Molded pulp is an eco-friendly packaging product popularly chosen nowadays. It is mostly used to replace plastic containers such as polypropylene (PP), polystyrene (PS) and polyethylene (PE). Besides, the non-wood pulps from agricultural crops and residues have been increasingly studied as alternative materials in pulp production. Therefore, this study aimed to investigate the possibility of utilizing rice straw (R), pineapple leaf (P) and banana stem (B) as raw materials to prepare pulps by using a soda-anthraquinone (AQ) pulping process. The pulping was carried out with 4-7% sodium hydroxide solution and 0.1% AQ, a liquid-solid ratio of 10:1, and pulping time of 15-30 min at 98 ± 2°C. Next, the obtained pulps unscreened (u-) were sieved into screened (s-) portions, and the molded sheets from both u-and s-portions were formed using compression molding technique under pressure of 0.6 MPa at 130°C for 5 min. The molded sheets from R pulp showed higher tensile strength and tensile index (62 MPa and 63.28 Nm/g, respectively) when compared to the sheets from P and B pulps. From SEM images, the cross-sections of the R pulp sheets revealed less voids between fiber layers and, hence, better fiber-packing and bonding. Based on their mechanical properties compared to commercial molded pulp products, it suggested that these agricultural residues and their pulps can be considered promising alternative sources for pulp and molded pulp production.
All-cellulose composites (ACCs) become growingly attractive materials in wide range applications due to its green profile, biocompatibility, and enable recycling. In this work, the ACCs was fabricated from cotton fabric (CF) by partial dissolution via aqueous NaOH/urea solution. The alternative ACC fabrication technique using vacuum bagging in the dissolution step was introduced in this study. SEM images confirmed that a vacuum aid during CF-ACC fabrication effectively improved the consolidation of resulting composites, showing better bonding and structure integrity. The CF-ACC prepared with vacuum bagging-assisted process showed almost two-fold enhancement in tensile strength as compared to another one prepared without vacuum bagging. The effect of dissolution time (15-45 min) on structure and properties of CF-ACCs was also investigated. The CF-ACC prepared with vacuum bagging at dissolution time of 15 min showed the highest tensile strength of 35.25 ± 1.39 MPa and elongation of 21.17 ± 1.46 %. The longer dissolution time, the larger portion of the crystalline fibers dissolved and converted into the amorphous matrix phase of CF-ACCs (confirmed by XRD). With longer dissolution times, the tensile strength of the prepared composites was decreased. However, it was found that with increasing dissolution time and using vacuum bagging in the fabrication of CF-ACCs could enhance their Young’s modulus values, indicating a greater interfacial adhesion gained in these composite structures.
The nanofibrillated celluloses (NFC) from different sources (i.e. bacterial cellulose (BC), pineapple leaf (PA) and banana pseudostem (BA)) were prepared using microfluidization. TEM and XRD results revealed diverse characteristics of the NFCs from different sources. Then, 0.1wt% of the prepared NFCs were integrated into the bagasse (BG) paper sheets. SEM images showed the densest surface of BG/NFC-BA sheet which also exhibited the highest sheet rigidity. Furthermore, the tensile tests indicated that the BG sheet reinforced with NFC-BC, possessing the highest fiber aspect ratio (L/D of 336) and crystallinity (80%), offered the highest strength and toughness. All tensile properties of the BG sheets were impressively enhanced with very low content (0.1wt%) of NFC addition. This confirmed that NFC is a highly effective reinforcement and suitable for use in paper making industry. However, suitable sources of NFCs for a particular paper product or application should be considered in advance.
Rice straw, an abundant agricultural waste, is shown to be a promising resource for pulp and paper packaging manufacturing. In this study, rice straw pulps or cellulose fibers were extracted using a soda-AQ process and then the rice straw pulp slurries were refined by a Valley beater. The effect of refining time (15-60 min) on the pulp fiber characteristics was studied. It was found that both initial fiber length and width were decreased with refining time. The refined fibers became fibrillated, finer, and also more uniform in size confirmed by SEM. The pulp freeness (CSF) was reduced with increasing refining time as expected due to higher water-holding capacity of more fibrillated pulps. Then, the molded sheets were formed from the prepared rice straw pulps and examined. From tensile testing, the results indicated that the tensile properties of the molded sheets from the refined pulps were significantly enhanced (p < 0.05), thanks to an increase in fibrillated fiber surface area and inter-fiber bonding degree. The Valley beater refined rice straw pulp provided the molded sheet with the highest tensile index of 51.96 ± 4.08 Nm/g which are comparable to that of the sheets prepared from PFI mill refining process. The tensile properties of the current refined sheets were also in the acceptable range for typical commercial molded pulp packaging. In addition, the freeness values of the optimal Valley beater refined pulps are relatively high (348-423 ml), implying a benefit in forming process and manufacturing of pulp products.
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