Biomedical Engineering Reference
In-Depth Information
After cutting ultrathin films of the composites transmission electron
microscopy (TEM) was carried out. In Fig. 5.2, TEM images of compos-
ites containing MCC and PEG without ultrasonication can be seen. Be-
cause of the large particles it was difficult to get a true view, but as the
(Fig. 5.2) shows the extrusion process itself may cause cellulose particles
size reduction. Ultrasonically treated cellulose particles can be seen in the
poly (lactic acid) matrix in Fig. 5.2 as well. The less the concentration of
the MCC-PEG suspension was the more effective the US treatment be-
came. There are small cellulose crystals under 100 nm in the PLA based
composite containing USMCC. The cellulose crystals created through ul-
trasonication in PEG400, just as [49] observed too after ultrasonic treat-
ment of cellulose in water media, have spherical shape instead of whisker.
Because of the sensitivity of the PLA to the relative high acceleration volt-
age closer images could not be taken.
FIGURE 5.2
TEM images of the modified samples.
DSC measurement (Fig. 5.3 and Table 5.2) was used to characterize the
thermal properties of neat PLA and PLA based composites. Glass transi-
tion temperatures (T
g
) of the modified materials were decreased or cannot
be observed due to the plasticizer, which provided more flexibility to the
polymer chains. In the DSC heating scans all PLA and PLA based samples
showed exothermic peak, which attributed to the cold crystallization (T
cc
).
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