Rheological study of eucalyptus tar pitches

Abstract

ABSTRACT:The development of advanced carbonaceous materials (ACMs) from biopitches is important to increase the revenue of the charcoal making industry and to stimulate the use of biomass, thereby attending to the appeals for environmental preservation. A pioneer study on the rheological behavior of eucalyptus tar pitches was carried out in this work. This behavior plays an important part in obtaining ACMs from pitch, particularly in the spinning step of carbon fiber production. Our results showed that biopitches have a strong dependence on the viscosity and temperature/softening point ratio. An Arrhenius-type law gave the activation energies for viscous flow. Different from conventional polymers, this energy was higher for more polymerized pitches because of their higher molecular stiffness. The results obtained by the Williams-Landel-Ferry equation showed that the viscosity can be associated with the free volume. Lower viscosities correspond to larger free volume. The plot of the apparent viscosity versus the shear time at constant temperature and shear rate showed that the pitches have a purely viscous flow. Experiments that changed the shear rate showed that biopitches behave as Newtonian fluids. Purely viscous and Newtonian behaviors are desirable for more stable spinning.

Composites based on eucalyptus tar pitch/castor oil polyurethane and short sisal fibers

“…5 Eucalyptus tar pitch, produced as a siderurgy charcoal residue mainly in Brazil, is a promising starting material for the production of PUs, including expanded PUs such as rigid, flexible, and semiflexible foams, compact PUs, such as elastomers, and pressed PUs, besides being a potential precursor of carbon fibers. 6 Biopitch (72% C, 6% H, and 22% O) is a solid residue from eucalyptus tar distillation with low aromaticity (50%) in comparison with fossil tars. 7 It is similar to lignin, in that it presents guaiacyl and siringyl in its oligomeric structure, but it is a thermoplastic material (softening point ϭ 123°C).…”

“…It is also a polyol with high hydroxyl contents, ranging from 7 to 15%. 6,7 Castor oil is a triglyceride derived from the plant Ricinus communis, and it presents low hydroxyl contents (5.5%). It is largely used in industries because it allows numberless exclusive modifying reactions.…”

Thermal and morphological study of polyurethanes based on Eucalyptus tar pitch and castor oil

“…They present chemical groups similar to those of lignin (guaiacyl and siringyl units), macromolecular network (Mw ϭ 200 -5000 g/mol), high hydroxyl content (10 -15%), glass transition temperature of about 25-60°C, thermal plasticity, and low aromaticity (50%) in comparison to mineral pitches, and a purely viscous flow. 1 They are constituted basically of carbon (72%), hydrogen (6%), oxygen (22%), and traces of nitrogen.…”

Analysis of volatile organic compounds in polyurethane coatings based on Eucalyptus sp. bio-oil pitch using comprehensive two-dimensional gas chromatography (GC × GC)

“…This yielded about 50% (w/w) pitch. Further details about pitch production and characterization are presented by Prauchner et al [4,5].…”

“…During bio-oil distillation, a solid residue called biopitch is generated, which corresponds to a large fraction (approximately 50%). Brazilian researchers have been developing new types of material that use biopitch as a precursor for carbon materials [3][4][5][6]. They can also provide polyol for the synthesis of elastomers [7,8], foams [9], composites [10] and polyurethane inks [11].…”