JOURNAL OF NATURAL FIBERS
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processes to give rigidity. These nanofillers could also cover the voids and improve the gaps in pulp and paper, thus improving the mechanical properties. Moreover, it is also used to enhance the gloss, opacity, and surface resistance of the coated paper (Gaikwad and Ko 2015; Ghanbari, Kasmani, and Samariha 2019). The nanoclay that is from montmorillonite (MMT) or bentonite is a very hydrophilic clay formed by layers of silica tetrahedral and alumina octahedral sheets in a ratio of 2:1 (Gupta, Sharma, and Nagpal 2025). The montmorillonite (MMT), which is composed of two tetrahedral silica sheets, is joined to an edge-divided, eight-sided aluminum oxide sheet (Majeed et al. 2013). Halloysite (Hal) is another type of nanoclay that is composed of natural aluminosilicate clay mineral with a unique hollow, cylindrical shape that forms nanotubes (Shankar, Kasapis, and Rhim 2018). The robust mechanical properties of Hal have been combined with the antimicrobial and photocatalytic properties of metal nanoparticles and metal oxides by attaching them to Hal through grafting (Zhang et al. 2013). It was also reported in a study by J. E. Kasmani and Samariha (2021) that the addition of nanoclay, montmorillonite (MMT), in an amount of only 2% could improve the opacity, brightness, and tensile strength properties. This study also indicated that the MMT would yield positive results in paper processing. The nanoclay is also suitable for use as a coating on paper for enhancing mechanical and barrier properties (de Oliveira et al. 2021; Ghanbari, Kasmani, and Samariha 2019). The nanoclay can be used on an industrial scale with a large amount of production due to its abundance and ease of obtaining the raw materials (Kumari and Mohan 2021). The production of nanoclay is also considered low-cost. It is commonly used in many applications, including in pulp and paper industries (de Oliveira et al. 2021). The presence of nanoclay in the paper sheet results in significant coverage of the fiber surfaces, thereby filling the paper surface with very few visible pores. This procedure led to an increase in air resistance compared to the control sample. Moreover, using a small amount of nanoclay resulted in higher strength properties. However, further increasing the amount of nanoclay led to the formation of coarse flocs due to excessive negative ionic charge, which in turn caused a decrease in resistance. The XRD findings indicate that the inclusion of nanoclay at various concentrations resulted in angles ranging from 2° to 11°, indicating that the morphological structure belonged to the interlayer type (J. E. Kasmani and Samariha 2021). Figure 2 shows nanoclay morphology in paper. Characterization. The burst strength of paper relies on both the fiber length and bonding, but it is primarily influenced by the connections between the fibers (Borodulina, Reza Motamedian, and Kulachenko 2018). When used as mineral fillers, nanoclay particles were found to weaken the inter-fiber bonds (Abdelatif et al. 2024). Previous studies have also indicated that adding fillers can decrease strength, with clay soil, talc, and calcium carbonate being particularly effective at reducing mechanical strength. Furthermore, the introduction of nanoclay led to the formation of coarser flocs and a more distributed floc structure, which further contributed to the weakening of strength.
Figure 2. Nanoclay in paper sheet (J. E. Kasmani and Samariha 2021).
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