Highly Insulative PEG-Grafted Cellulose Polyurethane Foams—From Synthesis to Application Properties

In this paper, native cellulose I was subjected to alkaline treatment. As a result, cellulose I was transformed to cellulose II and some nanometric particles were formed. Both polymorphic forms of cellulose were modified with poly(ethylene glycol) (PEG) and then used as fillers for polyurethane. Composites were prepared in a one-step process. Cellulosic fillers were characterized in terms of their chemical (Fourier transformation infrared spectroscopy) and supermolecular structure (X-ray diffraction), as well as their particle size. Investigation of composite polyurethane included measurements of density, characteristic processing times of foam formation, compression strength, dimensional stability, water absorption, and thermal conductivity. Much focus was put on the application aspect of the produced insulation polyurethane foams. It was shown that modification of cellulosic filler with poly(ethylene glycol) has a positive influence on formation of polyurethane composites—if modified filler was used, the values of compression strength and density increased, while water sorption and thermal conductivity decreased. Moreover, it was proven that the introduction of cellulosic fillers into the polyurethane matrix does not deteriorate the strength or thermal properties of the foams, and that composites with such fillers have good application potential.

Innovative ionic liquids as functional agent for wood-polymer composites

Chemical modification of lignocellulosic fillers is a hydrophobization process that has been used for years in the production of wood-polymer composites (WPCs). However, finding new, more effective modifiers is still a big challenge and remains the subject of much research. This study involved the chemical modification of wood with the use of newly designed ammonium and imidazolium ionic liquids containing reactive functional groups. The effectiveness of the modification was confirmed using FTIR and XRD techniques. The effect of modification of wood on the supermolecular structure and morphology of wood-polymer composites was investigated by X-ray diffraction, hot stage optical microscopy and differential scanning calorimetry. A significant influence of the modifier structure on the shaping of polymorphic varieties of the polymer matrix was demonstrated. The chemical modification also had significant effect on the nucleating properties of the wood fillers, which was confirmed by the determined crystallization parameters (crystallization half-time, crystallization temperature, crystal conversion). Moreover, the formation of a transcrystalline PP layer was noticed, which showed a large variation depending on the structure of the used ionic liquid. The obtained results correlated very well with the results of mechanical tests. It has been shown that it is possible to precisely design an ionic liquid containing a reactive functional group capable of interacting with hydroxyl groups of cellulose molecules. Moreover, the possibility of functionalizing the lignocellulosic material with innovative ionic liquids without the need to use organic solvents has not been demonstrated so far. Graphic abstract

Development of a spatially structured polymeric matrix under UV irradiation of polylactide-based composites filled with aluminosilicate microspheres

The relevance of the study is conditioned by the fact that increased consumption of synthetic polymers leads to an increase in environmental pollution due to the long decomposition time of plastic waste. As a result, it is necessary to develop polymer composites based on a biodegradable polymer matrix, and to improve the performance properties of finished plastic products, it is necessary to purposefully select cheap and affordable inorganic fillers. Thus, the purpose of this study is to investigate the regularities in the generation of a spatially structured polymer matrix under UV irradiation of polylactide-based composites filled with aluminosilicate microspheres (ASM). The leading approach to the given problem is to melt polymer composites of various compositions and to determine the physical, mechanical, and thermophysical characteristics of the prototypes, including the supermolecular structure of the polymer matrix under the influence of ultraviolet irradiation. The study suggests that the filling of polylactide with ASM particles leads to an increase in the elastic modulus, a decrease in the strength at static rupture and resistance to dynamic destructive effects, as well as heat resistance. Small aluminosilicate microspheres, when added to polylactide, perform the function of nucleation and, even with a small content, increase the crystallinity degree by 3.7 percentage points. In the range of ASM content from 1 pph to 10 pph, the absolute value of the crystallinity degree practically does not depend on the filler concentration in the polymer composite. UV (ultraviolet) irradiation in the presence of air oxygen initiates the thermooxidative destruction of polylactide and leads to the establishment of a spatially structured polymer phase using the electrostatic intermolecular interaction of additionally formed oxygen-containing functional groups in macrochains, as well as partial intermolecular crosslinking during recombination of macroradicals. The establishment of spatial structures in the polymer matrix under UV irradiation determines an increase in the resistance of experimental samples to thermal effects. It is manifested in an increase in the bending temperature under load by 7-10 percentage points, a decrease in the crystallinity degree by 1.2-2.6 percentage points, a decrease in the fluidity of the meltage and also an increase in the glass transition and melting temperature. The materials of the study are of practical value for the development of biodegradable composites based on polylactide filled with inorganic components.

