Crazing amorphous glassy polymers

In analogy to crazing in amorphous glassy polymers, the above difference in ceaze structure between these crystalline polymers may be attributed to molecular structure, e.g., chain entanglements etc. To date, there have been no studies on the craze microstructure of crystalline polymers in relation to their chain entanglements although this is now well understood in amorphous polymers. ss.tq)... 

Oxborough, R. J. and Bowden, P. B. (1973) A general critical strain criterion for crazing in amorphous glassy polymers, Phil. Mag., 28, 547-559. 

With respect to general criteria for craze initiation and growth, important contributions have been made for amorphous glassy polymers by many investigators during past years. Recognizing that crazing is also inherently a cavitational process for crystalline polymers leads to the criterion that craze initiation involves a dilatational stress component. In... 

R. J. Oxborough and P. B. Bowden, A General Critical-Strain Criterion for Crazing in Amorphous Glassy Polymers , Philos. Mag. 28, 547-559 (1973). 

R. Schirrer Damage mechanisms in amorphous glassy polymers Crazing, pages 488-499. In J. Lemaitre [92], 2001. 

The criterion (9.6) shows that amorphous glassy polymers yielding process is controlled by cluster structure stability loss (for more details see chapter four) and the condition of transition from shear to crazing can be written as follows [20] ... 

Kozlov, G. V, Beloshenko, V. A., Lipatov, Yu. S. (1998). Temperature Dependence of the Mechanisms of Crazing and Shear in Amorphous Glassy Polymers a Current Review and a New Approach. Intern., J. Polymer Mater., 39(3 ), 201-212. 

Growth of craze-like entities in equatorial disks of spherulites occurs via plastic deformation of the amorphous material between laterally aligned voids that is trmisformed further into fibrils. The thickness and length of these fibrils is related to the amount of the amorphous material between voids and that is comiected m the first approximation with the lamellae thickness. These fibrils may mimic tufts in crazes of amorphous glassy polymers. 

Although crazes are typical of amorphous glassy polymers, crazes or crazelike features have also been observed in many other amorphous polymers (see below), semicrystalline polymers (eg, in PE, PP, PA), and in rubber-modified high impact polymers (eg, HIPS, ABS). In the literature they were often designated as microcracks, deformation zones, or jdeld zones (28). 

The characteristic mechanical property of the amorphous polymers is high strength and a brittle up to ductile deformation behavior. The reason for this behavior is the formation of localized deformation zones under load, such as crazes, deformation bands, or shear bands [12]. The typical type of deformation seen in the amorphous brittle, glassy polymers is the craze. Crazes are often visible with the naked eye in reflected light see Fig. 1.4. The word craze recalls a macroscopic crack-like appearance craze comes from an old English word. 

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