THESIS - ROC CH ... - FINAL - resubmission.pdf - University of Guelph

SEM images of the cryo-fractured surfaces of SPI, SNF0.25, SMF0.5, SMF1.0, and SMF
2.5 are shown in Figure 6.5. The fractured plane was perpendicular to the machine direction
allowing for visual indication of fiber alignment if it were to be present. However, no visible
evidence of fibers was observed for any of the specimens. This was not expected as
homogenous dispersion of fibers was evident via polarized light. This may suggest that cellulose
and SPI have good interfacial adhesion preventing the pull out of fibers upon fracture. Poor
adhesion would result in the appearance of visible fiber structures due to the fiber surfaces
disengaging from the polymer matrix. The control specimen of SPI without fiber addition had
relatively smooth fracture surface in comparison to all other specimens. With the addition of
SNF’s at 0.25%w/w SNF/SPI, irregularities could be seen to scatter across the surface. Adding
SMF’s at the same loading concentration resulted in an increased surface roughness.
Compared to other specimens, edges with higher variances in the depth to height ratio were
observed. This jagged texture was also apparent with SMF0.5 but with a flatter appearance.
The serrated valleys can be seen to widen apart with further increase in SMF addition at 1.0 and
2.5% w/w SMF/SPI. In addition to the widening of the valleys, SMF1.0 and SMF 2.5 specimens
have additional sunken trenches that streak across the surfaces. The most apparent of this
behaviour can be seen with SMF2.5 at the highest fiber concentration with deep elongated
cavities. The increasing roughness with increasing fiber addition suggests the presence of filler
material. Although interfacial adhesion prevented the visual appearance of intact fibers, the
rough texture may indicate that interaction is not ideal (Wang et al. 2006; Wu et al. 2009). The
increased defects seen with high fiber content may negatively affect material properties.
73