Branched epoxy

Table 3 Properties of ternary nanocomposite comprising DGEBA epoxy branched epoxy resin and octadecylammonium-modified organo-silicate resin, hyper-...

Mohamed et al. [149] evaluated the use of several types of sulfosuccinate anionic surfactants in the dispersion of MWCNTs in NR latex matrices. Sodium l,5-dioxo-l,5-bis(3-phenylpropoxy)-3-((3-phenylpropoxy)carbonyl) pentane-2-sul-fonate showed the best dispersion capabihty and improved the electrical conductivity of the resulted composites. These results have significant implications in the development of new materials for aerospace applications because the filler s dispersiou directly influences the properties of the final material. Jo et al. [150] obtained pristine MWCNt-Ti02 nanoparticles filled with NR-CllR and epoxidized NR-CUR, concluding that the second blend proved higher thermal conductivity because the epoxy branches in ENR and the functionalized MWCNT form a stronger network. Conductivity in CNTs reinforced with rubber-based blends can be improved when reaching a critical concentration of the filler known as the percolation threshold, when a continuous network structure is formed. Thankappan Nair et al. [151] discussed the percolation mechanism in MWCNT-polypropylene-NR blends. 

As the length and frequency of branches increase, they may ultimately reach from chain to chain. If all the chains are coimected together, a cross-linked or network polymer is formed. Cross-links may be built in during the polymerisation reaction by incorporation of sufficient tri- or higher functional monomers, or may be created chemically or by radiation between previously formed linear or branched molecules (curing or vulcanisation). Eor example, a Hquid epoxy (Table 1) oligomer (low molecular weight polymer) with a 6-8 is cured to a cross-linked soHd by reaction of the hydroxyl and... 

In recent years, proprietary catalysts for advancement have been incorporated in precataly2ed Hquid resins. Thus only the addition of bisphenol A is needed to produce soHd epoxy resins. Use of the catalysts is claimed to provide resins free from branching which can occur in conventional fusion processes (10). Additionally, use of the catalysts results in rapid chain-extension reactions because of the high amount of heat generated in the processing. 

Side reactions involving branching through a secondary hydroxyl group can also occur. The extent of these side reactions should decrease as the ratio of epoxy to phenol decreases since phenolate anions are significantly more nucleophilic titan aliphatic hydroxyl groups. 

Bottle waste, hydrolysis of, 564 Bottles PET, 21 recycled, 532 Branched polymers, 8 Branching, 13 Branching agents, 8 Branching sequence distributions, 446 Brill temperature, 142 Brominated epoxy reagents, 414 Bromination-lithiation, 354 BTDA. See 3,3, 4,4 -Benzophenone-tetracarboxylic dianhydride (BTDA)... 

The 8-branch point present in PECH is absent in polymers of higher 1,2-epoxy-u-chloroalkanes. Such polymers are readily prepared by treatment of the neat monomers with the modified tri-ethyl al uminum catalyst introduced by Vandenberg (5, ) results for (2-chloroethyl)oxirane, (3-chloropropyl)oxirane and (4-chlorobutyl)-oxirane (2a-c) are summarized in Table I (7, 8). 

Rustamov, F. B. et al. Industrial Branch Coordination Conf. on Epoxy Resins and Materials on their Basis, Abstr., p. 5, Donetsk 1975... 

Branch and bound techniques, discrete optimization via, 26 1023 Branched aliphatic solvents, 23 104 Branched alkylbenzene (BAB), 77 725 Branched copolymers, 7 610t Branched epoxies, 70 364 Branched olefins, 77 724, 726 Branched polycarbonates, 79 805 Branched polymers, 20 391 Branched primary alcohols, synthetic processes for, 2 2 7t Branching... 

Another highly effect chain extender is trimellitic anhydride (TMA) which gives rise to branching of the PET structure. Note that the multifunctional epoxies (see Table 14.2) react quickly with the terminal carboxylic acid groups of PET but can also react with the film former and the silane coupling agent on glass fibre reinforcements. 

The first moment of the distribution is Pt0T the total, cumulative molar concentration of polymeric material. As the molecular weight of polymeric species increases, branching and crosslinking reactions yield a thermoset resin. Chromatography analysis of epoxy resin extracts confirms the expected population density distribution described by Equation 4, as is shown in Figure 2. Formulations and cure cycles appear in Table II. 

A special form of homofimctional hnking utihzes so called dendrimers. Dendrimers are nanospherical structures for which the exact size depends on the number of branching points and which carry reactive functional units in their periphery (for example aldehyde-, thiol-, epoxy groups etc). The structure of dendrimers is similar to a tree, and their ramifications consist of repetitive units. It should be noted that their size is limited due to the fact that the packing density of their terminal groups increases. With increasing size, their macroscopic structure approximates the form of a sphere. 

The application of the branching theories to acid curing was rather successful the discovery of the relative Importance of the transesterification following the epoxy-carboxyl addition initiated the theoretical treatment of branching. The prediction was that... 

These low molecular weight compounds with epoxy end groups are cross-linked by adding a curing agent such as ethylenediamine. Primary amines react with epoxides to form tertiary amines and branches. 

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