Composition of polymers Processing .pptx

Processing of polymer composites

1. T H E F U NDAMEN T ALS OF RHEOLOGY

2. Rheological Tests can be very helpful tools for polymer processing and development. This presentation is designed to be an informative introduction and guide to rheological tests, and finding correlations between equipment and processing techniques.

3. CAPILLARY RHEO L OGY “ t he flow a n d shea r proper t i es of ma t er i al s up t o h i gh pressures” Provides more information than melt flow testing How does the material behave when “melted”? What are the correlations between flow parameters and mechanical properties? Polymers are non-Newtonian material, consequently their flow is not proportional to the pressure applied

4. WHY C APILLARY RHEOLOGY? Determine the optimal working parameters for materials processing (injection moulding, blow moulding, extrusion, etc.) Investigate processing issues in a faster and non-disruptive manner Find which materials will work best for complex parts or long flow lengths Replicate manufacturing parameters for design, troubleshooting, and simulations

5. TYPES O F RHEOMETERS Extensional Capillary Rotational ROTATIONAL R H E O M E T E R S For Viscoelastic properties R o ta r y m o tion Plate geometry: Most common for thermoplastic melts E X T ENS I ON A L RHEOMETERS For Elongational viscosity (high viscosity materials) Rotating drum Extensional flows: Very sensitive to crystallinity & polymer long-chain branching CAPILLARY R H E O M E T E R S For Viscous properties Capillary action Capillary flow: Flow through a narrow space. Different piston speeds (shear rates) applied. Viscosity changes tracked relative to shear rates.

6. SHEA R FL OW θ Flow between two parallel plates of area A Moving with constant velocity V s A D F

7. SHEA R FL OW Flow between two parallel plates of area A Moving with constant velocity V Shear Rate Shear Stress Vis cosi t y

8. POLYM E R RHEO L OGICA L BEHAV I OR WA T ER POLYMERS P 1 1 1 2 Polymers flow is not proportional to the applied pressure P 2 P 3 1 2 3 Flow curve P r es s ure Flow W A T E R POLYMERS

9. M o l ecu l ar W e i ght Polymers’ structure influences all their mechanical, chemical, and rheological properties. MEC H A N IC A L & RHEO L OGICA L PROPERTIES V s . MO L ECU L AR WE I GHT

10. . 00 1.000 2.000 L o g( Vi s c o sit y ) -1.000 - 2 . 00 - 1 . 00 .0 1 .0 2 .0 3 .0 4 .0 5 .0 l o g ( s h ear r a t e) V i s c o s i ty v s . S h e a r R a t e 4.000 M = 50000 3 .0 00 M = 75000 M = 100000 RHEO L OGICA L PROPERTIES Vs . M OL E CULAR WE I GHT l o g (v i scosity) V i s c o s i ty v s S h e a r r a t e 4.000 M = 75000 MWD broad 3.000 M = 75000 MWD narrow 2.000 1.000 0.000 -1.000 -2.000 -2.00 -1.00 0.00 1.00 2.00 3.00 4.00 5.00 l o g ( s h ear r a t e ) Rheological curve at different MW (monodisperse polymers) Rheological curve at different MWD (monodisperse and polydisperse polymer) With same average MW, polydisperse polymers can be processed better than monodisperse ones.

11. High-molecular weight leads to : 1) Higher Strength: because of higher inter-chain forces, more entanglements 2 ) Hig he r I m pac t Strengt h : b e c au s e o f l o w er deg re e of crystallization at higher chain length, more entanglements 3 ) Hig he r Ch e mical R esis t anc e : b e cause o f high er in t e r - chain forces 4) Reduction of the “fluidity” (inverse of viscosity) of the polymer in the melted status: because of the presence of m o r e e n t a ng l e m e n t s MEC H A N IC A L & RHEO L OGICA L PROPERTIES Vs . M OL E CULAR WE I GHT

12. PO L YM E RS & P R OCESS E S MATERIAL P o l y car b on a t e (P C) Polyethylene T e r ep hth al a t e (PET) P o l y v i n y l ch loride (P V C) Process Injection molding Blow molding Extrusion A pp l ic a t i on (Exa m p l es) Spotlights Plastic bottles Electrical wires Advantages Transparency High optical clarity Acts as a barrier High impact resistance Chemical l y resistant Recyclable Insulator Light weight Durable Mechanical damage resistance

13. CAPILLARY RHEO L OGY Many polymer processing techniques can be simulated using a capillary rheometer This allows users to experiment with new parameters for various polymer processing equipment without having to stop operation and waste a batch of material Plastic extrusion, injection molding, blow molding, film blowing, co-extrusion...

