Effect of Pyrolysis Temperature on Biochar Microstructural Evolution, Physicochemical Characteristics, and Its Influence on Biochar/Polypropylene Composites  
[PERSON]  
1 SABIC Polymer Research Center (SPRC), Department of Chemical Engineering, King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia; [PERSON]_ADDRESS] (A.Y.E. ); [PERSON]DDRESS] (A.M.P. ); [PERSON]DDRESS] (S.M.A.-Z. ); [EMAIL_ADDRESS] (A.A.)  
2 Department of Chemical Engineering, King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia; [PERSON]ESS] (S.M.A.-Z. ); [EMAIL_ADDRESS] (A.A.)  
3 Soil Sciences Department, College of Food and Agricultural Sciences, King Saud University, Riyadh 11451, Saudi Arabia; [EMAIL_ADDRESS] (A.M.P.) 4 Correspondence: [EMAIL_ADDRESS]; Tel. : +966-41-11767474  
a viable method that can rapidly convert biomass into solid biochar by thermal decomposition. However, the physicochemical properties of biochar are very complex and depend on several factors, like feedstock type, carbonization processes, pyrolysis temperature, heating rate, and residence time. In order to utilize this biochar for further applications; it is desirable to understand the most important pyrolysis indicator such as proximate analysis, i.e., information of moisture, ash content, mineral composition, and carbon contents, as well as ultimate analysis such as C, H, N, S, and O composition; H/C and O/C atomic ratios; and surface area. Polypropylene is a versatile commodity polymer and has excellent processing characteristics that allow it to be converted into film, extrusion, and injection molding parts. In one of the studies, suitable biomass has been attempted to find out the fire susceptibility of biochar-polpropylene composites [11]; similarly, bamboo particles and biochar have been used to reinforce polypropylene (PP) matrix. The mechanical and thermal properties of the composites were reported to improve through the addition of BC [12]. Moreover, biochar was produced from miscanthus grass by two different experimental pyrolysis conditions (i.e., 500 \({}^{\circ}\)C and 900 \({}^{\circ}\)C), and their physical and chemical properties were evaluated [13]. These biochars were then used to reinforce polypropylene/poly (octane-ethylene) copolymer system. It was reported that higher pyrolysis temperature eliminates the surface functional groups, thereby making it less polar. However, it increases the specific surface area and pore volume. The composite based on this biochar was analyzed by surface morphology (impact factor surface), and shown to exhibit higher impact strength than the lower temperature biochar. This higher impact property was attributed to superior physical interactions affinity of the nonpolar fillers with the nonpolar polymeric chains of matrix [14]. In another study, the same biochar was used for polypropylene composites and its properties were then compared with those of talc based composites. It was reported that biochar-based PP composites have lower density but comparable specific tensile and flexural properties to talc based composites [15]. In our previous work, we used biochar obtained by pyrolysing date palm biomass at relatively higher temperature and used as fillers for the polypropylene. An increase in electrical conductivity and mechanical properties was observed, but a decrease in crystallinity was also observed [16]. However, systematic studies investigating the effect of pyrolysis, specifically at lower temperature on the surface characteristics and physicochemical properties of biochar need to be analyzed in detail. Moreover, it assumed that the polar groups that formed or present on the biochar at lower pyrolysis temperature could help for better adhesion with the selected polymer matrix. It should also be note that all above studies were related to ternary composites system, and much attention has been given to performance of types of biomass used than the biochar itself. In the case of a polymer composite, the biochar used was produced at a relatively higher temperature; compatibilizers were also used.