Quality of adhesives

In terms of processing there is no need for pre-drying PCHE granules, a standard extruder screw as used for polycarbonate may be used and discs are said to release well from the mould. Question marks remain on the oxidative stability of the polymer and on the quality of adhesion of the reflective layer but Dow claim that metallising is possible. 

Moreover, the interaction of the surface of the fillter with the matrix is usually a procedure much more complicated than a simple mechanical effect. The presence of a filler actually restricts the segmental and molecular mobility of the polymeric matrix, as adsorption-interaction in polymer surface-layers into filler-particles occurs. It is then obvious that, under these conditions, the quality of adhesion can hardly be quantified and a more thorough investigation is necessary. 

Then, in this two-term unfolding model remains to define this exponent 2q, since all other quantities and especially the r-radius are either given, or evaluated from the thermodynamic equilibrium relations. Then, in this model the 2q-exponent is the characteristic parameter defining the quality of adhesion and therefore it may be called the adhesion coefficient. This exponent depends solely on the ratios of the main-phase moduli (Ef/Em), as well as on the ratio of the radii of the fiber and the mesophase. 

Moreover, in many cases, a shift of Tg to lower values of temperature has been detected, but in these cases the quality of adhesion between phases may be the main reason for the reversing of this attitude 11,14). If calorimetric measurements are executed in the neighbourhood of the glass transition zone, it is easy to show that jumps of energies appear in this neighbourhood. These jumps are very sensitive to the amount of filler added to the matrix polymer and they were used for the evaluation of the boundary layers developed around fillers. 

Again, Eqs. (28) and (48) form a system of two equations and two unknowns, which can be solved and yield the values of the exponents q, and q2. Their difference A=r 1— q2, which expresses the quality of adhesion, is called the adhesion coefficient. The values of the exponents q, and q2> as well as of their difference A were given in Table 2 and plotted in Fig. 15 for the glass-fiber composites given in Ref. 22). 

In order to alleviate this singular and unrealistic situation, a series of models was presented in this study, in which a third pseudo-phase was considered as developed along a thin boundary layer between phases, during the polymerization of the matrix, whose properties depend on the individual properties of the phases and the quality of adhesion between them. 

The difference in the exponents of the two terms in the three-term model (the third term was a constant) and the exponent in the single power term of the two-term model gave a measure of the quality of adhesion between phases and they were called the adhesion coefficients. 

The technique may be said to combine the advantages of vacuum evaporation and sputtering, so that excellent qualities of adhesion are obtained without a limitation of maximum thickness of the coating—while at the same time the rate of deposition can be comparatively high. Many metals, alloys, and compounds may be deposited, on both metallic and non-metallic articles. However, its use at present is mainly for functional and protective applications, particularly where high resistance to corrosion is required. Thus, as examples, aluminium may be deposited on various types of steel and on titanium for uses in the aerospace and defence industries—and can be regarded as a less hazardous replacement for cadmium electroplating. 

In summary, today a multiplicity of different types of plastic is required to be printed, many in compositions with a number of different additives and often in rather complex presentations (such as co-extrusions and laminates). This means in turn that there is need for a variety of approaches to the problems of printing at the speeds required and to obtain satisfactory results—not only in terms of the choice of technique but also the design of machinery capable of handling the pieces of work and of formulations of inks with the correct qualities of adhesion, drying, and colour. 

Other workers, who have had occasion to repeat the work of Kalmus report considerable difficulty in obtaining thick deposits of cobalt consistent with a high quality of adhesion. The solutions recommended by Kalmus yield quite satisfactory results for very thin deposits, but the case is otherwise where deposits are required ranging in thickness from 3 to 5 thousandths of an inch and upwards. In these eases the deposited metal is found to separate very readily from its base.3 Furthermore, in view of more recent research on the rapid deposition... 

In any preparation of polymer-filler composites, there is concern about the quality of adhesion at the filler/matrix interface, and consequently over the interaction between filler and molten polymer at the compounding stage. Various technologies have been proposed to enhance adhesion in our laboratories, we have developed surface treatment (encapsulation) techniques in which mica is exposed to a "cold" microwave plasma (l.e. Tgiectron Tgas "Large Volume Microwave Plasma Generator"(LMP)... 

