Effects of chemical modification of wood with innovative ionic liquid on the supermolecular and morphology of wood/polypropylene composites were investigated using X-ray diffraction, hot stage optical microscopy, and differential scanning calorimetry. For the first time the chemical treatment of wood was conducted solely with newly synthesized ionic liquid, didecyldimethylammonium bis(trifluoromethylsulfonyl)imide. The modification was found to be responsible for significant changes in nucleating abilities of wood in polypropylene matrix. These findings were confirmed by crystallization temperature, crystal conversion, crystallization half-time parameters, as well as observation of transcrystalline structures. Ionic liquid treatment of wood influenced also formation of polymorphic forms of polymer matrix. In contrast to composites with untreated wood, in composites with modified wood filler formation of b-phase of polypropylene was observed. This fact was discussed in view of differences in nucleating activity of lignocellulosic filler, resulting from chemical treatment with ionic liquid. Moreover, a relationship between mechanical properties of composites and the phenomena taking place at the polymer-filler interface, controlled by chemical modifications of lignocellulosic components, was evaluated.

The article presents characteristics of wood/polypropylene composites, where the wood was treated with propolis extract (EEP) and innovative propolis-silane formulations. Special interest in propolis for wood impregnation is due to its antimicrobial properties. One propolis-silane formulation (EEP-TEOS/VTMOS) consisted of EEP, tetraethyl orthosilicate (TEOS), and vinyltrimethoxysilane (VTMOS), while the other (EEP-TEOS/OTEOS) contained EEP, tetraethyl orthosilicate (TEOS), and octyltriethoxysilane (OTEOS). The treated wood fillers were characterized by Fourier transform infrared spectroscopy (FTIR), atomic absorption spectrometry (AAS), and X-ray diffraction (XRD), while the composites were investigated using differential scanning calorimetry (DSC), X-ray diffraction (XRD), and optical microscopy. The wood treated with EEP and propolis-silane formulations showed resistance against moulds, including Aspergillus niger, Chaetomium globosum, and Trichoderma viride. The chemical analyses confirmed presence of silanes and constituents of propolis in wood structure. In addition, treatment of wood with the propolis-silane formulations produced significant changes in nucleating abilities of wood in the polypropylene matrix, which was confirmed by an increase in crystallization temperature and crystal conversion, as well as a decrease in half-time of crystallization parameters compared to the untreated polymer matrix. In all the composites, the formation of a transcrystalline layer was observed, with the greatest rate recorded for the composite with the filler treated with EEP-TEOS/OTEOS. Moreover, impregnation of wood with propolis-silane formulations resulted in a considerable improvement of strength properties in the produced composites. A dependence was found between changes in the polymorphic structures of the polypropylene matrix and strength properties of composite materials. It needs to be stressed that to date literature sources have not reported on treatment of wood fillers using bifunctional modifiers providing a simultaneous effect of compatibility in the polymer-filler system or any protective effect against fungi.

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

The thermal modification of wood can be an interesting way of improving adhesion in polymer composites, although the mechanical properties of composites with heat treated wood presented so far in many works arouse much controversy. In this work, effects of thermal modification of wood on the supermolecular structure and morphology of wood/polypropylene composites (WPC) were investigated using X-ray diffraction, hot stage optical microscopy,

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