The thesis proposed technology to graft polymers to wood pulps. / The value and performance of Canadian premium NBSK pulps can be enhanced by attaching copolymers of maleic anhydride (MA) to the fiber surfaces, thus leading them to new applications. Kraft pulps can be treated with MA copolymers as it enters the pulp drying machine, where drying and heating results in polymer fixation. However, polymers capable of forming covalent linkages with cellulose tend to be good adhesives, dried market pulps usually cannot be redispersed (repulped).
By carefully controlling the curing conditions (i.e., the time, temperature, and pH of the polymer solution) it is possible to fix MA copolymers to pulp fibers, while also maintaining repulpability. The impact of curing on repulpability can be probed by measuring the wet tensile indices of impregnated, cured pulp sheets. We have shown that the curing conditions can be condensed into a single parameter, the product , where is the estimated conversion of succinic acid moieties to the corresponding anhydrides during curing, and is the amount of added MA copolymers.
A survey of the common commercial MA copolymers identified high molecular weight (Mw) PEMA (100-500 kDa) as the most promising option, as it is possible to graft 1 and 29 kg of PEMA to each tonne of dried untreated pulp in high yield while still maintaining repulpability. PEMA grafting enhances the properties of pulp and paper in many ways, including increasing fiber swelling, increasing adsorption capacity of cationic additives, and increasing wet and dry paper strength. / Thesis / Candidate in Philosophy / Canada is home to 9% of the world’s forests, and a forestry industry that accounts for approximately $23.7 billion of its gross domestic product (GDP) in 2019. Pulp and paper manufacturing is an important subsector in the forestry industry, contributing roughly $7 billion to Canada’s real GDP each year. In 2019, 15.4 million tonnes of wood pulp were produced, with pulp and paper exports totalling $17.7 billion. Clearly, the pulp and papermaking industry is an integral part of the Canadian economy.
Canada is a leading global supplier of wood pulp, and the largest producer of northern bleached softwood kraft (NBSK) market pulp. NBSK pulp has become the industry’s benchmark grade pulp due to its long fibers, which makes them ideal for reinforcing paper. The core objective of this research is to expand the properties of NBSK pulp by attaching polymers to the fiber surfaces, thus making them suitable for completely new high-value-added applications.
This thesis describes a completely new technology that I have developed for grafting functional polymers onto market pulps. The resulting novel market pulps are characterized by high carboxyl group content that can give stronger products and a “clickable” surface suitable for biomedical and other novel applications.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/26427 |
| Date | January 2021 |
| Creators | Zhang, Hongfeng |
| Contributors | Pelton, Robert, Chemical Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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