Epoxy materials

In critical applications, cap bolts with grease-filled containers. In some instances, epoxy materials have been used to fill such caps (with limited success). 

Figure 22 shows a practical large anode. The anode started as a rough cylinder of YBD carbon about 20 cm in diameter and 120 cm long. A central cavity 10 cm in diameter and 110 cm deep was machined in as shown. The pores in the carbon were filled with a commercial epoxy material using standard techniques. (The material was a mixture of... 

Tewarson, A., and Pion, R.F., "Evaluation of the Flammability of a Glass Fiber Reinforced Epoxy Material," 1978, Factory Mutual Research Corporation, Norwood, MA, Technical Report J.I. 

Since no difference was found between FR and non-FR formulations in device aging studies, some other cause must account for the relatively early failures observed for devices molded in the electrical grade epoxy material and aged under bias at 200°C. These failures are attributed to chloride contamination present in the non-semiconductor grade epoxy resin. The extractable Cl concentration is a factor of four higher than Br, and this is correlated with a much higher concentration of CHoCl than CH Br in the EGA data below 200°C. The high Br concentration is also attributed to the... 

Thermoset molding compounds, when contained within a hardened steel mold, require heat and pressure to be polymerized into a solid mass. Molds may be heated by steam, electricity, or hot oil to temperatures of 280° to 425°F, depending entirely on the type of material and method of molding. Molding pressures may vary from a low of 50 p.s.i. to 15,000 p.s.i. Epoxy materials will mold at 50 p.s.i. whereas, phenolic fabric-filled material may require excessive pressures. Again, the method of molding dictates molding pressures. 

The theory has been examined by measuring the ratio K,c/Klcs as a function of j/g, as shown in Fig. 17. The theoretical lines have been fitted to the experimental points by choosing suitable values of the critical distance, c, which is the only fitting parameter. The agreement between theory and experiment has been found to be equally good for many different epoxy polymers cured with many different hardeners, both unmodified 44- 45,51), rubber-modified 45) and containing glass particles 22) and even, under certain circumstances, for structural adhesive joints S3). Values of critical stress, ct,c, and distance, c, for various epoxy materials, obtained from bulk and... 

The complex sorption behavior of the water in amine-epoxy thermosets is discussed and related to depression of the mechanical properties. The hypothesized sorption modes and the corresponding mechanisms of plasticization are discussed on the basis of experimental vapor and liquid sorption tests, differential scanning calorimetry (DSC), thermomechanical analysis (TMA) and dynamic mechanical analysis. In particular, two different types of epoxy materials have been chosen low-performance systems of diglycidyl ether of bisphenol-A (DGEBA) cured with linear amines, and high-performance formulations based on aromatic amine-cured tetraglycidyldiamino diphenylmethane (TGDDM) which are commonly used as matrices for carbon fiber composites. 

The tests in which the epoxy pins were rubbed on steel disks showed that the pins were initially worn by the abrasive action of the asperities on the steel surface. This initial wear correlated with the inverse of the values. During the initial wear, the steel surface was smoothed by the transferred epoxy material. The steady state wear which followed the initial wear was lower in magnitude than the first stage of wear. The highest wear rate was obtained with 15 wt,-% of the dimethyl siloxane modifier. 

GaAsP lias a high index of refraction, and consequently only light emitted toward the surface (4 f) js usable the remainder is reflected back A diode can be encapsulated in epoxy material to take on the shape and form uf a lens. These diodes are particularly effective where a number are fabricated in close proximity on a single-crystal chip... 

The aftercure and cooling conditions of epoxy materials have a major influence on the quality and properties of the final material. Orlova et al. 92) studied the adiabatic curing of EDS materials by varying the hardening temperature and the degree of conversion of the reactive groups. They developed a mathematical model of the... 

Syntactic foams are chemically very stable. The EDS, SPS, and EDM materials gain less than 1.5 mass% if exposed to environments such as propyl alcohol, transformer oil, gasoline, or petroleum for up to 12 months, whilst their compression strength is reduced by less than 12-20% (Fig. 19). However, epoxy materials have poor resistance to acids or alkali, and are completely decomposed within 24 hours by benzene or acetone 1). 

The adhesion of syntactic materials depends primarily on the adhesive and the substrate in question. Epoxy materials, for example, (in the absence of an extra glue) have the following adhesion strengths2) ... 

The possible use of graphite-epoxy material by screen-printing technology opens the possibility of mass production of disposable sensors for heavy-metal analysis using stripping techniques. The utilization of these sensors for an extensive application in real heavy-metal samples is underway in our laboratories. 

The increases in both emission intensity and emission lifetime of fac-ClRe(CO)3(4,7-Ph2-phen) are again related to a reduction in the nonradiative decay pathways as the epoxy material polymerizes and forms a rigid network. Significantly, though, the observed rigidochromic shifts in the epoxy-based net-... 

Photooxidation Diffusion Chemical changes due to photochemical reactions Introduction of contaminants from man-made materials, such as solvents from polyvinyl chloride (PVC) materials and PVC cement, plasticizers, and phthalates from polyethylene and polypropylene materials Protection from exposure to light, use of amber glass bottles Use of inert materials (PTFE, fiberglass-reinforced epoxy materials) steam-cleaning of groundwater well components prior to installation... 

In an alternative embodiment, channels 22 are etched through the detector layer 16 and into the transparent substrate 14 to a depth slightly exceeding the required thickness. The detector array portion and the silicon circuit 12 are bonded together by the aid of indium bumps 18, and an epoxy material 20 is back-filled into the space between the detector array portion and the read-out chip. 

The largest impediment to manufacturing molecularly mixed polyimide-epoxy materials has been the limited number of solvents in which polyimide is soluble. The improvement of solubility of polyimides, wherein solubility is increased by the incorporation of large pendant groups containing carboxylic or heterocyclic side groups, has been the focus of much attention, especially the works of Sillion et. al. [74] and others [75-81]. 

Some inorganic particulate fillers have also been considered as toughening agents for epoxy materials. Glass beads, fly ash, alumina trihydrate, and silica were used early on to improve the toughness of filled epoxy resins. Various studies, however, have demonstrated that the fracture energy of filled epoxies reaches a maximum at a specific filler concentration. 

These processes have an advantage in that the heat penetrates deeply into the joint and into the epoxy material itself. With conventional thermal energy processes, the heat must be conducted into the mass of the epoxy adhesive from outside the joint. This is hindered by the presence of the substrates, the substrate geometry, and the relatively low thermal conductivity of the epoxy itself. 

Fig. 19 Correlation between the ratio of the stress intensity factor to crack initatiation (Kci) to stress intensity factor at crack arrest (lCca) and the true yield stress (ayt) of epoxy materials (from [73])...

Fig. 20 Calculated maxima in the mode I stress intensity factor as a function of crack depth for a DGEBA/IPD epoxy material under cyclic loading. The dotted line corresponds to the experimental value of the mode I fracture toughness...

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