The transmission of pathogens via surfaces poses a major health problem, particularly in hospital environments. Antimicrobial surfaces can interrupt the path of spread, while photocatalytically active titanium dioxide (TiO2) nanoparticles have emerged as an additive for creating antimicrobial materials. Irradiation of such particles with ultraviolet (UV) light leads to the formation of reactive oxygen species that can inactivate bacteria. The aim of this research was to incorporate TiO2 nanoparticles into a cellulose-reinforced melamine-formaldehyde resin (MF) to obtain a photocatalytic antimicrobial thermoset, to be used, for example, for device enclosures or tableware. To this end, composites of MF with 5, 10, 15, and 20 wt% TiO2 were produced by ultrasonication and hot pressing. The incorporation of TiO2 resulted in a small decrease in tensile strength and little to no decrease in Shore D hardness, but a statistically significant decrease in the water contact angle. After 48 h of UV irradiation, a statistically significant decrease in tensile strength for samples with 0 and 10 wt% TiO2 was measured but with no statistically significant differences in Shore D hardness, although a statistically significant increase in surface hydrophilicity was measured. Accelerated methylene blue (MB) degradation was measured during a further 2.5 h of UV irradiation and MB concentrations of 12% or less could be achieved. Samples containing 0, 10, and 20 wt% TiO2 were investigated for long-term UV stability and antimicrobial activity. Fourier-transform infrared spectroscopy revealed no changes in the chemical structure of the polymer, due to the incorporation of TiO2, but changes were detected after 500 h of irradiation, indicating material degradation. Specimens pre-irradiated with UV for 48 h showed a total reduction in Escherichia coli when exposed to UV irradiation.
The combination of fillers and polymers is used to influence the mechanical, optical and processing properties of the base material and is finding more and more applications. The addition of wood to polymers results in wood-polymer composites (WPC), whereby the wood content can be up to 80 wt. %. This composite is mainly processed to deckings by means of extrusion. The extrusion die is an essential part of the processing procedure, which determines both process parameters and the final product. A special feature of WPC extrusion dies is cooling plate, which leads to partial solidification of the melt before leaving the die. This solidification is necessary to ensure dimensionally stable extrusion without strand breakage. For the design of WPC extrusion dies, numerical simulations are increasingly used in addition to empirical data, whereby OpenFOAM is used in the present investigations. Based on rheological measurements, both the shear thinning flow behavior and the temperature dependence of the viscosity are modeled. The partial solidification of the melt at the cooling plate before the outlet is modeled in a single-phase over a step in viscosity. In addition, the solidified melt slips on the cooling wall, which is also taken into account in the model. In the parallel zone, there is a pure shear flow, while in the transition elements such as the flange to the extruder or at the mandrel, uni-and biaxial extension components are dominant due to the crosssectional changes. High-density polyethylen (HDPE) with wood flour exibits a shear thinning and extensional thickening behavior, so that different models are necessary for description. To calculate the stresses, interpolation is performed between the different models with respect to the invariants according to Böhme [1], depending on the type of flow present. To validate the numerical simulations, an extrusion die for a square hollow profile with pressure and temperature sensors along the flow direction is subject to experimental measurements. The aim of the numerical simulations is to investigate the flow in more detail and to give optimization hints. Liese, F. et al.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.