Thermal Behaviour and Crystallization of Green Biocomposites

The thermal behaviour of the green composites (GCs) was an interesting issue discussed in many studies of recent years. In the foreground, unquestionable is the role played by the interface between natural fibers or cellulose nanoparticles and the polymer matrix, which also is most presented in this chapter. There were presented the effects at interfaces on thermal behaviour of the different polymer matrix, most of them biodegradable, that was reinforced using various methods with natural fillers (fibers or cellulose nanoparticles) isolated and extracted from different bioresources. Before starts to present literature results, the most common thermal analytical techniques were reviewed. Thermal behaviour of the most representative from the GCs class was presented in this chapter. Because interfaces of GCs show a greater impact on thermal transitions, firstly were presented results related to the stable temperature range when the important thermal transitions like glass transition, melting or/and (cold) crystallization occurs. The modifications occurred on glass transition, melting and crystallization temperatures or on the crystallinity index were discussed as a function of their content in the GCs or by chemical treatment applied (e.g. hydrolyzation, alkalinization, silanization) or surface treatments on fillers. The role of fillers reinforced in a polymer matrix, which affects morphology development at interface region was highlighted, too. Then, in the next chapter subsection were presented representative works for a discussed domain that emphasize once again the interface effects on the thermal degradation temperatures or on the mechanism of the thermal degradation as well. Also, fibers content or applied chemical treatment showed a major effect on thermal degradation as will be seen next. Like a general conclusion on thermal behavior of the GCs, three important key factors in the preparing of a GCs were highlighted: the natural filler dimensions (high aspect ratio), a good dispersion (to prevent heterogeneity), and the last, but maybe most important, is the chemical treatment applied on the surface. If these conditions were fulfilled, a biomaterial presenting good thermal properties automatically will show good mechanical performances, too.