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M. van den Tempel
Colloids and Surfices, 65 (1592) iii-v Elsevier Science Publishers B.V.,Amsterdam
Macarius (Max) van den Tempel was born on 31 March 1919 at Haarlem in The Netherlands. At an early age he demonstrated academic ambition by refusing to attend nursery school any longer because progress there was too slow for his liking. As an adolescent his academic ability did not go unnoticed, in spite of difficult circumstances after the early incapacitation of his accountant father. With the help of his mother he was able to secure a grant on which he entered Delft Technical University in 1937. He obtained his degree in Chemical Engineering in 1942, choosing physical chemistry as one of his major subjects. After the war he joined the Rubber Institltte at Delft (1947), initially in its patent office but later as a scientist in latex research. Here he became involved with the colloid chemistry of natural latex and with the formation and rheology of its gels. This work led to his Ph.D. degree which he obtained at Delft University in 1953. His thesis was entitled “1 he Stability of Oil-in-Water Emulsions”. Meanwhile, he had married Ria Penning, from Delft, in 195 1 and their daughter, Rita, was born in 1955. The same year saw the demise of the Rubber Institute, which had been funded out of contributions from Indonesian rubber plantations. He was asked to build up a physical chemistry section at the newly opened Unilever Research Laboratorium at Vlaardingen, near Rotterdam. This laboratory was intended not only to give technical support to factories, but also to carry out fundamental research on detergents and edible fats. Here he rapidly acquired the reputation of being an excellent scientist. Because of his fundamental approach to practical and theoretical problems, his qualities were soon recognised by the scientific community outside tJnilever. Hallrnarks of his work were a clear vision of the physical
... 111
principles behind technological problems, a strong personal involvement and a strict control of the scientific standards in internal reports as well as in external publications emerging from his group. As a result, his department grew from three members in 1956 to over forty in 1970. In the research on edible fats, his aim was to correlate the qualitative behaviour of butter and margarine, such as ease of spreading and texture, with quantitatively measurable rheological properties. At an early stage he found that these could be explained on the basis of the presence of a network of triglyceride crystals. The size and number of such crystals, together with the nature of the bonds between them, constituted the essential parameters of his model. This development resulted in the expansion of the research in his group to the new areas of phase behaviour, crystallization and growth of triglyceride crystals. Both the elaboration of the rheological model and the related studies on crystallization resulted in a large number of publications, extending over a period of twenty years and including several Ph.D. theses written under his guidance (J.M.P. Papenhuijzen, H. Kamphuis). Analogous network models were later used to describe the properties of protein gels and polymer-stabilized emulsions (Ph.D. thesis, T. van Vliet). A second problem tackled in this product area was the stabilization of the water droplets in fat spreads. Once again, triglyceride crystals were found to play an important part, this time by stabilizing the drop!ets through the Pickering mechanism (Ph.D. thesis, E.H. Lucassen-Reynders). These results established the practical importance of the wetting properties of fat crystals at the oil/ water interface, and in subsequent years led to a series of publications on contact angles (D. Bargeman).
iv
The initial research on dctergenrs was ;limea at findin%; a rclarionship between the equilibrium properties of surfactant solutions and their chcmicat constitution (Ph.D. thesis, F. van Voorst Vader). Subsequently, the study of the dynamic propcrtics of surfactant so1uLior.s was found to rcquirc I more precise description of the change in surface tension with surfactant concentration. This initiated a number of papers on the “Surface Equation of State” of surfactan: solutions, i.e. the re!ationship between their adsorption. ~onccntr~ltion and surface tension. In the late fiftics, van den Tcmpel was among the first to recognize that many characteristic properties ofsurfactant solutic:ns. a.g. their foaming and I~mLtlsil~cation behaviour. could not bc explail:ed solely on the basis of their equilibrium proper&s. Exter.sivc discussiorls on surface rhcology, especially with Professor B. Stukc of Munich Univers.ty, Icd to the fornlulation and experimental vcrificati.3n of a theory on the ~‘ilational surface: properties of surfactant solutions. Subsequently, van den Tempcl applied this theory to an analysis of ;he damping characteristics of capillary waves. An important development was the discovery of an alternative surface wave with a longitudinal character (J. Lucasscn). This two-dimensional analog of sound waves opened the way, both cxpcrimentally and thcoretica!ly, to a better formulation of the dilational rheology of surfactant solutions. Again this resulted in a number of publications. 3.A. de Feijter used an analogous forlnalism to describe shear waves at the surface of polymer solutions. This work was not quite finaliscd at the time, some of his results are published for the first time in this issue. In order to apply the concepts of surface rhcology to the foaming and emulsifying properties of surfactant solutions, the dynamic pt operties of surfactant films were studied (A. Prins). The Gibbs elasticity of such films was shown to be closely related to the diiational modulus of the surface of a surfactant solution, and could be interpreted theoretically in terms of the surfactant’s adsorption parameters. As a result, some. though not. all,
