Degree of bonding

In the equation, Db, is the interfacial bond strength normalized with respect to the maximum bond strength in the composite and the integration variable, t, represents the time an incremental area came into intimate contact. 

The degree of bonding analysis has been verified for both compression molding and online consolidation of thermoplastic composites. In these studies, composite test specimens were consolidated under controlled processing conditions. The most common types of tests performed to measure the interply bond strength were the interlaminar (short beam) shear test [21,25] or the lap shear test [12,21,26]. 

The process by which a thermoplastic matrix composite consolidates to form a laminated structure has been attributed to autohesive bond formation at the ply interfaces. Autohesive bond formation is controlled by two mechanisms (1) intimate contact at the ply interfaces, and (2) diffusion of the polymer chains across the interface (healing). The rate of autohesive bond formation and hence the speed of the composite consolidation process is directly related to the temperature-pressure-time processing cycle. 

Once intimate contact is achieved, bonding of the ply interfaces can occur. The mathematical relationships between interply bond formation and processing temperature and time were discussed in Section 7.3. The analyses are based on the theories explaining strength development of a polymer-polymer interface and crack healing in polymers. 

GICoo Critical strain energy release rate at infinite time 

---

In the [3,2-c ] series the spectra of the parent compound and some closely related analogues have been compared with those predicted from MO calculations of electron densities. The results confirm the predicted occiurence of a considerable degree of bond localization in these compounds <80KGS54l), as was previously found in their deaza (cinnoline) analogues <67JCS(B)1243). Other comparisons of NMR values with those expected from MO calculations for a series of azanaphthalenes have included some results with pyridopyridazines <75MI21500). 

The above evidence shows that a high degree of bond-making in the rate-determining step of bimolecular nucleophilic substitutions seems... 

In addition to the nature of resin and fibre, the laminate properties also depend on the degree of bonding between the two main components and the presence of other additives including air bubbles. Because of this some parts, fabricated by simple hand building techniques, may exhibit strengths no better or even worse than unreinforced materials. This problem is often worst with glass fibres which are therefore normally treated with special finishes to improve the resin-glass bond. 

In the transition state, the torsional strain involving the partially formed bond between the nucleophile and the carbonyl group represents a substantial fraction of the total strain, even when the degree of bonding is low. Thus, in the case of acyclic carbonyl compounds, a staggered conformation is preferred in the transition state (Figure 6). 

The experimental isotope effects have been measured for the reaction of 2-methylbutene with formaldehyde with diethylaluminum chloride as the catalyst,27 and are consistent with a stepwise mechanism or a concerted mechanism with a large degree of bond formation at the TS. B3LYP/6-31G computations using H+ as the Lewis acid favored a stepwise mechanism. 

A theoretical and structural analysis of [Ir2(/i-Cl)2L4], where L4 = (PF3)4, (PH3)4, (cod)2, ((C2F5)2PC2H4P(C2F5)2)2, debates the factors which determine the degree of bonding between the coordination planes of the two metal centers.651 One driving force would appear to be the attractive metal/metal interactions resulting from donor-acceptor interactions between the dz2 and pz orbitals of the two metal atoms. 

We also examined the fold statistics in this Ciooo system. The distribution of the inter-stem vectors connecting stems linked by the loops, and their radial distribution function again indicated that about 60-70% of the folds are short loops connecting the nearest or the second and third nearest stems, though the crystallization did not complete. The presence of local order in the under cooled melt in the present Ciooo system is also examined through the same local order P(r) parameter, the degree of bond orientation as a function of position r, but again we did not detect any appreciable order in the undercooled melt. 

The weak aromaticity of oxazole is reflected by its chemical behavior, demonstrating a high degree of bond localization (illustrated by the propensity for cycloaddition reactions),137 and is supported by theoretical calculations (ring current indices, i.e., the bond... 

In solution the situation is more complicated still, because the solvent can play a more or less active role in the reaction. For example, solvent turns out to be involved to some extent as a nucleophile in many SNl-type processes, where highly electrophilic intermediates are involved (Lowry and Richardson, 1987, pp. 335 ff.). Here a degree of bond making accompanies what had originally been regarded as uncomplicated rate-determining bond-breaking reactions. 

On first consideration it may be concluded that if suitable crystals are available X-ray crystallography is the ideal method to decide unambiguously if a candidate compound is, in fact, homoaromatic (Childs et at., 1986a). The bond equalization and planarization associated with homoaromaticity should be readily detected by this means. However, the degree of bond equalization and the size of the homoconjugation gap necessary for homoaromaticity are open to debate (vide infra) (Childs et al., 1986a Haddon, 1988a). In addition, for systems capable of fluxional behaviour, dynamic or static disorder may lead to erroneous conclusions in the interpretation of the X-ray data (see Jackman et al., 1989). In suitable cases very careful X-ray studies can probably avoid this confusion (Dunitz et al., 1988). 

It is interesting to attempt to extend this type of analysis in the direction of a more quantitative assessment of the degree of bond-making or breaking in the... 

---