Six 15-year-old Eucalyptus globulus trees, ranging in wood density from 474 to 575 kg.m-3, were s... more Six 15-year-old Eucalyptus globulus trees, ranging in wood density from 474 to 575 kg.m-3, were sampled at breast height for anatomical study and fiber measurement. Vessel and fiber dimensions showed an increase from pith to bark, while vessel frequency decreased. Cell wall thickness, fiber length, runkel ratio and coarseness were significantly superior in the high-density genotypes (group A) in almost each section along the radius analyzed. Average cell wall thickness for samples of group A was 3.35 μm, while in group B (the low-density genotypes) was 2.86 μm. The average runkel ratio and coarseness in groups A and B were 0.73 and 7.6 mg/100 m, 0.56 and 6.7 mg/100 m, respectively. Lumen width was significantly different among the groups, being higher in group B, but no significant differences were found for vessel features. Pooled data showed significant correlations between wood density and cell wall thickness (r = 0.52), coarseness (r = 0.40) and runkel ratio (r = 0.41), while co...
The chemical structure of dioxane lignins isolated from two groups of Eucalyptus globulus genotyp... more The chemical structure of dioxane lignins isolated from two groups of Eucalyptus globulus genotypes with contrasting pulpwood characteristics were evaluated. Six genotypes were selected and separated in two groups (G1 and G2) based on differences in wood density, pulp yield and chemical characteristics. Lignin was isolated from both milled wood and kraft pulps produced at kappa number 16, and were characterized by different techniques such as FTIR, elemental analysis, molar mass distribution and 31 P NMR spectroscopy. From the different characteristics evaluated, some were determined as more relevant, such as syringyl (S) and guaiacyl (G) amounts, S/G ratio and condensed biphenyl units, were correlated with the pulp yield. High correlations were found between pulp yield and syringyl units (R 2 = 0,69), and pulp yield and syringyl/guaicyl ratio (R 2 = 0,88). The condensed 5-5 biphenyl units presented a negative correlation with pulp yield (R 2 = 0,76). The information obtained explained part of the difference in pulpability of the contrasting genotypes and can be used for the selection and improvement of the species for the pulp and paper industry.
Tension and opposite wood, divided in the corresponding heartwood and sapwood regions, from 8-yea... more Tension and opposite wood, divided in the corresponding heartwood and sapwood regions, from 8-year old Eucalyptus globulus trees were characterized for chemical composition and fibre anatomy in the transverse section in order to identify the main differences. Thicker and poorly lignified cell walls were found in tension wood. Cellulose content was similar for both woods, although tension wood contained 30% higher xylose and 15% less lignin than opposite wood. Lignin of tension wood contained 24% more syringyl units and a higher frequency of β-O-4 linkages. Principal component analysis (PCA) performed separately with anatomical and chemical data showed a clear separation between tension and opposite wood. The principal characteristics used for separation were: cell wall thickness, vessel diameter, lumen diameter, lignin and xylose content, and amount of syringyl units.
Tension (TW) and opposite wood (OW) of Eucalyptus globulus trees were analyzed for its chemical c... more Tension (TW) and opposite wood (OW) of Eucalyptus globulus trees were analyzed for its chemical characteristics and Kraft pulp production. Lignin content was 16% lower and contained 32% more syringyl units in TW than in OW. The increase in syringyl units favoured the formation of β-O-4 bonds that was also higher in TW than in OW (84% vs. 64%, respectively). The effect of these wood features was evaluated in the production of Kraft pulps from both types of wood. At kappa number 16, Kraft pulps obtained from TW demanded less active alkali in delignification and presented slightly higher or similar pulp yield than pulps made with OW. Fiber length, coarseness and intrinsic viscosity were also higher in tension than in opposite pulps. When pulps where refined to 30°SR, TW pulps needed 18% more revolutions in the PFI mill to achieve the same beating degree than OW pulps. Strength properties (tensile, tear and burst indexes) were slightly higher or similar in tension as compared with oppos...
Eucalyptus globulus Labill. is a short-fibre resource for pulp and paper production. Ten differen... more Eucalyptus globulus Labill. is a short-fibre resource for pulp and paper production. Ten different E. globulus genotypes with varied pulpwood quality and chemical composition were evaluated under kraft pulping conditions. Characterisation of the wood and pulp samples by thioacidolysis indicated that the content of syringyl units in β-O-4 linkages (S-β-O-4) was distinct for the studied genotypes. The highest S-β-O-4 levels were detected in the samples with the lowest original lignin and highest glucan levels. This group of samples provided the pulps with the lowest final lignin content at higher yields. UV microspectrophotometric (UMSP) evaluation of the wood chips revealed that the samples with the lowest lignin levels have the lowest UV absorbances at 278 nm (A278 nm) in the secondary walls (S2). During kraft pulping, lignin from the S2 was dissolved, whereas lignins from the middle lamella and cell corner lignin was not removed not even for prolonged reaction periods, independentl...
