Читать книгу The Rheology Handbook - Thomas Mezger - Страница 173

1 Borderline pumping temperature (BPT)

2 Cloud point (CP; ISO 3015; ASTM D2500, D7467, D5771 – stepped cooling method, D5772 – linear cooling rate method, D5773 – constant cooling rate method, D7397; DIN EN 23015)

3 Cold filter plugging point (CFP; ASTM D4539, D6371, DIN EN 116, DIN EN 16329, IP 309)

4 Congealing point (ISO 2207; ASTM D938; DIN ISO 2207)

5 Crystallization point

6 Drop melting point (ASTM D127)

7 Dropping point (ISO 2176; ASTM D566, D2265, D3954; DIN ISO 2176)

8 Flocculation point

9 Freezing point (ISO 3013; ASTM D2386)

10 Gelation point

11 Melting point (ASTM D87)

12 No-flow point (ASTM D7346)

13 Pour point (PP; ISO 3016; ASTM D97, D5950; DIN ISO 3016; IP 15). When cooling under the specified conditions, PP is the lowest temperature at which a petrochemical sample is still able to flow.

14 Solidification point

15 Wax appearance point (ASTM D3117)

Here, some frequently used methods of determination and criteria are explained briefly.

M1) Optical method: When cooling, the cloud point is reached at the temperature at which the previously transparent sample becomes turbid and “cloudy” due to the precipitation of paraffin crystals.

M2) Filter method: When cooling, the period of time increases which is needed to pump a certain amount of sample through a fine-meshed filter (e. g. CFP point).

M3) Sagging method: When cooling, the pour point (PP) is reached at the temperature at which the sample still flows off a vertical surface. First the solidification point (SP) is determined as the point at which the sample is no longer able to flow at the transition from the liquid to the solid state. Afterwards is added ΔT = 3 K, thus: PP = SP + 3 K.

M4) Yield point method: When cooling, the yield point occurs at the critical temperature when measuring with a simple rotational viscometer, for example, at a constant low shear rate or shear stress, respectively. This gives insight into problems with pumping processes, such as start-up of pumping and continued pumping (e. g. BPT point).

M5) Flow cup method: When heating, the dropping point is reached at the transition temperature from the solid state to the liquid state, i. e., when the sample begins to flow through the orifice in the bottom of the flow cup (e. g. dropping point acc. to Ubbelohde [3.84]).

Comment: All the above-mentioned simple methods are dependent on the test conditions and the skill of the tester. The methods therefore can only deliver relative values, as well as those obtained by the simple tests covering cooling behavior, described in Chapter 11.2.11 (d to f and h to k). Recommended methods for determining the crystallization or melting temperature are explained in Chapter 8.6.2.2a (oscillatory tests).