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journal of materials research and technology 2022;20:4630 e 4658
Fig. 10 e Three-layer particleboard with green coconut fiber as outer layers (OL) and sugarcane bagasse fibers as an inner layer (IL) (Fiorelli et al. [113], with permission).
comply with the standard requirements. The highest density and IB values of 0.98; 0.97 g/cm 3 and 0.24; 0.23 N/mm 2 were determined for the samples fabricated with 30% rice husks þ 70% groundnut shells and 50% rice husks þ 50% groundnut shells, respectively. The best mechanical proper- ties were obtained for the panels manufactured from 30% rice husks and 70% groundnut shells.
tea leaves boards emitted significantly lower formaldehyde compared to conventional poplar particleboard, indicating that tea leaves could act as formaldehyde scavengers. One of the waste tea leaves particleboard issues is its inferior mechanical properties. Board with higher density or incorporation of a certain amount of wood particles is necessary. Batiancela et al. [126] incorporated 10 e 80% P. fal- cataria (L.) Nielsen wood particles in the waste tea leave particleboard. Compared to wood, waste tea leaves are less hygroscopic as they have a smaller amount of cellulose and hemicellulose [127]. Particle boards with 100% waste tea leaves have significantly lower TS and WA values. In addition, blades of tea leaves consist mainly of thin-walled parenchyma cells, making them easily compressed during mat consolida- tion and resulting in good IB [128]. However, adding P. falca- taria wood particles enhanced the MOR and MOE of the boards. Particleboard produced with incorporation of 20 e 50% wood particles surpassed the minimum requirements of TS, WA, IB, MOR, and MOE for general use particleboard set by EN 312-2. Tree leaves are another underutilized biomass that could be converted into particleboard [129]. However, conventional UF resin is not suitable to be used as a binder for bonding tea leaves as the leaves have a waxy epidermal surface layer [130]. Extractives such as wax, inorganic silicon, and fat are found in this waxy layer and could interfere with its compatibility with a water-based adhesive such as UF [131]. Therefore, iso- cyanates such as MDI are commonly used for bonding agri- cultural residues that are difficult to glue. A comparison between the physical and mechanical properties of leave- based particleboard, bonded with UF resin and MDI, is
4.5.
Leave-based particleboard
Owing to its high phenolic content, waste leaves of Camelia sinensis L. are considered a promising alternative material for particleboard manufacturing [66]. A study by Yalinkilic et al. [124] reported that tea leaves, as a substrate for growing mushrooms, resulted in very poor mycelial development and almost no fruit body formation. Therefore, it is anticipated that particleboard made from waste tea leaves should have superior biological durability. Yalinkilic et al. [66] fabricated three-layer particleboard from waste tea leave bonded with UF resin. The boards were exposed to brown-rot fungus ( Tyromyces palustris (Berk. et Curt) Murr.), white-rot fungus ( Coriolus versicolor (L. ex Fr.) Quel.) and subterranean termites ( Coptotermes formosanus Shiraki). Particleboard made from waste tea leaves proved biologically resistant against decay fungi and termites. However, the boards ' dimensional stability and mechanical properties should be further improved. Apart from its superiority in biological durability, tannins, protein, and amino acid that exists in abundance in tea leaves could actively react with formaldehyde [125]. As a result, lower formaldehyde emission from the resultant particleboard is expected. The same authors reported ha the UF-bonded waste
Table 6 e Physical and mechanical properties of particleboard manufactured from selected bagasse. Raw Materials Adhesive type Adhesive (%) Density (kg/ m 3 ) MOR (MPa) MOE (MPa) IB (MPa) TS, 24h (%) WA, 24h (%)
References
Sweet sorghum bagasse
Citric acid
20 20 12
800 800 800 800 800 800 800 672 657 654
21.8 12.5 32.9 34.1
5200 2500 4500 4600 3361 3429 3944 2095 2823 2621
0.89 0.41 0.78 1.33 0.73 0.98 1.03 0.46
10.1 20.1 20.6 23.1 5.42 5.48 4.43 17.8 14.9 15.6
N/A 35.2 N/A N/A
[79,114]
Citric acid-sucrose
PF
PMDI
8
Sugarcane
Citric acid
15 20 25
17.38 18.22 21.88
42.92 30.47 29.48
[115]
Sugarcane Eucalyptus
UF UF UF
8 8 8
12.5 16.7 15.2
47.1 37.8
[110] [110] [110]
1
Pinus
0.84
39
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