Emulsions, freeze/thaw stability

Acrylics. There are two principal classes of acrylic sealants latex acrylics and solvent-release actylics. High molecular weight latex acrylic polymers are prepared by emulsion polymerization of alkyl esters of acrylic acid, The emulsion polymers are compounded inlo sealants by adding fillers, plasticizers, freeze-thaw stabilizers, thickeners, and adhesion promoters. As is true of the silicone lalex sealants, die acrylic latex sealants are easy to apply and clean with water. 

Specifications and Standards. Borax stability is an important property in adhesives, paper, and textile applications. Ollier emulsion properties tabulated by manufacturers include tolerance to specific solvents, surface tension, minimum film-forming temperature, dilution stability, freeze-thaw stability, percent soluble polymer, and molecular weight. 

Understanding surfactant phase behavior is important because it controls physical properties such as rheology and freeze-thaw stability of formulations. It is also closely related to the ability to form and stabilize emulsions and microemulsions. Micelles, vesicles, mi-croemulsions and liquid crystal phases have all been used as delivery vehicles for perfumes or other active ingredients. 

Vinyl acetate is polymerized in aqueous emulsion and used widely in surface coating and in adhesives. Copolymerized with vinyl esters of branched carboxylic acids and small quantities of acrylic acid, it gives paint latices of excellent performance characteristics. G. C. Vegter found that a coagulum-free latex of very low residual monomer content can be produced from a mixture of an anionic and a nonionic emulsifier according to a specific operating procedure. The freeze/thaw stability of polymeric latices has been investigated by H. Naidus and R. Hanzes. 

Many polymerizations are performed by the emulsion technique to prepare a polymeric substance. The latex obtained is then coagulated, and the polymer is isolated. A paint latex, however, is used as such in the paint formulation, which leads to some special requirements for its stability, such as storage, mechanical, electrolyte, and freeze/thaw stability. 

The essential ingredients in an emulsion polymerization are the water, monomer, surfactant, and free-radical source. Other ingredients are frequently added for a variety of reasons. Stabilizers, which are usually water-soluble high polymers or carbohydrate gums, are employed to control latex viscosity and freeze-thaw stability of products that are used in the latex form. 

Gu, Y. S. Decker, E. A. McClements, D. J., Application of multi-component biopolymer layers to improve the freeze-thaw stability of oil-in-water emulsions beta-Lactoglobulin-iota-carrageenan-gela-tin. Journal of Food Engineering (2007) 80, 1246-1254. 

Uses Emulsifier for emulsion polymerization of vinyl acetate, acrylates, methacrylates, styrene, butadiene for paints, adhesives, paper, textile, and industrial coatings stabilizer wetting agent, dispersant for agric. formulations food pkg. adhesives, paper Features Provides mech. and freeze/thaw stability Regulatory FDA21CFR 175.105,176.180 BGA XIV compliance Properties Pale yel. liq. sp.gr. 1.06 vise. Ill cks pour pt. 8 C surf. tens. 40 dynes/cm (1%) anionic 30% solids Abex EP-277 [Rhodia HPCII]... 

Features Exc. low temp, film formation exc. scrub resist. good blocking resist., freeze/thaw stability exc. aging chars., water resist., flexibility Properties Milky wh. emulsion 0.5 p avg. particle size si. odor dens. 9.0 Ib/gal vise. 200-600 cps pH 4.8-5.5 nonionic 55% solids Airflex 4500 [Air Prods./Poiymers]... 

Uses Pigment dispersant emulsion polymerization paints/coatings contributes mech. and freeze/thaw stability to latexes food pkg. adhesives, paper emulsifier in mfg. of food-contact articles Features Allows control of particle size Regulatory FDA 21CFR 175.105,176.180,178.3400 Properties Pale clear liq. oil-sol. nonionic 100% act. 

Apart from coalescence solvents to improve the freeze/thaw stability of emulsion paints are used. Typical... 

Sodium stearoyl lactylate is also used as an emulsifier in food emulsions such as icings, fillings, toppings and coffee whiteners. It is especially recommended for improving freeze-thaw stability of emulsions and foams. 

Anionic surfactants (such as sodium dodecyl sulfate), cationic surfactants (such as cetyltrimethylammonium bromide) (163), and nonionic surfactants (such as the polyoxyethylenated alkylphenols) (136,338) have been used in preparing emulsions. Different types of surfactants can be used in the same recipe (377) to provide additional stability under specific conditions. For example, mixtures of anionic and nonionic surfactants are common. The anionic surfactant controls the particle nucleation stage, and the nonionic surfactant imparts additional electrolyte tolerance, mechanical shear stability (345), and freeze-thaw stability. Mixtures of anionic and cationic surfactants tend to coagulate and are to be avoided. 

In addition, emulsions have a limited freeze-thaw stability. Finally, there is an equilibrium between the silicone, emulsifier, and substrate being treated. Often, the emulsifier also has detergent properties and majority of the silicone ends up in the wash water. 

Latex paints have a number of additives that act as stabilizers, coalescing aids, emulsion stabilizers, freeze-thaw stabilizers, and so on. 

The molecular weight of xanthan gum is >10 dal. In spite of this weight, it is quite soluble in water. The highly viscous solution exhibits a pseudoplastic behavior (Fig. 4.41). The viscosity is to a great extent, independent of temperature. Solutions, emulsions and gels, in the presence of xanthan gums, acquire a high freeze-thaw stability. 

A typical gun-grade acrylic emulsion sealant (Table 15) contains about 18% acrylic polymer solids and 9-10% of a polymeric plasticizer. Sodium polymetaphosphate is a primary pigment dispersant aided by a water-soluble polyacrylate. A nonionic surfactant acts as a wetting agent and emulsifier. Often small amounts (up to 2%) of glycols are included for additional freeze-thaw stability. Mineral spirits (about 2%) retards skin formation. Acrylic emulsion caulks are used indoors as bathtub caulks, baseboard and trim seams, and outdoors for glazing, masonry joints, and roof and siding joints. 

Features Rec. for bright wh. cosmetic w/o emulsions with exc. heat and freeze/ thaw stability very broad range of applies. 

Uses W/o emulsifier for cosmetic creams, topical pharmaceuticals Features Low odor, easy to use forms emulsions with good heat and freeze/thaw stability good oxidative stability natural-based Regulatory JCIC registered DSL listed... 

Uses Vise, control agent, film-former for pharmaceutical tablet coating, foods improves freeze/thaw stability in bakery glazes provides elasticity and improves adhesion of candy coalings emulsion stabilizer, dispersant for flavor oil emulsions and encapsulation... 

Features Eiegant sensory props. iong flow props. economical version of OptaSense RMA52 aids in freeze-thaw stability of emulsions and suspensions Properties Milky wh. liq. vise. 10,000->100,000 cps 30% act. 

Uses 0/w emulsifier, solubilizer for floor finishes freeze/thaw stabilizer in latexes intermediate for solv. emulsion cleaners wetting agent in adjuvants and liquid flowables dispersant in liquid flowables Features c. stability at high temps. 

Uses Emulsifier for cosmetic w/o creams with high amounts of paraffins coemulsi-f er for water-miscible metal working fluids Features Provides emulsions with stability at elevated temps, and with good freeze/thaw stability Regulatory DSL listed... 

Features Produces brilliant appearance good elevated temp, and freeze/thaw stability stable emulsions from pH 5.5-8.5 Regulatory Canada DSL listed... 

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