Strength enhancement of fiber network by carboxymethyl cellulose during oxygen delignification of kraft pulp
Sorption of carboxymethyl cellulose (CMC) on the fiber surface was applied during oxygen delignification to enhance the strength properties of softwood kraft pulp. Unlike many previous efforts, the focus was not set on the improvement of selectivity of oxygen delignification, i.e. retaining stable viscosity vs. decreasing kappa number. Instead, without an improved selectivity, handsheets from CMC-treated fibers exhibited a 15% improvement in tensile index and 25% improvement in tear index after a full bleaching sequence in comparison to the untreated reference pulp. Since it is demonstrated that the CMC addition can be incorporated as an integral step in the fiberline process, the method offers an effortless and viable option to produce pulp resulting in stronger paper products.
Wet Strength Improvement of Pineapple Leaf Paper for Evaporative Cooling Pad
This research aimed to modify pineapple leaf paper (PALP) for using as wet media in the evaporation cooling system by improving wet mechanical property (tensile strength) without compromising water absorption property. Polyamideamine- epichorohydrin resin (PAE) and carboxymethylcellulose (CMC) were used to strengthen the paper, and the PAE and CMC ratio of 80:20 showed the optimum wet and dry tensile index values, which were higher than those of the commercial cooling pad (CCP). Compared with CCP, PALP itself and all the PAE/CMC modified PALP possessed better water absorption. The PAE/CMC modified PALP had potential to become a new type of wet media.
Structural and Molecular Properties of Residual Birch Kraft Lignins
The residual lignins from unbleached and oxygen-bleached birch kraft pulps were isolated by acid hydrolysis and characterized by elemental analysis, methoxyl content, permanganate degradation, size exclusion chromatography and quantitative 13-C NMR. Calculations based on the reduction in kappa number after the acid hydrolysis revealed that only about one third or less of the material assumed to be lignin could be isolated as polymeric lignin. This was shown to be a syringyl-guajacyl type of lignin with a syringyl-to-guaiacyl ratio of approximately 1:1. The rest of the material found in the acid solution after hydrolysis and identified by GC-MS and by pyrolysis-GC-MS was to a large extent low molecular weight furanoid structures probably originating from polysaccharide degradation products, with only traces of lignin-derived compounds present.