In a relatively simple form, a microcapsule is a small sphere with a uniform wall around active core material. The material inside the microcapsule is referred to as the core, internal phase or active, whereas the wall is sometimes called a shell, coating or membrane. It protects the inside core of actives from environmental conditions like temperature, oxidation, degradation and volatilization with time.
The reasons for microencapsulation are countless. It is mainly used to increase the stability and life of the active being encapsulated, facilitate the manipulation of the active and control its liberation in an adequate time and space. In some cases, the core must be isolated from its surroundings, as in isolating actives like essential oil extracts from the deteriorating effects of oxygen, retarding evaporation of a volatile core, improving the handling properties of a sticky material, or isolating a reactive core from chemical attack. In other cases, the objective is not to isolate the core completely but to control the rate at which it leaves the microcapsule, as in the controlled release offragrances or drugs or pesticides. The problem may be as simple as masking the taste or odour of the core, or as complex as increasing the selectivity of an adsorption or extraction process. In environmental sciences, pesticides, insecticides, bactericides, fungicides need to be microencapsulated to minimize leaching or volatilization risks.
The other reason for microencapsulation lies in the fact that it is a perfect technique for developing insecticides, fungicides and pesticides which are more environment friendly and therefore, more sustainable. An ideal insecticide, fungicide or pesticide is one which is very specific in activity against a target organism, is effective at low dosages and when the action is over is quickly degraded in the environment. However, the very idea of quick degradation of the active in the environment works against its usage and that is where microencapsulation helps.
Microencapsulation helps in targeted release of this ideal active to the time or place where it is required most and then the active quickly degrades. Thus, microencapsulation brings about sustainability benefit in these applications. We have seen typically that actives which are very effective and very stable in the environment; for example, tin salts and DDT, start building up as environmental residues and eventually need to be banned. Microencapsulation allows use of otherwise environmentally degraded actives in a safe manner.
Benefits of Microencapsulation
This technology is helpful to deliver
- lo
ng lasting effect of the active with a control release at a stage where it will have the best effect; for example, fragrances on dry fabric after wash and not during wash only - reduced dosing frequency and amount needed of pesticides/insecticides
- Slow release of antibacterial, antimicrobial, antifungal, fragrance actives
- Non leaking phase change materials coatings for automotive interiors or construction/building
- UV absorbers or reflectors for military applications
- Slow release cooling agents, Insect repellents and thermochromic inks on a micron scale
- Antimicrobials which stops the growth of microbes on surfaces like fabric, paper, wood, cardboard, carpet and curtain
For the hospitality industry, microencapsulation allows us to deliver actives to fabric surfaces which remain even after washing and tumble drying or to deliver actives which last for a very long time like on surfaces near the pool or gardens which are prone to humid/severe conditions. Thus, we can deliver long lasting actives like fragrance or essential oils to fabric surfaces eventually delighting our end consumers as well as deliver antimicrobials to protect our staff’s health from unhealthy bacteria and fungus. Microencapsulation helps deliver very effective low dosage antifungals to take care of mildew and moulds on carpets and upholstery, neutralizing these microbes at source.
Types of Microencapsulation
Typically, two types of Microencapsules are prevalent for various non-food/pharma uses:
- Water Soluble Matrix type microcapsules: Here the active is embedded in the wall of the capsule resembling a sponge structure. Typical active loading achieved are of 40-55%. It is a dry powder with 30-80μ mean particle size. Release of active happens when this dry powder comes into contact with water.
- Water Insoluble, Shell & Core functional microcapsules with high temperature (160- 250°C) resistance, pH resistance and leakage resistance. These give triggered release through burst or diffusion. Temperature activation can be designed for specific applications. Typical active loading achieved is of 80-95%. Mean Particle size ranges between 5-15μ. They are typically delivered in a water dilutable slurry form which can be a proprietary mix of surfactants, capsules etc. Types of Microencapsulation Capsules showing burst release on fabric
Effort is not only required in making the best microcapsules suitable to the application but also integrating these capsules into the final product which will be used, e.g. shampoo, liquid detergent or cationic, in ready to use format.
Applications and Uses
In the use of product, the capsules get attached to fabric or fibre and give burst release of actives after friction, abrasion or rubbing.
The applications and uses of microencapsulation are numerous. The mentioned below are some of the most common ones.
- Textiles
- Adhesives
- Fragrances
- Slow release Antibacterial
- Heat resistant Antifungal
- Heat resistant /slow release Antimicrobial
- Thermochromic ink
- Phase change material
- Carbonless copy paper
- E-paper or e-ink
- Essential oils, Flavours and other volatile bioactives for food or in Feed additives
- Insecticides, Pesticides and herbicides
- Powder perfume
- Scratch-n-sniff
- Insect Repellents
- Thermochromic dyes and inks
- Time release technology for pharmaceuticals
- Visual indicators and brighteners
- Pigments and Dyes
- Self healing coatings & paints
- Slow release Fungicide
- Slow release Antistatic agents
- Long lasting dry delivery of fragrances
- Fabric softener actives
- Hard surface cleaning actives
- Skin and/or hair conditioning agents
- UV protection agents
- Animal/vermin repellants
- Flame retardants
- Temperature release (controlled release)
Vineet Mital,
MD, Tanishka Products
