| 1. |
- van Hamersveld, EMS, et al.
(författare)
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Oil-acrylic hybrid latexes as binders for water-borne coatings
- 1999
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Ingår i: Progress in organic coatings. - 0300-9440 .- 1873-331X. ; 35, s. 235-246
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Tidskriftsartikel (refereegranskat)abstract
- The combination of the characteristics of oil, or alkyd, emulsions and acrylic latexes in a waterborne binder has been the object of various studies in the past. Strategies for combining the positive properties of alkyds, e.g. autoxidative curing, gloss and penetration in wood, with the fast drying and gloss and color retention properties of acrylic latexes have mainly been directed towards the modification of the alkyd with an acrylate during alkyd synthesis followed by emulsification. This paper describes the preparation and application of oil-acrylic hybrid latexes as binders for waterborne coatings. The hybrid latexes were prepared using hydroperoxidized triglycerides as initiators for the mini-emulsion polymerization of acrylates in an Fe(II)/EDTA/SFS redox system, The particle morphology of-hybrids initiated by fatty-acid hydroperoxides was compared with tert-butyl hydroperoxide-initiated systems. Cryo-TEM analysis indicated that, whereas tert-butyl hydroperoxide initiation resulted in the formation of heterogeneous particles, fatty-acid hydroperoxide-initiated hybrid particles showed no intra-particle heterogeneity. an AFM study of the film formation process of the oil/alkyd-acrylic hybrid latexes showed that phase separation occurred between the oil and the acrylic phases upon drying, resulting in films that consist of deformed acrylic particles embedded in a continuous matrix of oil. This results in a very smooth surface of the film.
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| 2. |
- Weissenborn, PK, et al.
(författare)
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Drying of alkyd emulsion paints
- 2000
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Ingår i: JCT. - 0361-8773. ; 72, s. 65-74
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Tidskriftsartikel (refereegranskat)abstract
- The drying and film formation of long oil alkyud emulsions was investigated with emphasis on loss of dry upon storage. The main reason for loss of dry was adsorption of the cobalt (drier) on pigment surfaces as a precipitated hydroxide. Titanium dioxides with alumina surface treatment and organic pigments were most detrimental to drying. Acrylate- and phosphate-based dispersants also deactivated the cobalt, presumably due to complexation and precipitation of the cobalt. Emulsions prepared with an emulsifiable cobalt drier containing 2,2'-bipyridyl (complexing agent for cobalt) showed the best resistance to loss of dry. Atomic force microscopy of films formed from the emulsions showed that the emulsifier migrated to the film surface which, when washed with water, leaves holes or pits in the film. The pits were arranged in a hexagonal pattern characteristic of Bénard cells, which form due to surface tension and/or temperature gradients generated in the film during evaporation of water.
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| 3. |
- Weissenborn, PK, et al.
(författare)
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Drying of alkyd emulsions
- 2000
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Ingår i: Double Liaison. - 0291-8412. ; 513, s. 44-52
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Tidskriftsartikel (refereegranskat)
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| 4. |
- Weissenborn, PK, et al.
(författare)
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Emulsification, drying and film formation of alkyd emulsions
- 2000
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Ingår i: Progress in organic coatings. - 0300-9440 .- 1873-331X. ; 40, s. 253-266
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Tidskriftsartikel (refereegranskat)abstract
- A method was developed and optimised for the emulsification of a conventional short oil alkyd resin which was solid at room temperature. The method was based on the emulsion inversion point (EIP) method whereby hot water (90°C) was added to molten alkyd resin (90°C) containing the emulsifier. Under slow mixing and addition of water, a point was reached where the emulsion instantaneously phase inverted from a water in oil emulsion (W/O) to an oil in water emulsion (O/W). Using optimum conditions, emulsions with droplet of diameters less than 0.8 m were obtained. The drying and film formation of long oil alkyd emulsions were investigated with emphasis on loss of dry upon storage. The main reason for loss of dry was adsorption of the cobalt (drier) on pigment surfaces as a precipitated hydroxide. Titanium dioxides with alumina surface treatment and organic pigments were most detrimental to drying. Acrylate- and phosphate-based dispersants also deactivated cobalt presumably due to complexation and precipitation of cobalt. Emulsions prepared with an emulsifiable cobalt drier containing 2,2'-bipyridyl (complexing agent for cobalt) showed the best resistance to loss of dry. Films formed from the emulsions showed that surfactant migrated to the film surface which when washed with water leaves holes or pits in film. The pits were arranged in a hexagonal pattern, characteristic of Bénard cells which form due to interfacial tension gradients generated in the film during evaporation of water.
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| 5. |
- Weissenborn, PK, et al.
(författare)
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Surface tension and bubble coalescence phenomena of aqueous solutions of electrolytes
- 1995
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Ingår i: Langmuir. - 0743-7463 .- 1520-5827. ; 11, s. 1422-1426
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Tidskriftsartikel (refereegranskat)abstract
- The inhibition of bubble coalescence by electrolytes beyond a critical transition concentration has been assessed by the relationship between transition concentration and surface tension gradients of electrolytes (d(Ay)/dc) and gas solubility. The correlation between transition concentration and [d(Ay)/dc]~2 was mediocre (0.74), suggestingthatthe Gibbs-Marangoni effect cannot fully account forinhibition of bubble coalescence. Preliminary bubbling experiments on mixed electrolytes supported this conclusion. A much better correlation was found between the transition concentration and gas solubility (represented by the exponential decay coefficient of 02 solubility with increasing electrolyte concentration). Hence, the inhibition of bubble coalescence may be linked with the decreased dissolved gas concentration in the electrolyte solution.
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| 6. |
- Weissenborn, PK, et al.
(författare)
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Surface tension of aqueous solutions of electrolytes : Relationship with ion hydration, oxygen solubility, and bubble coalescence
- 1996
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Ingår i: Journal of Colloid and Interface Science. - 0021-9797 .- 1095-7103. ; 184, s. 550-563
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Tidskriftsartikel (refereegranskat)abstract
- The surface tension of aqueous solutions of simple inorganic electrolytes (36 in total) have been measured by the maximum bubble pressure method as a function of electrolyte concentration up to 1M. In most cases the surface tension increased, however in a minority of cases, certain combinations of cations and anions had a negligible effect or decreased surface tension. Results were analysed in terms of surface tension/electrolyte concentration gradients (d(∆g)/dc) and this parameter was found to correlate with the entropies of ion hydration, Jones-Dole viscosity coefficients and dissolved oxygen gradients. Calculation of Gibbs surface deficiencies for selected electrolytes were carried out using the raw surface tension data. Discussion of the surface tension/electrolyte concentration gradients was extended to the mechanism of inhibition of bubble coalescence by electrolytes. The Gibbs-Marangoni effect did not provide a satisfactory explanation for the inhibition of coalescence for all electrolytes and from the present study we suggest that dissolved gas (microbubble) gradients between macroscopic bubbles plays an important role in the coalescence process. Key words: surface tension; electrolytes; bubble coalescence; dissolved gases.
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