Cellulose is the most important and the most abundant plant natural polymer. It shows a number of interesting properties including those making it attractive as a filler of composite materials with a thermoplastic polymer matrix. Production of such composite materials, meeting the standards of green technology, has increased from 0.36 million tons in 2007 to 2.33 million tons in 2012. It is predicted that by 2020 their production will reach 3.45 million tons. Production of biocomposites with lignocellulosic components poses many problems that should be addressed. This paper is a review of the lignocellulosic materials currently used as polymer fillers. First, the many factors determining the macroscopic properties of such composites are described, with particular attention paid to the poor interphase adhesion between the polymer matrix and a lignocellulosic filler and to the effects of cellulose occurrence in polymorphic varieties. The phenomenon of cellulose polymorphism is very important from the point of view of controlling the nucleation abilities of the lignocellulosic filler and hence the mechanical properties of composites. Macroscopic properties of green composites depend also on the parameters of processing which determine the magnitude and range of shearing forces. The influence of shearing forces appearing upon processing the supermolecular structure of the polymer matrix is also discussed. An important problem from the viewpoint of ecology is the possibility of composite recycling which should be taken into account at the design stage. The methods for recycling of the composites made of thermoplastic polymers filled with renewable lignocellulosic materials are presented and discussed. This paper is a review prepared on the basis of currently available literature which describes the many aspects of the problems related to the possibility of using lignocellulosic components for production of composites with polymers.

Titanium dioxide powders were prepared via the sol–gel method, using titanium alkoxide as a precursor. It was investigated how the addition of a catalyst (ammonia) and chelating agent (acetylacetone), as well as the temperature of calcination, affects the properties of the resulting TiO₂ powder. The physicochemical properties of samples were determined, including the dispersion, morphology and microstructure of the systems (particle size distribution, TEM images), crystalline structure (XRD), characteristics of porous structure (BET), and thermal stability (TGA/DTA). The samples were also analyzed using Fourier transform infrared spectroscopy. In addition, for selected TiO₂ systems, their photocatalytic activity in the decomposition of C.I. Basic Blue 9 was investigated. Our research results show that the presence of chelating agent in the synthesis of titanium dioxide caused significant changes in dispersive properties, crystalline structure and porous structure parameters. The novel feature of this work is the proposed method of synthesis of highly photoactive titanium dioxide with desirable physicochemical properties in the presence of a chelating agent such as acetylacetone.

Biodegradability and interesting physical and mechanical properties of polypropylene (PP)/cellulose composites are the essential motive for undertaking fundamental studies of various properties of such materials. An addition of lignocellulosic particles to polymers results in a change in properties of the product obtained which is a resultant of properties of lignocellulosic material and those of polymer and depends on the proportion of both materials. It is also reflected in the flammability characteristics of the composites. In this study we have analyzed flammability of PP composites with long flax fibers obtained by compressing. The amounts of natural fibers were 12.5%, 20%, 30% and 40%. The thickness of the investigated samples was 5 mm. The samples were tested in accordance with ISO 5660 (Cone Calorimeter) at heat flux of 35 kW/m². Heat release rate (HRR) and mass loss rate (MLR) curves show that thermal decomposition and combustion of the mentioned samples occur in a different way. When flax fiber content was 12.5%, a reduction in maximum heat released (HRR peak) by about 35% was observed. However, time to sustained ignition of composites was shorter than that of PP. The characteristics of the composite are closer to those of lignocellulosic material. The addition of 12.5% fibers resulted in an increase in fire retardancy of the composite compared to polypropylene alone. The addition of fibers in the amount exceeding 20% made the composite material characteristics similar to those of lignocellulosic materials.