Micro-encapsulation is one upcoming technology that textile and garment manufacturers are looking at to keep ahead of the competition. The technique is being used to make climate-control materials, incorporate fragrances into clothing, and to add cosmetic, therapeutic and medical properties to fabrics. But will it be anything more than a fad? asks Geoff Fisher.

Ever scraped a fingernail across a "scratch-and-sniff" perfume advertisement in a glossy consumer magazine? This is just one example of the many applications of micro-encapsulation, a technology that is just beginning to be employed by the textile and apparel industries.

Companies in these sectors are being challenged to find innovations and to seek new materials that provide tangible benefits. Properties such as easy-care, anti-microbial, anti-static, flame retardant, stain resistant, water and oil repellent, crease and abrasion resistant, thermal and moisture control are now ubiquitous as consumers come to expect higher performance from their everyday wear. And the race is now on to find new ways of adding performance features to textile products.

There are basically two ways to achieve this. The benefits can be built into the fibre itself or a chemical compound can be applied during the fabric finishing process. Of the latter options, micro-encapsulation is one upcoming technology that textile and garment manufacturers are looking at to keep ahead of the competition. The technique is being used to make climate-control materials, incorporate fragrances into clothing and home textiles, and to add cosmetic, therapeutic and medical properties to fabrics.

"The technique is being used to make climate-control materials, incorporate fragrances into clothing and home textiles, and to add cosmetic, therapeutic and medical properties to fabrics"
What is micro-encapsulation?
Micro-encapsulation is the process of enclosing a substance in the form of small particles or droplets within a permeable or dissoluble miniature "capsule" so that the substance can be easily released.

The technique is used to trap solids, liquids or gases within a barrier layer made from gelatine, plastic, starch or other materials, which isolates and protects them from evaporation, oxidation and contamination by the external environment. The encapsulated product is released either by breaking the shell or by slow, progressive diffusion through the microcapsule.

Developed in the 1950s and 1960s, micro-encapsulation has applications in many industries. For example, it is used to make carbonless copy paper, timed-release medicines and washing detergent enzymes that remove bloodstains.

Fabric treatment
Micro-encapsulation treatment is relatively simple. The microcapsules containing the active agent are emulsified or dispersed in a carrier liquid, usually water. This results in a suspension of microcapsules, which can vary in size from 0.5 microns to 2 millimetres, in a concentration of 20-45 per cent (by weight).

The orange/pink colourway of Welbeck's CX 1435 is encapsulated with a citrus fragrance.

In the textile sector, the microcapsules are generally applied as the final fabric finishing process by padding, coating, spraying or immersion - processes that do not alter the fabric's handle or colour.

For most textile applications, each capsule measures around 3-8 microns in diameter, giving a maximum concentration of about 1 million microcapsules per square centimetre. The active substance such as a fragrance or moisturiser is released as the capsules break, through natural body movement. A high concentration gives multiple releases from the same area until all the microcapsules are broken.

The process requires a binder made from acrylic, polyurethane, silicone, starch or other materials and a thermal fixation method. This attaches the microcapsules onto the fabric and holds them in place during washing and wearing.

The technique can be applied to virtually all manmade and natural fibre fabrics. The durability of a micro-encapsulated product does vary, although most generally last for around 20-30 gentle (40°C) washes. Durability to washing and handle can be improved by incorporating suitable formaldehyde-free binders and softeners.

Fabrics with fragrance
A novel use of the technology is the encapsulation of fragrance onto textiles. French designers, in particular, have been among the first to use fragrance micro-encapsulation for top-of-the-range products. For example, Hermès produced a scarf containing Calèche perfume, Lancôme designed small silk squares perfumed with Poème to celebrate the Chinese New Year, and Neyret has developed scented lingerie.

