46
2 Review of Literature: Motorcycle helmet
2.14.4 Chemical Techniques
In this process of encapsulation, there is a reaction between the aqueous solutions
of cationic and anionic polymers such as gelatine and gum arabic. These polymers
generate a concentrated phase known as complex coacervate. The coacervate exists
in equilibrium with a dilute supernatant phase. Thin films of the polymer coacervate
coat the dispersed droplets of core material, when water-immiscible core material is
introduced into the system. The capsules are then made harvestable by solidifying
the thin films and can be used to produce capsules for carbonless paper and other
similar applications.
2.14.4.1 Mechanical/Physical Techniques
The mechanical microencapsulation technique was developed in the 1930 s. In this
technique, an emulsion is prepared by dispersing the core material, usually an oil or
active ingredient immiscible with water, into a concentrated solution of wall material
until the desired size of oil droplets is attained. The resultant emulsion is atomised
into a spray of droplets by pumping the slurry through a rotating disc into the heated
compartment of a spray dryer. There, the water portion of the emulsion is evaporated, yielding dried capsules of variable shapes containing scattered drops of core
material. The capsules are collected through continuous discharge from the spray
drying chamber. This method can also be used to dry from aqueous slurry small
microencapsulated materials that are produced by chemical methods.
2.14.5 Applications of Microencapsulation
There are numerous applications of microencapsulated materials in different areas
such as agriculture [243], pharmaceuticals, cosmetics, heat storage systems for buildings [218, 244], textiles [175, 177, 183], paints, adhesives and many other industries.
In the textile industry, the microencapsulation process is used to enhance the properties of finished materials. There are many applications of fibres and fabrics containing
microencapsulated PCM such as active/outdoor wear, sports apparel, footwear for
comfort and protection from cold, protective clothing, bedding and furnishing. Other
applications include insect repellents, dyes, vitamins, antimicrobial agents, durable
fragrances and skin softeners.
Microcapsules are also used in various other applications such as carbonless copy
paper, pesticides and scented strips [245]. In the food industry, microencapsulation
is used to protect, isolate or control the release of a given substance [246]. Several
researchers have applied the process of microencapsulation for the formation of inks
for ink-jet printers [247, 248]. Hong and Park [249] prepared microencapsulated
melamine-formaldehyde systems containing fragrant oil and applied to them cotton
2 Review of Literature: Motorcycle helmet
2.14.4 Chemical Techniques
In this process of encapsulation, there is a reaction between the aqueous solutions
of cationic and anionic polymers such as gelatine and gum arabic. These polymers
generate a concentrated phase known as complex coacervate. The coacervate exists
in equilibrium with a dilute supernatant phase. Thin films of the polymer coacervate
coat the dispersed droplets of core material, when water-immiscible core material is
introduced into the system. The capsules are then made harvestable by solidifying
the thin films and can be used to produce capsules for carbonless paper and other
similar applications.
2.14.4.1 Mechanical/Physical Techniques
The mechanical microencapsulation technique was developed in the 1930 s. In this
technique, an emulsion is prepared by dispersing the core material, usually an oil or
active ingredient immiscible with water, into a concentrated solution of wall material
until the desired size of oil droplets is attained. The resultant emulsion is atomised
into a spray of droplets by pumping the slurry through a rotating disc into the heated
compartment of a spray dryer. There, the water portion of the emulsion is evaporated, yielding dried capsules of variable shapes containing scattered drops of core
material. The capsules are collected through continuous discharge from the spray
drying chamber. This method can also be used to dry from aqueous slurry small
microencapsulated materials that are produced by chemical methods.
2.14.5 Applications of Microencapsulation
There are numerous applications of microencapsulated materials in different areas
such as agriculture [243], pharmaceuticals, cosmetics, heat storage systems for buildings [218, 244], textiles [175, 177, 183], paints, adhesives and many other industries.
In the textile industry, the microencapsulation process is used to enhance the properties of finished materials. There are many applications of fibres and fabrics containing
microencapsulated PCM such as active/outdoor wear, sports apparel, footwear for
comfort and protection from cold, protective clothing, bedding and furnishing. Other
applications include insect repellents, dyes, vitamins, antimicrobial agents, durable
fragrances and skin softeners.
Microcapsules are also used in various other applications such as carbonless copy
paper, pesticides and scented strips [245]. In the food industry, microencapsulation
is used to protect, isolate or control the release of a given substance [246]. Several
researchers have applied the process of microencapsulation for the formation of inks
for ink-jet printers [247, 248]. Hong and Park [249] prepared microencapsulated
melamine-formaldehyde systems containing fragrant oil and applied to them cotton