Rheologie komplexer Flüssigkeiten

Investigated complex fluids comprised polymer-surfactant-mixtures (PTMs) and oil-in-water (o/w)-emulsions. The mechanical properties were probed by oscillatory and continuous flow rheometry, microstructures of emulsions were evaluated by optical microscopy while droplet size and droplet size distribution were studied by flow particle image analysis (FPIA). 0.3 - 4.0 wt% of hydrophobically modified (hm)-(acrylic acid)copolymers and hm-(poly)urethans were combined with 0.0 - 2.0 wt% low molecular surfactant (sodium dodecylsulfate (SDS) - anionic, cetyltrimethylammonium-bromide (CTAB) - cationic, ethoxylated fatty alcohol (Arylpon F, Dehydol LS 9.5) - nonionic). The resulting PTMs revealed different polymer-surfactant interactions, due to surfactant / polymer charge and structure. In case of nonionic surfactants and SDS, polymer-surfactant interactions resulted in a more or less pronounced "thin-to-thick"-effect of PTMs depending on surfactant concentration and structure, whereas in CTAB-PTMs thickening as well as phase separation were observed depending on CTAB concentration. For PTMs from 1.0 wt% crosslinked polymer and surfactants an uncommon second shear thinning region, which is not mentioned in the literature so far, region was observed in the flow curves, which could be related to shear induced structural changes. The investigations on PTMs gave basic understanding of a possible applicability of polymeric thickeners in emulsions. Because low molecular surfactants showed some disadvantages in emulsions, only polymeric stabilized emulsions were investigated which contain silicon-based polymeric emulsifiers (dimethicones). Rheological properties and microstructures of polymer stabilized emulsions were compared to properties of classic emulsions with low molecular emulsifiers as stabilizing components. The investigations concerning rheological properties and droplet size of emulsions, presented here, dealt with o/w-emulsions containing polymeric thickener Pemulen TR-1 (TR-1) and silicone based emulsifier (DC 193). By varying thickener and emulsifier content rheological properties and droplet size of emulsions changed significantly. Experimental results and a statistical analysis showed that the physical network, build up by TR-1 in a concentration range from 0.1 - 1.0 wt%, was the dominating factor for rheological properties and increased moduli and viscosity of emulsions. The development of droplet diameters revealed that a systematic control of droplet parameters was possible by increasing the DC 193 concentration from 0.0 - 5.0 wt%. In contrast, increasing TR-1 concentration led to either large or small droplets. The influence of larger droplets in the emulsions was revealed when the arithmetic diameter and the Sauter diameter were compared and displayed huge differences. These differences resulted from a rather small amount of big droplets with diameters above 40 micrometer, which could be seen in the droplet size distributions of emulsions. An influence of oil droplets on emulsion elasticity was only observed for emulsions with low TR-1 concentration (~ 0.1 wt%), because at higher concentrations the influence of oil droplets was superimposed by thickening properties of TR-1

Rheologie komplexer Flüssigkeiten

Investigated complex fluids comprised polymer-surfactant-mixtures (PTMs) and oil-in-water (o/w)-emulsions. The mechanical properties were probed by oscillatory and continuous flow rheometry, microstructures of emulsions were evaluated by optical microscopy while droplet size and droplet size distribution were studied by flow particle image analysis (FPIA). 0.3 - 4.0 wt% of hydrophobically modified (hm)-(acrylic acid)copolymers and hm-(poly)urethans were combined with 0.0 - 2.0 wt% low molecular surfactant (sodium dodecylsulfate (SDS) - anionic, cetyltrimethylammonium-bromide (CTAB) - cationic, ethoxylated fatty alcohol (Arylpon F, Dehydol LS 9.5) - nonionic). The resulting PTMs revealed different polymer-surfactant interactions, due to surfactant / polymer charge and structure. In case of nonionic surfactants and SDS, polymer-surfactant interactions resulted in a more or less pronounced "thin-to-thick"-effect of PTMs depending on surfactant concentration and structure, whereas in CTAB-PTMs thickening as well as phase separation were observed depending on CTAB concentration. For PTMs from 1.0 wt% crosslinked polymer and surfactants an uncommon second shear thinning region, which is not mentioned in the literature so far, region was observed in the flow curves, which could be related to shear induced structural changes. The investigations on PTMs gave basic understanding of a possible applicability of polymeric thickeners in emulsions. Because low molecular surfactants showed some disadvantages in emulsions, only polymeric stabilized emulsions were investigated which contain silicon-based polymeric emulsifiers (dimethicones). Rheological properties and microstructures of polymer stabilized emulsions were compared to properties of classic emulsions with low molecular emulsifiers as stabilizing components. The investigations concerning rheological properties and droplet size of emulsions, presented here, dealt with o/w-emulsions containing polymeric thickener Pemulen TR-1 (TR-1) and silicone based emulsifier (DC 193). By varying thickener and emulsifier content rheological properties and droplet size of emulsions changed significantly. Experimental results and a statistical analysis showed that the physical network, build up by TR-1 in a concentration range from 0.1 - 1.0 wt%, was the dominating factor for rheological properties and increased moduli and viscosity of emulsions. The development of droplet diameters revealed that a systematic control of droplet parameters was possible by increasing the DC 193 concentration from 0.0 - 5.0 wt%. In contrast, increasing TR-1 concentration led to either large or small droplets. The influence of larger droplets in the emulsions was revealed when the arithmetic diameter and the Sauter diameter were compared and displayed huge differences. These differences resulted from a rather small amount of big droplets with diameters above 40 micrometer, which could be seen in the droplet size distributions of emulsions. An influence of oil droplets on emulsion elasticity was only observed for emulsions with low TR-1 concentration (~ 0.1 wt%), because at higher concentrations the influence of oil droplets was superimposed by thickening properties of TR-1