Sensory Effect on Hydrogels Using Endothermic and Hydration Properties of Urea
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Presented by: EUNSOL CHOI
[PURPOSE OF PAPER]
Urea, as a component of the Natural Moisturizing Factor(NMF), is a hygroscopic material that attracts and retains water molecules. In addition, urea lowers the surrounding temperature through an endothermic reaction when it is dissolved in water and changes its phase into an aqueous solution. As the exposure to heat stress increases due to environmental changes such as the aggravation of global warming and increasing outdoor activities, consumers’ interest in skin moisturizing is keep increasing. The aim of this study is to show the developed moisture and the sensory properties of urea in a hydrogel, utilizing the urea’s hygroscopic and endothermic characteristics.
[METHOD]
Prepare an algin-based hydrogel and a general thickener-based gel in order to validate the effect of urea on formulation. The gels are then combined with urea and compare the mixtures. Separately, prepare an aqueous sodium alginate solution and a powder phase containing calcium and urea, and mix them to make a hydrogel. Measure the loss of moisture and the real-time temperature changes, using a probe thermometer and infrared moisture determination balance.
[RESULT]
In order to determine the heat of dissolution of urea, urea was added to deionized water by concentration and temperature change according to the concentration was measured. As a result, it was confirmed that the higher amount of the urea addition, the greater the temperature drop, and the characteristic was directly proportional to concentration. When urea was applied to the hydrogel and the general gel, there was no difference in the minimum temperature value for temperature drop, but the hydrogel formulation showed a longer temperature retention time. However, when urea is separated into powder, the powder is agglomerated due to the hygroscopic properties of urea, and it is difficult to disperse the powder in an aqueous solution and interferes with the formation of a hydrogel. To solve this problem, a bulking agent was added, and the effect of preventing the aggregation of urea was shown. In addition, when the loss-on-drying experiment was conducted at a high temperature, the hydrogel with urea showed a higher moisture content than that of the general gel formulation and the same result was shown in hydrogel without urea.
[DISCUSSION]
Since urea rapidly dissolves in water and absorbs energy, the phases were divided to take advantage of the change in enthalpy. But due to the hygroscopic nature of urea, the powder gradually absorbs moisture and aggregates. In this study, we added a bulking agent to solve the problem, but as the content increased, the proportions of the phases change, giving a difference in texture and the rate of hydrogel formation. In addition, since urea is known to have a keratolytic effect at a high concentration, it is likely that appropriate content is necessary rather than simply adding a large amount for the cooling effect.
Urea, as a component of the Natural Moisturizing Factor(NMF), is a hygroscopic material that attracts and retains water molecules. In addition, urea lowers the surrounding temperature through an endothermic reaction when it is dissolved in water and changes its phase into an aqueous solution. As the exposure to heat stress increases due to environmental changes such as the aggravation of global warming and increasing outdoor activities, consumers’ interest in skin moisturizing is keep increasing. The aim of this study is to show the developed moisture and the sensory properties of urea in a hydrogel, utilizing the urea’s hygroscopic and endothermic characteristics.
[METHOD]
Prepare an algin-based hydrogel and a general thickener-based gel in order to validate the effect of urea on formulation. The gels are then combined with urea and compare the mixtures. Separately, prepare an aqueous sodium alginate solution and a powder phase containing calcium and urea, and mix them to make a hydrogel. Measure the loss of moisture and the real-time temperature changes, using a probe thermometer and infrared moisture determination balance.
[RESULT]
In order to determine the heat of dissolution of urea, urea was added to deionized water by concentration and temperature change according to the concentration was measured. As a result, it was confirmed that the higher amount of the urea addition, the greater the temperature drop, and the characteristic was directly proportional to concentration. When urea was applied to the hydrogel and the general gel, there was no difference in the minimum temperature value for temperature drop, but the hydrogel formulation showed a longer temperature retention time. However, when urea is separated into powder, the powder is agglomerated due to the hygroscopic properties of urea, and it is difficult to disperse the powder in an aqueous solution and interferes with the formation of a hydrogel. To solve this problem, a bulking agent was added, and the effect of preventing the aggregation of urea was shown. In addition, when the loss-on-drying experiment was conducted at a high temperature, the hydrogel with urea showed a higher moisture content than that of the general gel formulation and the same result was shown in hydrogel without urea.
[DISCUSSION]
Since urea rapidly dissolves in water and absorbs energy, the phases were divided to take advantage of the change in enthalpy. But due to the hygroscopic nature of urea, the powder gradually absorbs moisture and aggregates. In this study, we added a bulking agent to solve the problem, but as the content increased, the proportions of the phases change, giving a difference in texture and the rate of hydrogel formation. In addition, since urea is known to have a keratolytic effect at a high concentration, it is likely that appropriate content is necessary rather than simply adding a large amount for the cooling effect.