Melt tension measurement (Haul-Off)

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1 Göttfert Werkstoff-Prüfmaschinen GmbH Siemensstraße Buchen info@goettfert.de Internet: WERKSTOFF-PRÜFMASCHINEN GMBH Melt tension measurement (Haul-Off) The Haul-Off system is a melt tension measurement for polymer melts. The Haul-Off system measures the extensional properties of polymer melts by drawing a vertical melt strand at a constant pull-off speed or with a linear or exponentially accelerating velocity. The Haul-Off system measures the force needed to elongate the strand, and calculates elongation stress, draw ratio and apparent elongation rate and viscosity. The instrument is best used in combination with a suitable capillary rheometer (e.g. GOETTFERT RHEO-TESTER 1 or GOETTFERT RHEOGRAPH 6) where the device can be located close to the exit of the capillary. It may also be used with an extruder (e.g. GOETTFERT Extrusiometer) using a 9 deflection head (or exit) die. The melt strand is taken-off only vertically. Technical features of the Melt tension measurement device: Freely selectable speed Freely selectable acceleration, either in linear or in exponential mode The software provides full control over the instrument s parameters, running and evaluation Pull-off-wheels with coated with anti-adhesion surface Picture: Schematic view of melt tension measurement Rev. 1

2 Melt tension measurement device Picture: Drawing of Melt Tension measurement device Melt Tension device underneath a Rheograph 6 Pair of anti adhesion coated pulling wheels Turning wheel connected to load cell underneath a Rheograph 6 Picture: Melt Tension device Rev. 2

3 The Melt Tension measurement device is made up of the following modules: Measuring Instrument The Melt Tension measurement device consists of one turning wheel connected to a load cell and a pair of anti adhesion coated pulling wheels. The extruded melt strand makes a first U- turn around a first wheel (turning wheel connected to a load cell) and then is pulled by coated wheel pair (see also figure Melt Tension measurement device below Rheograph6), which is connected to a drive system pulling the strand with a selected speed. The Melt Tension measurement device measures the force exerted as the melt strand is pulled at a user-selected speed or acceleration. To minimize possible interference from the environment, keep the melt strand as short as possible. The Melt Tension measurement device is positioned at a fixed position to the die exit of a capillary rheometer. Using Melt Tension device in combination with an extruder with 9 deflection head a position to the die exit should be selected as near as possible. Electronic Box A separate electronic box contains the measuring amplifier for the force measurement, the control electronics and the power supply. Software All functions of the Melt Tension measurement device are directed by using the software program "Melt Tension". The parameters necessary to run the measurement are set in the program and can be saved a file. Using the Melt Tension measurement underneath a capillary rheometer or extruder from Göttfert only one PC for both instruments is necessary. Technical Data: Pull-off-wheels: Leading wheels: See options See options Force measuring range: DMS sensor 2. N Resolution: Speed: Drive system: 1mN Freely adjustable 6m/min, -2 m/min (option) AC servo motor, 2 rpm Allowed power fluctuations: ± 1% Rev. 3

4 Power supply: Ground: Allowed power fluctuations: Power consumption: Allowed ambient temperature: Humidity: Dimensions: Weight: 23V 5 Hz / 115V 6 Hz Grounding resistance smaller than 5 Ohm Shorter than 1 msec. About 5 W C Up to max. 9% non condensing Measuring instrument: Length: 23 mm, Width: 145 mm, Height: 15 mm Electronic box: Length: 472 mm, Width: 412 mm, Height: 155 mm Measuring instrument : about 1 kg Electronic box: about 5 kg Included with the base instrument 1 Power cable 1 Operation manual 1 Technical documentation 1 Force calibration device 1 Quick connection coupling for the air supply (for calibration air-bearing) 2 Keys for the main switch 1 Set of cleaning tools 1 Set of service tools Personal Computer Informations about the equipment features of the PC, you will find in the separate product description " Visualization PC ". Attention: Again we would like to emphasize that several types of unfilled polymers (e.g. PA and PBT) can demonstrate excessive sticking behavior. This might cause problems for the Melt Tension measurement, even make it impossible to run experiments successfully. Göttfert GmbH provides full warranty for machines that have been supplied as complete system that means with PC and printer by Göttfert. PC means generally the complete system comprising of PC, monitor, keyboard, interfaces, mouse and if applicable joysticks. Principally, we do not give a functioning guarantee for connecting externally supplied PCs and printers (non-göttfert supply). If the customer provides the PC by himself, Göttfert cannot guarantee the trouble free functioning of PC and Göttfert unit Rev. 4

