In cosmetic textiles, the major interest in microencapsulating is currently in the application of vitamins, essential oils, skin moisturizing agents, skin cooling agents, anti-aging agents etc.
Focusing on the field of cosmetic textiles, the techniques of producing microcapsules containing essential oils and cosmetic substances have been studied extensively in the past.
Yamato et al. prepared microcapsules comprising of active substances acting to improve the physiological conditions of human skin. The microcapsule would not break during production, but was gradually released when the textile structure was subjected to light pressure created by movement of the human body (US Patent, 1993).
The possibilities of using B - cyclodextrin as wall material have been investigated by a number of researchers (Hak et al. 2000; Wang et al, 2003).
Hak et al. investigated the flexibility of B-cyciodextrin as a protective wall. B-cyclodextrin was embedded onto cellulose fibers by using N-methylolacrylamide. Benzoic acid and vanillin, which acted as an anti-bacterial agent and an aroma respectively, were encapsulated. It was claimed that the anti-bacterial activity was retained after 10 laundering cycles (Hak et al., 2000).
Wang and Chen developed aroma therapeutic textiles by using fragrance with B-cyclodextrin inclusion compounds and fixing them onto cotton fabrics with low temperature by using a conventional pad-thermo fixed method. The fragrance release rates were greatly decreased and the results of sensorial evaluations showed that the performance of the fabric lasted for over 30 days (Wang et al., 2005).
Nelson et al. introduced the use of waste yeast cells in the microencapsulation process. After encapsulating the core material, the yeast cells were attached to both cotton and wool fibres by using cross linking agents and binders. The processes of filling the yeast cells were very simple and the use of yeast cells as wall material generally provided several advantages, such as high loading, inthermoplastic, protection from light, oxygen and hazardous environments, and cost effectiveness (Bishop et aI., 1998).
Copete Vidal et al. invented chitosan based microcapsules containing various active components and investigated their durability with a mixture of microcapsules and a binding agent.
With a finishing that used microcapsules and a binder, the active ingredients were released and found to wash out less quickly, and a high degree of hydration was also achieved (US Patent, 2005).
Korean researchers prepared melamine resin microcapsules containing Migrin oil by the in situ polymerisation method. The structure, mean particle size and size distribution, morphologies, thermal properties and released behaviours were characterised and discussed (Hong et aI., 1999).
They also prepared poly (L-lactide) microcapsules for fragrant fibres by an interfacial precipitation method through solvent evaporation from water-in-oilin-water emulsion. The microcapsules were then uniformly printed on cotton fabrics and the resulting fabric could withstand 15 cycles of washing (Hong et al., 2000).
Boh and Knez reported microencapsulation development in textile applications and prepared melamine-formaldehyde micro capsules containing essential oils and phase change materials. An in situ polymerisation method was used and the process was modified to achieve the desired characteristics of a microcapsule wall (Boh et aI., 2006).
The special features of Questice provide a brainstorming development in a fully encapsulated system. Questice is a slow release coolant which is very mild and has little or no odour. On contact with skin, Questice is hydrolysed by the skin's natural enzymes to produce menthol, giving an extended cooling sensation.
Pyrrolidone carboxylic acid, a natural moisturising factor (NMF), is also released during this process. Equipped with the functional effects of Questice on fabric, a cooling effect is slowly released and is body responsive, providing cooling when it is needed (Kumar, 2004; In-Cosmetics, 2007).
At the same time, many researchers have also put forth much effort on improving the durability of microencapsulated functions. This is relatively the most difficult task in preparing cosmetic textiles.
Li et al. investigated the effects of UV curing for encapsulated aroma finishing on cotton. The aroma function was prolonged to 50 wash cycles whereas the traditional curing method could only withstand 25 wash cycles. If a cotton fabric was finished with the selected aroma capsule and UV resin, and cured under optimal conditions, the aroma function could withstand 50 wash cycles (Li et al., 2005).
Chang integrated the processing procedures of fabric treatment techniques with low temperature plasma, natural oil essence microencapsulation and fabric coating techniques to improve the adhesion property of microcapsules with fabrics. This invention increased not only the adhesion area of microcapsules on the fabric, but also enhanced the use for oil essences and promoted the additional value of the fabric (US Patent, 2005).
Potential Development and Conclusion
The textiles industry is currently experiencing a revolution that aims at the unique needs of the modern consumer. Cosmetic textiles are increasingly popular and expanding considerably in the textile industry as its marketing message becomes more widely appreciated. Many textile auxiliaries companies are now targeting this specific enhancement in apparel performance.
Owing to the increasing supply of commercial cosmetic textiles, systematic characterisation and representative measurements are thus concededly essential to prove and verify their performance and efficiency.
The integration of aromatherapy in textile application is a novel and user-friendly idea that enables an alternative means for essential substance delivery systems. At present, the application of aromatherapy in textiles is commonly concentrated on skin care benefits and stress management. More innovative ideas can be anything imaginable, such as hair care and treatment, body slimming and even medical applications etc.
Microencapsulation technology is an effective technique to achieve satisfactory performance; even it is still relatively new to the textile and apparel industry. The wide range of benefits for aromatherapy and controlled release of essential oils is expected to be appreciated by consumers.
Several commercial cosmetic finishing products are currently available in the market. However, practical methods for proving the effectiveness of these products are doubtful. Hitherto, many research works have focused on the material characterisation methods and the release mechanism of cosmetic finishing products. Yet the fabric performance properties and their responses to human skin are often neglected. In other words, there is still a lack of empirical characterisation methods to assess the performance of cosmetic textiles. A systematic characterization system should be developed for evaluating the effectiveness of cosmetic textiles.
As a whole, it is anticipated that the development of cosmetic textiles will continue to grow and explore completely new possibilities for providing bioactive bodily care functions to wearers in the near future. It is a challenging and exciting time for the textile industry. The textile industry must continue to explore and develop functional textiles that fit capricious consumer behaviours.
This article was originally published in the December issue of the magazine, New Cloth Market the complete textile magazines from textile technologists."