Adhesion static

By analogy with friction, we may distinguish static and kinetic adhesion. Static adhesion is measured by the force of resistance to the onset of detachment, and kinetic adhesion is measured by the interaction between particles and surface in the course of detachment. In order to detach particles, the force of static adhesion is the primary barrier that must be overcome since the kinetic adhesion is always smaller than the static. This situation attracted the attention of G. I. Fuks, who pointed out that static friction is measured by the force directed tangential to the substrate [12]. 

PEGMA on PU UV polymerization PEGMA molecular weight (400 g/ mol-lOOOg/mol) Platelet adhesion Static, in vitro Rabbit PRP Higher molecular weight=more hydrophilic least adhesion with 800g/mol [6]... 

Fluorocarbon oligomers on PU Grafting - Platelet adhesion Static, in vitro Human PRP Less adhesion, no aggregation or shape change [60]... 

Ti(C, N)-layeronPU Plasma-activated chemical vapor deposition Type of PU Cell proliferation and platelet adhesion Static cell culture static in vitro Endothelial cells human PRP Confluent cell layer, modified PCU nearly no platelet adhesion [83]... 

PDMS Protrusions and ridges rf=39.7nm 20 pm length Platelet adhesion Static, in vitro ADP-activated platelets Double-structured surfaces most effective [98]... 

Figure 6.2 Forces acting on a captive bubble on an inclined surface, (a) Vertical net force and its tangential and normal components, (b) Lateral adhesion (static friction) force.

By analogy with friction, we may distinguish static and kinetic adhesion. Static adhesion is characterized by a resistance to the onset of detachment, and kinetic adhesion by the interaction between the particles and the surface in the course of detachment. 

A number of friction studies have been carried out on organic polymers in recent years. Coefficients of friction are for the most part in the normal range, with values about as expected from Eq. XII-5. The detailed results show some serious complications, however. First, n is very dependent on load, as illustrated in Fig. XlI-5, for a copolymer of hexafluoroethylene and hexafluoropropylene [31], and evidently the area of contact is determined more by elastic than by plastic deformation. The difference between static and kinetic coefficients of friction was attributed to transfer of an oriented film of polymer to the steel rider during sliding and to low adhesion between this film and the polymer surface. Tetrafluoroethylene (Telfon) has a low coefficient of friction, around 0.1, and in a detailed study, this lower coefficient and other differences were attributed to the rather smooth molecular profile of the Teflon molecule [32]. 

Chemical treatments commonly appHed to cormgated paperboard packaging materials include additives that impart various degrees of water resistance, humidity resistance, oil and grease resistance, product abrasion resistance, product corrosion resistance, adhesion release properties, flame-retardant properties, nonskid properties, and static electricity control properties to the finished package (1,2). 

Static Adhesion Tests for Organic-Based Yarns, Cords, and Fabrics. The most commonly used static adhesion tests are the H-test... 

Applications of ISS to polymer analysis can provide some extremely useful and unique information that cannot be obtained by other means. This makes it extremely complementary to use ISS with other techniques, such as XPS and static SIMS. Some particularly important applications include the analysis of oxidation or degradation of polymers, adhesive failures, delaminations, silicone contamination, discolorations, and contamination by both organic or inorganic materials within the very outer layers of a sample. XPS and static SIMS are extremely comple-mentar when used in these studies, although these contaminants often are undetected by XPS and too complex because of interferences in SIMS. The concentration, and especially the thickness, of these thin surfiice layers has been found to have profound affects on adhesion. Besides problems in adhesion, ISS has proven very useful in studies related to printing operations, which are extremely sensitive to surface chemistry in the very outer layers. 

Another example of static SIMS used in a more quantitative role is in the analysis of extmded polymer blends. The morphology of blended polymers processed by extrusion or molding can be affected by the melt temperature, and pressure, etc. The surface morphology can have an effect on the properties of the molded polymer. Adhesion, mechanical properties, and physical appearance are just a few properties affected by processing conditions. 

It must also be recognized that adhesive interfaces are not static entities, but may deteriorate or even strengthen over time, and often it is the time course of interfacial strength or durability under different conditions and in different environments that is of greatest concern [4]. As important as durability issues are, they too will not be a direct concern of this chapter. 

In this chapter, we overview basic techniques for making nanoscale adhesion and mechanical property measurements. Both quasi-static and dynamic measurements are addressed. In Section 2 of this chapter, we overview basic AFM instrumentation and techniques, while depth-sensing nanoindentation is overviewed in Section 3. Section 4 addresses recent advances in instrumentation and techniques... 

Quasi-static measurements force-distance curves and adhesion... 

Eqs. 1-5 hold whether failure is interfacial or cohesive within the adhesive. Furthermore, Eq. 5 shows that the reversible work of adhesion directly controls the fracture energy of an adhesive joint, even if failure occurs far from the interface. This is demonstrated in Table 5, which shows the static toughness of a series of wedge test specimens with a range of adherend surface treatments. All of these samples failed cohesively within the resin, yet show a range of static toughness values of over 600%. 

One of the other benefits of incorporating polar monomers in the PSA is the enhancement in cohesive strength. This can be observed in the form of higher shear holding in a static shear test and/or better creep resistance of the adhesive when subject to a constant load. 

---