5 Service work, which will be essential due to appearing problems in regard to configuration, serial interfaces, connection cables, communication etc. do not belong to the warranty obligations and will therefore be invoiced on an actual expense basis. Due to the various printer executions that are available on the market, we do not give any function guarantee for printers not supplied by Göttfert. Support for possible adjustments will be charged on an actual expense basis. If you order the Melt Tension device in combination with a capillary rheometer or extruder no additional PC is necessary. Melt Tension measurement Basic instrument ready for operation with control box Order number Rev. 5

6 Operating Program Melt Tension Parameter input Material, sample number, remarks etc. can be assigned to several available fields Melt strand feeder parameters: Temperature, Capillary, Piston diameter Mode extrusiometer: Input for time, weight and density Mode rheometer: Input for piston speed or shear rate Available capillaries and pistons in their respective fields Melt tension parameters: Strand length the distance between the end of the capillary die and the center axis of the measuring wheels Speed at beginning of test Sample rate Acceleration of strand (acceleration = constant speed). Choose to either input speeds directly or select one of given speeds. Speed at end of test Choose mode for end of test with either wheels coming to a dead stop, or running continuously Scalable measuring values: Time t Pull-off-force F Pull-off-speed v Elongational stress z Draw ratio λ Apparent elongation rate ε& Apparent elongational viscosity e η Measuring Process Start measuring module, select parameter file, calibrate zero point Start the pulling wheels with the velocity of the extruding strand Guide the strand around the turning wheel into the nip of the pair of pulling wheels) Start the measuring process. Real-time plot while measuring: Pull-off-force and speed over time, pull-off-force over speed Stop measurement (different possibilities): Stop measurement by the stop function of the software Measurement stops automatically when the preset end speed has been reached Measurement stops automatically when strand breakage is detected All measuring data will be saved to a measuring data file table. Measuring data file table with all calculations of all the chosen measuring curves: Number of the measuring run, date, time (Year 2 compliant) Rev. 6

7 Melt strand speed at start v S (at F S =) Force at break-point of melt strand F b Speed at break v b Draw ratio when melt strand breaks b λ Elongational stress when melt strand breaks b (=tensile strength) Statistical evaluation of above-mentioned data (with standard deviation F max and v max ) Select measuring curves, elongational stress z (=tensile strength) over draw ratio λ The data of a selected curve is being displayed in a numerical field as well. Strand length L S (Distance from the end of the capillary to the edge of the melt Tension device turning wheel) Apparent elongational speed &ε when the strand breaks Apparent elongational viscosity η e when the strand breaks Strand speed at capillary exit (extrusion speed) v Strand speed (at nip of wheels) at start of run v S (at F S =) Strand speed (at nip of wheels) when strand breaks v b Force when strand breaks F b Swell ratio SR It is possible to delete unwanted curves from the group of measurements marked for statistical analysis (strand broke and could not be removed before the next measuring run, or the result was an outlier). This deletion can be undone too. All curves can be saved or printed, together with the statistical analysis. End of measuring runs with the appropriate steps. Formulas Formula for elongational ratio λ λ = v v S The beginning speed v S is the speed of the strand through the nip of the wheels at the start of the test. The speed of the wheels has been adjusted to match the speed of the strand as if it were falling naturally (i.e. the measured force is zero) Rev. 7

