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(D8 Advance/TSM, AXS-Bruker, Germany) as a function of 2 q ranging from 10° to 60° at 40 kV and 40 mA using a CuK a ( l = 1.5406 Å) source.
2.10 Tensile strength of single bres The tensile strength of single calcium alginate bres was measured in accordance with a modi cation of the preparation procedure described in ASTM D3822-07. Mechanical tests were conducted using a tensile and compression tester (MCT-2150, A&D Company, Japan) at a crosshead speed of 10 mm min − 1 . Each bre specimen with a length of approximately 20 mm was glued to the paper frame. Both ends of a bre were glued with an adhesive to the paper frame, as shown in Fig. 3. Upon clamping the ends of the supporting frame using the jaws of the tensile testing machine, the frame edges were carefully cut at the centre. The tensile parameters were determined when the bres broke immediately a er the maximum elongation. In this experiment, 25 bre samples were prepared to obtain the average data. 2.11 Tensile strength of the paper composites The tensile strength of the paper composites was measured using ISO standard 5270. Mechanical tests were conducted using a tensile and compression tester (MCT-2150, A&D Company, Japan) installed under environmental conditions of 23 °C and 50% RH with a crosshead speed of 10 mm min − 1 and a clamping span of the specimens of 100 mm. Each specimen had a width of 15 mm and a length of 130 mm or longer (Fig. 4). The tensile strength was determined and recorded immediately a er the paper broke when the maximum elongation was reached. 2.12 Thermal stability based on thermogravimetric analysis (TGA) The thermal stability of alginate bres and paper composites was measured using a thermogravimetric analyser (TG/DTA 7300 Exstar, Seiko, Japan). Approximately 5 – 10 mg samples were heated from 50 to 900 °C at a heating rate of 20 °C min − 1 under an argon atmosphere at a ow rate of 200 mL min − 1 . 2.13 Analysis of inorganic particle formation X-raydi ff raction patterns of the composite paper (HBKP, CA (25, 50, 75), and KA (25, 50, 75)) and the samples a er the thermal treatment of calcium alginate bres (CA and KA) thermally treated at 200, 400, 600 and 800 °C were recorded using an XRD
2.14 Analysis of chemical composition The chemical compositions of the samples were analysed using XPS (JPS-9010TR, JEOL, Tokyo, Japan) with an AlK a radiation (1486.6 eV) source at 10 kV and 20 mA.
3. Results and discussion 3.1 Sodium alginate yield
The yield of sodium alginate is shown in Fig. 5. It shows that the yield of sodium alginate obtained through the calcium route was higher. In general, alginate content in brown seaweeds varies from 20 to 30% of the dried weight of seaweeds. 24 The amount of sodium alginate extracted in this study from S. pol- ycystum was 14.4 – 26.8% and that from L. japonica was 17.4 – 28.9%. Additionally, the amounts of alginate were found to vary from species to species of brown seaweed all over the world from previous studies, such as 16.9% in S. muticum , 25 22.0 – 33.7% in Madagascan Sargassum species, 18 10.0 – 33.3% in Indonesian Sargassum species, 13 21.1% in L. japonica , 26 and 14.6 – 29.5% in L. japonica . 27 The yield of sodium alginate ob- tained in this experiment was in the range of general results. 24 The bleached sodium alginate gave a lower yield than the unbleached one. The yield of sodium alginate in Fig. 5 resulting from the di ff erent processes of precipitation between the acid and calcium routes showed that S. polycystum and L. japonica species were 3.8% (USCR to BSCR), 6.2% (USAR to BSAR), 6.4% (UKCR to BKCR) and 9.1% (UKAR to BKAR). The result also agreed with that of Istini et al. , 28 in which the bleaching process reduced the yield of sodium alginates obtained due to the possible oxidation and material loss during the process.
Fig. 4 The preparation of the paper specimen for tensile strength measurement.
Fig. 5 Yield of sodium alginate from S. polycystum and L. japonica .
RSC Sustainability , 2025, 3 , 599 – 610 | 603
© 2025 The Author(s). Published by the Royal Society of Chemistry
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