MFFT Bar: The Industry Standard for MFFT Testing

Liquid Coatings Testing

The Rhopoint MFFT Bar, distributed by GARDCO, is a precision bench-top instrument designed to measure the Minimum Film Forming Temperature and white point of water-based coatings, polymer dispersions, synthetic latexes, and emulsion. The MFFT also tests adhesives temperature optimization in such areas as coalescence of water-borne adhesives and minimum temperature for epoxy resin cure. The apparatus, which consists of a block with an electronically controlled plate ensuring a smooth temperature transition, allows the temperature to be read at the point where the non-cracked film is formed. This self-contained system provides a highly accurate and controlled determination of MFFT, helping manufacturers and formulators optimize their products for specific environmental conditions while ensuring their paints and coatings perform correctly.

The MFFT Method

The MFFT Bar operates on a simple but effective principle. A dull, nickel-plated copper plate is cooled electronically at one end and warmed at the other. Air or nitrogen flows uniformly over the plate, creating a controlled temperature gradient. The sample is applied as a thin film across the temperature gradient.

The air or gas is delivered via a carefully designed sintered metal distribution block to achieve the required uniformity. The design is such that freezing does not take place at the inlet. A drying system is incorporated into the housing with a flow controller for air use. The air dryer contains indicator crystals visible in their transparent container. The complete air conditioning system is accessible at the side of the instrument.

Water at standard mains pressure removes the excess heat from the coolers. In environments where the ambient water temperature is high, use a recirculating chiller to reduce the temperature. Quick-release couplings are provided. Water is usually drawn from a laboratory tap and the outlet is run to drain by gravity. Alarms, both audible and visible, protect the cooling water supply.

Temperature sensors are mounted at intervals under the surface of the platen and are used to control the platen's temperature in accordance with the chosen program. They are also used to indicate platen temperatures down the length of the bar. A hinged viewing cover over the platen provides thermal insulation while allowing visual inspection of the determination as it progresses. As the sample dries, the temperature at which it forms a continuous, non-cracked film is recorded as the MFFT.

This method is described in ASTM D2354, which details the MFFT Bar procedures. While the test is generally performed directly on the copper plate, standards like ASTM D2354 recommend placing a polyester film between the sample and the plate to prevent contamination. ISO 2115 suggests using aluminum foil and a thin layer of glycerin as an alternative.

H2 Applications of MFFT Testing

• Paints and Coatings: The MFFT test is essential for water-based paints and coatings to ensure they form a continuous film at the specified application temperatures. Accurately determining MFFT helps formulate paints that perform reliably in varying environmental conditions, preventing failures such as cracking or peeling.
• Adhesives: The MFFT of one-part adhesives is determined similarly to coatings. While two-part adhesives do not exhibit an MFFT, the minimum cure temperature can be established using the MFFT Bar. The minimum cure temperature ensures optimal adhesive performance in different temperature environments.
• Epoxy Resins: MFFT testing is also used to optimize the curing temperature of epoxy resins, ensuring that they coalesce and cure correctly without cracking or defects.

Importance of MFFT in Product Development and Quality Control

Accurate MFFT determination is vital in product development and quality control for paints, coatings, and adhesives manufacturers. With a known MFFT, formulators can adjust the use of coalescing agents, plasticizers, and other additives to optimize their products' curing and film-forming properties. The MFFT test is also crucial for ensuring batch-to-batch consistency, which is vital for maintaining the performance and durability of coatings in real-world applications.

Standards & Certifications

• ASTM D2354: Standard Test Method for Minimum Film Formation Temperature (MFFT) of Emulsion Vehicles. The MFFT test is performed directly on the MFFT Bar plate; however, to keep the instrument clean, the ASTM D2354 standard suggests that a drawdown should be performed on a polyester film placed on the build plate and electrostatically equalized with a cloth.
• ISO 2115: Plastics—Polymer dispersions—Determination of white point temperature and minimum film-forming temperature. The MFFT test is performed directly on the MFFT Bar plate. However, to keep the instrument clean, the ISO 2115 standard suggests a drawdown should be performed on aluminum foil, with thinly dispersed glycerin used as the temperature-conducting layer from the working plate to the foil.

Both standards provide excellent guidelines for accurately determining the MFFT

Frequently Asked Questions

1. How can I verify that the MFFT operating temperature is correct?
   

   To verify the MFFT is functioning correctly at a set temperature, set the instrument to program range one and allow the platen to stabilize. Then, check the temperatures at points 1 through 10. Point 1 should read -5°C and point 10 should read 13°C. There should be an even temperature gradient between all points.

2. Is Calibration of the MFFT recommended?
   

   The MFFT instrument is equipped with precision temperature sensors on the back of the measurement platen. These sensors are referenced to highly stable precision resistors that maintain accuracy over time and under different ambient conditions. Because of this, the instrument is self-calibrating and requires no manual calibration.

The Minimum Film Forming Temperature (MFFT) is a critical parameter for effectively applying and performing paints, coatings, adhesives, and polymer dispersions. The Rhopoint MFFT Bar provides a reliable, standards-compliant method for determining the MFFT, helping manufacturers optimize their formulations for different temperature conditions. Accurate MFFT testing ensures that products form consistent, high-quality films, reducing the risk of defects and improving overall performance.