Prepolymers epoxy

On the whole, curing procedures appear a promising way to obtain very stable polymer films. Thus, the structure of already mentioned polylysine has been revised as a block polymer involving either the a or e amino groups of lysine Vitamin Bj2 modified carbon electrodes were prepared by thermal curing of a mixture of a diamino functionalized derivative 5 and an epoxy prepolymer 6 of the araldite... 

Much attention has been paid to the synthesis of fluorine-containing condensation polymers because of their unique properties (43) and different classes of polymers including polyethers, polyesters, polycarbonates, polyamides, polyurethanes, polyimides, polybenzimidazoles, and epoxy prepolymers containing pendent or backbone-incorporated bis-trifluoromethyl groups have been developed. These polymers exhibit promise as film formers, gas separation membranes, seals, soluble polymers, coatings, adhesives, and in other high temperature applications (103,104). Such polymers show increased solubility, glass-transition temperature, flame resistance, thermal stability, oxidation and environmental stability, decreased color, crystallinity, dielectric constant, and water absorption. 

The epoxy prepolymer can be cured, that is, converted to a three-dimensional network, in several different ways. A trifunctional amine, such as NH2CH2-CH2NHCH2CH2NH2, can be mixed in and will extend the chain of the polymer and form cross-links by reacting with the oxide rings ... 

Exercise 29-13 Show the reaction whereby butenedioic anhydride would be able to cross-link an epoxy prepolymer with n = 1. 

The value of Tg is important, since rigidity decreases in the glass transition region, Tg is closely related to the structure and crosslinking density of the cured resin. The structure of the cured resin can be derived from the initial starting materials, the epoxy prepolymer and hardener, and reaction conditions. However, the structures of many cured resins is still unclear which prevents to establish the structure-mechanical properties relationships. Further studies are needed. Furthermore, the commercial epoxy formulations may contain several components and also diluents, plasticizers, liquid rubbers, etc. which makes a prediction of Tg and mechanical properties even more difficult. 

The epoxy prepolymers mentioned above would lie in the zero-strength region of curve B in Fig. 1-1. They have low molecular weights and are therefore sufficiently fluid to be used conveniently in surface coatings, adhesives, matrices... 

Another development that has triggered the revival of liquid polysulphides as modifiers for epoxy resins has been the introduction of polysulphide-epoxy prepolymer compositions which have no mercaptan odour in the uncured state. The manufacture of such compositions involves the co-reaction of epoxy resin in molar excess with a suitable liquid polysulphide in the absence of a catalyst to give ... 

Epoxy Prepolymers. These prepolymers are commonly formed from Bisphenol A and epichlorhydrin (Figure 4). A variety of other materials are also employed, but to a lesser extent. The lowest member of the series might well be considered structoterminal, while all the others must be considered as structopendant prepolymers. Molecular weights range from a few hundred to about 4000 for commonly used industrial epoxy prepolymers. Most common cross-linking agents are amines and anhydrides however, epoxies may also be combined with a variety of other prepolymer systems (25). 

Liquid crystalline thermoset epoxy prepolymer Not applicable Nematic to isotropic 176... 

Degree of cure. The titration results given in Table III reveal that from 98% to 100% of the functional groups had reacted. Similarly no evidence for incomplete cure was observed by DSC or by dynamic mechanical spectroscopy (DMS). However, it may be pointed out that 2% unreacted functional groups could result in detectable incoherence (see reference 29) in the networks prepared from high-MW epoxy prepolymers. 

Morphological Differences. In epoxy prepolymers, the reactivity increases with the number of hydroxyl groups present in the prepolymer chain (44). Thus, an increase in the molecular weight of the epoxy prepolymer would not only reduce its diffusivity but would also increase its reactivity, resulting in a reduced time of microgel formation. This combined effect would result in a smaller size of the primary microgels, as observed exper imentally. 

