Microencapsulation Techniques


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Microencapsulation Techniques, methods and applications in Textiles

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Microencapsulation Techniques

  1. 1. Finishing usingMicrocapsules
  2. 2. Microcapsules - DefinitionIt is the process by which individual particlesor droplets of solid or liquid material (thecore) are surrounded or coated with acontinuous film of polymeric material (theshell) to produce capsules in the micrometerto millimetre range, known as microcapsules.
  3. 3. Microcapsules - MorphologyDepends mainly on the core material and the deposition process ofthe shell.Mononuclear (core-shell)microcapsules contain theshell around the core.Polynuclear capsules havemany cores enclosedwithin the shell.Matrix encapsulation in whichthe core material is distributedhomogeneously into the shell material.In addition, microcapsules can also be mononuclear with multipleshells, or they may form clusters of microcapsules.
  4. 4. Microcapsules – CoatingCoating materials for the Shell- properties requirements•Stabilization of core material.•Inert toward active ingredients.•Controlled release under specific conditions.•Film-forming, pliable, tasteless, stable.•Non-hygroscopic, no high viscosity, economical.•Soluble in an aqueous media or solvent, or melting•The coating can be flexible, brittle, hard, thin etc.
  5. 5. Microcapsules – CoatingCoating materials:•Gums: Gum arabic, sodium alginate, carageenan.•Carbohydrates: Starch, dextran, sucrose•Celluloses: Carboxymethylcellulose, methycellulose.•Lipids: Bees wax, stearicacid, phospholipids.•Proteins: Gelatin, albumin.
  6. 6. Microcapsules - Benefits1- microorganism and enzyme immobilization: - Enzymes have been encapsulated in cheeses to accelerate ripening and flavor development. - The enzymes are protected from low pH and high ionic strength in the cheese. • The encapsulation of microorganisms has been used to improve stability of starter cultures2- Protection against UV, heat, oxidation, acids, bases (e.g.colorants and vitamins). e.g. Vitamin A / monosodium glutamate, appearance (white) protection (water, T, ligth)3- Improved shelf life due to preventing degradative reactions (dehydration, oxidation).4- Masking of taste or odours.
  7. 7. Microcapsules - Benefits5- Improved processing, texture and less wastage of ingredients. • Control of hygroscopy • enhance flowability and dispersibility • dust free powder • enhance solubility6- Handling liquids as solids7- Delivering Nutritious foods for children which provides them with much needed vitamins and minerals during the growing age. Microencapsulation could deliver the much needed ingredients in children friendly and tasty way.8- Enhance visual aspect and marketing concept.9- Carbonless copy paper - A coating of microencapsulated colorless ink is applied to the top sheet of paper, and a developer is applied to the subsequent sheet. When pressure is applied by writing, the capsules break and the ink reacts with the developer to produce the dark color of the copy.
  8. 8. Microcapsules - Benefits10- Textile industry makes use of microencapsulated materials to enhance the properties of finished goods. One application increasingly utilized is the incorporation of microencapsulated phase change materials (PCMs). Phase change materials absorb and release heat in response to changes in environmental temperatures. When temperatures rise, the phase change material melts, absorbing excess heat, and feels cool. Conversely, as temperatures fall, the PCM releases heat as it solidifies, and feels warm. This property of microencapsulated phase change materials can be harnessed to increase the comfort level for users of sports equipment, clothing, building materials, etc.
  9. 9. Microcapsules - Benefits11- Pesticides are encapsulated to be released over time, allowing farmers to apply the pesticides less amounts than requiring very highly concentrated and toxic initial applications followed by repeated applications to combat the loss of efficacy due to leaching, evaporation, and degradation.12- Ingredients in foods are encapsulated for several reasons• Most flavorings are volatile; therefore encapsulation of these components extends the shelf-life of these products• Some ingredients are encapsulated to mask taste, such as nutrients added to fortify a product without compromising the products intended taste.• Alternatively, flavors are sometimes encapsulated to last longer, as in chewing gum.
  10. 10. Microcapsules - Benefits13- Controlled and targetted release of active ingredients.• Many varieties of both oral and injected pharmaceutical formulations are microencapsulated to release over longer periods of time or at certain locations in the body.• Aspirin, for example, can cause peptic ulcers and bleeding if doses are introduced all at once. Therefore aspirin tablets are often produced by compressing quantities of microcapsules that will gradually release the aspirin through their shells, decreasing risk of stomach damage.14- Microencapsulation allows mixing of incompatible compounds.
