Application of isothermal calorimetry to evaluate thermal properties and cooling effect of poly(urethane-urea) microcapsules containing xylitol

F. Salaün1,2, G. Bedek1, 3, E. Devaux1, 2, D. Dupont1, 3, O. Maret4 and B. Tillman4

1ENSAIT, GEMTEX, F-59100 Roubaix, France
2Univ Lille Nord de France, Lille, France
3HEI, Lille, France
4Damartex, Roubaix, France

Keywords: microcapsules
property: cooling effect; heat of solution
material: xylitol; semi-permeable particles

As an important consideration in active wear, clothing comfort is closely related to microclimate temperature and humidity between clothing and skin. Amongst the various possibilities to functionalize textiles, microencapsulation is a suitable technique to achieve satisfactory performance to improve comfort range. Thus, recently, we have developed a new type of microcapsules with semi-porous membranes as sweat sensor system prepared by an interfacial polymerization [1]. The prepared microcapsules were featured with a reservoir-type porous microcapsule membrane structure and with numerous straight open pores across the membrane allowing the water molecules diffusion to promote the dissolution reaction of xylitol [2]. Differential Scanning Calorimetry (DSC) analyses have shown that the xylitol crystalline content and crystallization process depend mainly on the drying time at room. The combination of a porous shell with moisture-sensitive compound as xylitol would be useful for a material design of new functional microparticles for thermal and moisture management [3].

In this work, the correlation between the heat of solution and the loading crystalline xylitol content in the particles is examined by both DSC and isothermal calorimetry at 35°C experiments. The analysis has shown that the permeation properties involved in the heat of solution process between crystalline xylitol and water are mainly correlated to the yield of shell formation and urethane content. The formation of the microcapsule shells around the xylitol droplets previously solubilised in water allows to create sufficient free volume to promote this endothermic reaction. The active xylitol contents (xylitol reacting with water) are strongly lower than the expected values in regard to the crystalline xylitol content. Furthermore, the dissolution of crystalline xylitol, monitored by isothermal calorimetry, occurs in several steps according to the relative porosity of the microcapsules shell and to the loading content. Higher yields of shell formation lead to a more dense membrane which reduces the water permeability.

  1. O. Maret, B. Tillman, G. Bedek, F. Salaün, E. Devaux, D. Dupont, D. Deranton, EP2218498

  2. F. Salaün, G. Bedek, E. Devaux, D. Dupont, L. Gengembre, J. Membr. Sci. (in Press)

  3. F. Salaün, G. Bedek, E. Devaux, D. Dupont, Mater. Lett. 65, 381 (2011)

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