Resins, properties aqueous dispersions

Poly etrafluoroethylene is manufactured and sold in three forms granular, fine powder, and aqueous dispersion each requires a different fabrication technique. Granular resins are manufactured in a wide variety of grades to obtain a different balance between powder flows and end use properties (Pig. 1). Pine powders that are made by coagulating aqueous dispersions also are available in various grades. Differences in fine powder grades correspond to their usefulness in specific appHcations and to the ease of fabrication. Aqueous dispersions are sold in latex form and are available in different grades. A variety of formulation techniques are used to tailor these dispersions for specific appHcations. 

In the following decades, homo-, co- and terpolymers of VAM with other vinyl esters, (meth)acrylates, and ethylene were developed to give thermoplastic materials with tailored properties that are nowadays produced as solid resins, aqueous dispersions and dispersible powders. 

Gutierrez-Rocca, J.C. McGinity, J.W. Influence of aging on the physical-mechanical properties of acrylic resin films cast from aqueous dispersions and organic solutions. Drug Dev. Ind. Pharm. 1993, 19 (3), 315-332. 

Filled or compounded resins contain pigments, surfactants, and other additives to modify the plastic properties. These additives are likely to present risks and hazards in the processing of fluoropolymer compounds. For example, aqueous dispersions of fluoropolymers contain surfactants that may produce... 

Base materials for circuit boards based on phenolic resin/paper laminates are used primarily for low-performance materials, which are needed, for example, in consumer electronics. The actual properties standard of these materials meets the requirements of the market. The laminating adhesives used for the manufacture of base materials are organic solutions or aqueous dispersions of thermosetting resins such as poly(vinyl butyral)-phenolic resin or acrylate-phenolic resin. 

Hybrid aqueous dispersions were prepared containing both acrylic resins and polyurethane to provide enhanced properties for coating applications. Nanosized (approximately 50 mn) hybrid latexes were prepared at 30 C by the redox-initiated miniemulsion polymerisation of n-butyl methacrylate monomer in the presence of a urethane prepolymer. A stabiliser, of low molecular weight and low water solubility, was required to obtain stable particles of the required size. 7 refs. 

The discovery in 1807 that water resistance in paper could be achieved by precipitating partially saponified rosin with alum on pulp led to a market that has been the major use of rosin for many years. In addition to the simple aqueous dispersion of sodium resinate, called paste size, rosin sizes in emulsion and dry form are also used. The composition of the rosin, the amount of neutrals and oxidized components as well as the resin acid composion, affects the efficacy and physical properties of a size. The efficiency of rosin sizes is improved by fortifica-... 

Tackifying resins must be added to latex in the form of an aqueous dispersion. These are available commercially, although at present the choice is not as wide as with solid resins. Considerable expertise is required to formulate resin dispersions, as it is important that the particle size be small, preferably less than 1 fxm in diameter. Large particle dispersions may result in reduced tack and delay in attaining equilibrium between rubber and resin in the adhesive film. The most popular resins for natural rubber are based on rosin esters, and these may be extended with cheaper synthetic hydrocarbon resins depending on the adhesive properties... 

Although there is a continuous progression of properties from water soluble resins, through colloidal dispersions, to aqueous emulsions, it is possible to tabulate tbe typical properties of each as in Table 7-1. 

For printing inks that require specific properties not obtainable by conventional styrene acrylic emulsions, an aqueous dispersion of an add functional polyurethane-epoxy acrylate hybrid (self crosslinking for improved chemical resistance) [9] patented by Air Products and Chemicals, Inc. or a self crossHnking styrene acrylic emulsion which reacts upon evaporation of water [10] patented by Akzo Nobel Resins BV, may be used. The Air Products novel dispersion contains a quaternary ammonium polyurethane acrylic hybrid carboxylate salt and pendant acrylate epoxide that selfcrosslink upon evaporation of water and ammonia. Akzo s novel polymer contains a diacetone acrylamide reactive monomer and a bishydrazide. The crossHnking reaction between ketone groups and a bishydrazide proceeds rapidly at room temperature, after evaporation of water from the ink. 

Suspension Polymerization. At very low levels of stabilizer, eg, 0.1 wt %, the polymer does not form a creamy dispersion that stays indefinitely suspended in the aqueous phase but forms small beads that setde and may be easily separated by filtration (qv) (69). This suspension or pearl polymerization process has been used to prepare polymers for adhesive and coating appHcations and for conversion to poly(vinyl alcohol). Products in bead form are available from several commercial suppHers of PVAc resins. Suspension polymerizations are carried out with monomer-soluble initiators predominantly, with low levels of stabilizers. Suspension copolymerization processes for the production of vinyl acetate—ethylene bead products have been described and the properties of the copolymers determined (70). Continuous tubular polymerization of vinyl acetate in suspension (71,72) yields stable dispersions of beads with narrow particle size distributions at high yields. 

In aqueous epoxy resin dispersions, based on poly(glycol)s, bisphenol epoxies and 3-amino-1,2,4-triazole in propylene glycol monobutyl ether, the triazole compound imparts enhanced corrosion protective properties. The composites have good shelf lifetimes. ... 

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