Water-based epoxy resins

The purpose of this paper is to present a new water based epoxy resin system which will meet the current requirements of the industry. In addition, an experimental system will be presented which will approach the emerging requirements of the industry. 

A new water based epoxy resin system has been developed for the electrical reinforced plastics industry. 

Chem. Deserp. One-part, water-based epoxy resin with conosion inhibitors Bisphenol /Vepichlorohydrin epoxy (< 10%), bisphenol A novolac epoxy resin (< 10%), ethanol (2-10%), propylene glycol (5-15%), carbo) zircoaluminate sol n. (< 5%), etc. 

The results were positive and promising. Bagherzadeh et al. [81] found that the anticorrosion performance of a two-component water-based epoxy resin coating system was improved by adding only 0.02 wt% nano-PANI. Ahmad et al. [82] investigated the corrosion protection behavior of waterborne resorcinol formaldehyde (RF)-cured composite coatings of poly(l-naphthylamine) (PNA)/poly(vinyl alcohol) (PVA) on mild steel, and even superior corrosion protective performance was observed in different corrosive media when compared with the reported solvent-based conductive polymer coatings. 

Water-based epoxy resins not applied by electrodeposition are mostly of the anodic type and maleinized epoxy esters are frequently used. Another class is the epoxy acrylic graft copolymer, where the epoxy resin is rendered water-soluble by attaching side chains of acrylic polymer containing a high amount of methacrylic acid. The process of grafting is similar to that of chain transfer (p. 67), where acrylic chains are attached by hydrogen abstraction. This process is illustrated in Fig. 14.2, where C- represents a radical site, and represents an extended acrylic chain containing both methacryclic acid and styrene components. 

The first step reaction example involves the preparation of water-based epoxy resins via ring-opening polymerizations of different epoxides with various diamines, dithiols or diols residing in the miniemulsion droplets at 60°C [75]. The basic requirement for successful miniemulsion polymerization is that both reactive components exhibit relatively low solubility in the continuous aqueous phase. The diepoxide Epikote E828, triepoxide Decanol EX-314, and tetraepoxide EX-411 are potential candidates for this purpose. Furthermore, incorporation of conventional costabilizers such as hexadecane into the... 

FIGURE I 1.7 Chromatogram of an amine-based epoxy resin. The analysis of an amine-based epoxy resin was obtained on a column bank of 7.8 x 300 mm Styragel HR O.S, HR I, HR 2, and HR 3 columns. (Courtesy of Waters Corp.)... 

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. 

Bromide analysis, of water, 26 41 Bromide ions, in development solution, 79 205-206 Bromides, 4 319-330 thorium, 24 763 titanium, 25 54 tungsten, 25 379 uranium, 25 439 Bromimide, 4 299, 319 Brominated additive flame retardants, 77 461-468, 471-473t Brominated Anthanthrone Orange, pigment for plastics, 7 367t Brominated aromatic compounds, 7 7 459 Brominated bisphenol A-based epoxy resins, 70 366... 

In particular, they found enhanced bonding between metal surfaces and resins such as acrylics (solvent- and water-based), epoxy chlorinated rubbers, silicones, and polysulphides. It was noted that titanium complexes caused colouration with phenolics, whilst zirconium complexes did not. 

Glycidyl Ethers of Aliphatic Polyols. Glycidyl ether epoxy resins based on polyols provide greater flexibility and lower softening temperatures for the final cured epoxy system. The polyol is reacted with epichlorohydrin to produce these resins. These resins are generally not used alone because of water sensitivity and overall lack of toughness. However, they serve as modifiers for DGEBA-based epoxy resins. An idealized structure for a flexible resin based on this chemistry is shown in Fig. 2.9. 

Water-based epoxy primers are ideal for damp porous substrates, as such primers will penetrate to an adequate depth to ensure good adhesion and produce a sound surface for bonding. Emulsifiable resins and hardeners are available, and the better systems deactivate the emulsifier system during cure to ensure that the cured system is not unduly water sensitive (Section VI.A). Solventless epoxy primers are used for bonding new concrete to existing concrete. Polyamide hardeners are preferred because of their ability to cure satisfactorily in the presence of water. Accelerators and diluents may be added, but fillers are generally omitted. The primer is applied to the existing concrete, and the fresh concrete cast before the resin has set (Section VI.B). 

Figure 12.12 DMT A tan d spectra of a cured, untoughened Fibredux 924 base epoxy resin showing the reduction of Tg with water absorption and the development of secondary peaks (Tg2, Tgs) on moisture absorption (a) isothermally and (b) dynamically in the presence of thermal excursions to 100, 140 and 200 °C [4],...

There are many examples in the literature of the structural characterization of polymeric systems by FD-MS. Some of these will be briefly mentioned here. Saito and coworkers in Japan have studied a number of polymers by FD-MS. FD spectra were used to identify various poly(ethylene glycol) and poly(pro-pylene glycol) initiators (water, ethyleneimine, glycerol, sorbitol, sucrose). Structures of bisphenol A-based epoxy resins were elucidated. The degree of methylation in methylol melamine resins was assessed. Various novalak resins (made from phenol, alkylphenols, and epoxidized phenols) were characterized. Styrene polymerized with various initiators and chain transfer agents was studied in some cases deuterium labeling was used to help... 