aspects of the: complex relationship between dy;lamic surfacianl properties and foam properties are now better undczrstood. In research on mechanisms of rfetcrgency. the adhesion bctwccn solid particles and textile surfaces was studied in cooperation with the Battclle Institute, Frankfurt am Main (H. !k back on their time under his gu&mce with gratitude and respect. His introductory talk to one new arrival is still vividly remembered thirty-three years after the event. Hc had didactic gifts in large measure. and his exposition of complex problems generally w:fs a model of clarity. His contributions to the rheology of disperse systems were acknowledged by the British Society of Rhc3logy which awarded him an honorary membership. Moreover, hc was for many years a member of the editorial board of the Journal of Non-Newtonian Fluid Mechanics and of the advisory board of the Journal of Colloid and Interface Science.
In 1972, llnilever began to integrate its strongly expanded research activities more closely with its general business objectives. In the course of the following reorganization, van den Tempel’s department was assigned to provide basic stipport for projects controhed by product development departments. As a result, his freedom to take decisions as to the direction of research became more and more restricted. Max found it difficult to adapt to the changed situation and resigned as a manager in 1977. During his last years in Unilever Research, he was active in various advisory functions until his early retirement in 1981. He died on 9 November 1990 at home in the seaside resort of Burgh-Haamstede, having been nursed with exemplary devotion by his wife throughout a long and devastating illness.
.
After van den Tempel’s retirement, the physicochemical research in his former department first moved in a more applied direction to improve its integration with product research. Many of the studies ini?iated by him proved to be a fruitful sotime for product I?lnovation. In this way, the memory of the scien:ific accomplish’?ents in the past remained ative bnd in recent years long term physico-chemical rese;:rch has been re-established at thr Viaardingen laboratory. Outside Unilever, van den Tempel’s contributions to colloid chemistry, rheology and crystallization will long be remembered by the international community of surface chemists and rheologists. F. van Voorst Vader E.H. Lucassen-Reynders J. Lucassen
Macarius (Max) van den Tempel was born on 31 March 1919 at Haarlem in The Netherlands. At an early age he demonstrated academic ambition by refusing to attend nursery school any longer because progress there was too slow for his liking. As an adolescent his academic ability did not go unnoticed, in spite of difficult circumstances after the early incapacitation of his accountant father. With the help of his mother he was able to secure a grant on which he entered Delft Technical University in 1937. He obtained his degree in Chemical Engineering in 1942, choosing physical chemistry as one of his major subjects. After the war he joined the Rubber Institltte at Delft (1947), initially in its patent office but later as a scientist in latex research. Here he became involved with the colloid chemistry of natural latex and with the formation and rheology of its gels. This work led to his Ph.D. degree which he obtained at Delft University in 1953. His thesis was entitled “1 he Stability of Oil-in-Water Emulsions”. Meanwhile, he had married Ria Penning, from Delft, in 195 1 and their daughter, Rita, was born in 1955. The same year saw the demise of the Rubber Institute, which had been funded out of contributions from Indonesian rubber plantations. He was asked to build up a physical chemistry section at the newly opened Unilever Research Laboratorium at Vlaardingen, near Rotterdam. This laboratory was intended not only to give technical support to factories, but also to carry out fundamental research on detergents and edible fats. Here he rapidly acquired the reputation of being an excellent scientist. Because of his fundamental approach to practical and theoretical problems, his qualities were soon recognised by the scientific community outside tJnilever. Hallrnarks of his work were a clear vision of the physical
... 111
principles behind technological problems, a strong personal involvement and a strict control of the scientific standards in internal reports as well as in external publications emerging from his group. As a result, his department grew from three members in 1956 to over forty in 1970. In the research on edible fats, his aim was to correlate the qualitative behaviour of butter and margarine, such as ease of spreading and texture, with quantitatively measurable rheological properties. At an early stage he found that these could be explained on the basis of the presence of a network of triglyceride crystals. The size and number of such crystals, together with the nature of the bonds between them, constituted the essential parameters of his model. This development resulted in the expansion of the research in his group to the new areas of phase behaviour, crystallization and growth of triglyceride crystals. Both the elaboration of the rheological model and the related studies on crystallization resulted in a large number of publications, extending over a period of twenty years and including several Ph.D. theses written under his guidance (J.M.P. Papenhuijzen, H. Kamphuis). Analogous network models were later used to describe the properties of protein gels and polymer-stabilized emulsions (Ph.D. thesis, T. van Vliet). A second problem tackled in this product area was the stabilization of the water droplets in fat spreads. Once again, triglyceride crystals were found to play an important part, this time by stabilizing the drop!ets through the Pickering mechanism (Ph.D. thesis, E.H. Lucassen-Reynders). These results established the practical importance of the wetting properties of fat crystals at the oil/ water interface, and in subsequent years led to a series of publications on contact angles (D. Bargeman).
