Epoxy Dispersions

Two-component epoxy resin water thinned dispersions are now being used as floor sealers. They have good adhesion to concrete as well as good chemical resistance. However, the particle size of the dispersion is comparatively large (approximately 1-1.5 microns) and consequently penetration into good-quality concrete is minimal and an on-surface seal is obtained. However, with porous low-quality concrete substances, considerable binding/strengthening, etc. of the surface can be achieved with water-dispersible epoxy resin-based floor sealer. 

Woo et al. (1994) studied a DGEBA/DDS system with both polysul-fone and CTBN. The thermoplastic/rubber-modified epoxy showed a complex phase-in-phase morphology, with a continuous epoxy phase surrounding a discrete thermoplastic/epoxy phase domain. These discrete domains exhibited a phase-inverted morphology, consisting of a continuous thermoplastic and dispersed epoxy particles. The reactive rubber seemed to enhance the interfacial adhesive bonding between the thermoplastic and thermosetting domains. With 5 phr CTBN in addition to 20 phr polysul-fone, Glc of the ternary system showed a 300% improvement (700 Jm-2 compared with 230 J m 2 for the neat matrix). 

Water is also sometimes used as a solvent for water-soluble resins. In the case of epoxy resins, water is generally used to disperse epoxy particles in an emulsion. These waterborne epoxy adhesives are discussed in Chaps. 4 and 14. 

Casamid . [Air Prods. Pacific Anchor] Water-dispersible epoxy curing agents. 

Water Dispersible Epoxy-g-Acrylic Copolymer for Container Coating... 

In recent years, water-dispersed epoxy resins also have gained importance in a variety of applications. Water-soluble epoxy resins are prepared by the esterification of epoxy resin with drying oils/ fatty acids of drying oil, followed by the formation of either half esters of dicarboxylic epoxy esters, or maleinised epoxy esters through reaction with polybasic acid anhydrides. They become water soluble on neutralisation with dimethyl etha-nolamine (Fig. 7.4). The cationic polymerisation of emulsified epoxy resins by 1 % perchloric acid has also been reported. The polyols obtained were cross-linked with MF resin to produce waterborne coatings, which are free from co-solvent and show excellent solvent resistance at low bake temperatures. ... 

Hydantoin-Based Epoxy Resins. These resins were commercialized by Ciba-Geigy. Hydantoins are prepared from carbon dioxide, ammonia, hydrogen cyanide, and ketones via the Bucherer reaction and can be epoxidized with epichlorohydrin (67). Cured and imcured resin properties depend greatly on the nature of the substituents R and R. The hydantoin derived from acetone furnishes a low viscosity, water-dispersable epoxy resin, 5,5-dimethyl-l,3-bis(2,3-epoxypropyl)-2,4-imidazolidinedione (R = R = CH3 145 EEM rj at 25°C 2.5 Pa s). A nonsintering solid epoxy resin is obtained if R = R = —(CH2)5—. 

It is enlightening to be able to handle a sample of the soUd polymer. A useful method for forming a sheet of polymer is to cast the Uquid into a silicone rab-ber mould, say 75 x 75 x 1mm deep. A silicone mould can only be used with materials that do not seriously swell the rubber, e.g. dispersions, epoxies and wax. Preparing a hand sample for a liquid that reacts with the mould material, e.g. solutions in organic solvents, is more difficult. One can allow a puddle on polyethene to dry or cast in a well made by waxed microscope slides (Bradley and Wilthew, 1984), but it is difficult to achieve uniformity between samples in this way. Equipment is commercially available for the purpose from polymer and paint test instrument manufacturers, and is usually more cost-effective and the results more transferable than trying to make one s own equipment. 

Balakrishnan S and Raghavan D (2004) Acrylic, elastomeric, particle-dispersed epoxy-clay hybrid nanocoinposites Mechanical properties, Macromol Rapid Commun 25 481-485. 

T. Naganuma, Y. Kagawa (2002) Effect of particle size on the optically transparent nanometer-order glass particle-dispersed epoxy matrix composites. Compos. Sci. Technol. 62, 1187. 

The use of silanization as treatment for clays prior to their use in UV-curable formulations is based on the availability and reactivity of hydroxyl groups in the clay strucmre. Thus, the surface modification of MMT by glycidyl-propyl-triethoxysylane (GPTS) allowed new highly dispersed epoxy resin-based nanocomposites with enhanced scratch resistance and low susceptibility to crack formation and propagation [240]. 

Microscopic studies of basic epoxy adhesive and silicate nano powder dispersed epoxy adhesive is carried out under scanning electron microscope (SEM). The fractured surfaces of the adhesive joints are also examined under SEM. Typical features of the fi-actured surfeces are photographed. 

Meeske, C. J., Van derTuin, E. H., Racey, M. J., Reichold Chemicals, US Patent 4,166,054, Water Dispersible Epoxy resin Copolymers and Methods of Making Same, 1979. 

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