Acrylic emulsions: film formation

Acrylic emulsion - The emulsion consisted of suspended crosslinked (gel) particles that are not water-soluble and form a film upon evaporation of the aqueous phase. However, the water did not evaporate quickly enough to form a continuous film on agar because agar is 95% water, and it continuously provided moisture that prevented film formation. The result was a porous barrier, but a continuous film was later obtained by dissolving dried emulsion solids in ethanol. 

The freeze/thaw (F/T) stability of a polymer emulsion serves as a macroscopic probe for investigating the properties of the average particle in a polymer emulsion. A review of the factors which contribute to this stability is included. A study of styrene-ethyl acrylate-methacrylic acid polymers shows the existence of a minimum in the plot of minimum weight percent acid required for F/T stability vs. the minimum film formation temperature (MFT) of the polymer. This is considered to be a function of both the amount of associated surfactant and the minimum acid content. Thus, both the type of surfactant and the copolymer ratio—i.e., MFT—play major roles. Chain transfer between radicals and polyether surfactant resulting in covalently bonded surfactant-polymer combinations is important in interpreting the results. 

A series of latex copolymers were prepared using a typical emulsion polymerization recipe and procedure only the monomer composition was varied. The control composition (80/20 vinyl acetate/butyl acrylate) is similar to that used for interior latex paint. Table V lists the compositions and properties of the latexes. Percent solids, pH, and particle size are similar for all the latexes. Viscosity varies somewhat, but is within limits for this type of latex. The only unreacted monomer detected was the vinyl acetate. Thus, the incorporation of VEC into the emulsion polymerization via the monomer mixture did not affect the latex synthesis. The Tg and minimum film formation temperature (MFFT) of the latexes increase with increasing VEC content, which is expected based on the previous results. 

A majority of the acrylic emulsion polymers used in textile and non-woven applications are crosslinked or cured after film formation to provide wet stroigth, solvent resistance and durability to laundering and dry cleaning. As with architectural coatings binders, the principal monomers used are BA, EA and MMA,... 

Uses Acrylic for very low VOC coatings, esp. low VOC concrete and tile sealers, wood sealers, concrete stains and sealers Features Hard, fast drying good water resist. extremely low min. film formation temp. good hold out in wood sealers Properties Off-wh. translucent emulsion dens. 8.6 Ib/gal vise. 30 cps pH 8.3 hardness (Konig) 37 42% NV by wt. 

Uses Acrylic for coatings, automotive interior rigid plastic applies. Features Very hard emulsion with lower than expected min. film formation exc. chem., detergent, and water reset. exc. weathering resist, and adhesion to plastics... 

Surfmers , i.e. surfactants which also acted as copolymerisable monomers, were synthesised from the hemi-ester of a fatty alcohol and maleic anhydride and were then used in the preparation of self-crosslinking dispersions by seeded semi-continuous emulsion polymerisation of acrylate monomers. Water-borne exterior wood stains were prepared from the dispersions and their properties were studied. The use of surfmers as sole emulsifiers in emulsion polymerisation was considered and data were obtained on the effects of surfmers on film formation, water barrier properties, gloss retention and mechanical properties. Environmental aspects of the use of products involving surfmers were examined. 6 refs. 

It is well-known that viscosity, self-diffusion coefficient and glass transition temperature are a strong function of molecular weight (MW). The film formation characteristics of an acrylic (BM A/MM A/M AA) latex as a function of its average MW is reported. The latex with the high MW is compared to an identical formulation with a low MW. The latex dispersions are prepared by standard techniques of emulsion polymerisation using an anionic surfactant, ammonium dodecyl benzene sulphonic add, and ammonium persulphate... 

The effect of the Tg of the latex on the film-formation behaviour of a series of 2-ethylhexyl acrylate/methyl methacrylate emulsion copolymers was studied. Stage 1 of fihn formation was examined using a combination of DMA and conductivity measurements. Stages 2 and 3 were investigated using calorimehic compensation, DSC, dielectric spectroscopy and atomic force microscopy. Comparison of the results from the different methods employed led to a detailed model of the film-formation process in which the temp, used relative to the minimum film-formation temp, determined the effectiveness of the processes. The relative usefulness of the techniques used in their ability to characterise the various stages in the film-formation process was assessed for these copolymer systans. 23 refs. 

No.6,23rd March 1999, p. 1715-21 LATEX BLENDS OF FLUORINATED AND FLUORINE-FREE ACRYLATES EMULSION POLYMERIZATION AND TAPPING MODE ATOMIC FORCE MICROSCOPY OF FILM FORMATION... 

Poly(methyl methacrylate) is quite resistant to alkaline saponification the problem lies with the polyacrylates [6], However, acrylic emulsion polymers cannot be composed solely of methyl methacrylate because the resulting polymer would have a minimum film formation temperature of over 100°C. Forming a film at room temperature with methyl methacrylate would require unacceptably high amounts of external plasticizers or coalescing solvents. For paint formulations, acrylic emulsion polymers must be copolymerized with acrylate monomers. 

Thus, it follows that proper selection of the types and amounts of monomers is critical in deriving acrylic copolymer resins with the correct T, which in turn controls many physic-chemical properties of their coatings. Besides considerations, monomer selection also takes into account such important properties of coatings as outdoor durability, film clarity, gloss, gloss retention, film formation capability and emulsion stability. 

Cast films of emulsion blends comprised of non-fluorinated acrylics and fluorinated acryhcs exhibited surface enrichment of the fluorinated acryhc upon exposure of the film above the film formation temperature of the fluorinated acryhc [546]. Similar results were observed for smaU particle size fluorinated acryhc copolymer emulsion blends with large particle size S-nBA copolymers [547]. The combination of low free energy and smaller size of the fluorinated acryhc particles (excluded volume/percolation) yielded much higher concentration of the fluorinated polymer at the surface than in the bulk film. 

Emulsions resulting from the emulsion polymerisation of acrylic or vinyl monomers are unique compared to other resins used for surface coating applications. As such they have properties which are totally different to a conventional solution acrylic, polyester or alkyd resins. Their mechanism of film formation is totally different to other types of resins. Because particles are present it is necessary for them to coalesce to film form and pigmentation is also different to conventional solution polymers. Consider first the unique properties and test methods of emulsion polymers. 

NeoCiyl A-1049-U is an anionic aciylic dispersion, 40 %nvc with a MFFT of 40 C. NeoCiyl BT-21 is an acrylic dispersion, 40 %nvc. Sudranol 100 is a wax emulsion to improve water repellency. Steinapol SBDO-70 (Rewo) can be used as the wetting ad tive. For good film formation, a combination of coalescents and plasticisers are added. 

Uses Wetting agent, dispersant, antistat, defoamer, gellant, solubilizer, lubricant base for cosmetic, medical, paper, pharmaceutical and textile industries coalescing solvent for plasticizing acrylic emulsion polymers, latex caulks, epoxies, alkyds, polyesters, phenolics increases flexibility and toughness, improves film formation... 

Substituted vinylindolizines sometimes polymerize spontaneously and also copolymerize with styrene. Polymers of similar structure have been prepared by formation of indolizines on the polymer chain using methods outlined in Sections 3.08.3 and 3.08.6 (see Scheme 36 for an example). Moreover, indolizine dyes such as (214) have been bound to an ethyl acrylate/acrylic acid copolymer by heating to give dyes that do not migrate in photographic colour film emulsions. 

Application Dedusting agent for dry cleaning detergent, alkaline powders, water-repellent fabric finishes. Used in emulsion polymerization for formation of polyvinyl acetate and acrylic films. 

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