Paper degradation on a macroscopic scale is characterised primarily by yellowing, an increase in brittleness, and other destructive changes caused by the hydrolysis of glycoside bonds and oxidation reactions. Until now, lignin has been believed to cause these changes. However, contemporary analysis has not confirmed this assumption and has attributed low paper resistance to ageing with acidification owing to the production in acid environments that involve aluminium sulfate. In view of the common belief this manuscript presents studies on the accelerated ageing of papers with different lignin contents that are produced in neutral environments. To achieve the objective, artificially aged papers under conditions of increased humidity and temperature were investigated using chromatographic (SEC) and spectroscopic (FTIR and UV–Vis spectroscopy) techniques. Mechanical tests were used to determine the decrease in tensile properties of the samples. We observed no effects of the lignin content on the ageing rate of paper produced at neutral pH. This work also reveals the extent to which spectroscopic methods are useful for studying the papers containing lignin.
a This paper describes an attempt to use long fibres from fast growing hemp (Cannabis sativa L.) as a raw material for the production of boards for the building and furniture industry. Hemp fibre boards with densities of 300 to 1100 kg/m 3 were studied. The board surfaces were finished using a one-cycle method in which birch veneers were pressed to make the boards. The pulp was glued with pMDI (9 wt.% based on dry weight). The basic mechanical and hydrophobic properties of the boards were tested. The static bending strength and modulus of elasticity of the boards with a density of about 650 kg/m 3 were comparable to P2 furniture boards. Only the higher density boards had adequate properties that met standards for the building industry, which were comparable to those of OSB/3 and MFP boards. Hemp fibre boards were characterised by relatively good water resistance, which was manifested by low swelling and low soaking susceptibility.
This review paper is related to the utilization on bacterial cellulose in many applications. The polymer produced from bacterial cellulose possessed a very good physical and mechanical properties, such as high tensile strength, elasticity, absorbency. The polymer from bacterial cellulose has a significantly higher degree of polymerization and crystallinity compared to those derived from plant. The collection of selected literature review shown that bacterial cellulose produced are in the form pure cellulose and can be used in many of applications. These include application in various industries and sectors of the economy, from medicine to paper or electronic industry.
In this study, wood plastic composites (WPC) made of poly(lactic acid) PLA and a bark-filler were manufactured. Two degrees of bark comminution (10–35 mesh and over 35 mesh) and varied content of bark (40, 50 and 60%) were investigated. The studied panels were compared with analogically manufactured HDPE boards. The manufacture of composites involved two stages: at first, WPC granules with the appropriate formulation were produced using the extruder (temperatures in individual extruder sections were 170–180 °C) and crushing using a hammer mill after cooling the extruded composite; secondly, the obtained granulate was used to produce boards with nominal dimensions of 300 × 300 × 2.5 mm3 by flat pressing in a mold, using a single daylight press at a temperature 200 °C. The study proved that comminuted bark can be applied as a filler in PLA composites. However, an increase in bark content decreased mechanical properties (MOR, MOE) and deteriorated humidity resistance (high TS and WA) of the panels. Along with the increase in bark content, an increase in the contact angle of the composite surfaces and a decrease in the total surface energy were noted. It was also found that PLA composites have higher strength parameters and lower moisture resistance compared to HDPE composites with the same bark content.
Graphical abstract
Preliminary studies are presented showing to what extent nutrients available in the growth environment of Kombucha microorganisms affect the physical and mechanical properties of synthesized cellulose. With an increase in the amount of sucrose in the growth medium and with the presence of additional nutrients, peptone and tea extract, the thickness and strength of the biopolymer increased, while elongation was reduced. The best physical and mechanical parameters were obtained for bacterial cellulose from cultures with the addition of 10% sucrose and 0.25% peptone content. The increase in elongation correlated with the decrease in the degree of polymerization, which means that in media rich in nutrients, the number of molecules building the polymer decreases. The presented data is important in order to select ingredients that will help synthesize bacterial cellulose with the desired physio-mechanical properties.
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