Bamboo is a very interesting bio resource for building materials because of its combination of strength properties and low density. However, its susceptibility to fungi and insects is problematic. Thermal modification is used in Vietnam to improve the durability and dimensional stability of bamboo. Changes in the chemical composition during this modification are the reason for such physical changes as color, equilibrium moisture content, and strength. This paper will describe the changes in the chemical composition depending on the modification conditions. Furthermore correlations between chemical composition and physical properties, which are presented in Part I, are shown.
The influence on the resistance formation of polymers attached to antibiotics has rarely been investigated. In this study, ciprofloxacin (CIP) was conjugated to poly(2-methyl-2-oxazoline)s with an ethylene diamine end group (Me-PMOx-EDA) via two different spacers (CIP modified with α,α'-dichloro- p-xylene-xCIP, CIP modified with chloroacetyl chloride-eCIP). The antibacterial activity of the conjugates against a number of bacterial strains shows a great dependence on the nature of the spacer. The Me-PMOx-EDA-eCIP, containing a potentially cleavable linker, does not exhibit a molecular weight dependence on antibacterial activity in contrast to Me-PMOx-EDA-xCIP. The resistance formation of both conjugates against Staphylococcus aureus and Escherichia coli was investigated. Both conjugates showed the potential to significantly delay the formation of resistant bacteria compared to the unmodified CIP. Closer inspection of a possible resistance mechanism by genome sequencing of the topoisomerase IV region of resistant S. aureus revealed that this bacterium mutates at the same position when building up resistance to CIP and to Me-PMOx-EDA-xCIP. However, the S. aureus cells that became resistant against the polymer conjugate are fully susceptible to CIP. Thus, conjugation of CIP with PMOx seems to alter the resistance mechanism.
Polytetrafluoroethylene (PTFE) exhibits excellent non-stick properties and a very low coefficient of friction under tribological stress, but it is incompatible with almost all other polymers. In the first part of this study we presented the generation of the novel tribological material based on unsaturated oil, radiation-modified PTFE (MP1100) and Polyamide 66 (PA66). To get a better understanding of the chemical properties and chemical composition of the compounds, the PA66-MP1100-oil-cb (chemical bonded) compounds were examined by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). In this part, the mechanical properties of the compounds are compared with plain PA66 and PA66-MP1100-cb. The tribological investigation was carried out using the Block-on-Ring tribometer. It was found that the mechanical properties of PA66-MP1100-oil-cb with 20 wt.% MP1100-oil-cb only show slight differences compared to PA66, but the tribological properties of the compounds have been significantly improved through chemical coupling between the three components. Finally, the amount of the compound that was deposited on the surface of the steel disc counterpart was analyzed after the tribological testing.
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