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Title: Torrefied biomass-polypropylene composites

item Chiou, Bor-Sen
item Valenzuela-Medina, Diana
item WECHSLER, MARK - Renewable Fuel Technologies Llc
item Bilbao-Sainz, Cristina
item Klamczynski, Artur
item Williams, Tina
item Wood, Delilah - De
item Glenn, Gregory - Greg
item Orts, William

Submitted to: Journal of Applied Polymer Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2014
Publication Date: 11/4/2014
Citation: Chiou, B., Valenzuela-Medina, D., Wechsler, M., Bilbao-Sainz, C., Klamczynski, A., Williams, T.G., Wood, D.F., Glenn, G.M., Orts, W.J. 2014. Torrefied biomass-polypropylene composites. Journal of Applied Polymer Science. doi: 10.1002/app.41582.

Interpretive Summary: Torrefaction of biomass involves heating the sample under an inert atmosphere at temperatures between 200-300'C for one hour or less. Torrefaction has mostly been examined as a method to produce high density fuel as a drop-in replacement for coal. However, little research had been performed on using torrefied biomass as filler in polymer composites. Torrefied biomass has several advantages over natural fillers currently in use, such as wood flour and natural fibers. One is that it is more hydrophobic than raw biomass, which should lead to better dispersion in polymer matrices. Another advantage is its low moisture content, which should result in better moisture resistance properties and provide more resistance to microbial attack. In this study, torrefied almond shells and wood chips were incorporated into polypropylene to produce torrefied biomass-polymer composites. The composites were able to withstand higher temperatures before deforming compared to neat polypropylene. This improvement will enable these composites to be used in higher temperature applications.

Technical Abstract: Torrefied almond shells and wood chips were incorporated into polypropylene as fillers to produce torrefied biomass-polymer composites. Response surface methodology was used to examine the effects of filler concentration, filler size, and lignin factor (relative lignin to cellulose concentration) on the material properties of the composites. The heat distortion temperatures, thermal properties, and tensile properties of the composites were characterized by thermomechanical analysis (TMA), differential scanning calorimetry (DSC), and tensile tests, respectively. The torrefied biomass composites had heat distortion temperatures of 8°C to 24°C higher than that of neat polypropylene. This was due to the torrefied biomass restricting mobility of polypropylene chains, leading to higher temperatures for deformation. The incorporation of torrefied biomass generally resulted in an increase in glass transition temperature, but did not affect melting temperature. Also, the composites had lower tensile strength and elongation at break values than those of neat polypropylene, indicating weak adhesion between torrefied biomass and polypropylene. However, scanning electron microscopy (SEM) results did indicate some adhesion between torrefied biomass and polypropylene.