  11. 11. . Microcapsules - Technologies
  12. 12. Microcapsules - Processes with their relative particle size rangesPhysico - Chemical Processes Physico - mechanical ProcessesCoacervation (2 - 1200 um) Spray-drying (5 - 5000 um)Polymer-polymer incompatibility Fluidized- bed technology (20-(0.5-1000 um) 1500 um)Solvent evaporation (0.5-1000 Pan coating (600 - 5000 um)um)Encapsulation by supercritical fluid Spinning disc (5 - 1500 um)Encapsulation by Polyelectrolyte Co-extrusion (250-2500multilayer (0.02-20 um) um)Hydrogel microsphere Chemical Processes Interfacial polymerization (0.5-Phase Inversion (0.5—5.0 um) 1000 um) In situ polymerization (0.5-Hot Melt (1—1000 um) 1100 um)
  13. 13. Microcapsules - TechnologiesCoacervation Polymer-polymer Solvent incompatibility Evaporation (phase separation)
  14. 14. Microcapsules - TechnologiesRapid Expansion of Supercritical Fluids Hydrogel microspheres
  15. 15. Microcapsules - Technologies Spray-Drying & spray-congealing
  16. 16. Microcapsules - Technologies Fluidized-Bed Technology
  17. 17. Microcapsules - Technologies Pan coating
  18. 18. Microcapsules - Technologies Co-Extrusion
  19. 19. Microcapsules - Technologies Spinning Disk
  20. 20. Applications in TextilesIn microencapsulation in general the number of commercial applications inthe textile industry continues to grow.Microencapsulation processes as a means of imparting finishes andproperties on textiles for• Developed textiles with new properties.• New innovations and applications in Medical and Technical Textiles.• Application in the area of cost-effectiveness required.• Application where the technologies are not sufficient or not possible in imparting some finishes.• Increasing the durability of finishes.Few Textile applications more interested in the area of• Durable fragrances to textiles• Skin softeners and other potential applications include,• Insect repellents,• Dyes,• Vitamins,• Antimicrobials,• Phase change materials and in• Specific medical applications, antibiotics, hormones and other drugs.
  21. 21. Applications in Textiles – Phase Change Material The Technology was utilised in the early 1980s by the US - NASA with the aim of managing the thermal barrier properties of garments, in particular for use in space suits. They encapsulated phase-change materials (PCMs) (e.g. nonadecane) with the hope of reducing the impact of extreme variations in temperature encountered by astronauts during their missions in space. The potential was recognised where they can applied. Outlast has exploited the technology in textile fibres and fabric coatings and PCM capsules are now applied to all manner of materials.
  22. 22. Applications in Textiles – Phase Change MaterialApplications inOutdoor wear - (vests, thermals, snowsuits and trousers) andIn-house - {blankets, duvets, mattresses and pillowcases).As well as being designed to combat cold, textiles containing PCMs also helps tocombat overheating, so overall the effect can be described as thermoregulation.The microcapsules have walls less than 1 nm thick and are typically 20-40 nm indiameter, with a PCM loading of 80-85%.The small capsule size provides a relatively large surface area for heat transfer. Thusthe rate at which the PCM reacts to an external temperature changes is very rapid.Accordis - UK, developed the technology of in-fibre incorporation of the Outlastmicrocapsules, loading the fibre with 5-10% of microcapsules.The process utilises late injection technology that was also used to produce theantimicrobial fibre.In this way the PCM is permanently locked within the fibre; there is no changenecessary in subsequent fibre processing (spinning, knitting, dyeing, etc.) and the fibreexhibits its normal properties of drape, softness and strength.
  23. 23. Applications in Textiles – Fragrance FinishesFragrances to textiles has been carried out for many years in the form of fabricconditioners in the wash and during tumble-dry-ing; all are designed to impart a fresharoma to the textile.But the effect is relatively short-lived.Numerous attempts have been made at adding fragrances directly to fibre and fabricsbut all fail to survive one or two wash cycles.Only through microencapsulation are fra-grances able to remain on a garment during asignificant part of its lifetime.Microencapsulation of essential oil flavours has led to many novelty applications,particularly for childrens garments, but it has also allowed exposure at home and in thework place to the beneficial effects.The majority of the work has been in microencapsulated scratch and sniff T-shirts andin womens hosiery.The nature of the microcap-sules is claimed that the durability can be (typically 8-20cycles), depending on the active agent encapsulated, and the hosiery up to ten washes.The capsules also survive drying in conventional tumble-dryers.
  24. 24. Applications in Textiles – Fragrance FinishesInitial Applications:Drawer liners, paper hand-kerchiefs, gift wrapping, stationary, greetingcards, advertising brochures, books, cartons and labels.Now, the basic technology of encapsulating fragrances in gelatin orsynthetic capsules, which protects the contents from evaporation,oxidization and contamination.The capsules range in size from 1 to 20 nm.The technology allows a textile manufacturer to add a fragrance, vitamin,moisturizer or even an insect repellent to all types of textile substrates.Depending on application weights and the wash cycle used, up to 30washes can be achieved without complete loss of fragrance.In practice, the smaller the capsules the greater the covering of theproduct and the longer the fragrance will last, as it takes longer for thecapsules to be ruptured by physical pressure.Larger capsules release more fragrance when ruptured.
