Influence Of Addition Of Aspen BCTMP And APMP On Paper Properties

High-yield pulping is being rapidly developed in its technologies, and extending more and more its application to papermaking industry. High-Yield Pulp (HYP) demonstrates some superior characteristics for manufacturing papers, such as higher paper bulk property, higher stiffness, higher opacity and better ink-absorption ability, meanwhile, with lower production costs. It should be noticed that HYP has some intrinsic disadvantage, for example, with lower strength properties and rougher paper surface smoothness. Therefore, how to fully extend advantages of HYP fibers to improve paper properties and minimize its negative effect on paper surface smoothness should be paid attention for the paper scientist.Effect of addition of two typical aspen HYPs - bleached chemithermal mechanical pulp (BCTMP) and alkaline peroxide mechnical pulp (APMP) to the deinked pulp (DIP), wheat straw pulp (WSP) and bleached hardwood kraft pulp (BKP) on the paper bulk and other properties of papers were studied in this thesis. Firstly, effect of blending aspen BCTMP or APMP with WSP and DIP, respectively, on paper bulk and some major properties were investigated. Then the effect of addition of aspen APMP to aspen kraft pulp on paper bulk and other properties were discussed. Priliminary study of applying aspen APMP to wood-free light weight coated base paper (LWC) was also examined. Furthemore, fiber morphology of refining HYP under different PFI conditions was investigated.Aspen BCTMP or APMP was added to DIP and WSP, respectively, and influences on paper properties were studied. To further understand the contribution of different pulp fibers to the paper bulk, fiber flexibility was measured by using combination of a Bauer-McNett classifier and a Fiber Quality Analyzer. Comparing with DIP and WSP fibers, aspen BCTMP and APMP has a greater coefficient of fiber flexibility, i.e. the pulps with stiffer fibers. By blending BCTMP or APMP with both DIP and WSP, the paper bulk and porosity can be significantly improved. Adding BCTMP improved the paper formation (PPF) but decreased the paper opacity for the blend of DIP/BCTMP and DIP/APMP, while increased the paper opacity for the blends of WSP/BCTMP and WSP/APMP. Increasing ratio of BCTMP or APMP deteriorated to some extent the paper surface smoothness and tensile strength for both pulp blends, but the negative effect depends on the addition level of BCTMP or APMP. When applying aspen APMP to aspen kraft pulp, the paper bulk and paper opacity can be increased by 39% and 9% respectively at the APMP ratio of 50%. The paper smoothness and some strength properties may decreases, but the negative effect can be compensated to certain extent because of the high fines content of aspen APMP.Under laboratory conditions, to substitute hardwood KP with aspen APMP and make base paper of LWC improved paper bulk, but slightly increased paper surface roughness. It can be explained by the coarser and stiffer fibers of APMP, although its fiber length is almost similar to hardwood KP fibers. Tensile index of the base paper reached the highest value as the substitution rate around 30%. There is no significant change for the folding and tear indexs before the substitution ratio of 30%. The burst index changed a little with increasing ratio of APMP. It may suggest that better paper properties can be obtained at substitution level around 30%. Paper surface smoothness will be negatively affected at a higher level of substitution.Effect of fiber morphology on paper strength and optical properties were investigated by refining HYP with both the standard condition and refined pulp at a higher consistency and a lower refining pressure. Results showed that some differences exsited in fiber morphologies. Fibrillation developed for the long fiber and medium fiber fractions treated under the standard PFI refining condition, more flake components were observed in the fines fraction for the pulp refined at a higher consistency and a lower refining pressure.