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Insect Repellent Textile Finishing using Natural Bio-molecules

Mosquito repellents created with essential oils extracted from aromatic plants found to be an alternative to artificially created mosquito repellents. The article briefs how the textile substrates with mosquito repellent finish provide better protection against mosquito bites.

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Considering the eco-friendliness and biodegradability, essential oils extracted from aromatic plants were found to be best in protection as well, since ancient times, considering the medicinal, insecticidal, and antibacterial effects of the herbs. Basil, cedar, cinnamon, citronellal, garlic, lavender, peppermint are examples of few plants which own very good repellent properties. The essential oils are excreted in aqueous form or could be biosynthesized.

Essential oils extracted from plants contains complex mixtures of volatile organic compounds. Mosquito repellence of plant extracts such as Eucalyptus Oil, Rosemary Oil, and Clove Oil are already been recognized.

Mosquitoes are the reason for transmitting diseases such as dengue, malaria, chikungunya, and so on. The symptoms of mosquito-borne diseases are from mild to severe which cause unpleasant feel, rash, joint pain, muscle pain, conjunctivitis, fever, and deadly disease such as dengue. Thus textile substrates with mosquito repellent finish provide better protection against mosquito bites.

            Plants Plant parts for mosquito repellence Repellent
Basil Leaves Mosquito repellent
Betel Leaves Mosquito repellent
Citronella Grass Leaves Mosquito repellent
Eucalyptus Leaves Repellent to mosquitoes, flies
Garlic Garlic bulbs Repellent to flies, mosquitoes, bug
Lavender Flowers Repellent to flies, mosquitoes, moths
Lemon Grass Leaves Mosquito repellent
Lemon Rind Mosquito repellent
Marigold Flowers Repellent to mosquitoes, flies
Neem Leaves Repellent to mosquitoes, flies
Orange Rind Repellent to mosquitoes, flies
Pepper Mint Leaves Repellent to mosquitoes, bugs
Rosemary Leaves Mosquito repellent
Thyme Leaves Mosquito repellent
Tulsi Leaves Mosquito repellent

Plants with repellence properties

The large extent of plant products such as roots, stem, seeds, flowers, fruits, leaves has been investigated for mosquito repellent properties to be applied to the textiles. Plant extracts such as eucalyptus oil, rosemary oil, and clove oil are recognized for mosquito repellence. Essential oils are extracted from plants which are complex mixtures of volatile organic compounds.

Many essential oils have the repellence property with the existence of lower isoprenoids. Monoterpenes such as citronella, camphor, limonene, thymol are few examples of essential oils that have mosquito repellent property. Natural essential oils such as lemongrass, citronellal grass, lemon eucalyptus oil, eucalyptus oil, peppermint, neem, thyme oil, lavender, holy basil are few products which possess mosquito repellent property. Essential oils such as eucalyptus, Lawsonia inermis leaf extract, Cryptomeria japonica, Nerium oleander L flower extract showed great larvicidal activity against mosquito larvae. Azadiractin, a chemical compound that is present in the seed of the neem tree had been identified for mosquito larvicidal activity.

Photo by monicore from Pexels

Mosquito repellent finishes on fabrics

The main disadvantage of using natural extracts for mosquito repellent finish is all about a lack of durability in the finish. Most of the repellents are removed during washing as they don’t have a permanent affinity on textile substrates. The better way of finishing is microencapsulation and by using inclusion forming compounds like β-Cyclodextrin.

In a research study, thyme oil, cypress oil, and grapefruit oil were taken in the ratio of 2:1:1 and microencapsulated using sodium alginate, Acacia arabica, and Moringa oleifera gum as wall material and applied on 50:50 bamboo/tencel blended fabric using exhaustion method. On which the wall material with Moringa oleifera gum had shown better durability up to 30 washes. It was skin-friendly too.

In other research, wall materials such as gum arabic, chitosan as wall material on microencapsulated citronella oil showed better insect protection on textile finishes up to three weeks when compared to spray technique using ethanol solution of essential oil.

By finishing with chrysanthemum oil nanoemulsion on nylon net fabrics also showed superior mosquito repellent efficiency and better durability up to 25 washes. In another research, citriodiol, a natural resource amalgamated to β-cyclodextrins was finished on cotton fabric, showed durable mosquito repellence. In another study, one option with lemongrass methanol extract and another option with aqueous lemongrass extract was microencapsulated and finishing was given to polyester fabric; in which, finishing with aqueous lemongrass extract microcapsules showed 92% efficiency towards mosquito repellent activity, whereas lemon grass methanol extract microcapsules showed only 80% efficiency towards mosquito repellent activity.

Citronella oil along with lavender oil finishing on cotton fabrics showed the result of mosquito repellence with fragrance. Chemically active components present in botanical compounds could inhibit the biological process of mosquitoes and decrease the problem and spreading of disease associated with mosquitoes.

The cotton and trevira knitted fabrics were treated with eucalyptus oil using a padding method where acrylic-based binder was used. The researcher has concluded that with the field test conducted for analyzing the effectiveness of mosquito repellency, eucalyptus oil extract with 15% and 30% have shown better results. The fragrance of the eucalyptus oil extract was which restricts the mosquitoes.

The field test

In the field test, the observer was allowed to walk for a certain distance and allowed to sense the fragrance and distance travelled was measured. This way the test was carried out for about 5 weeks. It was concluded that the fragrance of the eucalyptus oil decreased over a period which was measured using the distance travelled. It was also concluded that using the superior binders in optimized quantity will, in turn, increase the performance of the finish.