"A novel use of the technology is the encapsulation of fragrance onto textiles"
In the UK, a number of dyers and finishers have introduced new added-value finishing effects. Berne-Welbeck International Limited, for instance, has developed fabrics incorporating fragrance as part of its latest collection for the lingerie market. Around 40 fragrances are now available in fruit, floral, and herbs and spices scents. Recent innovations have included the incorporation of musk and sandalwood fragrances, as underwear manufacturers attempt to appeal to the male consumer.

AromaPrint success
Also in the UK, commission textile printer Alexander Drew of Rochdale is has pioneered the use of encapsulation technology by developing fragrances and deodorisers for furnishing fabrics. The company has trademarked AromaPrint, a patented long-lasting micro-encapsulation technique, in which aromas can be built into fabrics for fun as well as therapeutic benefits.

"Our new AromaPrint treatment offers endless opportunities to develop fabrics that stimulate the sense of smell in specific circumstances, whether it is to create the mood for intimacy and romance in the bedroom or the scent of a freshly cut lawn in a summer room," says managing director Malcolm Campbell.

Other new products from its Tech Print range clearly show the direction in which the company is heading. GRF (germ-resistant fabric) is a treatment for roller blinds for kitchens and bathrooms, while FRF (fungal-resistant fabric) is for shower curtains and garden furniture. TRF (tobacco-resistant fabric) features a micro-encapsulation process that is claimed to absorb tobacco smoke for up to two years, and MagicPrint is a process for shower curtains on which printed logos only become visible when wet.

According to Campbell, Drew's patented microencapsulated products perform best on cotton, but the company is now working to make them adhere better to polyester. He also says the US children's wear market is also hugely receptive to the AromaPrint product, both for the novelty factor (curtains smelling of sweets or bubble-gum) and for the aromatherapy aspect (lavender to encourage sleep).

Microcapsules attached to the fabric withstand washing and wearing.

Micro-encapsulation techniques have taken a step further with the incorporation into fabrics of cosmetic ingredients such as moisturisers, skin-tightening creams and toners, and essential oils. The next development will include textiles integrating medication, vitamins, insect repellents, bactericides and acaricides. Like fragrances, these active ingredients will be released gradually onto the skin.

In France, lingerie and knitwear producer Dim launched moisturising and "energising" tights onto the market several years ago, and Berne-Welbeck has now incorporated the moisturising properties of aloe vera into its 2001/02 lingerie collections. Microcapsules containing aloe vera juice are supplied in a suspension adhesive, which is then fixed to the fabric using a thermal process.

In what is being termed "cosmeto-textiles," UK-based Croda International has teamed up with a French micro-encapsulating company to launch three products. Aimed at the hosiery market, the products are: Moistegy, which is claimed to have a moisturising effect; Microlisse, which has a slimming effect; and PhytoFresh, which has a cooling effect.

According to Croda subsidiary Brookstone Chemicals, the microcapsules are made from cationic gelatine. Application to pantyhose is by means of a single exhaust method without the need for pre-treatment with a synthetic resin. This is claimed to give durability for the expected life of the garment. The company also has in the pipeline a micro-encapsulated insect repellent says development chemist Andrew Sinclair.

With concerns about the potentially adverse effects of chemicals being released next to the skin, all ingredients used in these cosmeto-textiles must be fully tested to health and safety standards. With the encapsulating polymer used by Brookstone, for example, the trace levels of free formaldehyde used in the solution are typically lower than industry guidelines for cosmetic and even oral hygiene products. Similarly, the fragrance microcapsules marketed as Aroma Granules from the UK's LJ Specialities are said to be stable for several years and contain no toxic components.

Phase change materials
A related application of micro-encapsulation is the production of climate control materials, which are being used in the manufacture of gloves, hats, apparel, footwear and bedding. A number of fibre and fabric companies now offer advanced thermal management products that use micro-encapsulated phase change materials (PCMs), a patented technology that grew out of the NASA space research programme of the late 1970s and early 1980s.

