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OPERATING CONDITION OF FUTO FABRICATED EXTRUDER FOR EXTRUSION OF POLYETHYLENE (ELPENE) AND POLYPROPYLENE (ELPROP) BY EJIOGU, IBE KEVIN (B.Eng.) ( ) Polymer Science & Engineering Federal University of Technology, Owerri, (FUTO), NIGERIA © 2008 MASTER THESIS PRESENTATION

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Supervised by: Prof. M. E. Enyiegbulam B.Sc. (Nigeria), M.Sc., Ph.D. (Lancaster, UK) (FPIN)

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Abstract Capillary rheometer was used to obtain data for two polymers: Polyethylene (ELPENE) and Polypropylene (ELPROP). The data obtained were analyzed using two flow models viz; Two Parameter Model and Casson’s Model. These flow equations were used to study the psuedoplasticity of the polymers and the machine characteristics of FUTO extruder and two commercial extruders (A and B) in terms of screw and die characteristics. The screw and die characteristics of the FUTO Extruder was obtained for extrusion of Elpene at 200°C and Elprop at 230°C. The plot of these characteristics on the same graph gave the operating points of the FUTO extruder as the intersection of the 2 characteristics, showing the extrusion output (Q) and pressure (ΔP) required to overcome flow through the die at different screw speeds for Elpene and Elprop. There was significant increase in Extrusion output and pressure as screw speed was increased.

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The ratio of the characteristics for extrusion of Elpene and Elprop independently was 1.06 for the FUTO extruder. The ratio of the screw characteristics for extrusion of Elpene and Elprop independently was 2.54, for the FUTO Extruder. The melt viscosities of Elpene and Elprop were poise and poise at 200°C and 230°C respectively. The performance of the FUTO extruder improved by 29% for extrusion of Elpene at 200°C when screw speed was increased from 50 – 100 rev/min and 49% for extrusion Elprop at 230°C.

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TYPES OF EXTRUDERS Ram or Cylinder Extruder Pump Extruder Screw Extruder ZONES IN THE EXTRUDER Feed Zone Compression Zone Metering Zone

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FEATURES OF THE FUTO EXTRUDER

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SCREW AND DIE CHARACTERISTICS The cooperation of the screw and the die can be presented in a simplified way in a diagram showing the relationship between the output of the screw and the pressure it must produce to overcome the resistance of flow in the die (characteristics of a screw) and the relationship between die output and pressure produced by the screw (characteristics of die).

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SCREW AND DIE CHARACTERISTICS Fig 1.3: Diagram of cooperation of screw and die. Q,- Output, P- Pressure, E - Extruder operating point, Extrusion output, QE, Extrusion pressure, PE. (1.) Characteristics of screw. (2.) Characteristics of die

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PROJECT BACKGROUND Efficient manufacture of inexpensive high quality products depends on; Screw operating quality Extrusion output (Q) Extrusion pressure (P) This shows the quantity of polymer per unit time supplied to the die at particular pressure and screw speed. Therefore, characterization of the FUTO extruder by determining the extruder output and pressure becomes very important.

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AIM OF STUDY Identifying the operating points of the FUTO extruder vis-à-vis extrusion of pipe grades of EPCL’s Polyethylene (ELPENE) and Polypropylene (ELPROP). Characterizing the extrusion process for extrusion of pipe grades of EPCL’s Polyethylene (ELPENE) and Polypropylene (ELPROP), and comparing the results with other standard extruders. Determining the performance of FUTO extruder with increasing screw speed.

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RESEARCH METHOD Resin collection and preparation Determination of melt viscosities of resins and characterization of their operations Characterization of FUTO extruder for these operations Evaluate and characterize other Extruders, (Extruder A, and Extruder B) and compare their characteristics with that of the FUTO extruder Evaluate the effect of screw speed on output, performance and Energy requirements of the FUTO extruder

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EQUIPMENT USED FOR THIS STUDY Desiccators Digital Tachometer Capillary Rheometer FUTO Extruder {Extruder A}, Single screw Extruder; model: ALPHA 45-25B UT. (CINCINNATI ENGINEERING LTD.) {Extruder B}, Single screw Extruder; model: Proton A (WEYLOYD ENGINEERING LTD.)

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WORK DONE Obtained the melt viscosities of Elpene and Elprop at different shear rates Studied the Rheological behaviour of the melts Determined the High shear viscosity ( ) of Elpene and Elprop melt using capillary rheometer and standard Extruders. This represents the viscosity of the melts at the metering zone of the extruder Obtained screw characteristics of FUTO extruder Obtained the die characteristics of FUTO extruder

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Evaluated the operating conditions ie, (Extrusion output & pressure) of FUTO extruder at different screw speeds Characterized the FUTO extruder for these operations Obtained the screw characteristics of Extruder A and Extruder B Obtained the die characteristics of Extruder A and Extruder B Obtained the operating conditions of Extruder A and Extruder B Characterized the operations of Extruder A and Extruder B and compare with the characteristics of FUTO extruder

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To obtain the High shear viscosity using the standard Extruders and compare with the value obtained from the capillary Rheometer To Evaluate the Effect of increasing screw speed on output, Energy requirements and performance of FUTO extruder

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EXPERIMENTALS

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SAMPLE COLLECTION Elpene and Elprop resins were obtained from EPCL, Port-Harcourt. DETERMINATION OF VISCOSITIES OF ELPENE AND ELPROP The viscosities of the melts at varying shear rates were determined by using the capillary rheometer. This was done by measuring the force required to extrude a given quantity of molten resin through the capillary die.

