Factors influencing the crystallisation of highly concentrated water-in-oil emulsions: A DSC study

  • Karina Kovalchuk Cape Peninsula University of Technology
  • Irina Masalova Cape Peninsula University of Technology
Keywords: differential scanning calorimetry, surfactant type, electrolyte, highly concentrated emulsions, emulsion stability


Highly concentrated emulsions are used in a variety of applications, including the cosmetics, food and liquid explosives industries. The stability of these highly concentrated water-in-oil emulsions was studied by differential scanning calorimetry. Crystallisation of the emulsions was initiated by exposing the emulsions to a low temperature. The effects of surfactant type, electrolyte concentration and electrolyte composition in the aqueous phase on emulsion crystallisation temperature were studied. Surfactant type affected the emulsion crystallisation temperature in the following order: PIBSA-MEA=PIBSA-UREA < PIBSA-MEA/SMO < PIBSA-IMIDE < SMO. These results are in the same sequence as results obtained for the stability of these emulsions in aging studies, that is, PIBSA-MEA was the most stable with age and SMO was the least. The effect of the surfactant type on emulsion crystallisation can probably be attributed to the differing strengths of the surfactant–electrolyte interactions, which result in different molecular packing geometry and differing mobility of the surfactant lipophilic portion at the interface. These results enhance our understanding of the factors that affect the stability of explosive emulsions.


1. Masalova I, Malkin AY, Ferg E, Taylor M, Kharatiyan E, Haldenwang R. Evolution of rheological properties of highly concentrated emulsions with aging – Emulsion-to-suspension transition. J Rheol. 2006;50:435–451. http://dx.doi.org/10.1122/1.2206712

2. Masalova I, Malkin AY, Slatter P, Wilson K. The rheological characterization and pipeline flow of high concentration water-in-oil emulsions. J Non-Newton Fluid Mech. 2003;112:101–114.

3. Ganguly S, Mohan VK, Bhasi VCJ, Mathews E, Adiseshaiah KS, Kumar AS. Surfactant–electrolyte interactions in concentrated water-in-oil emulsions: FT-IR spectroscopic and low-temperature differential scanning calorimetric studies. Colloid Surface. 1992;65:243–256. http://dx.doi.org/10.1016/0166-6622(92)80180-A

4. Aronson MP, Petko MF. Highly concentrated water-in-oil emulsions: Influence of electrolyte on their properties and stability. J Colloid Interface Sci. 1993;159:134–149.

5. Villamagna F, Whitehead MA, Chattopadhyay AK. Mobility of surfactants at the water-in-oil emulsion interface. J Dispersion Sci Technol. 1995;16:105–114. http://dx.doi.org/10.1080/01932699508943663

6. Chattopadhyay AK, Ghaicha L, Oh SG, Shah DO. Salt effects on monolayers and their contribution to surface viscosity. J Phys Chem. 1992;96:6509–6513. http://dx.doi.org/10.1021/j100194a074

7. Ghaicha L, Leblank RM, Chattopadhyay AK. Influence of concentrated ammonium nitrate solution on monolayers of some dicarboxylic acid derivatives at the air/water interface. Langmuir. 1993;9:288–293. http://dx.doi.org/10.1021/la00025a055

8. Maheshwari R, Dhathathreyan A. Influence of ammonium nitrate in phase transition of Langmuir and Langmuir-Blodget films at air/solution and solid/solution interfaces. J Colloid Interface Sci. 2004;275:270–276.

9. Clausse D, Gomez F, Pezron I, Komunjer L, Dalmazzone C. Morphology characterization of emulsions by differential scanning calorimetry. Adv Colloid Interface Sci. 2005;117:59–74. http://dx.doi.org/10.1016/j.cis.2005.06.003, PMid:16253203

10. Coupland JN. Crystallization in emulsions. Curr Opin Colloid Interface Sci. 2002;7:445–450. http://dx.doi.org/10.1016/S1359-0294(02)00080-8

11. Gosch S, Rosseau D. Freeze-thaw stability of water-in-oil emulsions. J Colloid Interface Sci. 2009;339:91–102. http://dx.doi.org/10.1016/j.jcis.2009.07.047, PMid:19683718

12. Zhu L, Chen J-Q, Jiu Y, Pan Y, Chang J-Y. Differential scanning calorimetry analysis for water-in-oil emulsions. Abstract. Fresenius Environ Bull. 2011;20:1117–1123.

13. Malkin AY, Masalova I, Slatter P, Wilson K. Effect of droplet size on the rheological properties of highly concentrated w/o emulsions. Rheol Acta. 2004;43:584–591.

14. Yubai B, Munger G, Leblanc RM, Ghaicha L, Chattopadhyay AK. Crystallization of ammonium nitrate under organized monolayers of various amphiphiles. J Dispersion Sci Technol. 1996;17:391–405. http://dx.doi.org/10.1080/01932699608943511

15. Masalova I, Kovalchuk K, Malkin AY. IR studies of interfacial interaction of the succinic surfactants with different head groups in highly concentrated W/O emulsions. J Dispersion Sci Technol. In press 2011.

16. Adya AK, Neilson GW. Structure of a 50 mol kg-1 aqueous solution of ammonium nitrate at 373 K by the isotopic difference method of neutron diffraction. J Chem Soc Faraday Trans. 1991;87:279–286. http://dx.doi.org/10.1039/ft9918700279

17. Oxley JC, Kaushik SM, Gilson NS. Thermal stability and compatibility of ammonium nitrate explosives on a small and large scale. Thermochim Acta. 1992;212:77–85. http://dx.doi.org/10.1016/0040-6031(92)80222-I

18. Myers D. Surfaces, interfaces and colloids: Principles and applications. 2nd ed. New York: Wiley VCH; 1999. http://dx.doi.org/10.1002/0471234990

19. Tadros TF. Applied surfactants: Principles and applications. Weinheim: Wiley VCH; 2005. http://dx.doi.org/10.1002/3527604812