Porto, Portugal - A team from the University of Porto has developed a way to microencapsulate the fragrance limonene within a polyurethane-urea matrix and is evaluating the material to make textiles which smell good.
Some systems for doing this are already available commercially, but most are based on phenol-formaldehyde or melamine-formaldehyde resins, which are facing restrictions under present environmental policies, points out lead researcher Sofia Rodrigues, in a paper published in teh American Chemical Society's Industrial and Engineering Chemistry Research journal. Typical uses for fragrance encapsulation lie in shirts, underwear, home-wear, suits and many more articles of clothing, say the researchers.
Polyurethane-urea systems may offer a more environmentally attractive solution to the other resins, and can be tailor-made from a wide range of raw materials, to give the necessary physical, chemical and mechanical properties, Rodrigues said.
"Microcapsules are small particles with sizes between 1 and 100 µm that contain an active agent surrounded by a natural or synthetic polymeric membrane," said Rodrigues.
This encapsulation is used to protect fragrances or other active agents from oxidation caused by heat, light, humidity, and exposure to other substance, she says, pointing out that it has also been used to prevent evaporation of volatile compounds and control the rate of release.
The encapsulated agent can be released by various actions -mechanical, temperature, diffusion, pH, biodegradation, and dissolution.
Rodrigues' team made polyurethane-urea microcapsules for textile use using interfacial polymerisation technology, with limonene oil -widely used in the perfumery industry - as the test agent.
Tests on fabric impregnated with this material showed that, during dry cleaning, a quarter of the limonene was lost in the first cycle and up to 97 percent with five cycles. During abrasion, 40 percent of the limonene was lost in 3000 cycles and up to 60 percent after 9000 cycles.