  25. 25. Applications in Textiles – Fragrance FinishesThe aqueous disper-sions of encapsulates, which can be applied by pad,exhaustion or hydroextraction techniques to a wide variety of textilesubstrates.Durability to washing and handle (or feel) may be further im-proved byincorporating suitable formaldehyde-free binders and softeners.Microcapsules using melamine-formaldehyde systems containingfra-grant oil, When attached to cotton these capsules were able tosurvive over 15 wash cycles.Microcapsules containing perfumes or cosmetic moisturisers that can bepadded, coated or sprayed onto a textile and held in place using anacrylic or polyurethane binder.Paper-like products have been produced con-taining microencapsulatedessential oils such as lavender, sage and rosemary for odour controlapplications in shoe liners and insoles.
  26. 26. Applications in Textiles – Fragrance FinishesFor screen-printed application the encapsulates are simply mixed withwater-based, solvent-free inks or binders.The capsule printing must be the last pass under a screen to avoiddamage to the walls by further screens.Once printed, the fabric is then cured as with standard textile inks toachieve a good bond to the fibres.Usually a softener is also required, as unsoftened fabric containingmicrocapsules can sometimes appear to be stiffened.The capsules are colourless and can be applied over coloured fabric orprinted patterns without any adverse visible effects.The fragrant effect can last for a year and a half. Gloves and socks arealso available that have fragrance-release properties and someantibacterial effects, which the manufacturers claim to last for up to 25wash cycles.
  27. 27. Applications in Textiles – Colour ChangingPoly chromic and thermo chromic microcapsulesColour-changing technology has been generally applied to noveltyapplication such as stress testers, forehead thermometers and batterytesters.New applications are now beginning to be seen in textiles, such as productlabelling, and medical and security applications.In addition there is continued interest in novelty textiles for purposes such asswimwear and T-shirts.Two major types of colour-changing systems:Thermochromatic: Alter colour in response to temperature, andPhotochromatic : Alter colour in response to UV light.Both forms of colour-change material are produced in an encapsulated formas microencapsulation helps to protect these sensitive chemicals from theexter-nal environment.
  28. 28. Applications in Textiles – Colour ChangingPoly chromic and thermo chromic microcapsules Today, manufacturers are able to make dyes that change colour at specific temperatures for a given application. e.g. colour changes can be initiated from the heat generated in response to human contact. Physiochemical and chemical processes such as Coacervation and interfacial polymerization have been used to microencapsulate photochromic and thermochromic systems. To obtain satisfactory shelf life and durability on textiles, interfacial polymerization techniques are nearly always adopted, which is the same techniques used to produce textile fibres and films such as polyester, nylon and polyurethane. The most widely used system for microencapsulation of thermochromic and photochromic inks involves urea or melamine-formaldehyde systems.
  29. 29. Applications in Textiles – Flame RetardantFire retardants have been applied to many textile products.But in certain cases they can affect the overall handle, reducing softnessand adversely affecting drape.Microencapsulation has been used to overcome these problems forexample in fabrics used in military applications such as tentage.Others have incorporated the microencapsulated fire retardants duringspinning of a polyester fibre for blending with cotton.
  30. 30. Applications in Textiles – CounterfeitingIn high added value textiles, and in branded and designer goods there isgreat pressure to protect from illegal copying within the market-place.Microencapsulation can be used to help with this problem by offering acovert yet dis-tinctive marking system.This system for combating textile counterfeiting utilizes microcapsulescontaining a colour former or an activator applied to, for example, athread or a label.The microcapsules adhere to the tex-tile and, depending on the type ofchemical within the capsules can be detected at a later date to checkauthenticity.Detection may be achieved directly using UV light or more likely byusing a solvent to break open the capsules, releasing the contents andallowing a colour to develop.
  31. 31. Applications in Textiles – LiposomesIn recent years liposomes have been examined as a way of delivering dyesto textiles in a cost- effective and environmentally sensitive way.The liposomes used (for example, commercially available PC liposomesfrom Transtechnics SL) were cost-effective, and no specific equipment orskills were required to handle them within the dye house.The results were excellent with pure wool and wool blends, and as thetemperature of dyeing could be reduced there was less fibre damage.In their studies dye bath exhaustion was shown to greater than 90% at thelow temperature (80 °C) used resulting in significant saving in energy costs.The impact of the dyeing process on the environment was also muchreduced with chemi-cal oxygen demand (COD) being reduced by about1000 units.
  32. 32. Applications in Textiles – GeneralEncapsulated glycerol stearate and silk protein moisturizers forapplication on bandages and support hosiery.The material maintains comfort and skin quality through extensivemedical treatment where textiles are in direct contact with the skin.Polypropylene nonwoven material for application as a cleaning/wipingcloth containing microencapsulated octane, tung oil and paraffin oil ascleaning solvents.The cloths feel good in the hand and have very good cleaning properties.The application of insecticides to textiles to combat dust mites andinsects such a mosquitoes, etc.,Microencapsulation has been considered as a mechanism of retaining theeffect for significant periods without exposing the user to excessivedosages of hazardous chemicals.The use of alternative insecticidal compounds such as those found inmany essential oils and other plant extracts has made the production oflonglasting acaricide bed sheets possible.