rhopoint instruments ltd minimum minimum minimum minimum minimum film-forming film-forming film-forming film-forming film-forming tempera tempera tempera tempera tempera ture bar ture bar ture bar ture bar ture bar n self - contained bench-top instrument for the determination self - contained bench-top instrument for the determination self - contained bench-top instrument for the determination self - contained bench-top instrument for the determination self - contained bench-top instrument for the determination of the minimum film - forming temperatures of synthetic of the minimum film - forming temperatures of synthetic of the minimum film - forming temperatures of synthetic of the minimum film - forming temperatures of synthetic of the minimum film - forming temperatures of synthetic latices, emulsions, polymers & adhesives latices, emulsions, polymers & adhesives latices, emulsions, polymers & adhesives latices, emulsions, polymers & adhesives latices, emulsions, polymers & adhesives n electrically - controlled heating & cooling with integral air electrically - controlled heating & cooling with integral air electrically - controlled heating & cooling with integral air electrically - controlled heating & cooling with integral air electrically - controlled heating & cooling with integral air processor processor processor processor processor
specification platen ............................copper, dull nickel plated (other options available). platen dimensions ........483mm x 235mm. parallel tracks ................using 1" cube applicator supplied: max 10. weight ............................38kg. (851b). dimensions ....................550mm wide x 350mm high x 610mm deep. temperature sensing ....10 points on centreline at width intervals 37mm. display ...........................point temperature and temperature differential between adjacent points. sensor accuracy .............0.1 degrees c+.070c indication ......................lamps: instrument on, heating, cooling. alarms ............................audible and visual for water flow failure. minimum film-forming temperature bar services required mains 220-240 volts a.c. 110-115 volts a.c. air 4 litres/min @ 100 psig water normal mains supply water drain gravity complete instrument comprises MFFT instrument mains cable air connector water connectors roving temperature sensor type 166-177 c. cube applicator. 75 x 1" cube guide bar quantity - dessicant quantity - indicator crystals 5 hypodermic type dispensers spatula spare fuses instruction book hinged transparent cover plate raised allows clear access for track laying and cleaning. special options extended range by the addition of three programmes, 43-70, 53-80,63-90 deg c. unplated copper platen unit for nitrogen supply, no air processor fitted optional extras additional cube applicators frame for up to 5 applicators MFFT determina tion: one continuous track displays the evenness of the heating, cooling and air flow. a photographic record of the performance of every instrument is made before despatch.
minimum film-forming temperature bar a nickel plated copper platen is electronically cooled at one end and warmed at the other end. air or ni- trogen is caused to flow over the surface, from cool end to warm end as a uniform blanket. to achieve the required degree of uniformity the air or gas is delivered via a carefully designed sintered metal distribution block; the design is such that freezing does not take place at the inlet. for use with air, a drying system is incorporated into the housing together with a flow controller. the air dryer contains indicator crystals which are clearly visible in a transparent container. the com- plete air conditioning system is readily accessible at the side of the instrument. water at normal mains pressure removes the ex- cess heat from the coolers. quick release couplings are provided. water is normally drawn from a labo- ratory tap and the outlet is run to drain by gravity. alarms, both audible and visual are actuated in the event of cooling water supply failure. principle of operation the minimum film-forming temperature has been described as the minimum temperature at which a water-borne synthetic latex or emulsion will coa- lesce when laid on a substrate as a thin film. when this process occurs, in the absence of pigmenta- tion or other opacifying materials, a clear transpar- ent film is formed. at lower temperatures than the minimum, a white, powdery, cracked film will re- sult. the minimum film-forming temperature is usually closely related to the glass transition temperature tg but not synonymous with it; whilst the tg may be determined by predicted calculation, the minimum film-forming temperature is best determined by the use of a MFFT bar; the basic principles of which are described in astm d2354. early instruments were usually cumbersome, inaccurate and slow to achieve equilibrium. i.c.i. plc devised a simple inte- grated instrument which was able to achieve the de- sired results quickly and efficiently. the initial de- velopment was carried out in i.c.i. paints laborato- ries. temperature sensors are mounted at intervals under the surface of the platen. these are used to control the temperature of the platen in accordance with the chosen programme. they are also used to indicate the platen temperatures down the length of the bar, or they can be switched to indicate differential tempera- tures between adjacent sensing points, so providing an instantaneous indication of temperature gradient. a roving probe temperature sensor is provided to facilitate temperature measurement at every point on the platen, it also serves to check the static sensors. a hinged perspex cover over the platen provides thermal insulation whilst allowing visual inspection of the determination as it progresses. a transparent cursor is mounted on the cover to simplify the iden- tification of the exact minimum film-forming tempera- ture. programmes standard model MFFT-60 degrees c. cool end (left) -5 0 +5 +15 +23 +33 warm end (right) +13 +18 +23 +33 +50 +60 extended range model MFFT 90 additional programmes cool end +43 +53 +63 warm end +70 +8 +90
operation in practice the instrument is switched on and the programme chosen, air and water having been connected. an equilibrium con- dition is noted after about 20 minutes (the time may be less dependant on the pro- gramme chosen). at equilibrium the heat- ing cooling lamps illuminate at very low fre- quency. several tracks are laid down in quick succession using an applicator, normally a 75 micron (3 mil.) cube applicator. the tracks may be laid down left to right or right to left, but the most common form is a u horizon- tal, with the track starting and finishing at alarm and on module 1 mains switch -on/ off 2 coolant failure alarm 3 coolant failure lamp 4 heating lamp indicator 5 cooling lamp indicator the right, warm end. two tracks are nor- mally laid down last as a control, using an emulsion of known MFFT. a clearly defined limit of coalescence will show in about 80 minutes and the cursor may then be used to read off the MFFT temperature. pigmented emulsions may be tested but the determination is more diffi- cult to see. most operators, however, find that they can readily discern the determi- nation temperature. this can be proven by gently scraping the surface of the film us- ing a wooden spatula. indication module 6 temp. display 7 probe socket 8 temp. mode switch 9 temp. sensor selector the air conditioning and control unit, showing the air connection control module 10 heating led 11 cooling led 12 programme selector rhopoint instrumentation ltd rhopoint instrumentation ltd beeching road, bexhill-on-sea east sussex, tn39 3lg email: instrumentation@rhopoint,co,uk shipping details carton dimensions.. 29 x 18.5 x 26 737mm x 470mm x 661mm gross weight.......... 106lb, 48kg the roving probe the MFFT bar is manufactured under licence to i.c.i.plc 75 micron ring applicator 75 micron cube applicator
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