Epoxy Resin Characteristics

ASTM D883 defines a filler as "...a relatively inert material added to a plastic to modify its strength, permanence, working properties, or other quaHties or to lower costs." EiHers (qv) that modify the properties and characteristics of epoxies are employed in epoxy resins for a variety of reasons. Then principal functions are to control viscosity, reduce shrinkage and the coefficient of thermal expansion, effect a cost reduction, and color the epoxy resins. 

Viscoelastic characteristics of composite materials usually result from a viscoelastic-matrix material such as epoxy resin. General stress analysis of viscoelastic composites was discussed by Schapery [6-54]. An important application to laminated plates was made by Sims [6-55]. 

Figure 14 Influence of fiber drying on the characteristic values of jute reinforced epoxy-resin composites [121.

Table 2. The values of the characteristic parameters of a series of E-glass fiber, epoxy resin unidirectional composites for various fiber volume contents t>f... 

As is usually characteristic of crosslinked polymers of commercial importance, epoxy resins are prepared in two stages, with the initial reaction leading to a linear prepolymer and the subsequent reaction introducing the crosslinks between the molecules. The prepolymers from which epoxy resins are prepared are diglycidyl ethers with the structure shown in Figure 4.2. 

The products of the chemical degradation of PETP with triethylene tetramine and triethaneolamine can be used as epoxy resin hardeners, it is demonstrated. Products of PETP aminolysis with triethylene tetramine and aminoglycolysis with triethanolamine, were characterised using NMR and rheometric measurements. Characteristics of the crosslinking process for the system epoxy resin/ PETP/amine degradation product, and epoxy resin/TETA for comparison were investigated by DSC. Three classes of liquid epoxy resins based on bisphenol A, bisphenol F and epoxy novolak resins were used in the experiments. 16 refs. 

Composite Particles, Inc. reported the use of surface-modified rubber particles in formulations of thermoset systems, such as polyurethanes, polysulfides, and epoxies [95], The surface of the mbber was oxidized by a proprietary gas atmosphere, which leads to the formation of polar functional groups like —COOH and —OH, which in turn enhanced the dispersibility and bonding characteristics of mbber particles to other polar polymers. A composite containing 15% treated mbber particles per 85% polyurethane has physical properties similar to those of the pure polyurethane. Inclusion of surface-modified waste mbber in polyurethane matrix increases the coefficient of friction. This finds application in polyurethane tires and shoe soles. The treated mbber particles enhance the flexibility and impact resistance of polyester-based constmction materials [95]. Inclusion of treated waste mbber along with carboxyl terminated nitrile mbber (CTBN) in epoxy formulations increases the fracture toughness of the epoxy resins [96]. 

Because carbon fibers of different diameters are available and because construction parameters can be varied, it is possible to engineer composites having desired characteristics. By varying the orientation, concentration, and type of fiber, materials can be developed for specific applications. The fibers can be layered at different angles to minimize directional differences in properties. Also, layers of fibers can be impregnated with epoxy resin to form sheets that can be shaped prior to polymerization of the resin. 

Several classes of polymers including epoxies have been developed from 2-phenyl-l,l,l,3,3,3-hexafluoropropan-2-ol and its derivatives.1 Fluorinated epoxy resins are the key intermediates for the new types ofpractical organic coatings and plastics, which have fluorocarbon properties and convenient characteristics such as hydrophobicity, oleophobicity, light stability, low friction, and, in some cases, possibly high thermal stability. 

In 2000, NEC developed an epoxy resin with what it describes as a fire-retardant structure that avoids the need for either TBBA or phosphorus-based flame retardants in circuit boards. The new resin contains a metal hydroxide retardant. The company claims the new board is almost totally free of pollutants, and is easy to process and thermally recycle. By also integrating flame retardant properties within the board, use of the metal hydroxide is minimised, while offering good electrical properties, higher heat resistance and improved processing characteristics. ... 

Novolac epoxy flexibilizers Improve low and high temperature characteristics of novolac epoxy resins for inhibition of composite rocket propellants [164]. 

Kay and Fust postulated the use of epoxy resin for inhibition of composite propellants [335] and as a consequence, epoxy resins were tried for the first time for the inhibition of HTPB-based composite propellants at Thiokol Corporation, USA. Subsequently, use of the amido-amine hardened modified bisphenol-A-based epoxy resin was reported as inhibitor for fluorocarbon-based composite propellants [336]. Epoxy resins are the most versatile resins for bonding applications for a variety of substrates. This is because of the following characteristics. 

Agrawal, J.P., Dev, S.S., Gholap, D.H., Satpute, R.S., Tapaswi, M.A., and Nigde, B.N. (1986) Improvement of Low and High Temperatures Characteristics of Novolac Epoxy Resin Used for Inhibition of HTPB Based Composite Propellants. ERDL Report No. 8/86. 

Disk thermistors can be produced to dose limits of interchangeability, eg, 0.1 and 0.05° C. Disks cannot be made as small as the smallest beads 2 mm diameter seems an approximate practicable limit. Disks historically have been considered to be less stable than good beads. They are commonly protected with a coating of epoxy resin, which provides less compressive support than the glass coating of bead thermistors. More recent developments have resulted in interchangeable glass-encapsulated disk thermistors which have the stability characteristics of the best beads. 

Amines were one of the first hardeners of epoxy resins 1 12), and at present they retain their leading position among all known hardeners of this type. The amine hardeners will most likely also be used in the future because they are fairly accessible, highly reactive, and their properties can be readily modified. The mechanical properties of the cured resins obtained are far better than those of the known polymer binders 2 -4), they have high dielectric characteristics, chemical resistance, etc. 

Epoxy resins have likewise found many varied industrial uses (B-75MI11501). Catalysts are important in determining both the cure characteristics and the properties of the fully cured materials. 

These findings suggest strongly that the composition of the elastomeric molecule and the nature of the functional groups affect its compatibility and rate of reaction with the epoxy resin, which in turn affect the molecular and morphological structure of the heterophase system. These data indicate the importance of the acrylonitrile comonomer and the carboxyl groups in controlling the polarity of the rubber, and subsequently its compatibility characteristics with the epoxy. We could also... 

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