Preparation of Mosquito Repellent Fabrics
A mosquito repellent substrate includes a fabric which is impregnated with a repellent carrier composition. The carrier composition includes a mosquito repellent (e.g. permethrin, prallethrin etc.), binder, emulsifier and cross linker. The carrier composition is applied as a finish or printed onto the fabric.
1.1 About Mosquitoes
Mosquito-borne diseases, such as malaria, dengue fever and yellow fever, have plagued civilization for thousands of years. There are many kind of mosquitoes, each of which has a different habitat, behavior and preferred source of blood. About ten of these species are so numerous, and such vicious biters of man and animals, that an organized mosquito control is necessary because mosquitoes are not a nuisance as biting insects, but are also involved periodically in transmitting disease to humans and animals. Only female mosquitoes bite. When adult mosquitoes emerge from the aquatic stages, they mate, and the female seeks a blood meal to obtain the proteins for the development of her eggs. After a blood meal is digested and the eggs are laid, the female mosquito depending on her stamina and the weather may repeat this process many times without mating again. They usually feed every 3 to 4 days; in a single feeding, a female mosquito typically consumes more than its own weight in blood. Male mosquitoes feed primarily on flower nectar. He lives for only a short time after mating. Certain species of mosquitoes prefer to feed at twilight or nighttime; others bite mostly during the day. Mosquitoes home in on people because they are giving off carbon dioxide, lactic acid, body odor and also heat. Mosquitoes use carbon dioxide and lactic acid like sign posts to our body - following them until they find our skin and they bite us.
1.2 About Mosquito Repellents
Permethrin is a human-made synthetic pyrethroid. It does not repel insects but works as a contact insecticide, causing nervous system toxicity that leads to the death or "knockdown" of the insect. The chemical is effective against mosquitoes, flies, ticks, and chiggers. Permethrin has low toxicity in mammals, is poorly absorbed by the skin, and is rapidly inactivated by ester hydrolysis. Density: 1.19 g/cm³
Chemical Formula: C21H20Cl2O3
Boiling Point: 200°C
Prallethrin is also a pyrethroid. It works on the same principle as permethrin. It has been found to be more effective on Indian mosquitoes than permethrin. 1.2.3 DEET
DEET is N,N-Diethyl-m-toluamide. It works by evaporation, creating a shield a few inches above the area of application. The repellent vapor confuses mosquito so they can’t locate a target host.
1.2.4 Eucalyptus oil
It works on the same principle as DEET.
The main aim is to fix one or a combination of the above mentioned mosquito repellents to the fabric.
All the above mentioned repellents have no affinity for fabrics as such, so a system was required to keep them attached to the fabric. Also the system was required to withstand repeated washing. The prepared fabric should have the desired level of efficacy against mosquitoes and it should last even after repeated washings.
Samples were prepared using permethrin, prallethrin and eucalyptus oil using various combinations of their concentrations and methods of fixing. The various recipes used are mentioned below. 4.1 Recipe I
With Eucalyptus as Mosquito Repellent
Binder – 6%
Eucalyptus oil – 2%
DAP (Di-ammonium Phosphate) – 1%
Water – 91%
Initially, the samples were padded in the padding mangle and then dried at 80oC. Then curing was done at 120oC. But, the smell of eucalyptus oil, which is the main factor in repelling mosquitoes was found to be absent from the samples. Hence, the process was modified...
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