Epoxy network

Void-free phenolic-epoxy networks prepared from an excess of phenolic novolac resins and various diepoxides have been investigated by Tyberg et al. (Fig. 7.37).93 -95 The novolacs and diepoxides were cured at approximately 200°C in the presence of triphenylphosphine and other phosphine derivatives. Network densities were controlled by stoichiometric offsets between phenol and... 

Nonsegmented, monophase polymers, 221 Novolac-epoxy networks, 414 Novolac-HMTA cures, hydroxyben-zylamine and benzoxazine decompositions in, 392-398 Novolac networks... 

Phenolic degradation, thermal and thermo-oxidative, 418-425 Phenolic-epoxy networks, 413 Phenolic monomers, second-order reaction rate constants of formaldehyde with, 403... 

Phenolic networks, 411 Phenolic-novolac-cured systems, 415 Phenolic novolac-epoxy networks, flame retardance of, 415 Phenolic oligomers, 375... 

Other reports on the morphology and mechanical behavior of organosiloxane containing copolymeric systems include polyurethanes 201 202), aliphatic 185, 86) and aromatic117,195> polyesters, polycarbonates 233 236>, polyhydroxyethers69,311, siloxane zwitterionomers 294 295) and epoxy networks 115>. All of these systems display two phase morphologies and composition dependent mechanical properties, as expected. 

Pathak, S.K. and Rao, B.S. (2006) Structural effect of phenalkamines on adhesive viscoelastic and thermal properties of epoxy networks. 

For imperfect epoxy-amine or polyoxypropylene-urethane networks (Mc=103-10 ), the front factor, A, in the rubber elasticity theories was always higher than the phantom value which may be due to a contribution by trapped entanglements. The crosslinking density of the networks was controlled by excess amine or hydroxyl groups, respectively, or by addition of monoepoxide. The reduced equilibrium moduli (equal to the concentration of elastically active network chains) of epoxy networks were the same in dry and swollen states and fitted equally well the theory with chemical contribution and A 1 or the phantom network value of A and a trapped entanglement contribution due to the similar shape of both contributions. For polyurethane networks from polyoxypro-pylene triol (M=2700), A 2 if only the chemical contribution was considered which could be explained by a trapped entanglement contribution. 

In the foregoing considerations, formation of elastically inactive cycles and their effect have not been considered. For epoxy networks, the formation of EIC was very low due to the stiffness of units and could not been detected experimentally the gel point conversion did not depend on dilution in the range 0-60% solvent therefore, the wastage of bonds in EIC was neglected. For polyurethanes, the extent of cyclization was determined from the dependence on dilution of the critical molar ratio [OH] /[NCO] necessary for gelation (25) and this value was used for the statistical calculation of the fraction of EIC and its effect on Ve as described in (16). The calculation has shown that the fraction of bonds wasted in EIC was 2-2.5% and 1.5-2% for network from LHT-240 and LG-56 triols, respectively. 

In this chapter, which is a follow-up to an earlier discussion,7 we report on two specific synthetic methodologies using a fluorodiimidediol 3 to prepare the heavily fluorinated epoxy networks as shown in Schemes 1 and 2. 

Some of these oligomers have later been used in the synthesis of various segmented urea or imide type copolymers and in the modification of epoxy networks, which have been discussed elsewhere (5,11). ... 

Selection Criteria for the Preparation of Solvent-Modified and Macroporous Epoxy Networks with Tailored Morphologies Prepared via CIPS. 

---