Adhesion enthalpy

Cure kinetics of thermosets are usually deterrnined by dsc (63,64). However, for phenohc resins, the information is limited to the early stages of the cure because of the volatiles associated with the process. For pressurized dsc ceUs, the upper limit on temperature is ca 170°C. Differential scanning calorimetry is also used to measure the kinetics and reaction enthalpies of hquid resins in coatings, adhesives, laminations, and foam. Software packages that interpret dsc scans in terms of the cure kinetics are supphed by instmment manufacturers. 

Upon combining Eqs. 88 and 85, one finds that the total work of adhesion is related to the surface energies of the contacting materials as well as the enthalpy associated with acid-base interactions by... 

FIG. 19 Proposed mechanism for the difference of adhesive force between cations of low and high hydration enthalpies. (Reprinted from Ref. 88. Copyright 2000 by Academic Press.)... 

When we compared the viscosities of solutions of natural rubber and of guttapercha and of other elastomers and later of polyethylene vs.(poly)cis-butadiene, with such bulk properties as moduli, densities, X-ray structures, and adhesiveness, we were greatly helped in understanding these behavioral differences by the studies of Wood (6) on the temperature and stress dependent, melting and freezing,hysteresis of natural rubber, and by the work of Treloar (7) and of Flory (8) on the elasticity and crystallinity of elastomers on stretching. Molecular symmetry and stiffness among closely similar chemical structures, as they affect the enthalpy, the entropy, and phase transitions (perhaps best expressed by AHm and by Clapeyron s... 

For the system with very high adhesion strength between the clay and the stickers, the favorable enthalpy of the sticker-clay interaction dominates the unfavorable entropic contributions. Accordingly (Figure 11c), the composite now becomes exfoliated, as demonstrated by both compressible and incompressible models. Interestingly, within the compressible model, the old minimum at H 1.6-2 nm has not disappeared completely, indicating the presence of a metastable intercalated morphology. 

In this chapter, we concentrate on the role of the intermolecular interactions at interfaces based on the surface dynamics, the surface free energy at a given temperature and the surface energy (or enthalpy) of a solid. Contact angle and gas chromatographic techniques are respectively chosen for the studies of wettability and adsorption phenomena because of their simplicity and clearness. The degree of adhesion at interfaces between unlike solid substances is also discussed from a viewpoint of intermolecular interactions. 

In the gas-solid interaction studies at infinite dilution, it is found that the surface free energy and surface enthalpy (or adsorption enthalpy including acid-base character) of a solute are strongly influenced by the most active sites on the solid surface. The surface free energy and surface enthalpy have been applied as a typical value of the surface, which can be directly related to the adhesion level [70]. 

T o identify the nature of predominant interactions at interfaces between non-reactive metal M and ionocovalent oxide AO, different attempts have been made to correlate the energetic properties of interfaces (work of adhesion, work of immersion) to the energy of formation of M oxide or other quantities characteristic of the contacting phases, such as the surface energy of the metal or the gap energy of the ceramic. Any successful correlation between an energetic quantity of interfaces and the formation energy or enthalpy of MO oxide indicates the occurrence of a chemical interaction between M and AO at the interface, even... 

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