Spike temperature is more important than the presence of water. This is illustrated in Fig. 3.8, where the heat distortion point of the laminates (defined as the onset of the relaxation region from the temperature dependence of the storage modulus) is plotted against thermal spike temperature. The reduced stability of the resins at higher thermal spike temperatures appears to reflect the chemistry by which the modifiers interact with the base epoxy resin. 

A variety of poly/dihydric oils are used for the preparation of glyddyl ether-type epoxy resins. These include bisphenols, namely bisphenol-A (BPA), bisphenol-F (BPF), bisphenol-S (BPS) and bisphenol-H (BPH) and so on. Other aromatic diols and polyols such as phenolic resin, MF resins and hyperbranched polyol may also be used in the preparation of vegetable oil-based epoxy resins. Bisphenol-A (2,2-bis(4-hydroxyphenyl)propane) is one of the most widely used aromatic diols for the synthesis of epoxy resin. The resins are commonly used as lacquers for coated metal products such as food cans, bottle tops and water pipes. There are also reports on the use of bisphenol-S (BPS) (bis(4-hydroxyphenyl) sulphone), in the synthesis of epoxy resin. The advantages of resistance to deformation by heat and improvement of thermal stability were observed for such epoxy resins. The presence of sulphone group (BPS-based epoxy resin) in the epoxy resin exhibits better gel time than BPA-based epoxy. Another important diol, namely bis(4-hydroxydiphenyl)methane or bisphenol-F (BPF) is used for the synthesis of low viscosity epoxy resins. BPF generally comprises several isomers such as bis(2-hydroxylphenyl)methane (i.e. ortho-ortho isomer), bis(4-hydroxylphenyl)methane (i.e. para-para isomer) and... 

Epichlorohydrin (l-chloro-2,3-epoxy propane), is obtained by the chlorination of propylene, followed by the reaction of allyl chloride with hypochlo-rous acid. The resultant product is treated with Ca(OH)2 and is a colourless liquid with a density of 1.18 g cm mp -57°C and bp 115°C. It is a colorless liquid with a pungent garlic-like odour, moderately soluble in water but miscible with most polar organic solvents. Its principal use is as a reactant in the manufacture of diglycedyl ether-based epoxy resin. 

Metal cans that contain food or beverages employ a thin film of an epoxy polymer on its inside surface to control corrosion of the metal and to limit food contact with metal. Epoxy is ideally suited for this application, and the type of epoxy used is predominantly (over 98%) BPA-based. Both aluminum and steel beverage cans are typically sprayed with a water-based epoxy-acrylic system, often with an amino resin (or phenolic resin) to cross-link the lining (Oldring and Nehring, 2007). 

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—. 

Most of the BPA-based epoxy resins are quite rigid and are based on petrochemicals. A quite different type of flexible epoxy resin is based on cardanol, derived from cashew nut shell liquid. Mono-, di- and multifunctional derivatives are possible. Mono- and difunctional low viscosity derivatives are used as modifiers and diluents, while complex di- and multifunctional epoxies are used in two-component ambient cure epoxy systems. They give the cross-linked matrix excellent flexibility, toughness and impact resistance. They possess very good water, chemical and corrosion resistance. 

Photographic films Epoxy blends for thermosetting materials Air-drying water-based paint resins... 

Epoxy resins absorb water depending on relative humidity and release it again when redried. Cycloaliphatic epoxy resins and glycidyl ester-based epoxy resins behave similarly and absorb >2% water. Figure 5.365. Bisphenol A-based epoxy resins also absorb up to approx. 3 to 4% water. 

Figure 5.365 shows the change in water content of glycidyl ester-based epoxy resins at elevated temperatures. Water absorption causes a decrease in tensile strength and electrical strength with the onset of exposure. Figure 5.366. 

Figu re 5.366 Property changes in glycidyl ester-based epoxy resins with silica and aluminum fillers as a function of water absorption, see Table 5.118 [881]... 

Long chain aliphatic epoxy resins based on a poly glycol or a vegetable oil fatty acid, when reacted with epichlorohydrin, are used as additives to flexibilize epoxy resin adhesives. They are not used alone because of their water sensitivity and overall lack of toughness. They serve as modifiers for Bisphenol A based epoxy resins. An idealized structure for flexible epoxy resins is shown below ... 

The majority of internal lacquers for metal decorating are based upon either epoxy or vinyl systems. The latter are all solvent based. Epoxy phenolic lacquers for food cans are generally solvent based. Epoxy resins are modified with acrylic resins or comonomers to make them water dispersible for use in internal lacquers for DWI spray applications. 

To make a typical nanocomposite, Lin and Wu [37] combined 100 g of a sodium-montmorillonite clay with 30 g of hexadecyltrimethylammonium bromide in 5000 ml of hot water nsing a homogenizer. After drying and grinding, the treated clay was combined with 20 g of a bisphenol-based epoxy resin (MW = 360) in a dough mixer. The product is termed a co-intercalated clay since the organic moieties now have... 

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