"During periods of activity, PCM's store the excess heat generated by the body, "charging" the embedded microcapsules"

PCMs are tiny paraffin-filled microcapsules that store and release energy. They are protected by an ultrafine plastic cover so that the paraffin cannot escape. (This differs from other encapsulation treatments in that the microcapsules do not rupture or release their contents.) During periods of activity, these materials store the excess heat generated by the body, "charging" the embedded microcapsules.

The USA's Frisby Technologies makes a range of ComforTemp dynamic climate control insulating and cooling materials that are embedded with microcapsules that absorb, store and return heat as needed. The company has more than 120 partners worldwide including Swiss performance fabric manufacturer Schoeller Textil.

In cold weather, these microcapsules act like a thermostat, automatically returning the stored heat when they sense the temperature dropping below a pre-determined level. In warm weather, the materials pull heat away from the skin, providing cooling comfort.

Comfortemp materials work by absorbing excess heat, storing it, and returning it as needed.

PCM microcapsules can be spun into acrylic fibre yarns, used in surface coatings on fabrics or placed into foams for footwear and otherapplications. European fibre producer Acordis makes Outlast thermal-regulating acrylic fibres under licence to Outlast Technologies, a US-based pioneer of temperature regulation technology in fibres, fabrics and foams. When made into a garment, the encapsulated PCMs in Outlast fibre respond to changes in the skin and external temperature, thereby helping to buffer against temperature change.

Meanwhile, Frisby has teamed up with Germany's Freudenberg group, the world's leading nonwovens manufacturer, to launch ComforTemp nonwovens for use in insulation and linings for apparel, footwear, bedding and home furnishings.

A limited number of products should be introduced at retail by the end of this year, with wide availability anticipated for the autumn/winter 2002 season. A patent infringement recently filed by Outlast Technologies against Frisby Technologies' ComforTemp nonwoven fabrics could delay this rollout, although Doug McCrossen, Frisby's vice president of business development, does not anticipate any changes to the marketing campaign.

Early days
Although the technology of micro-encapsulation has been around for several decades, textile and garment manufacturers have been slow in exploiting its potential. But will the incorporation of fragrances and moisturisers into fabrics be anything more than a fad? Clearly, these premium-priced treatments will appeal initially to consumers at the top end of the market. But whether the mass market is prepared to pay for them is another matter.

Certainly, such innovations are worth considering by manufacturers and retailers. Beyond the novelty aspect, the development of leisurewear and sportswear that encapsulate aromatherapy oils to relieve stress, the application of cosmetics and active medical substances, and even the encapsulation of bactericides, acaricides, insect repellents and deodorisers are being actively pursued by makers of speciality chemical products.

From a very small base, the use of micro-encapsulation in textiles has increased rapidly over the past three to four years. But while customers are always looking for something different, retailers will need to be enlightened on the technical benefits of these treatments and shown how the premium-priced end products can be marketed effectively.

Consumers may also take some time to be convinced of the benefits of aromatherapy bedsheets or moisturising hosiery. However, other household products already on the market, such as plug-in air fresheners, have highlighted latent demand from consumers wanting improved standards of freshness and hygiene.

It is also clear that micro-encapsulation finishes will be used in combination with other treatments. Alexander Drew, for example, is now offering a peach-skin finish for comfort together with an antibacterial treatment and an AromaPrint treatment for sleep enhancement on children's wear.

As many textile finishers try to jump on the micro-encapsulation bandwagon, buyers will need to beware of cheaper products that may not be as durable as others. Customers should insist on seeing the relevant wash fastness and health and safety standards.

Micro-encapsulation in the textile and clothing industries is here to stay. The key is to develop and introduce functional materials that offer real and tangible benefits to the market while not falling into the category of short-term gimmicks. The use of branding and even product re-positioning, backed up with sound technical marketing, will be essential strategies.

The future is smart textiles - fibres and fabrics that contain not only all the important textile properties that consumers have come to expect, but that can also respond and react to bodily functions and the external environment.

By Geoff Fisher.

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