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The molten sample was forced through the orifice at a given shear rate and temperature; 200ºC for Elpene and 230ºC for Elprop respectively. The viscosities were calculated according to the following: Viscosity ( ) = SHEAR STRESS ………………………3.1 SHEAR RATE SHEAR STRESS = F / (4APLC / dc) Where; (τ) = shear stress, dynes / cm 2 = force on plunger, dynes. AP= plunger area, cm2 (0.7114cm 2 ) LC= Length of capillary, cm (2.54cm) dc= Diameter of capillary, cm (0.127cm)

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At a given shear rate ( ), viscosity of the melt ( ) is = F/(4APLC / dc) = F/56.91 ……………………..3.3 ANALYSIS OF RHEOLOGICAL BEHAVIOUR OF ELPENE AND ELPROP MELTS The following graphs were plotted Shear stress vs shear rate (s) Viscosity vs shear rate and Log shear stress vs Log shear rate

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The power law equation was applied in studying the Rheological behaviour of the melts. τ=K n ……………………………3.4 Where; τ=shear stress (dyne\ cm 2 ) =shear stress (sec -1 ) n=flow behaviour index K=constant From Equation – 3.4: Log τ=Log k + n Log ….3.5 The slope in the log shear stress vs log shear rate plots gave the value of ‘n’ which is a measure of the degree of shear thinning or psuedoplasticity of the melts.

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HIGH SHEAR VISCOSITY A Rheological model, the casson Equation was used in establishing the high shear viscosities of Elpene and Elprop melts. The Equation was given as 1/2 = 1/2 + τ 1/2 - 1/2 ……………..3.6 Where; = viscosity of the melts (poise) = High shear viscosity (poise) τ= shear stress (dyne / cm 2 ) = shear rate (sec -1 ) The square root of viscosity was plotted against the reciprocal of the square root of shear rate. The square of intercept of the graph is , the high shear viscosity.

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THE SCREW CHARACTERISTICS OF FUTO EXTRUDER OUTPUT (Q):- WAS OBTAINED BY WEIGHING THE EXTRUDATE SEGMENTS CUT OFF AT DEFINITE TIME INTERVALS (2 MINS) MAXIMUM PRESSURE (ΔP MAX) This was obtained by calculating the maximum pressure exerted by the melts, when there is no discharge; ΔP max = 6 DLN /H 2 tan α …………………………….3.7 Where;D= Screw diameter (cm) L= Screw length (cm) N= Screw speed (rev/min) = High shear viscosity of the melts (poise) H= Screw depth (cm) α= Helix angle of screw The values of Q and ΔP max were obtained for different screw speeds (50, 60, 70, 80, 90, 100 rev/min).

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DIE CHARACTERISITCS OF FUTO EXTRUDER This was obtained by using the equation Q=KΔP …………………………………… Where;Q=Output of die (g/s) =High shear viscosity of melt (poise) K=die constant (cm 2 ) ΔP=pressure exerted on die (dyne/cm 2 ) AndK= R 4 / 8L ………………………………… 3.9 WhereL=Length of die (cm) R=Radius of die (cm) Different values of ΔP were substituted into equation – 3.8 to obtain various values of Q. A plot of output (Q) against pressure (ΔP) gave the die characteristics.

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OPERATING CONDITIONS OF FUTO EXTRUDER The screw characteristics and die characteristics were plotted on the same graph. The operating point of the extruder was at the points of intersection of the two graphs.

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CHARACTERIZATION OF FUTO EXTRUDER The FUTO Extruder was characterized for these operations by obtaining the slopes for the die characteristics for both Elpene and Elprop independently. The slope of each die characteristics gave a value which characterizes the flow of melt through the die for the Extruder / Die combination.

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QA = kAΔp {Polymer flow through the die is a pressure flow of an isothermal Newtonian fluid} …3.10 Where; QA = Output of die in the Extruder and die combination (g/sec). KA = slope of die characteristics (cm 3 /poise), for extrusion of polymer A Δp = pressure drop along the die (dyne/cm 2 ), Equation3.10, characterizes the flow of polymer A through the die for this particular Extruder /Die combination. Similarly a second polymer ELPROP, was extruded using the same Extruder / Die combination at given temperature and pressure. QB= KB Δp……………… 3.11

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The ratio of their slopes will be kB / kA = a ………………… 3.12 “a” is a value which will remain constant irrespective of the Extruder /die combination used in Extruding polymer A and polymer B respectively, provided the Extrusion conditions are kept constant. “a” is also unique and provides a sense of direction, if the work is to be replicated.

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RESULTS AND DISCUSSION

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CONCLUSION

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Conclusion The operating points of FUTO Extruder for extrusion of Elpene and Elprop were obtained. The extrusion constant for extrusion of Elpene at 200 ° C using the FUTO extruder was Q = 1.29 x P. The extrusion constant for extrusion of Elprop at 230 ° C using the FUTO extruder was Q = 1.37 x P. The ratio of their extrusion constants (Elprop / Elpene) was This constant is called the extrusion ratio. The Elpene and Elprop melts were pseudoplastic and newtonian, showing a flow behaviour index of the range 0 < n ≤ 1. The viscosity of Elpene was poise at 200 ° C and poise for Elprop at 230 ° C respectively. The performance of the extruder improved by 29% for Elpene and 69% for Elprop respectively.

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