Resin network epoxy

J. C. Hedrick, N. M. Patel, and J. E. McGrath, Toughening of Epoxy Resin Networks with Functionalized Engineering Thermoplastics, in Rubber Toughened Plastics, K. Riew (Ed.), American Chemical Society, Washington, DC, 1993. 

The control resin network used in this study was a diglycidyl ether-based epoxy resin crosslinked with a cycloaliphatic diamine. Cooligomeric modifiers were prepared having varying percentages of TFP and DP siloxane and aminoethylpiperazine end groups. Both siloxane and ATBN and CTBN elastomers were used as epoxy modifiers, the latter two having been included to facilitate direct comparisons between modifiers in similarly prepared networks. 

The mechanical dispersion peaks in low-Tg epoxies such as Bisphenol-A based resin (Epon 828, products from Shell Development Company) have been the subject of numerous studies 143,145148,152 "155, l59>. The alpha-dispersion peak related to the glass transition can undoubtly be attributed to the large-scale cooperative segmental motion of the macromolecules. The eta-relaxation near —55 °C, however, has been the subject of much controversy 146,153). One postulated origin of the dispersion peak is the crankshaft mechanism at the junction point of the network epoxies (Fig. 17). The crankshaft motion for linear macromolecules was first propos-ed 163 166> as the molecular origin for secondary relaxations which involved restricted motion of the main chain requiring at least 5 and as many as 7 bonds 167>. This kind of... 

Numerous studies have been reported on the effect of diffusion of water into epoxy resins 177 178>. It is generally agreed that moisture acts as a plasticizer which lowers the Tg of the resin uo 134). Very little work, however, has been reported on the effect of physical aging on the diffusion behavior of water into network epoxies. This Section of the review summarizes the first attempt to study such an effect on TGDDM-DDS epoxy/water interactions. 

Hedrick, J.L. Yilgdr, I. Wilkes, G.L. McGrath, J.E. Chemical modification of matrix resin networks with engineering thermoplastics. I. Phenolic hydroxyl terminated poly(aryl ether sulfone)-epoxy systems. Polym. Bull. 1985, 13, 201-208. 

The material is raised to the cure temperature T ne and reaction commences. There is an increase in the molar mass of the epoxy-resin network as the oligomers react, so that in the equation for the entropy of mixing there will be a decrease in the number of molecules, N2, and thus the entropic component (A5 ) to the free energy of mixing (AG ). The resultant decrease in the solubility of the rubber in the network produces phase separation before the resin has undergone gelation (characterized by the formation of an infinite network, i.e. 

Carbon-13 Magic Angle NMR Spectroscopic Studies of an Epoxy Resin Network... 

In summary, we have shown here the usefulness of solid state carbon-13 NMR spectroscopy to characterize an epoxy resin network. Curing of epoxy resins can be followed using carbon-13 NMR spectroscopy. This technique is useful for characterization of Insoluble polymers. Our data anlaysls enable us to find the Important parameters required In the network analysis such as the gelation point. 

Later, in 1974, amine reactive versions of the liquid nitrile polymers (ATBN) were issued, thereby offering another way to introduce rubbery segments into a cured epoxy resin network. References are cited which provide detailed discussions of nitrile rubber, carboxylic nitrile rubber and both carboxyl- and amine-terminated nitrile liquid polymers (1-4). Table I illustrates CTBN and ATBN products structurally. Table II provides properties for typical solid carboxylic nitrile elastomers. 

Shear yielding is well established as the principal deformation mechanism and source of energy dissipation in both uiunodified and rubbo -toughened epoxy resins [2,3,27,83,121]. As molecular mobility in the epoxy resin network chains decreases, the ability of the matrix to deform by shear yielding is reduced. This is the reason why epoxy resins become both more brittle and more difficult to toughen as the epoxy resin crosslink density increases and/or as the network chains increase in rigidity, e.g. by use of highly aromatic epoxy resin monomers (see Section 19.7.1.1). 

Hed Hedrick, J. L., Yilgor, I., Jurek, M., Hedrick. J. C., Wilkes, G. L., McGrath, J. E. Chemical modification of matrix resin networks with engineering thermoplastics 1. Synthesis, morphology, physical behaviour and toughening mechanisms of poly (arylene ether sulfone) modified epoxy networks. Polymer 32 (1991) 2020-2032. 

Koh Koh, J. S., Kang, D. W., Park, H. S. Synthesis and toughness improvement of amino-ethylpi-perazine terminated polydimethylsiloxane tetrafunctional epoxy resin network. Korea Polym. J. 4 (1996) 39 4. 

Interpenetrating polymer network varnishes are composed of the phenolic resin, an epoxy resin, flame retardants, for example brominated epoxies or acrylates, and triphenylphosphate, polymerization initiators for radical polymerization of the acrylates and curing accelerators to catalyze the reaction between epor groups and phenolic groups. 

The epoxy resins were first synthesized in the 1930s. In common with phenolic and polyester resins, the epoxy resins are thermosetting materials. When converted by a curing agent, the thermosetting resins become hard, infusible systems. The system may be visualized as a network crosslinked in all three dimensions. 

Rosu, D., Rosu, L., Brebu, M. Thermal stability of silver sulfathiazole-epoxy resin network. J. Anal. Appl. Pyrol. 92, 10-18 (2011)... 

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