Cream thixotropic

The longer you shear catsup, the runnier it becomes and the longer it remains so. We call such a fluid thixotropic. Other examples include margarine, latex paint, and shaving cream. 

Usually the surfactant concentration in ointments and creams is significantly lower than in surfactant gels. Ointments are non-aqueous preparations, whereas creams result from ointments by adding water. The microstructure of both ointments and creams may consist of liquid crystals, as long as a liquid crystalline network or matrix is formed by amphiphilic molecules. In a liquid crystalline matrix, it is easier to deform the system by shear such formulations show plastic and thixotropic flow behavior on shear. In comparison to systems with a crystalline matrix which are usually destroyed irreversibly by shear, those with a liquid crystalline matrix exhibit a short regeneration time of... 

Gelcarin GP-379 lota Elastic, medium strength Hot High, thixotropic 0.3-1.0 Creams, suspensions... 

SeaSpen PF lota Elastic, weak Cold, delayed gel formation Medium, thixotropic 0.5-1.0 Creams, suspensions, lotions... 

Properties (Wyoming) Light to cream-colored impalpable powder forms colloidal suspension in water, with strongly thixotropic properties. 

Thixotropy This refers to the reversible time-dependent decease of viscosity. When the system is sheared for some time the viscosity decreases, but when the shear is stopped (the system is left to rest) the viscosity of the system is restored. Practical examples of systems that show thixotropy include paint formulations (sometimes referred to as thixotropic paints), tomato ketchup, and some hand creams and lotions. 

Optigel. [United Catalysts] Bentonite, or smectite prods. thixotrope for aq. cosmetic creams and lotions. 

Thixotropic liquids, e.g. paints, tomato ketchup, salad cream. Here the apparent viscosity reduces with time as the material is sheared at a constant shear rate Figure I.JI). Usually after a large time of shearing, an equilibrium apparent viscosity is reached. If the shearing is now stopped the... 

Foundations are usually mixtures of a suspension and an emulsion (termed sus-poemulsiori) in which the emulsion portion is usually either O/W or W/O and the continuous phase generally contains the pigment particles. Foundations need to be formulated to be thixotropic to provide the desired smooth levelling effect. Ointments are similar to creams but may be more viscous. Many ointments are prepared from a base of anhydrous lanolin or white petrolatum, which is a mixture of iso- and cyclic paraffins. Waxes may be added to make the ointments harder. 

Most fluids exhibit non-Newtonian behavior—blood, household products like toothpaste, mayonnaise, ketchup, paint, and molten polymers. As shown in Figure 7.9, shear stress, t, increases linearly with strain rate, y, for Newtonian fluids. Non-Newtonian fluids may be classified into those that are time dependent or time independent and include viscoelastic fluids. Shear thinning (pseudoplastic) and shear thickening (dilatant) fluids are time independent while rheopectic and thixotropic are time dependent. The shear stress (viscosity) of shear thinning fluids decreases with increasing shear rate and examples include blood and syrup. The viscosity of dilatant fluids increases with shear rate. The viscosity of rheopectic fluids—whipping cream, egg whites—increases with time while thixotropic fluids— paints (other than latex) and drilling muds— decrease their viscosity with the duration of the shear. 

Chem. Descrip. Montmorillonite CAS 1318-93-0 EINECS/ELINCS 215-288-5 Uses Thixotrope, oil adsorbent, texturizer, suspending agent, stabilizer for aq. systems, personal care creams and topicals Features Rec. where suspension is desired without a large increase in vise. 

Uses Thixotrope, antisettling agenL sag control agent for latex emulsion systems incl. coatings, sealants, and adhesives emulsion stabilizer, suspending agent for cosmetic and pharmaceutical creams and lotions, household cleaners Optigel LX [Siid-Chemie lnc[... 

Chem. Descrip. Bentonite, cellulose gum Uses Thixotrope, thickener for aq. cosmetic/toiletry creams and lotions, putties, caulks, cleaning compds., waxes, polishes, matte and semigloss emulsion and water-reducible paints, adhesives Properties Lt. cream powd. particle size 85% <125 pm sp.gr. 2.41 g/cc ... 

Chem. Descrip. Fumed silica CAS 112945-52-5 EINECS/ELINCS 231-545-4 Uses Thickener, thixotrope, antisettling agent for paints/coatings, phar-maceuticals/cosmetics (toothpaste, tablets, powds., aerosols, suspensions, ointments, creams), diazo paper, printing inks, PVC plastisols, rubbers, adhesives reinforcing filler in silicone rubber flow aid for powds., pigments, and salts Features Hydrophilic... 

Definitbn Reaction prod, of bentonite and stearalkonium chloride Uses Thixotrope, vise, control agent, antisagging agent, suspending agent for paints vise, control agent in cosmetics, pharmaceuticals, creams, ointments... 

Properties Clear liq. m.w. 289.47 Toxicology TSCA listed Uses Surfactant softener, conditioner, emulsifier, wetting agent, vise, builder, stabilizer, antistat for cosmetics emollient, lubricant, and slip agent for shave creams gel sensitizer for latex foaming agent for bubble baths hydrotrope, thickener for hypochlorite cleaners thixotrope for water-based paints emulsion stabilizer for textiles, petrol, additives, paper, plastics, rubber Trade Name Synonyms Aromox C/12-W [Akzo Nobel Surf. Chem. 

Function in Formula Suspending, thickening agent, colloidal thixotrope Use Concentration 1.2% in cosmetic, personal care suspensions 2% in reconstitutable suspensions 1-2% in pharmaceutical suspensions 1.5-2.5% in cosmetic creams and lotions Solubility Characteristics Water-dispersible... 

When that stress is exceeded, the shear rate grows. Further stress leads finally to linear (Newtonian) behaviour. Examples of plastic systems are chocolate, butter, cheese, various spreads and ice cream. In pseudoplastic systems the observed viscosity decreases with an increase in shear stress. An example of a pseudoplastic system is pudding. Dilatant systems resist deformation more than in proportion to the apphed force. The shear rate is growing much faster than that of Newtonian fluids and viscosity increases with an increase in shear stress. At low apphed forces, the system behaves as a Newtonian fluid. Examples of dilatants systems are honey with added dextran and a slurry of wet beach sand. Thixotropic systems become more fluid (they have lower viscosity) with increasing time of an apphed force. If the apphed force ceases to operate, the original viscosity of the system is restored due to a reversible transformation of the sol gel type. Examples of thixotropic systems are mayonnaise, ketchup, whipped and hardened fats, butter and processed cheeses. Rheopectic systems exhibit behaviour opposite to that of thixotropic systems. Their viscosity increases with increasing time of apphed force. An example is whipped egg white. 

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