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Dynamic Effects in Thin Liquid Films

Final Report Summary - DETLIF (Dynamic effects in thin liquid films)

DETLIF commenced on 1 September 2008. DEFFED started on 1 January 2009. Both projects were legally managed by S. Karakashev. He organised a team of Bulgarian and foreign experts to work on the topics of these projects. An interim report of DETLIF was delivered in the end of October 2009 and approved by Research Executive Agency (REA) subsequently. During the spring of 2010, Sofia University changed the correspondent bank of its project bank account letting know all the principal investigators. For this reason, S. Karakashev sent message to REA that a small correction in the bank accounts of his projects DETLIF and DEFFED should be made. He was unpleasantly surprised later on, when he was informed that the two projects are blocked and the financial support is stopped due to double financing. The later appeared to be violation of the legal rules of REA. This is a situation of confusion for both sides and S. Karakashev believes that this is just misunderstanding.

Despite the big nuisance a final report of DETLIF was delivered on time (in October 2010) reporting successful execution of all the tasks of the work programme prior to the official date of close of the project , namely 1 September 2010. This project was terminated in 2011 with back date 31 December 2008. S. Karakashev does not object to the rules of REA, but rather expects understanding and resolving of the problem. The full report about the achievements of DETLIF (1 September 2008 - 1 September 2010) is included together with the periodic report of DEFFED.

DETLIF aims to create a theoretical model on thin liquid film (TLF) drainage, which accounts precisely for the interaction between the films surfaces under dynamic conditions. The well-known DLVO theory, which is one of the largest achievements of 20th century, accounts for the electrostatic and Van der Waals interactions between phase boundaries under static conditions. Hence, the stability of lyophobic colloids has been modelled with the employment of the DLVO theory for many years. However, the dispersed systems (foams, gas and oil emulsions, suspensions, etc.) are exploited under dynamic conditions in many industrial (mineral processing, food industry, pharmacy, petroleum industry, etc.) and health care (medicine, biophysics, zoology, etc.) applications. Hence, creating the model accounting for the dynamic effects on the surface forces is of fundamental and industrial significance. For this reason, DETLIF was designed. A concise report about the achievements for the first 4 months DETLIF is presented hereafter.

The current theoretical approach not accounting for any dynamics of the surface forces was firstly validated by application on TLF stabilised by non-ionic surfactants (proceedings in third International Conference of Young Scientists, Plovdiv, Bulgaria, 18 -19 June 2009; Colloids and Surfaces A, 2010, Vol. 365 (1-3), pp. 122-136, Annuare of Sofia University, 2009, in press). For this reason, four different theoretical models based on the contemporary approach were applied. It was confirmed this way that the present theoretical approach describes very well the drainage of planar TLF stabilised by non-ionic surfactants. Further on, the same theory was applied to drainage of planar TLF stabilised by ionic surfactants. It was observed significant discrepancy between theory and experiment due to the dynamic effects on the surface forces. Hence, the scientific community was alarmed (Journal of Colloid and Interface Science, 2010, Vol. 343 (2), pp. 584-593) for this problem. It was defined as well theoretically by publishing the basic set of differential equations accounting for the dynamic effects on the electric surface forces.

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