The cotton fabric which was scoured, bleached, dyed was taken for the herbal-based mosquito repellent finish and the researcher had used mint leaves.

  • Fresh mint leaves were collected, dried under the shadow, and ground.
  • The powdered mint leaves were mixed with methanol and kept overnight in an airtight container.
  • After incubation throughout the night, the extract was filtered using filter paper.
  • Then from the extract methanol was evaporated and the mint extract was condensed. The mint leaves extract was taken about 25% and applied on to cotton fabric by the pad-dry-cure method. The processing time was 90 minutes and treated fabric samples were dried for 5 minutes at 90°C.
  • Then the fabric was evaluated for mosquito repellency performance.

For evaluation, the researcher had used a cage box repellency chamber, to conduct the test quickly and it is also cost-effective. A box of size 30cmx30cmx30cm was taken for this test which is made up of transparent glass. The temperature of about 25°C±2°C and 60% to 70% humidity was maintained inside the box.

The test was conducted during daylight. Each test was repeated four times. For evaluating the finish, both treated and untreated fabrics were taken.

  • 20 mosquitoes were collected and dispossessed all nutrition and water, approximately 4 hours before experiencing the test. 20 mosquitoes were sent inside the box and allowed it to stay for about 2 minutes.
  • The number of mosquitoes resting on the untreated and treated fabrics for that 2 minutes time duration were noted.
  • The anti-mosquito effectiveness was calculated. Under the washing test, it was found that the mosquito repellence activity remained up to 9 washes.
  • The finish was applied to the fabric by a direct method, where the extracts were coated on the fabric surface without bonding with the fabric.
  • The coatings on the fabric got removed on repetitive washings. The process with mint leaves finish was effective, inexpensive, eco-friendly and hygiene.

100% cotton fabric was taken and sweet lime peel was used for mosquito repellent finish. Dried and ground sweet lime peels were extracted using methanol. Citric acid was used as a mordanting agent. The finishing was applied with the pad-dry-cure method using different concentrations namely 25%, 30%, 35%, 40%, and 45%.

The concentration of 25% stated that 25 grams of sweet lime peel powder in 100 ml of methanol and the same way for other concentrations as well. The finished samples were tested for mosquito repellence finish, wash durability, tensile strength, thickness, bending length, and crease recovery angle. The optical density of five different concentrations of sweet lime peel powder for mosquito repellency was recorded at 765 nm λ max. The optical density of 40% concentration of sweet lime peel showed a maximum value of 0.93 and thus it was considered to be the best.

With the obtained result, the researcher had kept 40% as optimized concentration and evaluated the mosquito repellency of fabric samples with three different concentrations of extract 40%, 50%, and 60% respectively with padding time 60, 90, 120 minutes for each concentration. Among which 60% concentration of extract at 90 minutes padding time showed 80% mosquito repellency and it was considered to be the optimum one.

The samples were dried at 90°C in a hot air oven for 5 minutes. From the result, the extract concentration of 60% was analyzed further for wash durability and mosquito repellency of samples was mordanted with different concentrations 5%, 10%, and 15% of citric acid. The treatment time was fixed for 30 minutes, 60 minutes, and 90 minutes for each mordant concentration of citric acid respectively. Among the after treatment test results, a 10% mordant concentration of citric acid with 90 minutes of treatment showed better performance. And those samples were cured for 2 minutes at 120°C.

The results of each washing for 10% mordant concentration of citric acid with 90 minutes of treatment showed 80% mosquito repellency on the first two washes, 75% on the third wash, 60% on the fourth wash, 40% with the fifth wash, and 20% with sixth wash respectively.

Mosquito repellent finish was applied to single jersey cotton knitted fabric using the pad-dry-cure method with a commercial binder. In the subsequent stage, a commercial binder was replaced with natural polymer chitosan which is also used as a binder. The fabrics both treated and untreated were analyzed for mosquito repellency using the cage method.

Further tests

Other tests such as wash durability, tensile strength, air permeability tests were also conducted. Test results showed that the increase in the concentration of chitosan, in turn, had increased the tensile strength of the cotton fabric. Both commercial binder and chitosan had shown the same level of air permeability. Chitosan has shown better results on wash durability and mosquito repellence property as well.

Marigold petals were taken for the study and it was treated on white cotton fabric. Methanol, Ethanol was used for extracting the solution and mordanting of curing samples. The spectrophotometer was used to measure the mosquito repellency of optimizing concentrations (5%, 10%, 15%, 20%, and 25%) with the base of optical density.

Once optimization was done, marigold petals were extracted using methanol. Then the extract was diluted into three different concentrations namely 25%, 50%, and 75%. The fabric was dyed with extract for about 60, 90, and 120 minutes respectively. The samples were cured and mordanted with citric acid of 5%, 10%, and 15%.

Then the finished samples were tested for mosquito repellency and wash durability. Pad-dry-cured samples were tested with the cage box test for mosquito repellency. Research has shown the optimum result for optical density with 20% of marigold petals. Hence it was considered for finishing. The mosquito repellency test has shown the best results with a 25% concentration of marigold petal extract, dyeing time of about 120 minutes. The fabric samples mordanted with 10% citric acid concentration for 20 minutes showed better wash durability up to 10 washes.

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