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1.
Polymers (Basel) ; 14(1)2021 Dec 31.
Artigo em Inglês | MEDLINE | ID: mdl-35012177

RESUMO

Due to the content of lignocellulosic particles, wood plastic composites (WPC) composites can be attacked by both domestic and mold fungi. Household fungi reduce the mechanical properties of composites, while mold fungi reduce the aesthetics of products by changing their color and surface decomposition of the wood substance. As part of this study, the impact of lignocellulosic fillers in the form of sawdust and bark in poly (lactic acid) (PLA)-based biocomposites on their susceptibility to mold growth was determined. The evaluation of the samples fouled with mold fungi was performed by computer analysis of the image. For comparison, tests were carried out on analogous high-density polyethylene (HDPE) composites. Three levels of composites' filling were used with two degrees of comminution of lignocellulosic fillers and the addition of bonding aids to selected variants. The composites were produced in two stages employing extrusion and flat pressing. The research revealed that PLA composites were characterized by a higher fouling rate by Aspergillus niger Tiegh fungi compared to HDPE composites. In the case of HDPE composites. The type of filler (bark, sawdust) affected this process much more in the case of HDPE composites than for PLA composites. In addition, the use of filler with smaller particles enhanced the fouling process.

2.
Sci Rep ; 10(1): 19998, 2020 11 17.
Artigo em Inglês | MEDLINE | ID: mdl-33203985

RESUMO

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.

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