Epoxies resins

The epoxy resin can be defined as any molecule that contains two or more alpha-epoxy groups which can be reacted to form a thermoset system. An example of a difunctional epoxy resin is diglycidyl ether of Bisphenol-A (DGEBA) which is formed 

In addition to the Bisphenol-A backbone epoxy resins, epoxies with substituted aromatic backbones and in the tri- and tetra- functional forms have been produced. Structure-property relationships exist so that an epoxy backbone chemistry can be selected for the desired end product property. Properties such as oxygen permeability, moisture vapor transmission and glass transition temperature have been related to the backbone structure of epoxy resins5). Whatever the backbone structure, resins containing only the pure monomeric form can be produced but usually a mixture of different molecular weight species are present with their distribution being dictated by the end-use of the resin. 

Considering both the chemistry of epoxy resins and the reactants required to produce it, impurities, unreacted raw materials, catalyst and other monomeric species can be expected to be present in the resin in low levels (i.e. 100 ppm). Under the mechanical, thermal and chemical stress levels acting at the interface both during curing and after curing, concentration of these species at the interface could be quite high giving rise to an interface structure unrelated to the bulk. 

1 Pyrolysis Products of Flame-retarded Epoxy Resin 

Numerous studies [8-19] have been conducted on epoxy resins, which are essentially, high tensile strength materials (up to 80 MPa, see Table 2 ). 

Properties discussed include tensile storage modulus [20], tensile compression, bending and impact, electrical, thermal, corrosion and solvent resistance, viscoelastic, vitrification. Applications of epoxy resins include sporting goods [21], bolted joints 

Tasdemir and Yildirim [22] showed that rigid plastics such as epoxies, PS, PVC, polymethyl methacrylate (PMMA), PP, PC, unsaturated polyester resins and PA can be toughened and their impact properties improved by the incorporation in the formulation of 5-20% of a rubbery elastomer such as ABS terpolymer. 

Many conventional plasticizers such as phosphates and phthalates are not compatible with the majority of epoxy resins, especially at higher concentrations. They are easily lost from the system and if retained they do not affect flexibihty.  

Several groups of flexibihzers are used in epoxy resins to modify their mechanical properties. These include  

For these teasons plasticizers are not used to modify mechanical properties of the final product but are still quite useful, especially in the modification of processing characteristics (viscosity) of epoxy resins. 

The following concentrations of plasticizers have been nsed  

3 MAIN FUNCTIONS PERFORMED BY PLASTICIZERS A short list of the functions of plasticizers in epoxy resins includes  

---

Piezocomposite transducers are an advancement of piezoelectric ceramics. Instead of the classic piezoceramic material, a compound of polymer and piezoceramic is used for the composite element to improve specific properties. The 1-3 structure, which is nowadays mostly used as transducer material, refers to parallel ceramic rods incorporated in an epoxy-resin matrix (see Fig. 1). 

Luft J H 1961 Improvements in epoxy resin embedding methods J. Biophys. Biochem. Cytol. 9 409-14... 

Of course, in order to vary the mass transport of the reactant to the electrode surface, the radius of the electrode must be varied, and this unplies the need for microelectrodes of different sizes. Spherical electrodes are difficult to constnict, and therefore other geometries are ohen employed. Microdiscs are conunonly used in the laboratory, as diey are easily constnicted by sealing very fine wires into glass epoxy resins, cutting... 

In Figure 5.23 the finite element model predictions based on with constraint and unconstrained boundary conditions for the modulus of a glass/epoxy resin composite for various filler volume fractions are shown. 

In Figure 5.24 the predicted direct stress distributions for a glass-filled epoxy resin under unconstrained conditions for both pha.ses are shown. The material parameters used in this calculation are elasticity modulus and Poisson s ratio of (3.01 GPa, 0.35) for the epoxy matrix and (76.0 GPa, 0.21) for glass spheres, respectively. According to this result the position of maximum stress concentration is almost directly above the pole of the spherical particle. Therefore for a... 

Epoxy resin is prepared by the following condensation reaction ... 

The condensation leaves epoxy end groups that are then reacted in a separate step with nucleophilic compounds (alcohols, acids, or amines). Eor use as an adhesive, the epoxy resin and the curing resin (usually an aliphatic polyamine) are packaged separately and mixed together immediately before... 

BMI/Epoxy resins [COMPOSITE MATERIALS - POLYTffiR-MATRM - THERMOSETS] (Vol 7) Electrically charged membrane... 

ALKALI AND CHLORINE PRODUCTS - CHLORINE AND SODIUMHYDROXIDE] (Vol 1) -epoxy resins from [ADITESIVES] (Vol 1)... 

---