Adhesive strength, definition

The type of adhesion dealt with in the examples in the second paragraph above and Fig. 1 is mechanical or structural while for the lithographic resist adhesion requirements described in this paper a more practical definition of adhesion, one first proposed by Mittal [16], is being referenced and used. Resist patterning layer-substrate adhesion is required only to process or pattern a particular device layer. After the circuit layer is patterned, the resist layer is removed and does not become an integral part of the circuit, as opposed to a PI interlevel metal dielectric layer which does. As such, it is not required to possess high mechanical adhesion strength. In fact, the resist layer must be quantitatively removed after the circuit required layer has been patterned. If the resist layer adheres too well and becomes difficult to remove, it actually interferes with successful circuit fabrication. 

The curve Da(Gz 1) is limiting, because it corresponds to process parameters, which provide the minimum necessary level of adhesive strength. The area below this curve (at a definite mold temperature Tm) corresponds to the Da and Gzn Numbers, for which the degree of conversion is less than the critical level these parameters do not provide the maximum output. Points above this curve, represent inadmissible process parameters, which do not provide the required level of polymer-metal adhesive strength. 

It is possible to perform a physical analysis to predict either liquid lens or thick him formation, and the strength of adhesion between the two phases. In order to assess the adhesion strength, initially we need to formulate the work of cohesion and adhesion. In Section 2.1, we dehned the term cohesion to describe the physical interactions between the same types of molecule, so that it is a measure of how hard it is to pull a liquid (and solid) apart. In Section 3.5.3, we dehned, the work of cohesion, W), as the reversible work, per unit area, required to break a column of a liquid (or solid) into two parts, creating two new equilibrium surfaces, and separating them to inhnite distance. (In practice, a distance of a few micrometers is sufficient.) The work of cohesion required to separate liquid layers into two parts having unit area can obviously be expressed from the definition of surface tension as... 

The criterion of short-term adhesion strength for the case of interphase failure under combined action of direct and tangential stresses is suggested in [382]. This criterion presumes the existence of a definite dependence between octahedral stresses, which is assumed linear in the first approximation. The hypothesis of the octahedral direct and tangential stress dependence was proposed by Nadai for continuous isotropic materials and was further developed by Balandin [384] into the strength criterion, presenting a linear function from the component of the spherical stress tensor. 

On the other hand, the actual peeling of the LDPE film from the aluminum foil yields a specific peel work of 1 J/m, which is about 600 times that of the Thus, the specific peel energy is much larger than the stored electrostatic energy due to the presence of the EDL. This is an indication that the electrostatic component is only a fraction of the total adhesive strength. Thus, this result still cannot serve as definitive proof for Deryagin s hypothesis on the dominant role of EDL in adhesion. 

Displacement of epoxy by water definitely plays an important role in the strength loss of metal/epoxy adhesion systems. However, there are also other mechanisms by which water can reduce the strength of the interfacial region. 

Figure 11. The peel strength in g mm" vs. the % oligomerization of the 0.1 vol% APS primer solutions used lo couple PI 5878 (PMDA-ODA) to silica. The three lines represent from 0 to 500 h of 85°C/81% RH T H stress. A definite correlation of adhesion with T H stress, but liltle. if any, correlation with oligomerization is seen.

The development of methods for the use of MAP in wound repair required two parallel sets of definitions. The first involved MAP itself with the investigation of concentrations of protein and ratios of crosslinking catalyst that yielded sufficient bond strengths. The second was the choice of model systems and the analysis of tissue-related parameters that impinged on adhesion testing. The complexity of tissues necessitated that special attention be given to many details so that reliable test data could be obtained. 

Adhesives are nonmetaUic substances used to join two surfaces by means of surface adherence (adhesion) and inherent strength (cohesion), DIN 16920. This definition of adhesives does not cover water glass adhesives, adhesive ceramics, or adhesive mortars. The substances used as adhesives are polymers that go through a liquid phase at least once (reactive adhesives) or more than once (hotmelts, thermally activated adhesives). The liquid phase can also be achieved by dissolution in suitable solvents (nonreactive adhesives). In dispersion adhesives, the polymer molecules are dispersed (finely distributed) in a liquid - usually water - whereby the polymer molecules themselves are not dissolved. Fig. 6. These adhesives are also known as water-based or aqueous adhesives. It must be remembered that solvents are contained in these adhesives in addition to the water. Genuine aqueous adhesives contain less than 5% solvents in the liquid phase. The dispersions crnitain, in contrast to the solute adhesive molecules, additional substances, disposal of which requires specific additional measures. Since the dispersions represent stable systems in water, the water-resistance of such adhesives is reduced. Their thermal and water resistance can be increased by additional crosslinking (usually with isocyanates). 

The aim of the present contribution is to review the role of acid-base interactions in adsorption, wetting, and adhesion, and the methodologies and techniques to characterize the acid-base properties of materials. Examples have been selected from the authors research work and from a survey of the literature. This chapter is organized into the following three sections definition, properties, and strength of acid-base interactions theory of acid-base interactions in adhesion and experimental assessment of acid-base properties of polymers and other materials. 

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