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Jan 2, 2025 | 
blog.nature.org | Mark Spalding
It’s all about the mud. Following our release of a “best ever” map of tidal marshes (call them saltmarshes if you prefer, it’s approximately the same), in a new paper in the journal Nature Communications we’ve now calculated how much carbon is packed away in their soils. Tidal marshes are globally distributed, but for those of us working in the academic and financial hotspots of North America, Europe and East Asia these are our ecosystems.
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Dec 2, 2024 | 
ptonline.com | Mark Spalding
Figure 1: Schematic of a variable-depth thermocouple positioned in a flange of a transfer line. Source: Mark SpaldingTo be profitable, a single-screw extruder must operate at the maximum rate while discharging at a specified pressure and temperature. Measuring the rate and discharge pressure from an operating extruder is easy and straightforward. Measuring the discharge temperature, however, is not so simple, especially using thermocouples positioned in the transfer line just upstream of the die.
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Nov 25, 2024 | 
nature.com | Mark Spalding |Nicholas Murray |Kerrylee Rogers |Andre S Rovai |Lukas Weilguny |Maria Fernanda Adame | +7 more
AbstractTidal marshes are threatened coastal ecosystems known for their capacity to store large amounts of carbon in their water-logged soils. Accurate quantification and mapping of global tidal marshes soil organic carbon (SOC) stocks is of considerable value to conservation efforts.
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Nov 1, 2024 | 
ptonline.com | Mark Spalding
A well-designed screw using a barrier flighted melting section can provide higher rates — up to 20% — and lower discharge temperatures compared to a conventional flighted melting section. When combined with a downstream Maddock mixer, the quality and rate of the extrudate can be optimized for the application, maximizing productivity.
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Oct 1, 2024 | 
ptonline.com | Mark Spalding
Many plasticating, smooth-bore, single-screw extrusion processes benefit from decreasing the extrudate or discharge temperature. These processes include foam sheet, pipe and profile extrusion, and blown film. For example, foam sheet will typically have a higher quality when the extrudate temperature is decreased. This is because the foam will be less likely to collapse at the lower discharge temperature, maintaining a low foam density and high surface aesthetics.
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Sep 1, 2024 | 
ptonline.com | Mark Spalding
The melting process for plasticating, single-screw extruders is also an excellent mixing process. A low level of mixing can occur during pellet blending before being placed in the hopper. But the first major mixing process occurs during melting. Figure 1 – ABS resin in the transition section after a Maddock solidification experiment. The feedstock mixture was 200 parts white ABS and one part black ABS in pellet form. Source: M. SpaldingThis mixing is obvious by studying the photograph in Figure 1.
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Aug 1, 2024 | 
ptonline.com | Mark Spalding
Flow surging is defined as the oscillatory change in the rate of the extruder while maintaining constant set point conditions. Moreover, process parameters such as motor current, barrel temperatures and screw channel pressures can also oscillate. Flow surging can originate from many different sources, including improper solids conveying, melting instabilities and improper control algorithms.
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Jul 1, 2024 | 
ptonline.com | Mark Spalding
New and innovative products are constantly produced on pilot and manufacturing lines using a variety of processes, including PE blown and cast films using single-screw extruders. Many times, these films will be sent to end users for evaluation. Acceptable quality and properties of the films are key to the success of the new product. Most of the time, the new film produced has acceptable quality (very low gels) and great physical properties.
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May 1, 2024 | 
ptonline.com | Mark Spalding
Gearbox and motor selection are important keys to the successful and economically optimized single-screw extrusion process. That is, the motor and gearbox should be selected such that the extruder operates at near 70% motor current load and about 70% of the maximum normal screw speed. This will allow a rate increase in the future and the extrusion of resins that are more viscous while minimizing the capital costs for the motor and gearbox.
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Apr 29, 2024 | 
biorxiv.org | Mark Spalding |Daniel A. Friess |Nicholas Murray |Kerrylee Rogers
AbstractTidal marshes are threatened coastal ecosystems known for their capacity to store large amounts of carbon in their water-logged soils. Accurate quantification and mapping of global tidal marshes soil organic carbon (SOC) stocks is of considerable value to conservation efforts.