Six 15-year-old Eucalyptus globulus trees, ranging in wood density from 474 to 575 kg.m-3, were s... more Six 15-year-old Eucalyptus globulus trees, ranging in wood density from 474 to 575 kg.m-3, were sampled at breast height for anatomical study and fiber measurement. Vessel and fiber dimensions showed an increase from pith to bark, while vessel frequency decreased. Cell wall thickness, fiber length, runkel ratio and coarseness were significantly superior in the high-density genotypes (group A) in almost each section along the radius analyzed. Average cell wall thickness for samples of group A was 3.35 μm, while in group B (the low-density genotypes) was 2.86 μm. The average runkel ratio and coarseness in groups A and B were 0.73 and 7.6 mg/100 m, 0.56 and 6.7 mg/100 m, respectively. Lumen width was significantly different among the groups, being higher in group B, but no significant differences were found for vessel features. Pooled data showed significant correlations between wood density and cell wall thickness (r = 0.52), coarseness (r = 0.40) and runkel ratio (r = 0.41), while co...
The chemical structure of dioxane lignins isolated from two groups of Eucalyptus globulus genotyp... more The chemical structure of dioxane lignins isolated from two groups of Eucalyptus globulus genotypes with contrasting pulpwood characteristics were evaluated. Six genotypes were selected and separated in two groups (G1 and G2) based on differences in wood density, pulp yield and chemical characteristics. Lignin was isolated from both milled wood and kraft pulps produced at kappa number 16, and were characterized by different techniques such as FTIR, elemental analysis, molar mass distribution and 31 P NMR spectroscopy. From the different characteristics evaluated, some were determined as more relevant, such as syringyl (S) and guaiacyl (G) amounts, S/G ratio and condensed biphenyl units, were correlated with the pulp yield. High correlations were found between pulp yield and syringyl units (R 2 = 0,69), and pulp yield and syringyl/guaicyl ratio (R 2 = 0,88). The condensed 5-5 biphenyl units presented a negative correlation with pulp yield (R 2 = 0,76). The information obtained explained part of the difference in pulpability of the contrasting genotypes and can be used for the selection and improvement of the species for the pulp and paper industry.
Tension and opposite wood, divided in the corresponding heartwood and sapwood regions, from 8-yea... more Tension and opposite wood, divided in the corresponding heartwood and sapwood regions, from 8-year old Eucalyptus globulus trees were characterized for chemical composition and fibre anatomy in the transverse section in order to identify the main differences. Thicker and poorly lignified cell walls were found in tension wood. Cellulose content was similar for both woods, although tension wood contained 30% higher xylose and 15% less lignin than opposite wood. Lignin of tension wood contained 24% more syringyl units and a higher frequency of β-O-4 linkages. Principal component analysis (PCA) performed separately with anatomical and chemical data showed a clear separation between tension and opposite wood. The principal characteristics used for separation were: cell wall thickness, vessel diameter, lumen diameter, lignin and xylose content, and amount of syringyl units.
Tension (TW) and opposite wood (OW) of Eucalyptus globulus trees were analyzed for its chemical c... more Tension (TW) and opposite wood (OW) of Eucalyptus globulus trees were analyzed for its chemical characteristics and Kraft pulp production. Lignin content was 16% lower and contained 32% more syringyl units in TW than in OW. The increase in syringyl units favoured the formation of β-O-4 bonds that was also higher in TW than in OW (84% vs. 64%, respectively). The effect of these wood features was evaluated in the production of Kraft pulps from both types of wood. At kappa number 16, Kraft pulps obtained from TW demanded less active alkali in delignification and presented slightly higher or similar pulp yield than pulps made with OW. Fiber length, coarseness and intrinsic viscosity were also higher in tension than in opposite pulps. When pulps where refined to 30°SR, TW pulps needed 18% more revolutions in the PFI mill to achieve the same beating degree than OW pulps. Strength properties (tensile, tear and burst indexes) were slightly higher or similar in tension as compared with oppos...
Eucalyptus globulus Labill. is a short-fibre resource for pulp and paper production. Ten differen... more Eucalyptus globulus Labill. is a short-fibre resource for pulp and paper production. Ten different E. globulus genotypes with varied pulpwood quality and chemical composition were evaluated under kraft pulping conditions. Characterisation of the wood and pulp samples by thioacidolysis indicated that the content of syringyl units in β-O-4 linkages (S-β-O-4) was distinct for the studied genotypes. The highest S-β-O-4 levels were detected in the samples with the lowest original lignin and highest glucan levels. This group of samples provided the pulps with the lowest final lignin content at higher yields. UV microspectrophotometric (UMSP) evaluation of the wood chips revealed that the samples with the lowest lignin levels have the lowest UV absorbances at 278 nm (A278 nm) in the secondary walls (S2). During kraft pulping, lignin from the S2 was dissolved, whereas lignins from the middle lamella and cell corner lignin was not removed not even for prolonged reaction periods, independentl...
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