Polystyrene flaws

There are some additional applications of the theory which are presently under investigation. These are the effects of drawing on fibers for which the three-dimensional theory with transverse symmetry is applicable and the toughening mechanism in high impact polystyrene for which the flaw spectrum may be viewed as caused by the size, orientation, and spacing distributions of the rubber particles. 

Another type of initiator that has been evaluated for increasing polystyrene production rates are the multifunctional peroxides. Examples include 2,2-bis [4,4-bis(tert-butylperoxy)cyclohexyl]propane (I) [9], peroxyfumaric acid, 0,0-te/Y-butyl O-butyl ester (II) [10], ter t-butyl peritaconate (III) [11], and poly (monopercarbonates) (IV) (Figure 7.4) [12]. Although all of these initiators indeed show extremely fast production rates of high MW polystyrene, they all suffer from a flaw, i.e. the polystyrene produced is branched and special precautions must be taken to keep the continuous bulk polymerization reactors from fouling [13]. This is likely why none are currently used commercially for polystyrene manufacture. 

Fracture initiated in the tensile tested ABS samples, as noted also by Truss and Chadwick from either surface flaws or from internal flaws. Figure 33a shows an SEM picture of the tensile fracture surface of a sample broken at a comparatively high deformation rate of 12.7 cm/min. The fracture surface is unlike that of SAN (Fig. 27 a) or that of rubber modified polystyrene (Fig. 3 a). Fracture, for this specimen, has developed from both a surface source and from an internal source and fine radial flow lines emanate from both sources. The slow growth region adjacent to the source tends to develop a conical shape as has been noted This is probably a result of localized shear formation. In ABS specimens subject to creep deformation at low values of stress, the creep strain is found to be due almost entirely to shear but, at higher stresses, shear is accompanied by crazing Crazes can also be induced... 

Since then, spinodal dewetting at short times has been studied in some detail. It has been possible to monitor by AFM the thickness modulation and its amplification as a function of time. The literature contains discussions of the behavior of other materials. Nevertheless, results are typically poorly reproducible and the appearance of holes at short times (observed in ultra-thin polystyrene films less than 10 nm thick) is often unexplained. These anomalies arc usually blamed on flawed preparations... 

Even though stable operation and encouraging fuel cell lifetime over several thousand hours have been achieved using membranes with optimized composition (Fig. 8), sulfonated polystyrene remains a component intrinsically susceptible to chain degradation induced by radical species and the approach is therefore inherently flawed. 

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