Epoxy-acrylate hybrids

The GMA clear coatings have outstanding exterior durability, hence their acceptance in the automotive sector (see Fig. 2). Pigmented GMA acrylic powders have not foimd widespread use in market areas other than automotive, eg, architectural applications. Hydroxyl functional acrylic resins cured with blocked isocyanates or uretdione-based curatives have also found use in automotive applications and their exterior durability is only somewhat less than that of the GMA acrylic powders (50). Carboxyl functional acrylic resins are also commercially available. They can be cured with TGIC for exterior applications or with bisphenol A epoxy resins. The latter combinations are sometimes called acrylic-epoxy hybrid coating powders and are noted for their excellent hardness, stain, and chemical resistance. They find use primarily in appliance coatings (79). 

Lu, H.M., and Meng, X.K. (2009) Synthesis and characterization of silica-acrylic-epoxy hybrid coatings on 430 stainless steel. Surf. Coat. Technol, 204 (1-2), 91-98. 

Depending on the chemistry of the adhesive, the adhesion to different substrates (Dettner 1991) and the tolerance for surface contamination is different. Epoxy and acrylic-based adhesives bond well to a variety of different surfaces like metals, aluminium, or composites and tolerate some degree of surface contamination like oil if cured by heat. They do not adhere well to low-energy surfaces like plastic. Two-part epoxy formulations need a cleaning of the surface to remove any contamination. Special two-part acrylic-epoxy hybrid adhesives are able... 

The preparation for bonding is different, whether one-part heat-curing adhesives or two-part formulations are used. In the case of one-part epoxy adhesives, the surface just needs to be cleaned from any contamination like dust. Oil is tolerated in an amount lower than about 3 g/m. Higher viscous oils like dry lubes are tolerated up to about 2 g/m. In case of applying two-part formulations, with the exception of acrylic-epoxy hybrids, oil and any other contamination need to be carefully removed. 

Table 14.6 illustrates typical improvements noted in epoxy hybrid formulations with vinyl chloride, acrylic, and styrene butadiene lattices. Tensile strengths of cured, latex-saturated paper substrates are listed in absolute numbers while those of latex-epoxy hybrids are listed as percent increases in tensile strength over that of the latex alone. The mechanisms believed responsible for these improvements are (1) cocuring of the epoxy group with carboxyl and amine functional groups present on the latex backbone and/or (2) homopolymerization of the epoxy catalyzed by the tertiary amine included in some hybrid formulations. 

Kawahara et al. [187] prepared acrylic/epoxy composite latexes via hybrid miniemulsion polymerization. Landfester et al. [188] have incorporated PMMA... 

Binders for thermosetting powder coatings are often called a hardener. The hardeners are a mixture of a primary resin and a cross-linker. The major types of binders can be limited to polyester, epoxy, hybrid epoxypolyester, acrylic, and UV cure types. Polyester binders are used for good exterior durability, retention of gloss, and resistance to chalking. 

RTM is compatible with a variety of thermosetting polymers including polyester, vinyl ester, epoxy, phenolic, modified acrylic, and hybrid polyester-urethane. A convenient typical viscosity of thermoset precursors is in the range of 0.2-0.6 Pa s. The RTM process has the following advantages (i) emissions are lower than in open-mold processes such as spray-up or hand lay-up (ii) it can produce parts faster, as much as 5-20 times faster than open-mold techniques (iii) the mold surface can produce a high quality finish (iv) complex mold shapes can be achieved and... 

Chem. Descrip. Polyethylene wax CAS 9002-88-4 EINECS/ELINCS 200-815-3 Uses Surf, modifier, slip agenL scratch/abrasion resist, aid, processing aid for powd. coalings based on epoxy, hybrid, polyester urethane, acrylic Features Larger particle size Regulatory EDA 21 CFR 175.300 Lanco 1550 [Lubrizol]... 

Waterborne coatings. These are based on two-component epoxy-polyamine/polyamidoamine or epoxy-acrylic latex hybrids. One limitation of the water-borne systems is their poor cure in high humidity conditions. They have made some penetration in industrial maintenance coatings and are expected to grow more significantly in the future. 

Hybrids, or combinations of different polymer families, are also used. Examples of hybrids include acrylic-alkyd hybrid waterborne paints and the epoxy-modified alkyds known as epoxy ester paints. 

The most commonly used radiation-curable resin systems for cloth finishing are based on acrylated epoxies, acrylated urethanes, and patented hybrid systems which form interpenetrating networks. Mixtures containing 25-40% phenolic or other heat-curable resins are particularly useful. 

