2 Bimodal-Distribution Models of the Discrete Phase in Toughened Plastics Richard A. Hall and Ilene Burnstein 1
1
Downloaded by UNIV OF MELBOURNE on January 16, 2016 | http://pubs.acs.org Publication Date: May 5, 1996 | doi: 10.1021/ba-1996-0252.ch002
2
2
Amoco Polymers, Inc. 4500 McGinnis Ferry Road, Alpharetta, G A 30202 Department of Computer Science, Illinois Institute of Technology, Chicago, I L 60616
The efficient packing of spheres that have bimodal distribution can produce a high volume of the discrete phase of a toughened plastic and a corresponding small interparticle distance. A computational method has been developed to model plastics toughened with spheres that have a bimodal distribution. The modeling method al lowsgeometric simulation and graphic display of real materials con taining bimodal distributions of reinforcing spheres. Interparticle distance and other parameters can be calculated from the geometric models. This application also facilitates the study of hypothetical materials that may be difficult or impossible to synthesize.
T
H E I N C O R P O R A T I O N O F R U B B E R S P H E R E S alters many physical properties o f a glassy polymer. C o m p u t e r modeling offers a way of visualizing the geometry o f such systems. Interest i n the geometric m o d e l i n g o f rubber-toughened plastics w i t h graphic displays o f models dates back over a decade to the w o r k o f H o b b s et al. (J), w h o used high-resolution graphics to visualize rubber-toughe n e d nylons. M o r e recently, the discrete-phase geometry o f materials like h i g h impact polystyrene has been simulated, facilitating the calculation o f interparticle-distance parameters o f real a n d hypothetical resins (2). A previous paper explains h o w geometric simulations o f the discrete phase are used to obtain a surface m o d e l o f high-impact polystyrene (3). T h e w o r k is a graphic example, showing h o w the discrete phase might disrupt the surface o f a toughened plastic. Past w o r k has focused o n geometric m o d e l i n g of plastics toughened w i t h m o n o s i z e d spheres (4) and spheres having a log-normal size distribution (2), as i n the rubber phase o f high-impact polystyrene. T h e diameters o f discrete spheres i n toughened plastics can fit other size distributions. B i m o d a l systems, for example, can be made from b l e n d i n g two rubber-modified thermoplastics containing two distinct size distributions of r u b b e r particles. A potential advantage i n toughness results from the more efficient packing o f spheres i n a b i m o d a l system (5). However, even w h e n the volume o f the 0-8412-3151-6
© 1996 American Chemical Society 27
In Toughened Plastics II; Riew, C. Keith, et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1996.
28
T O U G H E N E D PLASTICS I I
Downloaded by UNIV OF MELBOURNE on January 16, 2016 | http://pubs.acs.org Publication Date: May 5, 1996 | doi: 10.1021/ba-1996-0252.ch002
discrete phase is constant, b i m o d a l systems may show a significantly higher fracture energy than conventional systems (6). It has been known for some time that rubber-toughened polystyrene containing small particles (
