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This work prepared eco-friendly biocomposites of polyurethane (PU) and sheath palm residues, using castor oil as a polyol. PU composites filled with natural fibers were prepared at different loading rates: 0 to 20 wt.%. Results indicated that the sheath palm was hydrogen-bonded to PU chains and increased the foams' density. Pore size decreased with an increase in fiber content, from 256 to 116 µm. The fiber's addition improved the ductility of PU foams (compressive modulus from 4.74 to 0.26 MPa) and the foams' crystallinity index (from 5.4 to 15.4%). Compared to pristine PU, the composites showed high hydrophobicity (reaching 123° of contact angle for PU-15%) and thermal stability (Tonset from 96 to 96.3°), and high density (from 41 to 60 kg.m−3), making the developed composites an excellent option for environmental applications, such as oil removal and contaminant adsorption. [ABSTRACT FROM AUTHOR]

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The stabilization of nanocellulose suspensions and their compatibility with polymer matrices are challenges that have been investigated in the scientific community. However, little work has resulted in significant electrostatic stabilization as well as improved the mechanical behavior of nanocomposites. Anionic surfactant modified nanocellulose, and the results demonstrated the impact of the concentration of this surfactant on nanocellulose surfaces and properties. The variation in electrostatic stability was evaluated by the zeta potential, which is key to the comprehension of dispersion and agglomeration in suspensions. Also, physicochemical tests were conducted to analyze the properties of nanocelluloses. The addition of the surfactant and its effects were verified by physicochemical characterization; it was evaluated the crystallinity, thermal stability, composition, adsorption effect, and other properties. Mechanical, thermal and physicochemical tests were conducted to understand the influence of nanoparticles on nanocomposites. The results of this study demonstrated that the surfactant-modified cellulose nanostructures presented excellent electrostatic and thermal stability, which made the developed materials potential reinforcing agents for the incorporation of polymeric matrices. These modified CNSs were incorporated in a poly(butylene adipate-co-terephthalate), and improvements of its mechanical properties were observed. Also, the thermal stability of the polymer was maintained, and the water diffusion coefficient was reduced, favoring applications that need this characteristic, like plastic packaging. [ABSTRACT FROM AUTHOR]

Cellulose is a renewable, sustainable, and high available biopolymer; their common form is the type-I polymorph. However, polymorphic changes are associated with different properties and a wide range of applications. In this study, we proposed a new method to prepare polymorphic cellulose nanostructures (CNSs): first, the CNS were isolated, and then the polymorphs were converted. CNS-I (type-I), CNS-II (type-II), and CNS-III (type-III) were successfully obtained, and the structure, crystallinity, superficial characteristic, morphology, and thermal stability were evaluated. The results showed that CNS-II and CNS-III are more amorphous than CNS-I due to the strong reagents used for the polymorphic conversion, which results in a swelling, increased chain spacing, and structural disorganization. This effectively changed the morphology of the CNS, from cellulose nanocrystals from irregular quasi-spherical nanoparticles. The proposed method allows a wide range of applications, from package and nanocomposites with CNS-I due to its high crystallinity and crystal morphology, to drug carrier, food thickener and biomedical products for CNS-II and CNS-III due to its quasi-spherical shape and more amorphous structure. [ABSTRACT FROM AUTHOR]

Abstract In recent year, the interest in environmentally friendly materials, like cellulose nanostructures (CNSs) has increased. Nanoscale dimensions, high surface area, low density, and high mechanical strength are examples of CNSs properties that attract researchers' attention. CNSs stability and dispersity are the main limitations that prevent its application as nanofiller in polymeric matrices. In this work, the surface modification of CNSs was investigated. To overcome CNSs limitation, they were modified with polyethylene glycol (PEG), in aqueous solution, in different proportions: 2, 5 and 10 wt%. FTIR, elemental analysis, NMR, and XPS were carried out to verify the adsorption efficiency. The results showed an excellent adsorption of PEG chains on the CNSs surface, with particle size increase of 50–90 nm and a considerable increase in thermal stability. XRD and AFM analysis observed no significant variation in crystallinity and morphology in modified CNSs. Thus, modification of CNSs with PEG is an environmentally friendly process and showed positive results regarding improving CNSs stability, in aqueous media. Highlights • PEG was successfully adsorbed onto cellulose nanostructures (CNS) surface in solution. • PEG dosage of 2% showed the best results for improving CNS dispersity. • Stabilization with PEG is an environmentally friendly methodology to improve CNS stability. • CNS crystallinity and morphology were not affected by the adsorption of PEG. [ABSTRACT FROM AUTHOR]