Fragrance oil microcapsules with low content of formaldehyde: Preparation and characterization

To reduce the residual formaldehyde content in melamine-formaldehyde (MF) microcapsules, glutaraldehyde was introduced to replace a portion of formaldehyde to prepare melamine-glutaraldehyde-formaldehyde (MGF) fragrance oil microcapsules via in-situ polymerization. MGF-lily oil microcapsules were obtained when the concentration of aldehyde groups provided by glutaraldehyde in the total aldehyde groups Cga∕Ca≤ 33.3 mol%. When Cga∕Ca≤ 9.5 mol%, the addition of glutaraldehyde reduced the residual formaldehyde content (235.05 ± 13.14 ppm to 21.79 ± 6.82 ppm) effectively without sacrificing the mechanical properties of microcapsules; it also improved the elasticity of microcapsules, in which Young’s modulus of MF shell was approximately 1.5 times to that of MGF shell. The approach was extended to encapsulate 2-hydroxy-3-(octanoyloxy)propyl decanoate (ODO), hexyl salicylate and lavender oil. All three fragrance oils were encapsulated successfully with low content of formaldehyde; however, the mechanical properties varied due to the difference on the hydrophobicity and viscosity of fragrance oil. This work provided an efficient and universal formaldehyde reduction method to encapsulate hydrophobic fragrance oil, which can not only reduce formaldehyde content but also maintain the mechanical properties and improve the elasticity of microcapsules, which has a potential application in consumer-friendly additives.