Minimum filming temperature

The minimum film temperatures (MFT) were determined using a MFT tester which consists of a graduated grooved metal temperature bar (13). Crack points were the highest temperatures at which visual discontinuities were present. The knife point MFT was the minimum temperature at which the film first exhibited continuity while being scrapped from low to high temperature. 

The surface characteristics of a two-stage polymer were compared against those of a corresponding blend and copolymer latex by minimum film temperature analysis (11) (Table XVI). 

Transmission and scanning electron microscopy, differential scanning calorimetry and minimum film temperature analysis supports a core/shell morphology for the two-stage latex polymers, consisting predominantly of a polystyrene rich core surrounded by a soft acrylic rich shell. 

The essential property of any polymer used as an adhesive is that it should have good cohesion and stick to the surfaces it joins. This can occur only if the polymer forms a film on application or at some stage during the joining process. In the case of a water suspension such as a PVA or an EVA adhesive, this involves a smooth coalescence of the polymer particles as the water evaporates. For this to occur, the polymer must be above its minimum filming temperature (MFT). Some applications lend themselves to the application of heat. However, most rely only on the evaporation of water at ambient temperature, coupled with absorbence (or wicking ) into the substrate, if porous. 

Various thermal material properties (as opposed to thermal stability. Chapter 9) are discussed in Chapter 16. These include coefficient of expansion, melting temperature, Vicat softening point, heat deflection/distortion temperature by thermomechanical analysis, also brittleness temperature, minimum filming temperature, delamination temperature, meltflow index, heat of volatilisation, thermal conductivity, specific heat and ageing in air. 

Low ambient temperature is quite detrimental to water-based emulsion adhesives. When the temperature is too low, the dispersed polymer particles will not coalesce or fuse together, and it will prevent the formation of a strong continuous film of adhesive. Instead, a powdery, cracked film will occur if the temperature is lower than a required minimum. There is a minimum film-forming temperature (MFFT) below which there will be no film formation and consequently no bonding. This temperature may be measured with several test methods ASTM D 2354 and ISO 2115, by using specific equipments such as the Sheen Instrument minimum film temperature bar (Fig. 19) a naicroprocessor controlled stainless steel plate is cooled at one end and heated at the other. The sample to be tested is laid down at 75 JLm film thickness and 25 mm width. After 45 -90 min, a clearly defined coalescence zone will be visually obvious, and the temperature at this point will be recorded as MFFT. 

Tlie minimum film temperature for this run may possibly have been as lu e li as 2.V( lower than the 400°C reported because of an error involved in i-lertiiig the actual cooling area. 

T and are the glass-transition temperatures in K of the homopolymers and are the weight fractions of the comonomers (49). Because the glass-transition temperature is directly related to many other material properties, changes in T by copolymerization cause changes in other properties too. Polymer properties that depend on the glass-transition temperature include physical state, rate of thermal expansion, thermal properties, torsional modulus, refractive index, dissipation factor, brittle impact resistance, flow and heat distortion properties, and minimum film-forming temperature of polymer latex... 

From the electron micrographs, assuming that PVAc particles in the latex are the same size, the formation model of the porous film from the latex film can be illustrated as in Fig. 3 [19]. When the latex forms a dried film over minimum film-forming temperature, it is concluded that PVA coexisted in the latex and is not excluded to the outside of the film during filming, but is kept in spaces produced by the close-packed structure of PVAc particles. 

Minimum boiling azeotropes, 3 802-807 Minimum film-forming temperature (MFFT), 16 291 20 378-379 Minimum film thickness equation, 15 211 Minimum fluidization velocity, 11 793, 797-798... 

Specifications and Standards. Borax stability is an important property in adhesives, paper, and textile applications. Ollier emulsion properties tabulated by manufacturers include tolerance to specific solvents, surface tension, minimum film-forming temperature, dilution stability, freeze-thaw stability, percent soluble polymer, and molecular weight. 

The freeze/thaw (F/T) stability of a polymer emulsion serves as a macroscopic probe for investigating the properties of the average particle in a polymer emulsion. A review of the factors which contribute to this stability is included. A study of styrene-ethyl acrylate-methacrylic acid polymers shows the existence of a minimum in the plot of minimum weight percent acid required for F/T stability vs. the minimum film formation temperature (MFT) of the polymer. This is considered to be a function of both the amount of associated surfactant and the minimum acid content. Thus, both the type of surfactant and the copolymer ratio—i.e., MFT—play major roles. Chain transfer between radicals and polyether surfactant resulting in covalently bonded surfactant-polymer combinations is important in interpreting the results. 

Minimum Film Formation Temperature (MFT). Equipment described by Protzman and Brown (24) was built, calibrated, and used for all measurements. A series of 25% emulsions, adjusted to pH 9.5 with NH3, was used throughout unless otherwise indicated. 

Note MFFT, minimum film-forming temperature. Source Arkema, Inc., 2008 (With permission). 

Minimum Film Formation Temperature C >90 Ionic Charge Anionic pH as packed 9.8 Density Ibs/US gal 8.7 Brookfield Viscosity, cP 100 Performance Properties ... 

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