Measuring Glass CTE, Glass Transition, and Softening Point with a Horizontal Push-Rod Dilatometer

The horizontal push-rod dilatometer measures the coefficient of thermal expansion (CTE), glass transition temperature, and softening point of glass. Under a programmed temperature profile and a load approaching zero, it measures specimen dimensional change as a function of temperature or time. Its horizontal furnace uses a tubular specimen carrier, a nearby thermocouple, and a c-DTA function that measures endothermic and exothermic effects during thermal-expansion testing.

Prepare a cylindrical specimen 6–8 mm in diameter and 50 mm long or a rectangular specimen of (6–8) × (6–8) × 50 mm. If the prepared length differs slightly from 50 mm, record the actual length. Switch on the instrument, open the furnace, place the specimen parallel to the specimen carrier with good contact against the displacement push-rod, and move the furnace so the specimen is centered in the heating zone.

Check the displacement display; if its reading is above or below approximately 2000, adjust the displacement knob when that function is available. Some instrument versions do not have this adjustment. Press the Work/Start button and allow the instrument to stand for 5–10 minutes until the displacement reading is stable. Set the temperature-control curve in the test software, enter the specimen length and end-temperature parameters, and start the test from the Test Control interface. The instrument heats according to the programmed curve, records and processes the data, and calculates the average linear expansion coefficient at each temperature point.