29.06.2013 Views

a) b - École Polytechnique de Montréal

a) b - École Polytechnique de Montréal

a) b - École Polytechnique de Montréal

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

icontinuous network with the HDPE. Thus, in both the L-PMMA case and the H-PMMA case,<br />

the morphological classification of bicontinuous/dispersed PMMA phase is unchanged.<br />

Nevertheless, the scale of the resulting morphological structures has been significantly modified<br />

by the viscosity of the PMMA as the system attempts to respond to the dramatically reduced<br />

interfacial area of the H-PMMA droplets. In addition, it is more difficult for the PS to penetrate<br />

the H-PMMA (as compared to L-PMMA) due to its significantly higher viscosity. Thus, the use<br />

of H-PMMA results in a significant increase in the interfacial area between HDPE and PS<br />

phases. A comparison of the thickness of the continuous HDPE branches in the L-PMMA blend<br />

as compared to that in the H-PMMA blend clearly show that the HDPE branches are<br />

significantly thicker in the L-PMMA case. This unambiguously supports the conclusion of an<br />

increased HDPE/PS interfacial area for the H-PMMA blend.<br />

The surface free energy for a blend system is given by the following equation:<br />

Equation 6-3 ∑ <br />

where G is the Gibbs free energy, represents the interfacial tension between phases i and j,<br />

and is the interfacial area between phases i and j. Since the system is unable to dissipate the<br />

applied mechanical energy applied during mixing by generating a high interfacial area between<br />

H-PMMA and PS, it must compensate by generating an increased interfacial area between the<br />

HDPE and PS phases (Figure 6-13g).<br />

6.4.9 Factors Influencing Phase Sizes<br />

It is well known that the composition, interfacial tension, and viscosity ratio are three of the most<br />

important factors influencing the phase size in binary polymer blends (A. K. Gupta, 1993; Guo,<br />

Packirisamy, et al., 1997; Hobbs, et al., 1988; Nemirovski, et al., 1995) . It will be shown in this<br />

section that these factors also play an important role in <strong>de</strong>termining the phase size in ternary<br />

polymer blends.<br />

201

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!