Used to determine the minimum film forming temperature of polymer emulsion. The film forming property of polymer emulsion is one of the important properties when it is used as surface treating agent for coating, adhesive, chemical fiber fabric, leather and paper.A polymer emulsion or latex paint is applied to a metal plate. Upon evaporation of water, the polymer particles interact to form a continuous transparent film at an appropriate temperature.The critical critical film forming temperature is called the minimum film forming temperature of the polymer emulsion or MFT temperature for short.
Test Standard:GB/T9267-2008 and ISO2115-76
Principle of the minimum film-forming temperature tester:
A suitable metal plate is provided with a cooling source and a heating source respectively, and the temperature is maintained at the constant temperature point of the set temperature. Different temperature gradients are generated on the metal plate through the principle of metal heat conduction.A sample of uniform thickness is coated on the gradient plate and the sample is subjected to evaporation of water at the gradient plate temperature to form a film.The phenomenon of film formation is different due to the different temperature on the gradient plate.Finding the dividing line is the MFT temperature of the sample.
Gradient plate temperature range: – 10 ℃ to 50 ℃ between arbitrary regulation
Gradient interval: 20 mm
Gradient board detection point: 13 points
Test coating tank: 6 (length 240mm, width 22mm, depth 0.25mm)
The inspection table shows: 16 points, 1 ~ 13 points are the working gradient temperature, 14 points are the instrument environment temperature, 15, 16 points are the cooling water inlet and outlet temperature.
Open the packing cases (the cases can be used again and again, please keep them for future maintenance and transportation) and check whether there is any breakage or shortage.After verification, place the instrument in the laboratory near the upstream and downstream water, and do the cleaning work first.Then check the power input, the inlet and outlet of the water connection is correct.
Preparation before use:
Connect the power cord to the power socket (220v, 50Hz three-hole socket, must be well grounded), connect the cooling water, turn on the main power switch, heating, inspection, refrigeration switch, the instrument panel immediately shows the corresponding action (indicator light, digital display table shows the number).
Different test conditions shall be set according to the different conditions of the film tested.It is mainly for refrigeration and heating presetting (see the manual of lu-906m intelligent regulator for setting method). The inspection table has been adjusted before leaving the factory, and generally no adjustment is required.
The time is about 120 minutes (depending on the setting temperature, if it is found that the inspection table is stable or has little change at every point from 1 to 13 within a certain time, it is the preheating), then the sample can be added.The equilibrium time depends on the minimum temperature setting. The lower the temperature setting, the longer the equilibrium time.The desiccant can be placed in the box at the same time, which can greatly avoid water vapor and freezing at the cold end.
Remove the glass cover and put the emulsion to be tested and known into the gradient plate groove with a spoon or dropper.(for glass products, please handle with care)
Sample film formation:
After about 60 to 90 minutes, a series of changes take place in the coating on the gradient plate. After water evaporates from the emulsion used in latex paint, the polymer molecules interact with each other and form a continuous film at an appropriate temperature. The part higher than the emulsion MFT is transparent, and the part lower than MFT is cracked or chalky.The clear dividing line is the minimum film forming temperature (MFT) of the emulsion. After determining the film forming line, the accurate temperature is calculated with the subdivision scale of the ruler according to its position.
After the test, shut off the power supply and water source, clean all parts well, and prepare for the next test.