Determination of MFFT

ASTM D 2354

 Minimum Film Forming Tester

Scope and Field of Application

Emulsion paint are formulated so that when they are applied to a substrate, the water evaporates and the resin particles that form the binder (latex) coalesce to form a continuous film. Low temperature hinders coalescence and for any latex there will be a temperature below which coalescence does not occur. This is known as the minimum film forming temperature (MFFT).

It is generally possible to improve the coalescing properties of latices by the addition of small amounts of relatively involatile organic solvents which remain in the film long enough to soften the latex particles and aid coalescence. This approach however conflicts with environmental pressures to produce coatings which are free from volatile organic compounds (VOC's).

It is important to emphasise that the test method described on this page only applies to latices i.e. one of the raw materials that is used to make emulsion paints. It cannot be used to determine the MFFT of emulsion paints as such. If you are interested in the film forming properties of emulsion paints, please refer to our scrub resistance test page.

There is no pass/fail criteria defined in the standard. This is a matter of agreement between the parties concerned.

The actual standard is a copyright-protected document and we are not able to provide you with copies. If required however, you can easily obtain copies from the American Society for Testing and Materials.

 

Summary of Method

We carry out this determination using a Rhopoint model MFFT-90 minimum film forming temperature bar. The apparatus consists of a horizontal metal stage across which a temperature gradient can be established by means of electric heating and Peltier cooling. The temperature obtainable ranges from about -5 to 90°C.

A film of the latex under test is cast along the stage and left to dry. A visual inspection of the dry film is then made to determine the position along the length of the film where it changes from the coalesced to the non-coalesced state. A non-coalesced film shows whitening and/or cracking. The lowest temperature at which the film is coalesced is reported as the MFFT.

 

Sample Requirements

We require no more than 100 g of sample.

 

Accreditation

Although PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS), we are not accredited to carry out this particular test.

 

Please contact Peter Collins for further details.

 

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