Craze filament

We have mentioned, earlier, the fact that a local, transient temperature rise has been observed in the peeling of pressure-sensitive tapes.0 3) peak temperature rise of 12.5 °C has been measured, in peeling at 1(X) cm/min (Figure 12). The temperature rise ATj appears to be associated with dissipative processes occurring in the filaments that are drawn, in the disbond-ment zone, when a pressure-sensitive tape is peeled off a solid. In fracturing a brittle polymer, the work (per unit area) done is converted into heat, and most of this heat is released in the craze filaments.2) A transient temperature rise, above 500 °C, has been reported with PMMA, and above 400 °C for polystyrene O) (see below). 

Kramer and co-workers (7) reported that acoustic emission occurred in polystyrene immersed in diflFerent swelling liquids only when the crazes ruptured but not during their formation and growth. As long as the bridging by filamental elements is still intact, the deformation at the craze tip and in the craze is still so slow that no acoustic bursts are generated. It is the final fracture of these elements which is abrupt enough to cause the emission of a detectable acoustic burst. 

Amine etching was used to reveal the structure of PET as early as 1959 [55] when PET fibers were etched with n-propylamine for replica formation. Methylamine was also used [248], although the selectivity of the reagent was questioned. Tucker and Murray [249] etched PET filaments with 42% aqueous solutions of n-propylamine at 30°C. Apparently, the first step in the reaction is the removal of the fiber skin and then crazing. A... 

Tough, versatile, bisphenol-A epoxy based vinyl ester resins dissolved in styrene offering outstanding mechanical properties and excellent resistance to cracking, crazing, chemicals and heat, for use in hand-lay, spray/projection lamination, filament winding and pultrusion. Available in standard and low monomer... 

A preaccelerated, low viscosity, thixotropic, resilient and corrosion resistant resin offering excellent wet-out, high impact strength and elongation with excellent crack and craze resistance. Can be used for hand-lay, spray/projection lamination and filament winding. 

The appropriate filament dimensions may be taken from data on crazes,(ii) e.g., filament radii of the order of 0.05 xm and bases no larger than 0.1 xm radius. We will employ the same assumptions made in the preceding section as to craze dimensions, e, at room temperature (at least 10 6 Pa-s), and AG = 5 J/m, together with p = 4. 

Second, if no such un wetted areas exist prior to loading, then such areas may develop by a two-dimensional analog of the Argon mechanism for filament formation in crazing,(i5 i7) i.e., propagation from an external edge of the phase boundary. This would amount to a mechanism of formation of filaments with isolated bases. It would probably lead to a slower rate of filament formation than would the first mechanism. 

The same concept of filament deformation was independently employed by Bartenev et al. [77] to the opening and growth of crazes (silver cracks) in PMMA. 

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