Cross-linking acrylated epoxy systems

Thermosetting acrylics can be produced from a variety of monomers in varying percentage compositions the systems utilize a variety of cross-linking mechanisms (Table IV). A typical thermosetting acrylic can be prepared from 15-80% styrene, 15-18% alkyl acrylate, and 5-10% acrylic acid (27). Acrylic acid provides the functionality for cross-linking with epoxy resins. 

Newer adhesives of the acrylic, anaerobic or radiation-curable types must, if they are structural, have a relatively high degree of toughness and durability if they are to compete with or challenge epoxy adhesive systems. Likewise, newer radiation-curable, pressure-sensitive adhesive systems must exhibit the properties of permanence largely associated with cross-linked adhesive masses deposited from an acrylic solution polymer base. Epoxy resin structural adhesives largely define the existing area on the one hand the cross-linked acrylics deposited on plastic or metallic films the other. 

Epoxy-amino and epoxyacrylate High molecular weight epoxy resins cross-linked with amino or acrylate resins Water reducible for reduced environmental impact Good Limited Universal lacquer for beer and beverage cans (water reducible) Side seam stripes Some food systems... 

As mentioned earlier, UV-curable resin formulations are very attractive for fiber coating because of the rapid cross-linking rates that are achievable. Most commonly, epoxy- or urethane-acrylate resins are employed (18-22), and viscosity and cross-link density are controlled through the addition of reactive diluents. With these systems work has focused on producing low modulus, low T properties (20-22) through the incorporation of appropriate chemical constituents to enhance higher chain flexibility, for example, ether linkages. 

There are strengths and weaknesses among the various acrylic thermosetting systems. For example, acid epoxies and urethane cross-linked systems produce no volatile byproducts. Cure temperatures differ widely (see Table VIII). These and other factors determine the acceptability of a particular system for a given application and allow the user considerable latitude in choosing an acrylic that best meets his requirements. 

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). 

Some of the resins introduced may form a film of their own but it is preferable to react them with a hardener or curing/cross-linking agent in order to produce a cross-linked resin network that cures fairly fast in either room temperature (RT) or at elevated temperatures. For instance, the epoxy-acrylate system can be cross-linked with an isocyanate-based silane with a structure shown below [61] ... 

---