Detection of rubber particle cavitation in toughened plastics using thermal contraction tests

Effect of rubber particle cavitation on the mechanical properties and deformation behavior of high‐impact polystyrene

“…The limited effectiveness of mechanically induced cavitations is due to significant changes in the material properties through the yielding of the matrix, and there are many deficiencies in traditional microscopy techniques for studying mechanically induced cavitation in polymeric specimens because of the disturbing effects of matrix distortion in revealing rubber particles and their substructure. 4 The salami structure in HIPS and the particular manner of cavitation that occurs in such systems (crazelike fibrillation) make the monitoring of the cavitation phenomenon very difficult. 5 Several studies have been conducted to explore an effective/sensitive method for monitoring rubber particle cavitation in different polymeric blends.…”

“…In addition to electron microscopy techniques, the limitations of which have been mentioned previously, 6 some other procedures that have been examined include measuring the intensity of the transmitted light from an incident laser beam (light scattering method), 7 detecting incipient rubber particle cavitation with dynamic mechanical tests, 8 and monitoring dimensional changes through the application of controlled thermal contraction/expansion cycles to specimens to provide a definite degrees of thermally induced cavitation. 4,8 Moreover, some attempts have been made to elucidate the effects of cavitation on the final mechanical properties. 3,[7][8][9][10] Nevertheless, because of the aforementioned cavitation monitoring restrictions, there is still not a clear understanding of the manner in which cavitation affects mechanical behavior.…”

“…2,3 Among the inducing and monitoring methods of cavitation mentioned previously, the thermal method of inducing cavitation and studying the resulting dimensional changes to monitor cavitation both qualitatively and quantitatively has been more successful, especially in the case of polymeric blends such as acrylonitrile butadiene styrene (ABS) in which large amounts of cavitation occur in the form of single, concentric voids in core-shell particles. 4 The thermal method for inducing cavitation was developed first by Bucknall and coworkers 4,8 in polymeric blends such as ABS and poly(methyl methacrylate). With this technique, although no deformation occurs in the matrix, rubber particles cavitate in a controlled manner.…”

“…4 According to eq. (1), the magnitude of s hr depends on the difference in the thermal expansion coefficients (b) of the two phases:…”

“…On the other hand, if DT increases so much that the temperature decreases below the glass-transition temperature of the rubbery phase, then both phases will be glassy, and no thermal contraction and expansion will happen to cause further stresses; hence, no cavitation will occur. 14 To monitor cavitation phenomenon in ABS, Bucknall et al 4 used a physical procedure by recording the thermal contraction behavior of cooled specimens (normalized specimen length changes, DL/L) versus a gradual decrease in the temperature between the ambient temperature and glass-transition temperature of the rubbery phase. When cavitation takes place, an anomalous S-shaped behavior appears in the curve of DL/L versus the temperature, which implies the occurrence of cavitation (Fig.…”