Epoxy-activated resins, comparison

Optimization in Affinity ChromatographY 415 Table 2. Comparison of different epoxy-activated resins. 

Furthermore, the comparison between dynamic mechanical results and NMR mobility observations will be more delicate since it requires extrapolation of the mechanical response over about 5 decades, and must take into account the experimental uncertainty of the activation energy values. In the other reported polymers, the use of dielectric relaxation techniques, which cover a frequency range up to 105 Hz, overcame the extrapolation difficulty. Consequently, for the epoxy resins the comparison will remain more qualitative [63]. 

Some typical results are shown in Figure 16.2 (LLE for PS/acetone), Table 16.4 (infinite dilution activity coefficient for PBMA solutions in a variety of solvents). Tables 16.5 and 16.6 (activity coefficients of low- and heavy-molecular-weight alkanes in asymmetric athermal-alkane solutions). Table 16.7 (VLB for ternary polymer-solvent solutions). Figure 16.6 (VLB calculations for systems containing the commercial epoxy resin Araldit), and Table 16.8 (comparison of LLE results from various thermodynamic models). 

In comparison to an uncoated fabric, the tensile strength can be doubled with an epoxy resin coating. Thus, tensile stresses up to 1400 MPa were achieved (Table 2). The concrete cannot penetrate into an uncoated roving and, thus, the inner filaments are not fully activated for load transfer. In contrast, the epoxy resin is able to penetrate into the roving and all filaments are activated resulting in a higher tensile strength, [3]. 

Relative reaction rates are often expressed in terms of the activation energy Ea (Arrhenins type relationship). allows comparisons of reaction rates at different temperatiues and is influenced by the type of chemical reactions involved in the ciue. Cining of epoxy resins with phenols or aromatic and aliphatic amines proceeds with a fairly low activation energy of 50-58.5 kJ/mol (12-14 kcal/mol). Activation energies are higher when epoxy compounds having low hydroxyl content are cnred alone in the presence of catalysts (92 kJ/mol = 22 kcal/mol) or with dicyandiamide (125.5 kJ/mol = 30 kcal/mol). 

The comparison of these data with the series of the catalytic activity of the metal acetylacetonates in the reaction of the epoxy oligomers with the phenolformaldehyde resins [Eq. (2)] as well as with the series of the thermal stability of these diketonates [Eq. (3)] indicates that the catalytic effect of these complexes depends on the stability of the chelate molecules. This stability is defined by the strength of the chelate rings whoch depends on the ligand structure (e.g., compare the decreased activity of Mn in [Eq. (4)] with its increased catalytic effect in [Eq. (2)]. 

Figure 5.277 shows an example of acceptable tensile strength as a function of outer fiber strain for a mat and a non-woven laminate with UP and EP matrix. Laminates with a polyester resin matrix and an epoxy resin matrix are also provided for comparison. The acceptable residual strength continuously decreases with increasing outer fiber strain. This is more pronounced in epoxy resin laminates than in polyester resin laminates. Sulfuric acid penetrates relatively easily into epoxy resins. The activation energy of penetration depends on the acid concentration and is higher for weakly concentrated acids than for highly concentrated acids. It is over-... 

To further understand the effect of the interaction between the nanoparticles and the epoxy resin, the curing reaction kinetics of the composites have been studied. Based on non-isothermal DSC measurements and the Kissinger equation, the activation energy E, the pre-exponential factor A, and the reaction order , of the curing kinetics are obtained (Table 4). Comparison of the kinetic data suggests that the presence of the nanoparticles in epoxy does not change the overall reaction... 

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