Abstract
Micro- and nanofibrillated cellulose (MNFC) was extracted from pineapple stems by acid hydrolysis, then characterized and tested in two concentrations (0.5 and 1.0 wt%) in polyvinyl acetate (PVAc) and urea-formaldehyde (UF) adhesives. The modified adhesives were used to glue three tropical wood species (Vochysia ferruginea,Cordia alliodora, andGmelina arborea), and their corresponding bond strength resistance was determined. MNFC and the correspondent adhesives were characterized by TGA, FTIR, SEM, TEM, AFM, and viscosity determination. The TGA analysis of MNFC showed three decomposition reactions. The SEM, TEM, and AFM evaluations demonstrated the presence of micro- and nanosized dimensions of particles after the acid hydrolysis of pineapple stems. Adding 1 wt% MNFC to PVAc and UF adhesives increased their thermal stability in similar manner. Viscosity diminished in both modified adhesives with MNFC; however, this reduction did not affect the adhesion properties in the tropical wood tested. MNFC added to PVAc and UF adhesives improved shear strength (SS) of the glue line in the three tropical species tested. The highest SS increase was obtained when adding 0.5 wt% MNFC to PVAc inV. ferruginea, and 1 wt% MNFC concentration in the case ofC. alliodoraandG. arborea. In the case of UF adhesives, the application of 1 wt% MNFC produced significant differences in SS for the three tropical species studied.
Highlights
In recent years, and considering their abundance, annual crops have been used as raw materials to extract micro- and nanofibrillated cellulose [1, 2]
Two inflexions appear in Micro- and nanofibrillated cellulose (MNFC), at 200°C and at 350°C (Figures 2(a) and 2(b)) which corresponds to degradation temperatures
These results agreed with values presented by Kargarzadeh et al [22], where temperatures of 230°C and 350°C are reported, and of Kumar et al [23], who reported values of 220°C and 330°C for MNFC extracted by acid hydrolysis from sugarcane and kenaf, respectively
Summary
Considering their abundance, annual crops have been used as raw materials to extract micro- and nanofibrillated cellulose [1, 2]. The annual crop pineapple (Ananas comosus), with a world production of around 24.8 million tons per year [2, 4], produces large amounts of residues in the form of leaves, stems, crowns, and fruit peel that are not used [5]. In Costa Rica for instance, this crop was introduced in 1970, and by 2014, there were approximately 37 660 ha of pineapple-sown fields available [6]. From these fields, nearly 300 tons of stubble are produced [6] which can be an important source of high-value materials [7]. One possible utilization for the pineapple wastes has been the extraction of natural fibers for rope and textile manufacturing [7] or pulp production [8]
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