Mass Spectrometry & Spectroscopy
Fast, easy, and non-destructive measurement of polymer properties
Jan 04 2022
Time domain NMR (TD-NMR) is widely used in a variety of industries to replace traditional wet chemical analytical methods, typically solvent extraction, for the measurement of oil content. However, TD-NMR can also distinguish the amorphous/crystalline phases which relate to either the chemical composition or physical properties of various polymers. TD-NMR is the method of choice because it is fast, non-destructive and requires little manual input.
The xylene solubles content which relates to various performance characteristics, particularly hardness, can be calibrated against TD-NMR to match the results of ASTM D721 and other methods.
Plasticiser is added to alter the softness and flexibility of PVC. TD-NMR can be used to monitor this process to ensure products are suitable for their intended applications.
Various grades of polyethylene are defined by their density (LLDPE, LDPE and HDPE) which correlates with crystallinity. Therefore, TD-NMR measurements are important for quality control of these polymers.
Both oil and polybutadiene are added to increase the flexibility and impact resistance of polystyrene. Both are measurable and therefore can be monitored by TD-NMR.
In addition to hydrogen, which is abundant in many polymers, TD-NMR can also selectively measure fluorine content in PTFE and various other fluorinated polymers and rubbers.
Rubber is heat treated with sulphur (vulcanisation) to increase its cross-linking density and as a consequence, hardness and durability. Oil is added to soften rubber for ease of processing or its intended use. In common with most polymer measurements, TD-NMR is sensitive to and therefore can be correlated to the hardness/softness which, in many cases, is altered by a chemical process or additive.
To read about measurement of these and other polymer measurements, visit our website.
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