Surface drawing

Usually, the molecular strands are coiled in the glassy polymer. They become stretched when a crack arrives and starts to build up the deformation zone. Presumably, strain softened polymer molecules from the bulk material are drawn into the deformation zone. This microscopic surface drawing mechanism may be considered to be analogous to that observed in lateral craze growth or in necking of thermoplastics. Chan, Donald and Kramer [87] observed by transmission electron microscopy how polymer chains were drawn into the fibrils at the craze-matrix-interface in PS films [92]. One explanation, the hypothesis of devitrification by Gent and Thomas [89] was set forth as early as 1972. 

This leads to a value of 129° for the ONO bond angle, which may be compared v-ith the accepted value of 134° for free NO2. The smaller bond angle for the adsorbed molecule may be rationalized by assuming that the surface draws the unpaired electron out of the p orbital. 

Craze growth occurs in a lateral direction by advance of a thin finger-like craze tip by the meniscus instability mechanism. Crazes increase in thickness by a surface drawing mechanism in which more polymer is drawn into the craze fibrils at essentially constant extension ratio X from the craze-bulk polymer interface. 

The miCTOstructure, in particular the mean fibril spacing D, of the growing craze is a consequence of the geometry of the surface drawing process and the surface energy of the fibrils being created. It is useful to model the polymer in the active zone as a strain-softened non-Newtonian fluid with the following flow law,... 

Use Study of atomic-scale structure of surfaces, drawing molecular-sized markings on surfaces and transport of atoms and molecules. 

Addition-Elimination Energy Surface Drawing Energy Diagrams the ApKa Rule Approaches to Addition-Elimination Mechanisms Addition-Elimination Flowchart... 

During stage 1 growth, the localised salt deposits react with the thin rutile surface scale, formed on the alloy surface. Drawing on the experience of hot salt corrosion of titanium alloys, then sodium litanate [27] and sodium hydroxide [30] should be expected to form. Possible reactions include ... 

Or an event might occur as an immediate sequel to an increase in local resistance to surface drawing. The resistance could increase on account of local structural fluctuations within the bulk polymer, e.g., of density of chain entanglements. The surface drawing mechanism would be replaced by elongation at constant mass and the local fluctuations could lead to an enhancement of sensitivity to rupture by one of the mechanisms just mentioned. 

Third, if any effectively bare areas of substrate appear, the stress on adjoining areas (the column bases) will increase and as the columns are stretched into fibrils, the areas of the bases of the fibrils will decrease. Then, it will be a matter of comparison of two force terms the strength of the interface, and the force requirement for drawing fibrils, by whatever mechanism. This comparison will determine whether detachment or fibril rupture (or further surface drawing) will occur. 

We have already mentioned that craze thickening (without rupture) may occur by one or both of two mechanisms. That discussion, above, may be taken over intact, for the case of interfacial crazes. The rheological analysis of the surface drawing mechanism is not available, so we cannot include it in the present analysis if it... 

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