To explore the effects on the mechanical properties of the composites that are due to changes in SESF in the composites that arise from different mixing temperatures, the composites prepared at 170 and 200[degrees]C were soaked in the solvent dichloromethane, and the resulting fibers were filtered off.
3c, we see that the SESFs have an uneven surface, so that the PBS melt may be embedded into the grooved SESF surface to form interludes, resulting in stronger interfacial adhesion between SESFs and PBS, which improves the mechanical properties of composites.
Sample [C.sub.1]% [C.sub.2]% [C.sub.3]% [C.sub.4]% Untreated SF 54.93 33.36 6.87 4.84 SESF 49.49 37.36 4.98 8.16 Sample [O.sub.1]% [O.sub.2]% [O.sub.1]/ [O.sub.2]/ O/C% [C.sub.1]% [C.sub.1]% Untreated SF 22.82 77.18 41.54 140.51 27.86 SESF 9.06 90.94 18.31 183.75 30.33 The results show that the [O.sub.2]/[C.sub.1] ratio increases after steam explosion, which indicates that the specific surface area of the fiber increases so that more hydrophilic groups are exposed after steam-explosion processing.
To further investigate the effect of temperature on the surface chemistry of SESF composites, the composites prepared at 170 and 200[degrees]C were soaked in the solvent dichloromethane, and the resulting fibers were filtered out.
This indicates that the content of C-O on the SESF surface in the composites is reduced (i.e., the hydroxyl content of fibers is reduced), which is in accordance with the decrease in [O.sub.2]%.
Increasing the mixing temperature results in the oxidation of the SESF surface that can produce aldehyde and carboxyl and the degradation of PBS, which in turn produces more hydroxyl and carboxyl.
1, curve 1 is the infrared spectrum of SESFs and curve 2 is the infrared spectrum of untreated SFs.
Figure 4a shows a lot of long fibers protruding from the tensile-fractured surface, which indicates that the interface combination between SESFs and PBS is very weak; fibers were pulled out from the matrix during the fracture process.
From the above XPS analysis, we see that PBS can graft onto SESFs at 200[degrees]C, resulting in better interfacial bond properties between PBS and SESFs so that the mechanical properties of the composites prepared at 200[degrees]C are greatly improved with respect to those of the composites prepared at 170[degrees]C.