Fractures polymer surface

Zhong, Q., Innis, D., Kjoller, K., and Elings, V., Fractured polymer/silica fiber surface studied by tapping mode atomic force microscopy. Surf. Sci. Lett., 290, 688, 1993. 

Destructive mechanical tests commonly are used to characterize autohesion of polymers. In the mechanical tests, two polymer surfaces normally are pressed together at a given temperature for a specified length of time. The fracture stress or fracture energy of the interface then is measured using the appropriate test. 

The relevance of bulk fracture properties has therefore been considered essentially within the context of cohesive wear modes such as abrasive and fatigue wear. During abrasive wear, the initial stage is considered to be the process of contact and scratch between the polymer surface and a sharp asperity. The accumulation of the associated microscopic failure events eventually generates wear particles and gives rise to weight loss. Early approaches initiated by Ratner and co-workers [15] and Lancaster [16] attempted to correlate the abrasive wear rate with some estimate of the work to failure of the... 

In literature the following methods of preparation of polymer material specimen and studying their morphology are described methods of ultrathin section and films with contrasting of osmium tetroxide (10.11). method of replication of the brittle fractur-ed surface (11.12) oxygen and chemical etch of the polished surface or the fractured surface with the following replication for electron microscopy (11. 

If the particle is relatively smooth and spherical wear to the polymer surface occurs by the formation of deformation flakes, fracture and sub-surface fatigue. Where the particle have sharp edges the wear process is dominated by cutting analogous to an abrasive grit. 

AFM is widely used in the analysis of polymer surfaces, such as morphology and molecidar structure of crystalline and oriented polymers, block copolymers, and polymer blends. The example shown in Figure 10.13(b) is the AFM three-dimensional smface image of the fracture surface of a composite. A lamellar structure is clearly observed, with periodicity of about 200 nm, comparable to values obtained from the SEM micrographs [Figure 10.13(a)]. 

All the methods described so far suffer from the disadvantage that they allow only the study of very thin films of polymer, by direct TEM, or of polymer surfaces, by replication. Thin enough films are difficult to make and neither they nor surfaces produced by casting or by fracture are necessarily typical of bulk material. It is therefore desirable to have a technique that can be used for any surface, including one cut from the interior of a larger sample. A technique that allows any type of surface to be prepared in a way suitable for the examination of the underlying structure is the use... 

L. H. Lee, "Surface Free Energies and Fracture Surface Energies of Glassy Polymers," in Physical Aspects of Polymer Surfaces, K. L. Mittal, Editor, Vol. 1, p. 523, Plenum, New York (1983). ... 

Shear Fracture. Polymer failure is initiated when critical shear stresses are exceeded. Stretching at the separation faces ultimately leads to lips and peaks that on two mating fracture surfaces point toward each other. Fracture due to shear failure can only be distinguished from that due to tear fracture on two mating fractme smTaces. The separating mechanism involved is that of normal stress fractme and tear fractme, since gliding along defined crystal planes as in metals cannot occur (Fig. 5). 

SEM micrographs of a polyacetal/polyur-ethane multiphase polymer are shown in Fig. 5.50. The outer surface and a fractured internal surface of this extrudate were chemically etched in order to determine the nature of the dispersed phase. The surface (Fig. 5.50A) shows a complex structure due to etching. The fracture surface after solvent extraction (Fig. 5.50B) is complex, as... 

In studies of polymers and chemical complexity, we have designed a broad spectrum of new polymeric materials with unique architectures significant for emerging technologies. New experimental techniques are presented and sophisticated instrumentation are introduced about phenomena occurring at polymer surfaces and interfaces and how polymers diffuse or fracture. These advances in the understanding of polymer systems and chemical complexity are highlighted in the second volume of this series. 

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