Mercury Dilatometer Facility |
| Measuring the volumetric shrinkage or expansion of polymeric materials, such as dental composites, has been limited to determining the final values by measuring changes in density resulting from polymerization. No method has been available for dynamically determining the rate and time dependence of shrinkage or expansion in polymers subjected to chemical or photo polymerization. An instrument has been developed that dynamically measures volumetric displacement of polymer samples as they cure. This instrument immerses the sample within a mercury tube, much like a thermometer, and records the change in height of the mercury column with time. The thermal changes in the mercury volume are factored out by simultaneously measuring the temperature in the mercury column and using the expansion coefficient for metallic mercury. The result is a dynamic plot of volume percent change of the polymer with time. Samples can be measured for prolonged periods to determine final volume changes and result correlate closely with those determined by density measurements and measures of degree of conversion. |
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Contact Information |
| Dr. Fred Eichmiller (301) 975-6813 Email: fred.eichmiller@nist.gov |
| NIST Materials Science & Engineering Laboratory - Polymers Division |
