Abstract
Carrageenans are commercially important sulfated gums found in various species of red seaweeds (Rhodophyta), wherein they serve a structural function similar to that of pectins in land plants. In this study, carrageenan was used independently or in combination with cationic polyacrylamide (CPAM) and/or Al2(SO4)3 to explore its application as a dry strength additive in papermaking. Strength index determination, ash content detection, FTIR characterization and SEM observation were performed on prepared handsheets. The results showed that with 0.6% Al2(SO4)3 and 0.2% carrageenan as additives, the tensile index increased by 13.53% and precipitated calcium carbonate (PCC) retention increased by 57.06%. With 0.6% Al2(SO4)3, 0.2% carrageenan and 0.03% CPAM as additives, PCC retention increased by 121% while the tensile index did not fall compared to handsheets without additives, indicating that carrageenan could enhance the strength of handsheets and be used as an anionic dry strength agent.
Highlights
Dry strength additives are important chemicals in the papermaking industry to increase paper strength
Carrageenan was used alone to assess its effect on paper properties at a precipitated calcium carbonate (PCC) addition level of 20%
In the handsheet drying process, the hydroxyl and sulfate groups of carrageenan formed numerous hydrogen bonds with hydroxyl groups of cellulose fibres, especially the sulfate groups of carrageenan, which contributed extra hydrogen bonds compared with hydroxyl [16]
Summary
Dry strength additives are important chemicals in the papermaking industry to increase paper strength. Many water-soluble polymers, which can form hydrogen bonds with cellulose fibres, can be used as dry strength additives. Dry strength additives are typically used to offset the decline of paper strength resulting from addition of fillers or secondary fibres (such as recycled fibres). Used dry strength additives are natural or synthetic polymers. Natural polymers include starch (cationic/anionic starch) and gums (guar gum, for example). Synthetic polymers comprise polyacrylamide and its derivatives, polyvinyl alcohol, etc. Most studies focused on the use of synthetic polymers, starch or terrestrial plant gums in papermaking [1,2,3,4,5]. As a gum from marine plants, carrageenan used in papermaking has been reported rarely
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