iv
The initial research on dctergenrs was ;limea at findin%; a rclarionship between the equilibrium properties of surfactant solutions and their chcmicat constitution (Ph.D. thesis, F. van Voorst Vader). Subsequently, the study of the dynamic propcrtics of surfactant so1uLior.s was found to rcquirc I more precise description of the change in surface tension with surfactant concentration. This initiated a number of papers on the “Surface Equation of State” of surfactan: solutions, i.e. the re!ationship between their adsorption. ~onccntr~ltion and surface tension. In the late fiftics, van den Tcmpel was among the first to recognize that many characteristic properties ofsurfactant solutic:ns. a.g. their foaming and I~mLtlsil~cation behaviour. could not bc explail:ed solely on the basis of their equilibrium proper&s. Exter.sivc discussiorls on surface rhcology, especially with Professor B. Stukc of Munich Univers.ty, Icd to the fornlulation and experimental vcrificati.3n of a theory on the ~‘ilational surface: properties of surfactant solutions. Subsequently, van den Tempcl applied this theory to an analysis of ;he damping characteristics of capillary waves. An important development was the discovery of an alternative surface wave with a longitudinal character (J. Lucasscn). This two-dimensional analog of sound waves opened the way, both cxpcrimentally and thcoretica!ly, to a better formulation of the dilational rheology of surfactant solutions. Again this resulted in a number of publications. 3.A. de Feijter used an analogous forlnalism to describe shear waves at the surface of polymer solutions. This work was not quite finaliscd at the time, some of his results are published for the first time in this issue. In order to apply the concepts of surface rhcology to the foaming and emulsifying properties of surfactant solutions, the dynamic pt operties of surfactant films were studied (A. Prins). The Gibbs elasticity of such films was shown to be closely related to the diiational modulus of the surface of a surfactant solution, and could be interpreted theoretically in terms of the surfactant’s adsorption parameters. As a result, some. though not. all,
aspects of the: complex relationship between dy;lamic surfacianl properties and foam properties are now better undczrstood. In research on mechanisms of rfetcrgency. the adhesion bctwccn solid particles and textile surfaces was studied in cooperation with the Battclle Institute, Frankfurt am Main (H. !
In 1972, llnilever began to integrate its strongly expanded research activities more closely with its general business objectives. In the course of the following reorganization, van den Tempel’s department was assigned to provide basic stipport for projects controhed by product development departments. As a result, his freedom to take decisions as to the direction of research became more and more restricted. Max found it difficult to adapt to the changed situation and resigned as a manager in 1977. During his last years in Unilever Research, he was active in various advisory functions until his early retirement in 1981. He died on 9 November 1990 at home in the seaside resort of Burgh-Haamstede, having been nursed with exemplary devotion by his wife throughout a long and devastating illness.
.
After van den Tempel’s retirement, the physicochemical research in his former department first moved in a more applied direction to improve its integration with product research. Many of the studies ini?iated by him proved to be a fruitful sotime for product I?lnovation. In this way, the memory of the scien:ific accomplish’?ents in the past remained ative bnd in recent years long term physico-chemical rese;:rch has been re-established at thr Viaardingen laboratory. Outside Unilever, van den Tempel’s contributions to colloid chemistry, rheology and crystallization will long be remembered by the international community of surface chemists and rheologists. F. van Voorst Vader E.H. Lucassen-Reynders J. Lucassen