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Over twenty million tons of pineapples have been produced annually worldwide, but their waste is mostly discarded or burnt after harvesting. In this work, the high-value added aerogels from the pineapple leaf waste are developed for the first time by using polyvinyl alcohol (PVA) cross-linkers and a cost-effective freeze drying process. The pineapple fibre (PF) aerogels have highly porous structures with the porosities of 96.98–98.85%, ultra-low densities of 0.013–0.033 g/cm3, and hydrophobicity with water contact angles of approximately 140°, after a surface modification with methyltrimethoxysilane (MTMS). The effects of PF concentrations (0.5–2.0 wt.%) on oil and organic solvent adsorption are investigated comprehensively. Experimental results indicate that the hydrophobic PF aerogels can adsorb motor oil up to 37.9 g/g, approximately two times greater than commercial polypropylene and polyurethane sorbents. The pseudo-second order model can provide a good fit for the oild adsorption kinetics of the developed aerogels. [ABSTRACT FROM AUTHOR]

Pineapple has been known as one of the most popular tropical fruits in Vietnam with a production of over 674,000 t in 2018. However, by-products from pineapple cultivation account for approximately 65 % of the fresh fruit weight and are mostly being dumped, decomposed or burnt now. Therefore, it has recently raised great concern about environmental pollution. For the first time, extracted fibres from pineapple leaves being utilized for developing successfully eco-friendly and cost-effective pineapple fibres (PFs) aerogels by using polyvinyl alcohol as a cross-linker and following a freeze-drying method. The morphology of the PFs aerogels can be controlled well by changing the PFs concentration (0.5 - 2.0 wt%). The PFs aerogels exhibit extremely low densities (12.7 - 32.6 kg/m3) and high porosities (96.9 - 98.8 %). The BET result shows that the surface area of the PFs aerogel has up to 5.6 m2/g and their pore size of 1.3 - 2.2 nm. The developed PFs aerogels show extremely low thermal conductivities ranging from 0.030 to 0.034 W/m.K. Due to the low Young's modulus values ranging from 0.47 - 7.86 kPa, the PFs aerogels are flexible and can be used for heat insulation of the buildings as well as food preservation. [ABSTRACT FROM AUTHOR]

Silica aerogels have attracted great attention owing to their outstanding properties such as ultralow density, high porosity, high surface area, and low thermal conductivities. Their poor mechanical properties and hydrophilicity constrain their practical applications. In this work, phenyltrimethoxysilane (PTMS) and polyvinyl alcohol (PVA) were added into methyltrimethoxysilane (MTMS)-based silica aerogels to enhance their mechanical properties. It was found that PTMS considerably improved the hydrophobicity of MTMS silica aerogels with an increase in water contact angles from 115° to 150°. The addition of PVA considerably increased the hardness, morphology, density, porosity, surface area, and thermal conductivity of MTMS silica aerogels. When PVA concentration was increased from 0 to 2 %, the aerogel hardness, density, and thermal conductivity were also increased from 0 to 14 %, 0.072 to 0.11 g/cm³, and 0.035 to 0.046 W/m.K. In contrast, the aerogel became less porous and the porosity reduced from 97.2 % to 95.72 % and BET surface area decreased from 389 to 43 m²/g. [ABSTRACT FROM AUTHOR]

This work presents for the first time, a simple, practical and scalable approach to fabricating recycled polyethylene terephthalate (rPET) aerogels for thermal and acoustic insulation applications. The rPET aerogels were successfully developed from recycled PET fibers and polyvinyl alcohol (PVA) and glutaraldehyde (GA) cross-linkers using a freeze-drying process. The effects of various PET fiber concentrations (0.5, 1.0 and 2.0 by wt.%), fiber deniers (3D, 7D and 15D) and fiber lengths (32 mm and 64 mm) on the rPET aerogel structures and multi-properties were comprehensively investigated. The developed rPET aerogels showed a highly porous network structure (98.3⁻99.5%), ultra-low densities (0.007⁻0.026 g/cm³), hydrophobicity with water contact angles of 120.7⁻149.8°, and high elasticity with low compressive Young's modulus (1.16⁻2.87 kPa). They exhibited superior thermal insulation capability with low thermal conductivities of 0.035⁻0.038 W/m.K, which are highly competitive with recycled cellulose and silica-cellulose aerogels and better than mineral wool and polystyrene. The acoustic absorption results were also found to outperform a commercial acoustic foam absorber across a range of frequencies., Competing Interests: The authors declare no conflict of interest.