Introduction
Experimental section
Materials
Oxidation of bleached kraft pulp
Determination of carbonyl content using hydroxylamine hydrochloride
Determination of carboxyl content by potentiometric titration
Intrinsic viscosity measurements
Determination of carbonyl content by CCOA-labelling
Compositional analysis
Wet durability test
Analysis of total organic carbon
Fibre image analysis
Results and discussion
Oxidation of cellulose in systems without a pH buffer
Cellulose (%) | Galacto-glucomannan (%) | Xylan (%) | ASL (%) | Klason lignin (%) | SUM (%) | Not detected (%) | |
---|---|---|---|---|---|---|---|
Bleached kraft pulp | 70.7 | 7.44 | 8.23 | 0.77 | 0.00 | 87.2 | 12.8 |
Acidic oxidation 30 min | 70.9 | 5.96 | 8.12 | 0.64 | 1.65 | 87.3 | 12.7 |
Acidic oxidation 60 min | 70.9 | 5.16 | 7.95 | 0.70 | 1.40 | 86.2 | 13.8 |
Acidic oxidation 90 min | 70.1 | 5.22 | 8.03 | 0.69 | 1.50 | 85.6 | 14.4 |
Alkaline oxidation 30 min | 69.9 | 6.43 | 8.49 | 0.66 | 1.70 | 87.2 | 12.8 |
Alkaline oxidation 60 min | 69.5 | 5.58 | 8.28 | 0.65 | 1.50 | 85.5 | 14.5 |
Alkaline oxidation 90 min | 69.6 | 5.97 | 8.25 | 0.67 | 1.40 | 85.9 | 14.1 |
Mn (kDa) | Mw (kDa) | Mz (kDa) | Dispersity (Mw/Mn) | Reg (µmol/g) | C = O (µmol/g) | |
---|---|---|---|---|---|---|
Bleached kraft pulp | (24.0) | (311) | (893) | (12.8) | (41.3) | (6.90) |
Acidic oxidation 30 min | (28.0) | (308) | (886) | (11.1) | (36.5) | (16.9) |
Acidic oxidation 60 min | 43.2 | 349 | 1230 | 8.09 | 23.3 | 32.3 |
Acidic oxidation 90 min | 33.6 | 218 | 858 | 6.48 | 29.8 | 82.1 |
Alkaline oxidation 30 min | 41.8 | 384 | 1440 | 9.41 | 24.7 | 13.8 |
Alkaline oxidation 60 min | 42.8 | 317 | 1250 | 7.40 | 23.4 | 15.9 |
Alkaline oxidation 90 min | 52.4 | 382 | 1560 | 7.34 | 19.2 | 15.5 |
Oxidation of cellulose in systems with a pH-buffer
Selection of buffer system
Sample | Carbonyl content (µmol/g) | Mv (kDa) |
---|---|---|
Phosphate buffer, pH 5.8 | 66.4 | 240 |
Acetate Buffer, pH 5.6 | 91.2 | 111 |
Acetate Buffer, pH 4.0 | 115 | 91.5 |
Influence of reaction temperature
Wet durability
Reference pulp | Oxidized pulp | |
---|---|---|
L (l) (mm) | 2.20 | 2.26 |
W (n) (µm) | 26.1 | 25.8 |