Effects of adhesion

Sjoerdsma S.D., Bleijenberg A.C.A.M., and Heikens D., The Poisson ratio of polymer blend, effects of adhesion and correlation with the Kemer packed grain model. Polymer, 22, 619, 1981. 

Locus and Mechanism of Adhesion Failure during Corrosion Effects of Adhesive Chemistry. In previous studies (4- on the corrosion induced adhesion loss of coatings from steel surfaces, a primary mechanism for coating deadhesion was polymer degradation at the coating/metal interface by corrosion reactions that generate hydroxide ion ... 

The Effect of Adhesive Primers. In practice, adhesive bonds involving metal adherends often use primers as pretreatments of the metal surface prior to bonding. Table IV shows the durability of composite-metal bonds prepared with adhesive C over a series of primers (of varying corrosion resistance) in 240 hour salt spray test. The results indicate that the performance of bonds is directly related to the corrosion resistance of the primer used to prepare the adherend surface. In general, the adhesion of the primer to the steel adherend, rather than the adhesive chemistry. 

Asloun, El. M., Nardin, M. and Schultz, J. (1989). Stress transfer in single-fiber composites Effect of adhesion, elastic modulus of fiber and matrix and polymer chain mobility. J. Mater. Sei. 24, 1835-1844. 

Sela N., Ishai O. and Banks-Sills L. (1989). The effect of adhesive thickness on interlaminar fracture toughness of interleaved CFRP specimens. Composites 20, 257-264. 

Sun. C.T. and Rechak. S. (1988). Effect of adhesive layers on impact damage in composite laminates in Composite Materials Testing and Design (8th Conf.) ASTM STP 972 (J.D. Whitcomb ed.), ASTM, Philadelphia, PA, pp 97-123. 

Fig. 6. Debonding of interfaces, effect of adhesion on PP/CaC03 composites filler CaC03, (pf=0.2,r=L8 pm...

Park, E.S., et al. 2001. Effects of adhesives and permeation enhancers on the skin permeation of captopril. Drug Dev Ind Pharm 27 975. 

Also adhesion between the tip and sample can cause deformation of the sample. Several theories have been developed to include the effect of adhesive forces. In the JKR theory adhesion forces outside the contact area are neglected and elastic stresses at the contact line are infinite [80]. Even under zero load, the adhesion force results in a finite contact radius a=(9jtR2y/2 E)1/3 as obtained from Eq. 7 for F=0. For example, for a tip radius R=10 nm, E=lGPa, typical surface energy for polymers y=25 mN/m, and typical SFM load F=1 nN, the contact radius will be about a=9.5 nm and 8=9 nm, while under zero load the contact radius and the deformation become a=4.5 nm and 8=2 nm, respectively. The experiment shows that under zero load the contact radius for a 10 nm tungsten tip and an organic film in air is 2.4 nm [240]. The contact radius caused only by adhesion is almost five times larger than the Hertzian diameter calculated above. It means, that even at very small forces the surface deformation as well as the lateral resolution is determined by adhesion between the tip and sample. 

SSadh =6274.307 SSPRA=4.380 effect of a preliminary surface preparation is insignificant, while the effect of adhesion systems is significant. 

Essentially, hot-melt adhesives are blends of polymers that are melted and kept at an elevated temperature until applied to a cooler substrate the second substrate is brought into contact immediately with the molten film and afterwards the adhesive cools rapidly, a bond being formed almost instantaneously. The temperature of the molten adhesive generally is in the region 160 to 200 °C, so that its viscosity is low enough for application—and this means that the substrates to be bonded must be capable of withstanding the effect of adhesive at this temperature (this can cause difficulties with some thermoplastics, especially expanded materials). 

TABLE 15.19 Effect of Adhesives on the Sustained Load Durability of FPL-Etched Aluminum Specimens46... 

Extensive information on durability of adhesive joints is more available on aluminum than on other substrates. Figure 15.17 illustrates typical results showing the effect of adhesive variations on joint durability during marine exposure. Vinyl-phenolics and nitrile-phenolics have... 

FIGURE 15.17 Effect of adhesive on the durability of etched 6061-T6 aluminum alloy joints exposed to a marine environment. (1) Two-part epoxy, (2) one-part epoxy, (3) nitrile-phenolic, (4) vinyl-phenolic, (5) vinyl-phenolic.33... 

Minford, J. D., Surface Preparations and Their Effect of Adhesive Bonding, Adhesives Age, July 1974. 

Figure V demonstrates the effect of adhesive dry coating weight on 180° peel strength and rolling ball tack with OH/NCO ratios of 1.7 and 1.3 for Hycar 2103 and Hycar 2106, respectively. Static shear tests run both at room temperature and 70°C show no creep for both systems throughout the thickness range tested.

Where Gp and GF are the shear moduli of the plastic matrix and the filler respectively, v is Poisson s ratio of the matrix, and V is the volume fraction. E s are Young s moduli. Recently this relation was verified for the rubber-reinforced thermoplastics (29). The effect of adhesion at the rubber-resin (or rubber-filler) interface has been studied (49, 57, 58) with mathematical models. 

Thermodynamic Work of Adhesion. One other important aspect of surface energetics (71, 72) is the use of surface free energy to calculate the maximum reversible work of adhesion, Wad, which has been correlated to the adhesive strength (41, 44) and should not be equated to the strength of an adhesive joint (6). Since neither wetting nor adhesion is controlled purely by thermodynamic factors, we should use the maximum reversible work of adhesion, Wad on the basis of an idealistic approach. When all other variables are equal, we can use Wad to compare the effectiveness of adhesives for a specific substrate. 

For surfaces that deform plastically, the contact area A is proportional to the applied load. A single elastic contact deforms as as load increases, and would not be expected to follow this rule. However, when considering an exponential surface height distribution, which leads to a multiplicity of elastic asperity contacts, a linearity between load and contact area is recovered. Using instrumentation developed in the last 15yr, notably the atomic force microscope (AFM) and surface forces apparatus (SFA), researchers have explored the universality of friction-load proportionality over a much wider range of dimensions and surface characteristics. Indeed, SFA experiments have shown friction-load proportionality between atomically smooth mica surfaces in dry air over square micrometers of contact area. A contact mechanics expression for elastic contacts that incorporates the effects of adhesion was used. Similarly, AFM experiments of... 

Fig. 5. Effect of adhesion inhibitors (A) on the colonization of the respiratory tract by Bordetella pertussis and (B) on pulmonary edema in animals challenged with the virulent BP536 strain, Anti-Le and anti-A are antibodies against blood group determinants Le and A, respectively anti-CR3 is the antibody against the receptor for complement fragment C3bi. VIR+, control without inhibitor. (Modified from ref. [157].)...

Figure 4. Effect of adhesion on load-displacement data obtained from testing two specimens containing PC spheres one with full (> 54 MPa) and one with reduced (22 MPa) adhesive strength. R/L = 0.125. Reproduced with permission from reference 26.

In the second experiment, the effect of adhesive type on yield strength was determined ... 

FIG. 6—Effect of adhesive thickness on load at failure and location from which cracks grow for button tensile test. Specimens made of PMMA with a diameter of 1,5 in. The model adhesive was Thiokol Chemical Corp. Solithane polyurethane. Crack growth was observed and recorded with a video camcorder. 

In contrast, in the case of the contact deformation displacement of ball-to-flat counterformal contacts discussed above no effect of adhesion was found as compared with the influence of the (bulk) viscoelastic properties of the materials. (This may be due to elastic relief forces which may burst adhesive junctions during the loadingunloading contact deformation cycles.)... 

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