No-stress adhesives

Adhesives formulated from flexible, elastomeric resins are now commercially available and effectively used to dissipate stresses. They are low-stress or no-stress adhesives that have a low modulus of elasticity. Several guidelines that can be followed to reduce stresses are the following ... 

Abstract—This work studies the effects of self-oligomerization of the aminosilane coupling agent 3-aminopropyltriethoxysilane—also called y-aminopropyltriethoxysilane. 3-APS, y-APS, APS or AUOO (Union Carbide)—on the adhesion of thin polyimide films to a native-oxide silica surface under no stress, i.e. T(0) conditions, and after standard 85°C/8I%T H (temperature and humidity) stress. Techniques have been developed using both silicon and hydrogen NMR to control and monitor the degree of oligomerization in aqueous solutions at low concentrations (0.1 vol %). 

Adhesive type Stress No stress Stress No stress Stress No stress... 

Adhesive Strengths. The strengths of the adhesive bonds between the inclusion materials and the epoxy were determined with an experimental technique described in detail elsewhere (24). The technique involves embedding a sphere of the candidate material in the contoured-neck portion of a cylindrical epow bar. The decohesion of the sample from the epoxy is then observed as the bar is strained in tension. The radial stress at decohesion is then detennined by means of a numerical solution of the deformation problem. Because no stress singularities exist at the interface prior to debonding, as is often the case with the usual popular tests, the technique used here provides a measure of the "true adhesive strength for the bimaterial systems employed. 

The important point to be stressed is that in all cases no surface adhesion promoters were used.The only precaution taken was to ensure a good cleaning of the substrates. The final step prior to application was a vapor degreasing operation with hot freon vapors. 

Following manufacturers instructions, mix Loctite ICHysol Epoxi-Patch Adhesive on a disposable surface. Dispense on either side of the sensor the mixed epoxy and inside the tube ( 2mm) such that the sensor is fixed in place. Place a dab of the epoxy at the far end to fix the wires to the tubing so that no stress is transmitted to the sensor when moving the wires. 

If, in the process of film production, the deposited atoms are mobile and if only a low localized adhesion of the film atoms exists to the substrate, then the film atoms (molecules) slip in the boundary surface and only low (or no) stresses are formed. However, increasing localized adhesion often causes increasing film stresses. 

The impact behaviour of HDPE/iPP (75/25) binary blend is of brittle nature with no stress whitening phenomenon. As shown in the SEM micrograph of Fig. 7a, the fractured surface of this binary mixture exhibits a "honeycomb morphology with evidence of dispersed particles (iPP) enclosed in the cells. Furthermore, there seems to be very negligible adhesion between the matrix and the dispersed phase. This observation accounts for the lower impact strength values compared with those obtained for the pure homopolymers. 

Excellent JP fuel resistance. High adhesion to AL and Ti substrates. No stress-corrosion imparted to Ti surface. Facile cure and processability. Available in 100 percent solid formulary. Excellent tensile properties... 

No stress concentration is present at the interface because no discontinuity exists in the physical properties. Cohesive energy density (CED, Eq. (1.1)) can be used to interpret diffusion bonding, as defined by Eq. (1.2). Bond strength is maximized when solubility parameters are matched between the adhesive and the adherend. 

In immiscible system with very little to no interfacial adhesion between phases, the properties can be unpredictable and sometimes can exhibit an antagonistic effect (negative nonlinear behavior) and be worse than those predicted by linear behavior. In addition to having poor and unpredictable properties, the morphology or microstmcture of immiscible mixture is unstable. The discrete phases can coalesce into larger domains in the molten state. Moreover, there could be delamination in the solid state when a stress is applied to the material. 

The second approach to determining basic engineering properties of the adhesive has been to employ specific joint geometries, where ideally (i) the stress state is simple, (ii) no stress concentrations are present and (iii) the... 

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