Failure modes amorphous polymers

In recent experiments, the application of stress orthogonally to a shearing surface caused a ductile failure of brittle polymer (5, 6). In the first series (5), a variety of plastomers and elastomers were made to slide one on the surface of another, at a constant velocity of 215 cm/sec, under increasing normal loads. The wear characteristics of polymers, including several brittle ones such as PMMA and PS, depend on the applied normal stress. At relatively low pressure, almost no wear was observable, even under magnification the little observed was apparently brittle, ill-defined, microparticulate debris. At intermediate normal loads, 3 to 20 kg/cm2, roll formation was the dominant mode of wear. Such rolls appear on the surfaces of all uncrosslinked polymers whose Tg is below the test temperature and on amorphous and semicrystalline polymers whose Tg is above... 

Resistance to Chemical Environments and Solubility. As a rule, amorphous plastics are susceptible, to various degrees, to cracking by certain chemical environments when the plastic material is placed under stress. The phenomenon is referred to as environmental stress cracking (ESC) and the resistance of the polymer to failure by this mode is known as environmental stress cracking resistance (ESCR). The tendency of a polymer to undergo ESC depends on several factors, the most important of which are appHed stress, temperature, and the concentration of the aggressive species. 

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