Adhesives relationship between performance

The relationship between performance reliability and adhesive formulation is not simple. The key step in improving the reliability of adhesives on cathodically protected substrates is fully understanding the cathodic delamination process. Various mechanisms have been proposed in the literature. A large number of investigators have focused attention on the damage hydroxide ion does to coating adhesion. 

Tackifying resins enhance the adhesion of non-polar elastomers by improving wettability, increasing polarity and altering the viscoelastic properties. Dahlquist [31 ] established the first evidence of the modification of the viscoelastic properties of an elastomer by adding resins, and demonstrated that the performance of pressure-sensitive adhesives was related to the creep compliance. Later, Aubrey and Sherriff [32] demonstrated that a relationship between peel strength and viscoelasticity in natural rubber-low molecular resins blends existed. Class and Chu [33] used the dynamic mechanical measurements to demonstrate that compatible resins with an elastomer produced a decrease in the elastic modulus at room temperature and an increase in the tan <5 peak (which indicated the glass transition temperature of the resin-elastomer blend). Resins which are incompatible with an elastomer caused an increase in the elastic modulus at room temperature and showed two distinct maxima in the tan <5 curve. 

Thus the study of surfaces has emerged as an important focus in the chemical sciences, and the relationship between surfaces of small systems and their performance has emerged as a major technological issue. Flow in microfluidic systems—for example, in micromechanical systems with potential problems of stiction (sticking and adhesion) and for chemistry on gene chips—depends on the properties of system surfaces. Complex heterogeneous phases with high surface areas—suspensions of colloids and liquid crystals—have developed substantial... 

Equation (5,33) tells that the fnction force is due to the shear strength of the junction, but here again is required the exact relationship between A, the externally vertical applied load, the work of adhesion and the tip shape. Recently, careful experimental work performed at the submicrometer scale has been satisfactorily described by using equations (5.2) and (5.13) [102]. But these tvb o equations describe the static case and do not consider the occurrence of a tangential force that certainly gives a reduced contact area (equation (5.10)), Other works currently performed at the macroscopic scale are suitably described by equation (5.12) [98,99]. 

RELATIONSHIP BETWEEN VISCOELASTIC PROPERTIES AND PRESSURE SENSITIVE ADHESIVE PERFORMANCE... 

Incorporation of the E-30 component usually improves the elongation at break but lowers the modulus and the strength of the resin. However, there was no simple relationship between adhesive performance and bulk properties of the resin. With respect to the tensile shear tests, a strength maximum at room temperature was found in the range of 30 to 40 phr E-30 (Fig. 3). 

The function of a structural adhesive joint is to transmit an external load to the structural member. If the joint fails to function as it is intended, it will undergo damage or failure. The damage could be actual fracture of the structure, excessive elastic deformation, or excessive inelastic flow. The criteria for what constitutes structural failure depend on the performance requirements of the joint. The fundamental problem in the mechanics of adhesives and joints is to obtain some relationship between the loads applied to the joint and a parameter that will adequately describe the criteria for strucmral failure. The most common criterion for such failure of lap-type joints is actual fracmre of the joint. For a given combination of adherend and adhesive, the stress analyst must decide what the mode or theory of failure would be if the applied loads become large enough to cause failure. The decision as to which theory would realistically determine the mode of failure is usually based on past experience, or upon some form of experimental evidence. ... 

Dependence of Adhesive Force on Size of Irregularly Shaped Particles. Experiments have been performed [194] to characterize the relationship between the adhesion of irregularly shaped particles and the size of these particles. The equivalent diameter (see Section 14) was taken as a single parameter characterizing the size of irregularly shaped particles. 

There are at least two examples in the literature which relate contact angles with the adhesion of structural adhesives. Barbarisi demonstrated a linear relationship between the tensile shear strength of an epoxy adhesive applied to polyethylene, which had been surface treated in various ways, and (1 + cos 6) DeBruyne performed a similar experiment and found that the tensile shear strength of chromic acid-etched polyethylene bonded with an epoxy adhesive was proportional to the contact angle that water made with the surface." ... 

Joint designing involves a complex relationship between the adhesive properties, the substrate properties, and the joint geometry. However, the designer must not be concerned solely with joint performance, but should also consider economic factors such as machining, processing, and labor costs. 

There have been a few earlier studies of the viscoelastic properties of rubber-resin pressure-sensitive adhesive systems.Sherriff and co-workers demonstrated the effect of adding low molecular weight resins to natural rubber. O 2) Compositions were selected for study which exhibited pressure-sensitive adhesive performance at an appropriate concentration of resin. Sherriff et al. found that addition of the resin to the rubber shifted the entry to the transition zone to a lower frequency and also reduced the modulus in the rubbery plateau. Later, Aubrey and Sherriff examined the relationship between viscoelasticity and peel adhesion of rubber-resin blends.(3)... 

The empirical, quantitative relationship between PSA performance and adhesive modulus values was obtained by correlating adhesion properties in Figures 34-40 with their G value at ( ) = 0.1 rad/sec and slope, G (o) = 1(X))/G (< ) = 0.1), as shown in Figures 49-51. 

THE RELATIONSHIP BETWEEN ADHESIVE SHEAR STRAIN PROPERTIES AND ADHESIVE PERFORMANCE IN AN ACTUAL STRUCTURE... 

The relationship between the chemical structure of polymeric adhesives and their physical structure, physical properties, and performance characteristics have interested scientists for many years. The very complex nature of these relationships have, however, resulted in a lack of broad generalizations about structure-property relationships instead, a myriad of technical papers have been published about the work done on specific systems of adhesives and adherends. These papers now form a large part of the adhesives literature yet many of the questions basic to the design of satisfactory adhesives remain unsolved. The relationships developed for a given series of adhesives seldom apply to another series directly. Thus further experimentation is always needed to optimize formulations and compositions of adhesive products. The objective of the papers in this session is to examine several relationships of molecular structure to properties of several systems of polymeric adhesives which are important in today s technology. 

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