summers. In addition, the fibre has many undesirable properties like – it acquires water spots and perspiration marks; colour crocking happens at creases and folds; losses strength when wet; attacked by moths; affected by moisture; absorbs body oils and odours; affected by alkali-based detergents; needs to be mostly dry cleaned resulting in high maintenance cost.

Wool provides warmth due to its serrated molecular structure. The fibres are in coils and therefore have spaces to hold air. This structure traps the internal body heat and makes the wearer feel warm. It loses its shape when wet. It does not dry quickly, and its handle and texture are greatly affected by normal alkali-based detergents. It has good absorbency capacity but does not provide a cool feeling to the wearer, making it uncomfortable to wear in the summer season.

Several synthetic fibres like polyester, nylon, acrylic, and others are also used to make fabrics that are light weight with good drapability, very good strength and good abrasion resistance to wear. They can be washed and dry cleaned easily with low maintenance cost. These fibres have excellent resiliency and good elasticity, are easy to wash and care, crease resistant, soft handle, dimensionally stable, very durable and have quick drying properties. They are also resistant to moths, oils, weather conditions and chemicals. However, the fibres are majorly hydrophobic in nature, and have extremely poor moisture regain capacity, due to which they develop static electricity during wear. Further, stain removal is difficult as these fibres do not absorb water and detergent. These fibres also absorb body oils and perspiration odour. Under very high temperatures the fibres melt and drip and can stick to the body resulting in extensive damage. These fibres form pills on the fabric and attract lint which affects the shine, lustre and aesthetic value of the fabric or garments. But these fibres provide warmth to the wearer.

Therefore, fibres should be carefully chosen to make season specific products. The above discussion clearly highlights the fact that cotton and linen are most suitable for summers and can provide greater comfort to the wearers. Even though linen is expensive and creases heavily, it is widely used to make apparel due to its comfort properties, aesthetics and fashion values. Cotton has always been the summer fibre due to its properties that make it the most desirable textile fibre.