Epoxy resin Modifier

S02-cured epoxy resin. Modified epoxy/acrylic resins (1.2 to 1.4% of sand weight) are mixed with organic peroxide (26 to 60% of resin weight), the mixture is blown into the core box and a hardening mechanism similar to the S02 process takes place. 

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]. 

Hou, M., Liu, W., Su, Q., and Liu, Y., Studies on the thermal properties and flame retardancy of epoxy resins modified with polysiloxane containing organophosphorus and epoxide groups, Polym. J. (Japan), 2007, 39, 696-702. 

Formulators in the adhesives industry do not normally manufacture epoxy resins. Generally, formulators buy epoxy resins, modify them with other materials, do similar compounding to the curative, and then package the product as a complete adhesive system ready for the end user. There are many excellent textbooks6-8 available giving information about the preparation, chemistry, and use of epoxy resins in general applications. It is not the intention here to go into such detail but to focus only on epoxy adhesive systems. 

Examples of epoxy resins modified for improved flexibility include the fohowing ... 

Epoxy-nitrile Nitrile-epoxy adhesives are composed of solid epoxy resin modified with carboxyl-terminated butadiene nitrile (CTBN) copolymer. The CBTN is introduced into die epoxy resin at elevated temperatures. The modification provides toughness and high peel strength without sacrificing heat and chemical resistance. The film adhesives are widely used in the aerospace industry in the construction of jetliners. 

The epoxy-nitrile adhesives were introduced commercially in the late 1960s. They consisted primarily of DGEBA epoxy resin modified with carboxyl-terminated butadiene nitrile (CTBN) rubber. These first nitrile copolymers were available from B.F. Goodrich under the trade name of Hycar. The most convenient form of epoxy nitrile adhesive, especially when one is bonding large parts (aircraft structures), is a supported film. However, solvent solutions of epoxy-nitrile adhesives have also been commercially available. 

Figure 10.4 The chemical resistance of a diglycidyl ether of bisphenol A (DGEBA) epoxy resin modified with LP-3 (50 parts LP-3 per 100 parts resin). A 5 cm x 3 cm x 2 mm coupon was immersed in the liquid for 28 days at 23°C. Open boxes = percentage volume swell shaded boxes = percentage weight change. Reproduced with permission from Morton International Ltd, Coventry, UK...

Barcia, F.L. Amaral, T.P. Soares, B.G. Synthesis and properties of epoxy resin modified by epoxy-terminated liquid polybutadiene. Polymer 2003, 44, 5811. 

Figure 8.35. SEM micrograph of the fracture surface of an epoxy resin modified with 10 vol% latex particles. [Adapted, by permission, from Bagheri R, Pearson R A, Polymer, 36, No.25, 1995,4883-5.]...

Table 21.8 Viscoelastic Properties of Epoxy Resin Modified with Functionalized Polyethylene.

Epoxy resin mortars have been used in repairing or conserving massive concrete structures. It has been found that the adhesive properties of epoxy resins modified with polysulfides is... 

Polysulfides are used in synthetic rubber compositions [1], epoxy resin modifiers [2], coatings [3], adhesives [4], sealants [5], and many other products as described in recent Chemical Abstract issues. 

Dispensible electrically conductive 25-40% epoxy resin, 5-10% epoxy resin modifiers Ablebond 84-1 LMI and %7-l series... 

Dispensible electrically insulative adhesive 20 0% epoxy resin, 10-20% epoxy resin modifier, 15% amine, and >50% silica filler Ablebond 84-3 (Henkel)... 

A large variety of epoxy resins, modifiers, and curing agents are available that permit the epoxy formulator to tailor the epoxy system to meet the needs of each application. 

Chem. Descrip. Epoxy resin modified with CTBN in 25% MEK Uses Epoxy for structurat adhesives, composites, maintenance coatings and primers... 

Chem. Descrip. Polyoxypropylenemonoamine, predominantly EO based Uses Curing agent for epoxy resins modifier for epoxies for water-reducible systems... 

Chem. Descrip. Epoxy resin modified with CTBN... 

And Andres, M. A., Garmendia, J., Valea, A., Eceiza, A., Mraidragon, 1. Fracture toughness of epoxy resins modified with polyethersuUbne Influence of stoichiometry on the morphology of the mixtures. J. Appl. Polym. Sci. 69 (1998) 183-191. 

Lu Lu, M. G., Shim, M. J., Kim S. W. Bulk properties of epoxy resin modified by epoxy-amino-silane copolymers. Polym. Intern. 48 (1999) 787-793. 

OlMim Mimura, K., Ito, H., Fujioka, H. Toughening of epoxy resin modified with in situ polymersized thermoplastic polymers. Polymer 42 (2001) 9223-9233. 

Har Harada, M., Morimoto, M., Ochi, M. Influence of the network chain orientation on the fracture toughness of a mesogenic epoxy resin modified with CTBN. J. Polym. Sci. Part B - Polym. Phys. 41 (2003) 1198-1209. 

Fra Francis, B., Thomas, S., Sadhana, R., Thuaud, N., Ramaswamy, R., Jose, S., Rao, V. L. Diglycidyl ether of bisphenol-A epoxy resin modified using poly (ether ether ketone) with pendent tert-butyl groups. J. Polym. Sci. B Polym. Phys. 45 (2007) 2481-2496. 

When epoxy resins modified by rubbers are cured with the tertiary amines, the following processes occur ... 

Studies of the dependence of EEC properties obtained as above on the formation method showed that the precipitated finely dispersed rubber that is not bonded to the epoxy matrix does not endow it with high mechanical characteristics. When reactive oligomers are applied with high-temperature cure, there is a sharp enhancement of the modifying efficiency, accounting for the more intensive separation of the phases in the system and for the increase of the yield of the epoxy rubber copolymer. Thus, the structure and properties of epoxy resins modified by rubbers are mainly determined by the mode of system curing, but the quantitative relationships between curing mode and final properties have not been sufficiently studied. 

Comparison of the concentration dependence of the Kic values of the compounds obtained by the above two methods with the concentration dependence of the X2,z thermodynamic interaction parameter of oligomer mixtures (epoxy resin-modifier and curing agent—modifier) displays the same dependences. The maximum value of of l.lMPa m / is observed at 5% content of the SKD-KTRA rubber. This is the region of maximal thermodynamic instabihty of the oligomer mixture. 

Thus, from the above data one could conclude that to achieve the maximal values of Kjc the method of modification with PER is most effective. Additionally, this method is more technologicsLlly apphcable because it can be used in formation of cold-cure compounds. Special attention must be paid to the correlation of the Kjc characteristic with X2,3 foi mixtures such as epoxy resin—modifier and curing agent-modifier. The presented characteristics of the ERG cracking resistance indicate the strong dependence of Kic on the structure of these materials, which enables the use of this characteristic in optimizing the compositions of new and already known epoxy rubber materials. 

In Fig. 13.41, results for the fracture energies of epoxy resins modified with rubber particles and glass spheres to a combined volume fraction of/ = 0.18 are given. We evaluate this toughening effect whereby cavitation occurs at the particles by means of the ratio of eq. (13.56) and eq. (13.57) for the quantities given above, obtaining... 

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