How much is solid, at which temperature
Waxes in oils crystallise when the temperature falls. The crystals make the oil cloudy, thicken it and can block filters and pipes. Time-domain NMR separates the solid wax from the liquid oil by how quickly their signals fade, so the solid content is read as a function of temperature, and the temperature at which wax appears can be located.
Where it is used
- Petroleum waxes, and the oil content of waxes
- Paraffinic crude oils and fuels
- Lubricating oils and base oils
- Greases and additive packages
Typical tasks are measuring the oil in a wax or the wax in an oil, locating the temperature at which wax appears, comparing oils, and studying how additives change the crystallisation.
A temperature series, or time at a fixed temperature
The sample is held at a series of temperatures in a temperature-controlled block, and the solid content is read at each. For crystallisation, the sample is cooled quickly to a chosen temperature and the solid content is followed over time. A crystallisation modifier shows up as a change in how early and how far the wax crystallises.
Wet references
The oil content of petroleum waxes is traditionally determined by a wet method such as ASTM D721. NMR gives a fast alternative after a calibration against it.
What it adds
- Quick, non-destructive and free of solvents
- Dark and opaque samples are no problem
- Shows how the solid content changes with temperature and with time
- Compares additives on the same scale
Points that matter in practice
- The sample history matters. Melt the sample, and cool it in a defined way, before comparing
- The temperature at which wax first appears depends on how sensitive the measurement is, so compare samples measured in the same way
- Additives change the crystal form and the structure. The solid content alone does not show everything, so combine it with other tests when the question is flow behaviour
- Calibrate with samples whose wax or oil content you know
From your samples to a routine method
Send or bring representative samples. MSY Consulting runs feasibility measurements, plans the temperature programme and the calibration with you, and trains your team until the method is part of your routine.
Let's talk about your application
Send an email describing your instrument and your application, and you will get a reply.
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