A Multifunctional 3D Supermolecular Co Coordination Polymer With Potential for CO2 Adsorption, Antibacterial Activity, and Selective Sensing of Fe3+/Cr3+ Ions and TNP

A 3D supermolecular structure [Co3(L)2 (2,2′-bipy)2](DMF)3(H2O)3 1) (H3L = 4,4′,4″-nitrilotribenzoic acid) has been constructed based on H3L, and 2,2′-bipy ligands under solvothermal conditions. Compound 1 can be described as a (3, 6)-connected kgd topology with a Schläfli symbol (43)2(46.66.83) formed by [Co3(CO2)6] secondary building units. The adsorption properties of the activated sample 1a has been studied; the result shows that 1a has a high adsorption ability: the CO2 uptakes were 74 cm3·g−1 at 273 K, 50 cm3·g−1 at 298 K, the isosteric heat of adsorption (Qst) is 25.5 kJ mol−1 at zero loading, and the N2 adsorption at 77 K, 1 bar is 307 cm3 g−1. Magnetic measurements showed the existence of an antiferromagnetic exchange interaction in compound 1, besides compound 1 exhibits effective luminescent performance for Fe3+/Cr3+ and TNP.

The Pretreatment of Lignocelluloses With Green Solvent as Biorefinery Preprocess: A Minor Review

Converting agriculture and forestry lignocellulosic residues into high value-added liquid fuels (ethanol, butanol, etc.), chemicals (levulinic acid, furfural, etc.), and materials (aerogel, bioresin, etc.) via a bio-refinery process is an important way to utilize biomass energy resources. However, because of the dense and complex supermolecular structure of lignocelluloses, it is difficult for enzymes and chemical reagents to efficiently depolymerize lignocelluloses. Strikingly, the compact structure of lignocelluloses could be effectively decomposed with a proper pretreatment technology, followed by efficient separation of cellulose, hemicellulose and lignin, which improves the conversion and utilization efficiency of lignocelluloses. Based on a review of traditional pretreatment methods, this study focuses on the discussion of pretreatment process with recyclable and non-toxic/low-toxic green solvents, such as polar aprotic solvents, ionic liquids, and deep eutectic solvents, and provides an outlook of the industrial application prospects of solvent pretreatment.

The influence of crystalline structure of cellulose in chitosan-based biocomposites on removal of Ca(II), Mg(II), Fe(III) ion in aqueous solutions

In this work, the influence of the supermolecular structure of cellulosic fillers in chitosan matrix on the process of adsorption of calcium, magnesium and iron metal ion was analyzed, while using techniques such as: X-ray diffraction, flame atomic absorption spectrometry, FTIR spectroscopy, particle size analysis, and wettability angle. It has been shown that polymorphic form of cellulose significantly affects its particle size. The introduction of cellulosic filler into polymer matrix was responsible for changes in the sorption efficiency of chitosan composites. It was found that materials with nanocellulose II were characterized with the highest efficiency of adsorption. This interesting relationship has not been reported in the literature, yet. It is important especially in terms of designing composite materials with high adsorption capacity. In the presented paper this issue was discussed, taking into account crystallographic aspects as well as changes in the hydrophilicity of the surface of composite materials. Composite materials were also subjected to mechanical tests which showed some interesting increase in tensile strength when compared to the unfilled polymer.

Production of Nanocellulose by Enzymatic Treatment for Application in Polymer Composites

In the last few years, the scientific community around the world has devoted a lot of attention to the search for the best methods of obtaining nanocellulose. In this work, nanocellulose was obtained in enzymatic reactions with strictly defined dispersion and structural parameters in order to use it as a filler for polymers. The controlled enzymatic hydrolysis of the polysaccharide was carried out in the presence of cellulolytic enzymes from microscopic fungi—Trichoderma reesei and Aspergillus sp. It has been shown that the efficiency of bioconversion of cellulose material depends on the type of enzymes used. The use of a complex of cellulases obtained from a fungus of the genus Trichoderma turned out to be an effective method of obtaining cellulose of nanometric dimensions with a very low polydispersity. The effect of cellulose enzymatic reactions was assessed using the technique of high-performance liquid chromatography coupled with a refractometric detector, X-ray diffraction, dynamic light scattering and Fourier transform infrared spectroscopy. In the second stage, polypropylene composites with nanometric cellulose were obtained by extrusion and injection. It was found by means of X-ray diffraction, hot stage optical microscopy and differential scanning calorimetry that nanocellulose had a significant effect on the supermolecular structure, nucleation activity and the course of phase transitions of the obtained polymer nanocomposites. Moreover, the obtained nanocomposites are characterized by very good strength properties. This paper describes for the first time that the obtained cellulose nanofillers with defined parameters can be used for the production of polymer composites with a strictly defined polymorphic structure, which in turn may influence future decision making about obtaining materials with controllable properties, e.g., high flexibility, enabling the thermoforming process of packaging.