The quality of adhesion between solids, e.g. between a film and its substrate, depends to a large extent on the condition of the interfacial layer that is formed as can be seen in Fig.2. The following types of interfacial layers can be distinguished [15,75,107]... 

FTIR spectra have been used for many years to monitor the quality of adhesives both prior to and after curing. The infrared spectra of the basic adhesive ingredients resins, hardeners, and additives and of the cured adhesive can be measured and retained as standards with which to compare subsequent lots. Changes in the absorption peaks are noted if a supplier has changed the formulation, for example, by introducing a new additive or by substituting one resin or hardener for another. 

While a static load test is the commonly accepted procedure, in practice many variations in areas and weights are used, to compensate for the various qualities of adhesive evaluated, so that the test results will fall into a similar time frame, so it becomes difficult to compare different adhesive systems from accumulated data. It has the disadvantage of giving variable results for the same adhesive system, and is essentially a pass/ fail test, as many products remain in place at the end of the test period. Experience has shown that the shear properties of pressure-sensitive adhesives to porous and nonporous substrates can be quite different, and each must be judged on its own merits. 

The choice of accelerator also has an effect on the quality of adhesion between cord and rubber. The accelerator should not form a stable copper complex which dissolves in the rubber. This would be quite corrosive to the brass plating. In this respect, benzothiazoles and their sulfenamides are much better than dithiocarbamates. DCBS is a particularly good sulfenamide accelerator for rubber-to-brass adhesion. 

The first phase of the quality-control system outlined in Figure 12.1 controls the quality of adhesive material and adherend details making up... 

The predominant failure mode in bonded joints was cohesive failure of the adherend. Only in those adhesively bonded joints with the polyurethane adhesive (1897) was a cohesive failure of the adhesive encountered. No adhesive failures were detected, indicating that the surface treatments performed had been sufficient. The quality of adhesive layers was in general satisfactory. However, in joints of laminates with a woven roving or a uni-directional surface layer (Table 7) the adhesive layers were thick and of poor quality, having large voids. With laminates of a uni-directional surface layer, this... 

Millare, B. Thomas, M. Ferreira, A. Xu, H. Holesinger, M. Vullev, V. I., Dependence of the Quality of Adhesion Between Poly(dimethylsiloxane) and Glass Surfaces. Langmuir 2008, 24,13218-13224. 

Recent advances have made radiation-curable laminating adhesives very attractive in terms of economics, automation, quality of adhesive bond and throughput, while offering distinct advantages with respect to both energy consumption and pollution control [4],... 

Industries concerned with the production of thin films on substrate materials have for some time sought routine methods to monitor the quality of adhesion between film and substrate. The characteristics of the indentation test, and in particular its ability to develop cracks beneath the surface, present a way to do so. 

The final locus of failure and fracture trajectory of an adhesive bond is the result of the interactions among the material properties such as the tensile strength of all the components, quality of adhesion at the interface, fracture toughness of the bonds, and the stress state at the crack tip of existing flaws or debonds [4]. To predict the locus of failure in an adhesively bonded joint loaded in an arbitrary manner such as illustrated in Fig. 1, the mechanisms controlling the... 

Filimonov, S.A., Resonance method as a means for inspecting the quality of adhesive joints. Sov. J. Nondestruct. Test., 26, 853-860(1991). 

Nondestructive Testing (NDT, NDE, NDi, NDC) -Techniques used to examine the quality of adhesive bonds without causing damage to the item or bond. The terms NDT (Testing), NDE (Evaluation), NDI (inspection) and NDC (Characterisation) tend to be Interchangeable. Nondestructive inspection systems may be manual or automated to some extent. Whilst effective for finding defects in the bond, no method currently exists which allows a reliable, quantitative measure of bond strength. 

Apply FRP sheets on dry surface with good quality of adhesive material. 

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