What Is a Dilatometer?

Dilatometers are completely manual devices designed to measure the linear thermal expansion of a variety of materials and are suitable for teaching, laboratory, and industrial applications. Just put the material you want to measure into the test box and push the test box into the furnace. When the test material is heated, it begins to expand. This is what people call thermal expansion. When the material undergoes thermal expansion, its expansion will be displayed on a digital displacement function converter.

Dilatometer is a completely manual device designed to measure the linearity of multiple materials

The structure is shown in Figure 1. The operation steps of the dilatometer are as follows: the expansion bubble 1 is weighed (W ₁ ), and about 1.0 ml of the monomer to be polymerized is filled and weighed (W ₂ ). The monomer in the expanded bubble is welded to the capillary under the freezing of liquid nitrogen. Mercury bubbles are filled with about 4 ml of pure mercury. The dilatometer is connected to the high vacuum system from 6 locations. The monomer in 1 is frozen under liquid nitrogen, the piston 8 is opened, and the vacuum is evacuated to 10 ^-3 -10 ^-4 mmHg.

Some monomers are in the gas phase at normal temperature, and they can be converted into liquid phase only under a certain pressure. To this end, we designed a bulk polymerization dilatometer suitable for pressure, and its structure is shown in Figure 4.

It is difficult to measure the polymerization progress of solution copolymerization under pressure using a dilatometer. We designed a dilatometer to measure the radiation copolymerization process of ethylene and trifluorochloroethylene with trifluorotrichloroethane as a solvent, and obtained satisfactory results. The structure of the dilatometer is shown in Figure 6.

Image 6

The operation steps are as follows:

1. The copolymerization solvent and monomer system configured in a certain proportion in the pressure map are quantitatively poured into the transfer bottle 4 under liquid nitrogen freezing. Under liquid nitrogen freezing, the bottle 4 was welded to 9 places.

2. Quantitative mercury injection from the branch tube 5 into the expansion bubble 1, and then 5 is connected with the rubber tube 15 for the high vacuum system. Close the piston 10.

3. Open the piston 6, the dilatometer is in communication with the vacuum system, and a part of the mercury in the expansion bubble rises along the capillary 12 to the mercury storage ball 2. Freeze immediately with liquid nitrogen. Therefore, the mercury remaining in the bottom of the expansion bubble is frozen, so that the mercury filled in the capillary tube and 2 will not fall, and at the same time, the lower mouth 13 of the dilatometer is sealed, and sufficient space is left in the upper part of the mercury surface in the expansion bubble. For body infusion.

4. Close piston 6, open 10, evacuate to 10 ^-3 -10 ^-4 mmHg, close 10. Remove the liquid nitrogen from 4 and freeze it, so that the monomers and solvents in 4 are vaporized (which can be slowly heated) and transferred to expansion bubble 1. Because 1 is kept in the liquid nitrogen frozen state, the solvents and monomers in 1 are transferred to 1. Immediately frozen. Open 10, evacuate to 10 ^-3 -10 ³⁴ mmHg, close 10. Fuse from 7 places.

5. Inject a small amount of comonomer of the same proportion into the pressure equilibrium bubble 3 under liquid nitrogen freezing from the piston 11. After evacuating from 6 locations, it melted from 8 locations.

6. Complete the above operation of the dilatometer, remove the liquid nitrogen to freeze, freeze the monomer and solvent and mercury. Mercury presses monomer and solvent from 2 to 13 to the upper part of the expansion bubble. Then the dilatometer was placed in the prescribed dose intensity position in the constant temperature water bath of the irradiation room, the recording instrument was switched on, the zero point was adjusted, and the source was polymerized by irradiation ^[2] .