Ageing of laser sintered glass-filled Polyamide 12 (PA12) parts at elevated temperature and humidity

Additive manufacturing is traditionally used to manufacture either prototypes or very small-scale demonstrators. In recent years though, it is being increasingly used to make low volume parts for the aeronautical and defence industry. One concern with laser sintered parts is that their relatively porous nature, means that they may be more susceptible to ageing than injection moulded parts. Parts were aged for 6 months in at different temperatures (18°C, 40°C, 50°C, 60°C, 80°C and 100°C) and in a humidity chamber at 60°C and 80% relative humidity. Each month samples were removed for characterisation. The testing included tensile testing, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and gas pycnometry. During ageing the samples displayed visible discolouration and embrittlement over the 6-month test period. This embrittlement was not observed in those samples aged at room temperature or an elevated humidity. The observed yellowing in the samples aged above ambient temperature is likely a result of the build-up unsaturated degradation products. No significant differences as a result of ageing were observed via DSC, TGA, SEM or gas pycnometry.

Sintered Glass Monoliths as Supports for Affinity Columns

A novel stationary phase for affinity separations is presented. This material is based on sintered borosilicate glass readily available as semi-finished filter plates with defined porosity and surface area. The material shows fast binding kinetics and excellent long-term stability under real application conditions due to lacking macropores and high mechanical rigidity. The glass surface can be easily modified with standard organosilane chemistry to immobilize selective binders or other molecules used for biointeraction. In this paper, the manufacturing of the columns and their respective column holders by 3D printing is shown in detail. The model system protein A/IgG was chosen as an example to examine the properties of such monolithic columns under realistic application conditions. Several specifications, such as (dynamic) IgG capacity, pressure stability, long-term performance, productivity, non-specific binding, and peak shape, are presented. It could be shown that due to the very high separation speed, 250 mg antibody per hour and column can be collected, which surpasses the productivity of most standard columns of the same size. The total IgG capacity of the shown columns is around 4 mg (5.5 mg/mL), which is sufficient for most tasks in research laboratories. The cycle time of an IgG separation can be less than 1 min. Due to the glass material’s excellent pressure resistance, these columns are compatible with standard HPLC systems. This is usually not the case with standard affinity columns, limited to manual use or application in low-pressure systems. The use of a standard HPLC system also improves the ability for automation, which enables the purification of hundreds of cell supernatants in one day. The sharp peak shape of the elution leads to an enrichment effect, which might increase the concentration of IgG by a factor of 3. The final concentration of IgG can be around 7.5 mg/mL without the need for an additional nanofiltration step. The purity of the IgG was > 95% in one step and nearly 99% with a second polishing run.

Sintered Glass-Ceramics, Self-Glazed Materials and Foams from Metallurgical Waste Slag

The materials used for the synthesis of parent glass are 70% wt. metallurgical slag and 30% wt. industrial quartz sand. The initial batch is melted at and then quenched in water. The resulting glass frit is milled bellow 75 microns and pressed 1400 °C into “green” samples. In a next stage, they are heat treated at different temperatures with various heating rates and holding times. As a result, it is demonstrated the possibility for production variations, allowing the manufacture of three types of new materials by using the same pressed glass powders. We highlight the flexibility of the synthesis obtaining namely well densified glass-ceramics at about 950 °C, self-glazed glass-ceramics at about 1000 °C or glass-ceramic foams at approximately 1100 °C. The first set of materials is characterized by very well sintered structure combined with reasonable crystallinity; the second one—by smooth self-glazed surface with an attractive appearance and good properties and the third one—by 80–90% closed porosity and very good thermal stability above 1000 °C.

Sintered Glass Monoliths as New Supports for Affinity Columns

A novel stationary phase for affinity separations is presented. This material is based on sintered borosilicate glass readily available as semi-finished filter plates with defined porosity and surface area. The material shows fast binding kinetics and excellent long-term stability under real application conditions due to lacking macropores and high mechanical rigidity. The glass surface can be easily modified with standard organosilane chemistry to immobilize selective binders or other molecules used for biointeraction. In this paper, the manufacturing of the columns and their respective column holders by 3D printing is shown in detail. The model system protein A/IgG was chosen as an example to examine the properties of such monolithic columns under realistic application conditions. Several specifications, such as (dynamic) IgG capacity, pressure stability, long-term performance, productivity, non-specific binding, and peak shape, are presented. It could be shown that due to the very high separation speed, 250 mg antibody per hour and column can be collected, which surpasses the productivity of most standard columns of the same size. The total IgG capacity of the shown columns is around 4 mg (5.5 mg/mL), which is sufficient for most tasks in research laboratories. The cycle time of an IgG separation can be less than 1 minute. Due to the glass material's excellent pressure resistance, these columns are compatible with standard HPLC systems. This is usually not the case with standard affinity columns, limited to manual use or application in low-pressure systems. The use of a standard HPLC system also improves the ability for automation, which enables the purification of hundreds of cell supernatants in one day. The sharp peak shape of the elution leads to an enrichment effect, which might increase the concentration of IgG by a factor of 3. The final concentration of IgG can be around 7.5 mg/mL without the need for an additional nanofiltration step. The purity of the IgG was > 95% in one step and nearly 99% with a second polishing run.

Reference material for the measurement of soil hydraulic properties

<p>Quality control of the measurement of soil hydraulic properties (water retention curve, saturated hydraulic conductivity) using soil cores is not very common in soil physics laboratories. The missing quality control in the labs might be due to the lack of a suitable reference material for the measurement of soil hydraulic properties (SHP). However, a standardized quality of these measurements is needed, especially when generated data from different laboratories are used.</p><p>So far no satisfying reference material has been presented that can be used for quality control during the measurement of SHP. Reference material should have a rigid pore system and pore surfaces properties that do not change over time. Additionally, the reference material should be very sensitive to provide a sufficient quality control for the measurement of SHP.</p><p>We present sintered glass cylinders with a defined pore size distribution that were tested in the laboratory for reproducibility. After a standardized cleaning procedure of the glass cylinders, water contents after equilibration at -63 hPa (field capacity) showed reasonably low standard deviations. Thus, it seems promising that these cylinders can be used as reference material for the measurement of the water retention curve.</p><p>First Results of repeated saturated hydraulic conductivity measurements (Ks) of the same sintered glass cylinders showed larger variability and an increasing trend over the time. Currently the reason for this trend is unknown. Therefore, it is worked on standardizing procedures of using the reference cylinders and on cleaning the cylinders to improve the reproducibility. The results show how sensitive the measurement of saturated hydraulic conductivity is and that we need to put more emphasis on quality control in our work.</p><p> </p>