Resin backbone

The binder system of a plastic encapsulant consists of an epoxy resin, a hardener or curing agent, and an accelerating catalyst system. The conversion of epoxies from the Hquid (thermoplastic) state to tough, hard, thermoset soHds is accompHshed by the addition of chemically active compounds known as curing agents. Flame retardants (qv), usually in the form of halogens, are added to the epoxy resin backbone because epoxy resins are inherently flammable. 

A waterborne system for container coatings was developed based on a graft copolymerization of an advanced epoxy resin and an acryHc (52). The acryhc-vinyl monomers are grafted onto preformed epoxy resins in the presence of a free-radical initiator grafting occurs mainly at the methylene group of the aHphatic backbone on the epoxy resin. The polymeric product is a mixture of methacrylic acid—styrene copolymer, soHd epoxy resin, and graft copolymer of the unsaturated monomers onto the epoxy resin backbone. It is dispersible in water upon neutralization with an amine before cure with an amino—formaldehyde resin. 

As a general rule, the addition of ethylene oxide to a resin backbone will tend to increase the water solubility of the compound. The addition of propylene oxide or butylene oxide to the resin will tend to increase the hydrocarbon solubility of the compound. Often, the dehazer or demulsifier can be made to perform selectively in oil-water systems by adding both ethylene oxide and propylene oxide to the same molecule. Performance and solubility of the alkoxylated compound can then be finely tuned by closely controlling the amount and order of epoxide addition. A random EO-PO based fuel demulsifier is shown in FIGURE 6-6. 

Table II. Effect of Graft Resin on Blend Optical Properties (Resin—Backbone Rubber = 2.5—1.0)...

The effect of the graft resin on the polyblend mechanical properties for this same system (2.5-1.0 resin-backbone rubber) can be seen in Table III. 

Despite the current success and popularity of polymer reagents, the availability of functional resins has been a severe limitation in recent years. For many synthetically important transformations, reliable reagents were not available. Moreover, polymer-assisted synthesis was usually restricted to small scale apphcations, and also suffered from the inherent limitations of the standard support material (e.g., cross-linked polystyrene) such as solvent incompatibihty, adsorption of reagents,14 or the chemical reactivity of the resin backbone. 

The large part of the epoxy resin backbone contains aromatic rings, which provide a high degree of heat and chemical resistance. 

From the limited fracture data available for similarly cured networks generated from these various resin types, little can be concluded as to the role of the resin in fracture. Certainly, the resin backbone contributes to the Tg of the network, and comparisons should take this into account because, as previously discussed, the initiation of crack growth is very sensitive to temperature. If the epoxy resin structure results in complicated network forming reactions, as is possible for TGDM/DDS networks, the structure of the final network will be affected and may likely influence fracture. 

Figure 10.10 (a) Grafting sites (ringed hydrogens) on the epoxy resin backbone (b) epoxy-acrylic graft structure... 

Recognizing that the proximity of the resin backbone and the incorporated reactive tin functionality can be a major drawback, several approaches have been developed for the incorporation of a two carbon unit by hydrostannylation of a vinyl group on the S/DVB polymer (Scheme 5.5.3).4 ... 

Finally, anionic surface dendrimers have been constructed as balloons attached along a Merrifield resin backbone.48 Using an elaboration method based on the diethyl malonate and triethyl methanetricarboxylate procedures previously described,61 dendrimers bearing double and triple branching hydrocarbon arms were prepared with carboxylate termini. These dendrimers are insoluble in all ordinary solvents and serve as high-capacity cation-exchange materials. 

Resin Backbone Functional Group Initial Base Capacity tmeq/ot Base Capacity Lost Durino Test f%)... 

The reaction which consumes epoxides yielding a higher viscosity resin presumably proceeds via reaction of the epoxide with a moiety on the epoxy resin backbone. This is consistent with the original observation that a non-modified epoxy resin undergoes this side reaction. Thus, this reaction ought to obey the rate law described in Equation (5) where R may be another epoxide, or the secondary alcohol. 

Graft epoxy-acrylic copolymer prepared with a free radical initiator is an example of the "grafting from" process. In the case where benzoyl peroxide was used as the free radical initiator, it is determined that about 77% of the free radical initiator instead of causing initiation of monomers, chain transfers with the epoxy resin backbone, followed by the "grafting from" of22onomers onto the epoxy resin. Benzoyl peroxide is known to decompose mostly (90 ) to the benzoyloxy radical and the (10 ) phenyl radical. Mechanisms of grafting can be demonstrated in the following two schemes. (Schemes A and B). 

Transfer with Epoxy resin backbone initially... 

Chart 1.2. Structures of ImPEG resin (1) and ImQ resin standard (2). Hie shaded circle represents the resin backbone. The protons important for NMR quantitation are numbered on the structures... 

The cure reaction in polyester gel coat systems makes them particularly useful model coatings materials since the cure kinetics can be studied by several analytical techniques. The initiation of cure in polyester gel coat resins begins with the decomposition of hydroperoxide (MEKP is predominately hydroperoxide) and the subsequent copolymerization of styrene with the unsaturated groups, either fumarate or maleate, incorporated into the resin backbone. ... 

Flame retardants containing bromine are twice as effective as those containing chlorine. However the price is higher and the UV resistance is lower. The products containing bromine are of aliphatic, cycloaliphatic, aromatic and aromatic-aliphatic type. Tetra-bromobisphenol A (TBBA) is condensed as a flame retardant in PC and expanded polystyrene (EPS). In phenolic and unsaturated polyester (UP) resins di- and tri-brominated phenols and tetra-bromophthalic anhydride serve as reactive components in the resin backbone. 

The mechanism of anhydride cure is complex and controversial because of the possibility of several competing reactions. The imcatalyzed reaction of epoxy resins with acid anhydrides proceeds slowly even at 200°C both esterification and etherification occur. Secondary alcohols from the epoxy backbone react with the anhydride to give a half ester, which in turn reacts with an epoxy group to give the diester. A competing reaction is etherification of an epoxy with a secondary alcohol, either on the resin backbone or that formed during the esterification, resulting in a -hydroxy ether. It has been reported that etherification is a probable reaction since only 0.85 eqiuvalents of anhydrides are required to obtain optimiun cross-linked density and cured properties (103). 

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