The Cambridge Trimaster 2013

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This presentation describes the Development of the "Cambridge Trimaster" filament stretch, thin and breakup device

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The Cambridge Trimaster 2013

  1. 1. Salcombe, Devon 2013The Cambridge Trimaster by Malcolm Mackley 1
  2. 2. The 1990s Filament stretching and thinning of fluids has been extensivelystudied for many decades and in particular in relation to the so called TroutonRatio, which is the ratio of the extensional viscosity to the simple shearviscosity. Newtonian fluids have a Trouton ratio of 3, however polymer basedfluids can have Trouton ratios much greater than 3. The Polymer Fluids Group at Cambridge had a long term interest inextensional behaviour and in the 1990s we had the opportunity to purchasewhat we called “The Russian Rheometer”. This was a period of great change inRussia and in order to purchase the rheometer, money had to be sent to aCanadian bank account and our Technical Officer, Robert Marshall was askedto collect the apparatus by hand from a pub in East London! Dr Ruifeng (Ray) Liang was working in the Group at the time and hecarried out a range of filament thinning experiments using the apparatus. Thetrigger mechanism to form the initial filament was not totally reproducable,however the optical centre line detector measuring filament thickness as afunction of time worked well. 2
  3. 3. Filament thinningA.V.Bazilevsky, V.M. Entov and A.N.Rozhkov3rd European Rheology Conference 1990 Ed D.R.Oliver The “Russian Rheotester” C A B E 15 cm D 3
  4. 4. Liang and Mackley (1994)- Extensional Rheotester Newtonian modelling • τzz τ zz = − p 0 + 2η γ zz = 0 • τrr Top plate τ rr = − p 0 + 2η γ rr = −2σ / D •1• D= εDBottom plate 2 • Extensional rheotester τ E = τ zz − τ rr = 3η ε = 2σ / D • 2σ ε= 3ηD • η E = τ E / ε = 3η σ D(t ) = D0 − t 3η 4 Newtonian fluids give a linear decay
  5. 5. Liang and Mackley (1994)- Viscoelastic fluidS1 fluid First approximation  1  D (t ) = D0 exp −  3λ t   R  Viscoelastic modelling • τ E = 3η ε d = 2σ / D • • • τ E = g ε s = −2σ D/ D 2 • •PIB solutions εd = εs • D/ D = − g / 3η  g  D (t ) = D0 exp − t   3η    5 Polymer fluids can give an exponential decay
  6. 6. The 2000s In the 2000s the importance of ink jet rheology became apparent toboth ink formulators and ink jet device manufacturers. Ink jet fluids usuallyhave a low viscosity and their filament stretch and breakup behaviour whenthe ink leaves the ink jet nozzle can be crucial in relation to performance. Thedrop breakup times of order ms can be particularly sensitive to formulation. The stretch and experimentally measurable filament thinning timescales for the “Russian Rheometer” were too long for ink jet fluidcharacterisation and so Dr Tri Tuladhar, working in the Polymer Fluids Groupat Cambridge, evaluated the Cambridge Multipass Rheometer (MPR) as apotential fast filament and stretch and breakup device. The MPR proved to be an excellent filament stretching device as thetwin piston movement was very fast and precise and the pistons werecontrolled by the servo hydraulics of the apparatus. An additional bonus ofthe apparatus was that the two pistons could move in opposite directions,leaving the centre of the fluid in a fixed position. We now call this MPRconfiguration the MK1 Trimaster. In order to capture the ms timescales of theexperiment it was necessary to use a high speed camera. 6
  7. 7. The Mk1 Trimaster, MPR Filament stretch Rheometer Vp D R(z,t) Top Piston Lf Rmid(t) L0 Bottom Piston Vp(a) Test fluid positioned (b) Test fluid stretched uniaxially (c) Filament thinning and break upbetween two pistons. at a uniform velocity. occurrence after pistons has stopped. t<0 t≥0 7
  8. 8. MK1 Trimaster resultsSequence of high speed video images showing filament stretching, thinning and break-up of Series I, DEP solvent and DEP-PS 8solutions, (the piston diameter in all sequence is 1.2 mm). Initial sample height of approximately 0.35mm fluid is stretched to1.35mm by moving each piston 0.5mm apart at a constant velocity of 200 mm/s.
  9. 9. MPR Filament stretching and thinning of DEP solution DEP DEP + 5.0 wt% PS1.2 mm Piston diameter = 1.2 mm Initial stretch velocity = 200 mm/s Initial sample height = 0.35 mm Final sample height = 1.35 mm (piston displaced by 0.5 mm each side) 9
  10. 10. The Mk2-4 Cambridge Trimasters The Mk1 Cambridge Trimaster was an effective apparatus, butwe felt at the time the use of the MPR servo hydraulics to activate thepistons was “rather like using a sledge hammer to crack a nut.” In additionwe wanted to produce a lower cost unit that potentially could be used byothers. In 2008 The Mk2 Cambridge Trimaster was designed as a purposebuilt Filament stretch, thin and breakup device. The unit worked on thesame principle as the MK1 with equal and opposite piston movements,however the drive was from a single stepper motor. The Mk2 Trimasterproved to be an effective apparatus and both Dr Tri Tuladhar and DrDamien Vadillo carried out useful experiments with the apparatus. In an attempt to achieve higher piston speeds than the Mk2Trimaster a Mk3 unit was prototyped using voice coil activation. Thisapparatus was designed and built by a Company “The Ideas Studio”,however it was not a success and the project was abandoned in 2010. Currently (2013) a Mk4 HB Trimaster manufactured by aCompany Huxley Bertram is being trialled and this instrument looks verypromising. 10
  11. 11. The Mk2 CambridgeTrimaster “A dream turning into a reality” Toothed belt Linear guide rail timing pulley Carrier Timing belt Replaceable top and bottom plateStepper motorattached to a pulley 11 Graphics courtesy of James Waldmeyer
  12. 12. Non Linear Viscoelasticity (NLVE) The Mk2 Cambridge TriMaster Filament stretch and droplet break uppistonsamplebeltpulley 12
  13. 13. Mk2 TrimasterFilament thinning a(a) DEP,(b) DEP + 0.2% PS110,(c) DEP + 0.5% PS110,(d) DEP + 1% PS110, b(e) DEP + 2.5% PS110.Initial gap size: 0.6mm,Stretching distance:0.8mm, cStretching velocity:150mm/s d e 13
  14. 14. “Trimasters”Tri Tuladhar Damien Vadillo 14
  15. 15. The Huxley Bertram MK4 HB Trimaster (2013) 15

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