All the blends have an upper critical solubility temperature (UCST) behavior. It is evident that the CE monomer is a better solvent of rubbers than the epoxy prepolymer. 

The third type of composition is exemplified by acrylate- and methacrylate-ester derivatives of epoxy resins combined with a photoinitiator 1. Epoxy prepolymers (e. g., glycidyl methacrylate-allyl glycidyl ether copolymers or Ciba ECN 1299) combined with a photosensitive aryldiazonium compound (e.g., -nitrobenzenediazonium hexaflourophosphate) (38,39) 2. Epoxy prepolymers (e.g., a diglycidyl ether of disphenol A-(3,4-epoxycyclohexyl)-methyl-3,4-epoxycyclohex-anecarboxylate-alkyl glycidyl ether mixture) combined with a photosensitive aryldiazonium compound (e.g., -chlorobenzenediazonium hexaflourophosphate) and l-methyl-2-pyrrolidone gelation inhibitor (40) ... 

Syntactic foam is made by dispersing hollow microballoons into a liquid polymer and then solidifying it. Microballoons are typically hollow glass or hollow phenolic microspheres, and the most common liquid polymer is an epoxy prepolymer, which is then cured. Although some products are notably woodlike in their properties and machinability, primary applications are high-performance products such as deep-sea instrumentation. 

After surface treatment, all substrates were stored less than 2 hours in an air-conditioned room (20 2°C and 50 5%r.h.), before polymer application. The epoxy prepolymer used was diglycidyl ether of bisphenol A (MW=348 g mol , DGEBA DER 332 from Dow Chemical). The curing agents were either IPDA from Fluka or DETA from Aldrich. Assuming a functionality of 4 for IPDA, 5 for DETA, and 2 for the epoxy monomer, the stoichiometric ratio aje used was equal to 1 (exceptions are mentioned). 

For aU systems except those on gold, after apphcation to metaUic surfaces amines were modified to form an organometaUic complex. Then, the initial Uq-uid epoxy-amine mixture was transformed into a mixture of organometaUic complexes and pure (i.e., unmodified) amine with pure epoxy prepolymer. 

Table III. Typical Hardners Used With Epoxy Prepolymers.

In view of the functionality thus created, it is interesting to consider possible applications for the epoxldlzed oils mentioned as epoxy monomers per se. Indeed, some epoxldlzed oils are commonly used as reactive diluents for other epoxy prepolymers in order to reduce cost or Improve processability (10,11) examples claimed in reference 11 Include epoxldlzed linseed, butylated linseed, soybean, and tall oils. However, although some fundfimental studies of the effects of monofunctional reactive diluents on the viscoelastic and other properties of epoxy resins have been published (see, for example, reference 12), little or no analogous Information on the effects of multifunctional reactive diluents appears to exist. At the same time, some reactive additives such as polyols (13), poly(ether esters) (14) and carboxy-terminated elastomers (15) have been used to provide an elastomeric toughening phase for epoxies. 

Thus it was decided to examine the viscoelastic response and ultimate mechanical behavior of several systems based on a typical cycloaliphatic and a blsphenol-A-type epoxy prepolymer, using a variety of epoxldlzed botanical oils as reactive diluents. This paper describes the first results of this Investigation, In which epoxldlzed linseed, lunarla, and crambe oils were selected as diluents. 

Where W is the weight fraction, and the subscripts A and B refer to the oil and epoxy prepolymer components. 

Such a conclusion is supported by the fact that the Tg s of all the ERL-4221 systems are much higher than predicted by any of the rules of mixtures (Equations 1 to 3). Indeed even with 50% of diluent, the Tg of the resin was reduced relatively little in comparison with that of the neat resin. This certainly suggests the likelihood of a phase-separated oil-based component. One might well expect a sigmoidal curve of Tg vs concentration of epoxy prepolymer If the epoxy resin constitutes the continuous phase a phase Inversion would then be expected at some value of epoxy resin content. 

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