Structure of cured resin

The Curing Mechanism of Epoxy Resins and the Structure of Cured Resins 174... 

The factors determining the structure of cured resins and affecting the physical and mechanical properties are as follows ... 

In addition of polyamines, acid anhydride hardeners are used but the structure of cured resins is less understood. 

Non-glycidyl ether epoxides Diluents, Rexibilisers tmd other Additives Structure and Properties of Cured Resins Applications... 

This paper rerports an investigation of the yield behavior of several amine and anhydride cured DGEBA resin systems. The Argon theory is used to assess the controlling molecular parameters from the experimental results. Such parameters are then compared with the known chemical structures of the resins. The mechanisms of plastic flow in thermoset polymers such as epoxies is demonstrated. 

The plastic deformation in several amine and anhydride cured epoxy resins has been studied. The experimental results have been reasonably interpreted by the Argon theory. The molecular parameters determined from the data based on the theory reflect the different molecular structures of the resins studied. However, these parameters are in similar enough range to also show the structural similarity in these DGEBA based systems. In general, the mechanisms of plastic deformation in epoxy resins below T are essentially identical to those in amorphouE thermoplastics. The yield stress level being related to the modulus that controls the intermolecular energy due to molecular deformation will, however, be affected by the crosslinks in the thermosets. 

Ozonization of lignin forms derivatives of muconic acid that have the unique chemical structure of conjugated double bonds with two carboxyl groups. These derivatives have great potential for chemical modification. The ozonized lignin of white birch was soluble in epoxy resin at 120°C, and the free carboxyl groups were found to react with epoxide. This paper discusses developmental work on the preparation of pre-reacted ozonized lignin/epoxy resins the dynamic mechanical properties of cured resins and preliminary results of the application of these resins as wood adhesives. 

Epoxy Resins The term epoxy refers to an epoxide group which is a three-membered oxide ring. An epoxy resin is defined as a molecule containing more than one epoxy group capable of being converted into a thermoset (cured) form. The simple structure of epoxy resin [Structure (4.37)] is ... 

The general properties of cured and uncured epoxy resins are reviewed in Chap. 3. The chemical structures of the resin and curing agent will determine these physical properties. They will also determine, to a great extent, the surface chemistry and adhesion properties of the final product. 

A number of papers deals with the dynamic mechanical properties of cured epoxy resins1 -5) and with the effect of the structure of basic resins and the degree of cross-linking s 8>. 

Carbohydrate-phenolic-based resins can be modified to change their physical and chemical properties, and faster curing adhesives can be made from these modified resins. However, the nature of the research presented here is exploratory, and much remains to be done. In particular, the molecular structure of these resins needs to be defined. 

A novel concept of the structure of cured urea-formaldehyde resin. J. of Adhesion. Vol 17(x), page xxx. 

Habermeier also pointed out the ready synthesis of hydantoins from aldehydes or ketones the substituents in the 5-position of the ring were thus determined by the carbonyl compound used as starting material. Most of the examples cited had methyl, ethyl, or cyclopentamethylene substitution in the 5-position. Data were presented on the properties of cured resins with these substituents and with a broad variety of the other structural features mentioned. 

Materials. The thermosetting resins investigated include (1) 1,2-dihy-drobenzocyclobutene and maleimide (BCB-MI) resin, (2) a modified version of the BCB—MI resin (BCB-MI-M), (3) cross-linkable epoxy thermoplastic (CET, which is chemically similar to TACTIX 695 epoxy resin from Dow Chemical Co.), and (4) DGEBA epoxy (D.E.R. 332, Dow Chemical Co.) cured with piperidine. The chemical structures of the resins are shown in Chart I. 

The water absorptivity of cured resins was found to depend greatly on the linking structure R. Polar groups in the linking structure are expected to attract water. The results of gravimetric measurements, shown in Figure 3, indicated that the bisphenol-A and bisphenol-A6F linked polymers had very low affinity for water, absorbing less than 1.5% water on immersion. 

With a decrease of the substitution degree of dimethylaminomethyl phenols (DAMPs), the density of the network structure of epoxy resins cured by DAMPs increases. Simultaneous improvement of impact, adhesive and cohesive strength, and chemical resistance of coatings in typical aggressive media takes place (Table 6.1). 

Many concurrent reactions are usually operative. Their relative importance depends on the structure of the resins and the type of curing agent. The degradation products are mostly phenolic compounds. Three mechanisms based on the principle of simple ether cleavage and on the experimental results obtained were proposed ... 

The synthesis and structure of MQ resins have been described above. The poly(siloxane) network is traditionally derived by free-radical cross-linking of a high molecular weight PDMS polymer or gum using a peroxide catalyst, such as benzoyl peroxide or 2,4-dichlorobenzoyl peroxide. The curing reaction is performed immediately after the PSA has been coated onto a tape substrate, such as PET, PTFE, or Kapton. Uncured PSAs are supplied as a solution in an organic solvent. Some silicone PSAs also incorporate phenyl groups onto the gum portion of the adhesive to increase the use temperature. 

The chemical reactivities of the unsaturated groups at the ends of vinyl ester resin and vinyl urethane resin chains are different in several respects from those of the same groups when situated in mid-chain positions, as they are in polyester resins. As a consequence of the different reactivity ratios, the two kinds of cured resin behave differently from moisture and chemical resistance points of view. The structural differences are also reflected in the mechanical properties, such as fracture toughness. 

The ether groups, the benzene rings, and, when present, the aliphatic hydroxyls in the cured epoxy system are virtually invulnerable to caustic attack and extremely resistant to acids. In the case of the phenolic resin, the sodium phenolate formed is readily soluble and when present will cause the ultimate disintegration of the resin chain. In the case of the polyester, the ester linkage is hydrolyzed back to the original alcohol and salt of the carboxyl group. The chemical inertness of the cured epoxy system is enhanced by the dense, closely packed structure of the resinous mass, which is extremely resistant to solvent action. 

In the narrow sense, bis-maleimide resin means the thermosetting resin composed of the bis-maleimide of methylene dianiline (BMl, bis(4-maleimidophenyl)-methane) and methylene dianiline (MDA, bis(4-aminophenyl)methane) (Fig. I). Because of the addition mechanism, the resin is cured without elimination, which is a characteristic of this resin. Bis-maleimide resin is used as a thermally stable matrix up to 204°C (400°F) which typical epoxy resins may not normally be used. However, in spite of having an imide structure, bis-maleimides are classified as being moderately thermally stable resins. The aliphatic structure of the resin is not stable for long periods above 232°C (450°F.) If a highly aromatic thermally stable thermosetting resin is necessary, acetylene end-capped aromatic imide-based oligomers should be used. 

Since the cured resins are infusible and insoluble in most solvents, little progress was made initially in determining structural features. It was only after analysis of the uncured resinous condensation products was attempted that some progress was realized in elucidating the structures of these resin systems. The research of Baekeland and Bender involved the synthesis of phenolic resins from various substituted phenols and the application of different condensation methods. ... 

Characterization of Epoxy Curing and Cured Networks. Cured thermoset polymers are more difficult to analyze than thermoplastics since they are insolnble and generally intractable. Their properties are influenced by factors at the molecular level, such as backbone structures of epoxy resin and curing agent natiue of the covalent bond developed between the epoxy resin and the curing... 

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