8 Formula for the tensile stress z (=tensile strength) is estimated to: z = F v 2 A v where F is the force applied to the strand, v is the speed with which the strand is being pulled off, A is the diameter of the strand when it exits the die and v is the extrusion speed of the strand. The formula for the diameter of the strand when it exits the die A is A π = D 4 2 where D is the diameter of the die. The extrusion speed v for the melt feeder (RHEOGRAPH) is calculated from: v 2 DP = v 2 D P where D P is the diameter of the piston, D is the diameter of the capillary and v P is the speed of the piston from the rheometer. For the extruder, the extrusion speed v is calculated with the output formula: v = Q A where Q is the volume and A is the diameter of the die. v 1 A Q 4 = = 2 D π M ρ M is the mass throughput (calculated with the output formula) and ρ is the density. Formula of the mass throughput: M = g where g is the strand weight and t is the time. t The apparent elongation speed &ε is calculated from following formula: v v & ε = ln( ) L v S S Rev. 8

9 Formula for the apparent elongational viscosity η e : Z ηe = & ε The swell ratio SR is SR v v S = Fundamental formulas for capillary rheology Formula for the shear rate &γ : 2 DP v &γ = 8 3 D P where D P is the diameter of the piston, v P is the speed of the piston and D is the diameter of the capillary die. Formula for the shear stress s : F D P 6 S = 1 or 2 2 DP π L S = D 1 8 L P P where L is the length of the capillary, F P the force exerted by the piston and P P the pressure exerted by the piston. The multiplication by 1 6 is only necessary when all values are using mm (millimeter) as their basis to convert to MKS units. Formula for viscosity η s : S ηs = & γ Rev. 9

10 Options The following optional units must be used in conjunction with the basic version of the instrument in order to render the unit fully functional: German or English version Power supply in either 23V or 115V These and other options are listed below. The software can be switched to either English or German. English Version User information in English. Order-number German Version User information in German. Order-number English User Information One user information is included with the instrument. Order-number German User Information One user information is included with the instrument Order-number Power Supply 23 V Voltage: 23V, + PE Permissible voltage fluctuations: +/- 1% Frequency: 5 Hz +/- 1% Power consumption: ca.,5 kw Order-Number Power Supply 115 V Voltage: 115V, + PE Allowed fluctuations: +/- 1% Frequency: 6 Hz +/- 1% Power consumption: ca.,5 kw Order-Number Strand rolling up mechanism Consisting of a taking up spool which by means of toothed belts is propelled by the main motor. The traction force of the taking up spool can be adjusted by an intalled torque limiter. The taking up spool is conical, so the rolled up strand can be removed easily. The mean diameter is about 85 mm. Order-Number Rev. 1

11 Stand The stand consists of aluminium profiles and is easily adjustable in the height from 75 to 112 mm in the middle of the take-off wheels to the soil. The weight of the RHEOTENS with swivel table is balanced by means of an integrated gas-pressure spring. The stand is provided with four adjustable feet to balance floor irregularities. The setting up surface is 44 x 4 mm. Order-Number Installation at RHEOGRAPH 6 To install the Haul-Off system at the Rheograph 6 fix the swivel arm at the column underneath the test chamber on the left side. The swivel arm is height-adjustable and can be swivelled out sidewards. The strand is directed over a propelled guide roller on the right side of the equipment. Order-Number Installation at RHEOTESTER 2 To install the Haul-Off system at the Rheotester 2 fix the swivel arm at the column underneath the test chamber on the left side. The swivel arm is height-adjustable and can be swivelled out sidewards. The strand is directed over a propelled guide roller on the right side of the equipment. Order-Number Installation at RHEOTESTER 1 To install the Haul-Off system at the Rheotester 1 fix the swivel arm at the column underneath the test chamber on the left side. The swivel arm is height-adjustable and can be swivelled out sidewards. The strand is directed over a propelled guide roller on the right side of the equipment. Order-Number We reserve the right to make technical and/or design improvements at any time Rev. 11

12 HAUL-OFF Short version of price list, order acknowledgement, packing list and invoice Order-Number Description 5..6 Haul-off English Version German Version English User Information German User Information Power supply 23V Power supply 115V Strand rolling up mechanism Strand Installation at RHEOGRAPH Installation at RHEOTESTER Installation at RHEOTESTER Rev. 12

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