Nanocomposites with polypropylene as matrix material and nanoclay as filler were produced in a double twin screw extruder. The extrusion was monitored with a spectrometer in the visible and near-infrared spectral region with a diode array spectrometer. Two probes were installed at the end at the extruder die and the transmission spectra were measured during the extrusion. After measuring the transmission spectra and converting into turbidity units, the particle distribution density was calculated via numerical linear equation system. The distribution density function shows either a bimodal or mono modal shape in dependence of the processing parameters like screw speed, dosage, and concentration of the nanoclays. The method was verified with SEM measurements which yield comparable results. The method is suitable for industrial in-line processing monitoring of particle radii and dispersion process, respectively.
For incorporation of nanoparticles into matrices, it is necessary to control the particle size distribution during processing. In this paper, a turbidimetric method was applied that uses spectroscopic data to determine the nanoparticle size distribution and, consequently, to control the material properties with a non-contact measurement method. This method is based on the scattering and absorption of light by the particles. Unlike conventional turbidimetric methods, this method uses not only a few wavelengths but a whole spectral range for evaluation. To determine the distribution parameters, a nonlinear numerical least squares fit routine was established. It was validated by comparing data of water-silica nanosuspensions with the results from the sedimentation method. The results show that this method is an accurate and easy-to-use analysis instrument for the characterization of nanosuspensions, emulsions, and aerosols.
The analysis of tar, mostly characterized as polycyclic aromatic hydrocarbons (PAHs), describes a topic that has been researched for years. An online analysis of tar in the gas stream in particular is needed to characterize the tar conversion or formation in the biomass gasification process. The online analysis in the gas is carried out with ultraviolet-visible (UV-Vis) spectroscopy (190-720 nm). This online analysis is performed with a measuring cell developed by the Fraunhofer Institute for Chemical Technology (ICT). To this day, online tar measurements using UV-Vis spectroscopy have not been carried out in detail. Therefore, PAHs are analyzed as follows. The measurements are split into different steps. The first step to prove the online method is to vaporize single tar substances. These experiments show that a qualitative analysis of PAHs in the gas stream with the used measurement setup is possible. Furthermore, it is shown that the method provides very exact results, so that a differentiation of various PAHs is possible. The next step is to vaporize a PAH mixture. This step consists of vaporizing five pure substances almost simultaneously. The interpretation of the resulting data is made using a chemometric interpretation method, the multivariate curve resolution (MCR). The verification of the calculated results is the main aim of this experiment. It has been shown that the tar mixture can be analyzed qualitatively and quantitatively (in arbitrary units) in detail using the MCR. Finally it is the main goal of this paper to show the first steps in the applicability of the UV-Vis spectroscopy and the measurement setup on online tar analysis in view of characterizing the biomass gasification process. Due to that, the gasification plant (at the laboratory scale), developed and constructed by the Fraunhofer ICT, has been used to vaporize these substances. Using this gasification plant for the experiments enables the usage of the measurement setup also for the spectroscopic analysis of the tar formation during the biomass gasification.
By the incorporation of nanoparticles into a polymer matrix the properties of the nanocomposites can be significantly improved compared to the starting polymer. As the incorporation process appears to be challenging due to possible agglomeration of the nanoparticles it is very important to control it online. In this research, transparent SiO 2-polypropylene(PP) nanocomposite was examined with the optical turbidimetric method directly at the extruder. Furthermore, comparative scanning electron microscopy measurements are presented. It is shown that the turbidimetric analysis can be used for online quality control of nanocomposites
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