Thermoplastic-modified epoxy resin

There has been much work on characterizing the phase separation and network development for thermoplastic-modified epoxy-resin systems. Initial work (Yamanaka and Inoue,... 

Thermoplastics are sometimes added to epoxy resins. Thermoplastic-modified epoxy resins [43,44] based on tri- and difunctional epoxy resins cured with DDS and blended with polyethersulfone form the basis for the matrix material in a composite used for the Boeing 777 aircraft. The incorporation of the thermoplastic helps the processing characteristics and also improves the mechanical properties, notably the toughness. The thermoplastic is able to phase separate from the epoxy phase and acts as a reinforcement for the epoxy matrix, enhancing its high temperature properties. The maximum use temperatures of all these resins will typically be 30 to 50 degrees lower than the cited Eg, assuming the same cure schedule. 

A J MacKinnon, S D Jenkins, P T McGrail and R A Pethrick, A dielectric, mechanical, rheological and electron microscopic study of cure and properties of a thermoplastic modified epoxy resin . Macromolecules 1992 25 3492. 

Mur Murakami, A., Saunders, D., Ooishi, K., Yoshiki, T., Saitoo, M., Watanabe, O., Takezawa M. Fracture behaviour of thermoplastic modified epoxy resins. J. Adhesion 39 (1992) 227-242. 

Mac MacKinnon, A. J., Jenkins, S. D., McGrail, P. T., Pethrick, R. A. Cure and physical properties of thermoplastic modified epoxy resins based on polyethersulfone. J. Appl. Polym. Sci. 58... 

Thermoplastic-modified epoxy resins cured with different functionalities amine mixtures. Kinetics and miscibility study. Journal of Thermal Analysis and Calorimetry, Vol.97, No.3, (June 2009), pp. 969-978, ISSN 1388-6150. 

Mackinnon, A.( Jenkins, S.D., McGrail, P.T., and Pethrick, R.A. (1993) Dielectric, mechanical and rheological studies of phase-separation and cure of a thermoplastic modified epoxy-resin -incorporation of reactively terminated polysulfones. Polymer, 34 (15),... 

Table 12.2 Moisture content of carbon fibre composites from thermosetting and thermoplastic matrices also shown is the benefit of modifying epoxy resin with thermoset and thermoplastic modifiers to reduce Mco...

Figure 12.11 Moisture enhancement of matrix resins Unmodified epoxy Fibredux 924E (o) thermoplastic modified epoxy Fibredux 924T ( ) Fibredux 924T within a composite (estimated) ( ) carbon fibre Fibredux 924C composite ( ) [7].

Nylon-epoxy is typically used in film and tape adhesive applications and has maximum service temperature of 138°C, compared with 177°C for unmodified epoxies. The addition of nylon provides increased flexibility and peel strength compared to unmodified epoxies. Nylon-epoxy is a tough material with excellent tensile lap shear strength and good fatigue and impact resistance. However, the addition of nylon results in deterioration in creep resistance and poor peel strength at low temperatures. Furthermore, the hydrophilic nature of nylon imparts poor moisture resistance in both uncured and cured forms of the resin. Consequently, nylon-epoxies are not as durable as elastomer-epoxies or other thermoplastic modified epoxies. 

Thermosetting-encapsulation compounds, based on epoxy resins (qv) or, in some niche appHcations, organosiHcon polymers, are widely used to encase electronic devices. Polyurethanes, polyimides, and polyesters are used to encase modules and hybrids intended for use under low temperature, low humidity conditions. Modified polyimides have the advantages of thermal and moisture stabiHty, low coefficients of thermal expansion, and high material purity. Thermoplastics are rarely used for PEMs, because they are low in purity, requHe unacceptably high temperature and pressure processing conditions. 

Diglycidyl ether of bisphenol-A (DGEBA), epoxy resin (YD 128, Kuk Do Chem., Mn = 378), and bisphenol-A dicyanate (BPACY, Arocy B-10, Ciba-Geigy) were used as the thermoset resin. 4,4 -diaminodiphenyl sulfone (DDS, Aldrich Chem. Co.) was used as a curing agent for epoxy. Polyetherimide (PEI, Ultem 1000, General Electric Co., M = 18,000) and 2-methyl imidazole (2MZ, Aldrich Chem. Co.) were used as the thermoplastic modifier and catalyst. 

For polystyrene and related thermoplastic copolymers, this inherent brittleness has been corrected effectively by including rubbery particles, properly modified by grafting with thermoplastic chains, for energy dissipation (6). With crosslinked epoxy resins, chemical attachment of the... 

Adhesion studies of epoxy resins modified with high modulus and high glass transition temperature thermoplastics have shown adhesion can reach or even exceed that of the unmodified resin. The use of flexible polyamides or flexible epoxides resulted in shear strength increases in epoxy systems employed by Cunliffe et al. [144],polyethersulfones [18,145],polyetherimides [109,146,147], and polyetherketones [148-150]. 

A variety of polymers, both thermosets as well as thermoplastics, can be blended and coreacted with epoxy resins to provide for a specific set of desired properties. The most common of these are nitrile, phenolic, nylon, poly sulfide, and polyurethane resins. At high levels of additions these additives result in hybrid or alloyed systems with epoxy resins rather than just modifiers. They differ from reactive diluents in that they are higher-molecular weight-materials, are used at higher concentrations, and generally have less deleterious effect on the cured properties of the epoxy resin. 

An acrylate-terminated polyurethane modified epoxy compound and a polyethylene polyamine homologue and fatty acid combination were formulated into a two-component adhesive system. The adhesive is useful for bonding various thermoplastic resins such as ABS, PC, PBT-PC blends, and PPO.22... 

The thermoplastic resins are usually blended with the epoxy resin in a solvent solution. Early researchers realized that to make this approach effective, it was necessary to increase the compatibility and interfacial adhesion of the thermoplastic modifier and the epoxy resins. The problem of poor miscibility of the thermoplastic resins and poor processabihty of the final product are the main reasons that these materials have not achieved commercial success. 

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