Influence of void formation on impact toughness in rubber modified styrenic-polymers

PS/EPDM blends prepared by in situ-polymerization of styrene in the presence of EPDM are immiscible and show two phases. Furthermore, the dynamic mechanical behavior of injected specimens is quite different from that of noninjected blends. This is attributed to the differences in morphology before and after injection molding. The morphology of the noninjected blends consists of PS spherical domains covered by a thin layer of EPDM, whereas the injected blends show elastomeric dispersed phase morphology in a rigid matrix. SEM analysis was important to elucidate the changes in the dynamic mechanical behavior of PS/EPDM blends, but TEM analysis is more precise for morphological characterization and yielded the real average diameter of EPDM particles. Comparing the average diameters for the PS/EPDM blends obtained from SEM and TEM analyses, the diameters obtained from the SEM analysis are wider than those of TEM which is due to the solvent extraction effect on the blend morphology.

Section: Introductionmentioning

confidence: 99%

Dynamic mechanical properties and morphological structure of PS/EPDM blends prepared by in situ‐polymerization of styrene

Lourenço¹,

Gonçalves²,

Felisberti³

2009

“…The incorporation of dispersed elastomeric particles in a rigid polymer matrix has attracted significant attention because of its industrial importance. [1][2][3] High impact polystyrene (HIPS) is one of the most important toughened commercial systems in which the brittle polystyrene (PS) becomes more ductile. 4,5 However, aging is a serious problem for HIPS and for other rubber-toughened plastics, especially those based on polybutadiene (PB).…”

Section: Introductionmentioning

confidence: 99%

Mechanical properties of photoaged in situ polymerized PS/EPDM blends

Lourenço

Felisberti

2007

In this study, the mechanical properties of in situ polymerized PS/EPDM blends with different composition were evaluated before and after accelerated photoaging and compared with the properties of commercial HIPS submitted to similar aging conditions (ASTM G53). The mechanical properties of the PS/EPDM blends as well as their photochemical stability are influenced by the polymerization temperature and blend composition. Although the initial mechanical properties of HIPS are superior in comparison with the in situ polymerized PS/EPDM blends, a pronounced drop of them was observed already for short time exposure. For example, after the aging period, all PS/EPDM blends showed higher strain at break than HIPS. Because PS/EPDM blends present higher resistance to photoaging stability than HIPS, the mechanical properties of the HIPS become worse than the other blends as the aging time increases.

“…A Hounsfield H10KS universal frame was also used in creep tests under a constant load of 325 N (on a trial and error basis). Three-point-bending specimens were machined from injected bars measuring 127 Â 12.8 Â 6.34 mm 3 . A side-edge notch with an angle of 458 and a 4-mm depth was machined on each specimen.…”

Section: Methodsmentioning

confidence: 99%

“…2,3 The main obstacles include (1) the limited effectiveness of mechanically induced cavitation methods in studying the effects of cavitation on mechanical properties and (2) the complex salami structure of rubber particles in some polymer blends such as high-impact polystyrene (HIPS). 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.…”

Section: Introductionmentioning

confidence: 99%

“…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).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

Serpooshan

Zokaei

Bagheri

2007

Rubber particle cavitation has been the focus of many investigations because it dramatically affects the mechanical properties of polymeric blends. In this work, the effect of rubber particle cavitation on the mechanical behavior of high-impact polystyrene was studied. The extent of cavitation in rubber particles was varied via different thermal contraction/expansion cycles in the range of À100 to 238C. Tensile, creep, and Charpy impact tests were conducted to evaluate the effects of the degree of cavitation on the general mechanical properties. The notch-tip damage zone and deformation micromechanisms were also investigated by a transmitted optical microscopy technique to reveal the effects of cavitation on toughness. The results of this investigation illustrate a close relationship between the degree of rubber particle cavitation and the mechanical performance of high-impact polystyrene.