ISSN:
0021-8995
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
The crazing behavior of blends of polystyrene (PS) and a low molecular weight polybutadiene (PB) was examined as part of a continuing study of toughening mechanisms in thermoplastic polymers. These PS/PB blends attain high levels of toughness from the stress-activated plasticizing action of the polybutadiene (PB), a mechanism that is active only in the region of a growing craze. The plasticization is therefore localized and leads to enhanced toughness without loss in stiffness. The net result of this plasticization is a reduction in craze flow stress accompanied by an increase in craze velocity, which, in turn, allows the specimen to reach substantial strains-to-fracture in uniaxial deformation under an imposed strain rate. The ability of the PB to plasticize a growing craze is expected to be a function of the mobility of the PB. To investigate the role of diluent mobility, tensile tests and craze velocity measurements were conducted at -20°C and compared with previously published results collected at 23°C. Although the blends displayed high levels of toughness at 23°C, the blends tested at -20°C showed brittle behavior. Craze velocities measured at -20°C were 2 orders of magnitude lower than the results at 23°C. Addition of 3 wt % PB at -20°C led to craze velocities only as large as those found in pure PS at 23°C. Comparison of the craze velocities with an asymptotic theoretical model describing the dependence of the craze velocity on the PB content showed good agreement with the results at -20°C and only fair agreement with the room-temperature results. © 1994 John Wiley & Sons, Inc.
Additional Material:
11 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/app.1994.070530912
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