Hybrid systems of acrylics with other technologies have been reported. Aciylic and epoxy polymers can be coupled through the use of 2-methacryloloxyethyl phosphate. The phosphoric acid functionality reacts with epoxy and the methacrylate group copolymerizes with the acrylic backbone [ 145] (Scheme 14). 

The effect of polymer-filler interaction on solvent swelling and dynamic mechanical properties of the sol-gel-derived acrylic rubber (ACM)/silica, epoxi-dized natural rubber (ENR)/silica, and polyvinyl alcohol (PVA)/silica hybrid nanocomposites was described by Bandyopadhyay et al. [27]. Theoretical delineation of the reinforcing mechanism of polymer-layered silicate nanocomposites has been attempted by some authors while studying the micromechanics of the intercalated or exfoliated PNCs [28-31]. Wu et al. [32] verified the modulus reinforcement of rubber/clay nanocomposites using composite theories based on Guth, Halpin-Tsai, and the modified Halpin-Tsai equations. On introduction of a modulus reduction factor (MRF) for the platelet-like fillers, the predicted moduli were found to be closer to the experimental measurements. 

However, newer adhesives systems having moderate temperature resistance have been developed with improved toughness but without sacrificing other properties. When cured, these structural adhesives have discrete elastomeric particles embedded in the matrix. The most common toughened hybrids using this concept are acrylic and epoxy systems. The elastomer is generally a amine- or carboxyl-terminated acrylonitrile butadiene copolymer (ATBN and CTBN). 

In this book I have confined discussion to those polymeric materials which are cured by chemical reaction and which have found widespread application in the construction industry. As such, the book covers materials based on epoxies, polyurethanes, silicones, polysulphides, alkyds and polyesters. In addition, there is a chapter on hybrid polymer systems and one on acrylics. It is true that acrylic emulsions are not strictly thermosetting polymer systems, but their widespread use and importance made their exclusion difficult. These materials find use as coatings, sealants, adhesives, grouts, flooring compounds, repair compounds and waterproofing agents. 

Among the countless number of applications of polymers, the construction industry is one which utilises several polymeric materials. In this book I cover those polymeric materials which are single or bicomponent systems and are cured at ambient temperature either with the aid of curing agents or atmospheric moisture. The various polymers used in manufacturing such products include epoxies, polyurethanes, acrylics, silicones, polysulphides, alkyds and polyesters. As a result of innovation, new technologies exist which utilise more than one polymer in a single product. Such systems are discussed in Chapter 10, on hybrid polymers. 

Another development has been reported by P.A. Lucas, W.E. Stamer and S.G. Musselman of Air Products and Chemicals Inc. (Lucas et al., 1994). An acrylate functional urethane flexibiliser has been used to modify epoxy resin, which optimises reactivity and is more compatible with epoxy. Urethane-acrylate flexibiliser offers very tough hybrid epoxy systems meeting the more demanding requirements of civil engineering applications. 

Relevant systems are mbber-toughened epoxy resins, high-impact acrylic (PMMA particles in mbber matrix, obtained by radical polymerization of 80/20 MMA/EVAc mixture), polyimide/silica hybrid materials (obtained using the sol-gel method), and a very high strength ( 60 MPa) mbbers (obtained by peroxide cure of a hydrogenated nitrile rubber/ zinc dimethacrylate system) [Inoue, 1995]. 

Worldwide use and sales for acrylic adhesives of the types discussed here are difficult to determine, particularly since so many of the chemistries involved are nowadays hybrids of more than one type. Acrylics would, no doubt, not be considered the major chemical family of adhesives, when compared to epoxies and urethanes. Nevertheless, due to the need for the unique handling characteristics and performance properties achievable with acrylics, they maintain and will continue to maintain an important position among high performance structural adhesive types. 

In one example, a UV aerobic acrylic replaced an epoxy adhesive in an aircraft application. Epoxy adhesives frequently have been used to bond through-hole hybrid eomponents onto PC boards. This prevents breaking of the fragile leads under common aircraft stresses sueh as temperature changes and vibration. 

Chem. Descrip. PTFE-modified polyethylene wax Uses Surf, modifier, slip agent, abrasion resist, aid, mar resist, aid for wood finishes, UV-cured coatings, can and coil coatings, powd. and industrial coatings based on acrylics, alkyds, PU, NC and blends, epoxies, polyesters, hybrid systems... 

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