TVI - Tomasetti Volatile Index
The TVI test, which measures residual moisture, is an inexpensive and accurate method of testing materials for acceptable dryness and only works with amorphous and uncharged or reinforced polymers.
Moisture test (TVI test)
The test, called the Tomasetti Volatile Indicator (TVI), requires very little equipment and is performed in just six easy steps. The necessary equipment consists of a heating plate capable of maintaining 274°C, two standard glass microscope slides, tweezers and a few wooden dowels. The procedure is the next:
Place the two slides on the surface of the heating plate (which has been preheated to 274°C) for 2 minutes, after 2 minutes, with the forceps two or three granules are placed on one of the slides after which the second slide, sandwiching two slides with the granules between the slides. Using the wooden plugs, the slides are compressed to flatten the granules to a diameter of approximately 12-13 mm. Using tweezers, they remove the paired display cases from the hot plate and allow them to cool for about 5 minutes. At this point an approximate calculation is made of the total area of any bubbles formed, compared to the area of the flattened granules. The proportion that can be interpreted as the percentage of moisture present in the original granules. Using the TVI test will provide approximate moisture content. The fewer bubbles there are, the less moisture there will be. This test is not accurate for glass reinforced polymers, but can still be used as a reference test. If only one or two bubbles are found, it could be trapped air rather than moisture, so the material can be considered dry. If the result is contradictory (granules with bubbles, granules without), repeat the test.