14. Pellets are added in the Feeder A co n s t an t temperat u re is m aintai n ed Screw is rotating continuously Polymer melts at a constant temperature Polymer is pushed through breaker plate into the die Polymer Gra n u l es PLASTIC EXTRUSION Feeder H e at e rs E x tru d ate Die Polymer Melt Screw/Barrel W ater tank Pull R o l l er

15. s F ee d er H e at e r Polymer Gra n u l e s Mold C a vity Die Molded Part Extrudate Screw/Barrel Pellets are added to the Feeder Screw is rotating (not continuously) Different temperature for different zones Screw moves along the barrel as a piston Polymer is injected into a mold The part is molded and ejected PLASTIC INJECTIO N MOLDING (IM)

16. Ext r udate drops Extrudate fits to the mold Mold closes & air blows Air Hose Residue is trimmed Cutter PLASTIC BLO W MOLDING Extrusion or injection blow molding Molten material (parison) drops in the mold Mold is closed Air is blown through an air hose Molded part is ejected Polymer Melt Ext r udate Mold open s , part drops

17. PLASTIC F I LM B LOW I NG Molten material is extruded through a circular die (usually vertically) Air is introduced in the centre of the die “Bubble–like” expansion The tube of film passes through nip rolls Ext r udate Air Nip Rolls Produ c t

18. Two or more materials fed into co-extrusion dies Constant temperature is maintained in the die Film is extruded Layer thickness controlled by relative speeds and sizes of extruders Example Application: food packaging PLASTIC C O - EXTRUSION Adhesive Polymer Resin Polymer Resin Co-extrusion Dies R o l l ers Co-extruded Tape Win d i n g Feeder 1 Feeder 2

19. L o g (  ) L o g (   ) 2 3 4 5 f ( T , P , m a t e r i a l ) I N JECTION M O L DING E X T R USI O N -1 0 1 R O T A TIO N AL R H E O M E T R Y M E LT F L O W CAPILLARY R H E O M E T R Y PROCESSING & FL O W CURVE O F PO L YMERS

20. CAPILLARY RHEOMETERS M E A S U RE L O A D O R PRESS U RE SE T D I E GEO M E T RY A ND P I S T ON S P E E D Shear Rate= Speed of Deformation Viscosity = Resistance to the Flow Shear Stress Pressure T ransducer M o t o r - Dr i v en Piston h    V F   A      Capillary Die (L/D) Force (Load Cell)

21. R A W D A TA: Constant shear rate steps with pressure reaching the equilibrium after a transient stage R H EO L O G ICAL CURVES: Viscosity (Pa· s) as a function of shear rates (s -1 ) Shear stress (Pa) vs shear rate (s -1 ) RH E OL O GICA L DATA

22. PP @ 230°C Filled PP @ 230°C RH E OL O GICA L DATA Virgin PP: Non–Newtonian shear thinning behavior η = 241 – 34 Pa·s max P ≅ 8 MPa Filled PP (50% wt flax): Non–Newtonian shear thinning behavior η = 1061 – 81 Pa·s max P ≅ 20 MPa

23. EXTRUSI O N/IM & THE CAPILLARY RHEOMETER Polymer Granules Feeding E x tru d ate Die B a rrel

24. C O - EXTRUSI O N & SQ C A N AL Y SIS

25. Die Swell Accessory EXTRUSION & SR DIE SWELL ACCESSORY E x tru da te Die Swelling of the Polymer

26. EXTRUSION/IM & MELT FRACTURE Unstable flow Polymer Granules Ba r rel Production Rate Outp u t Smooth Shark Skin Spurt F r acture Unstable flow D irecti o n of flow I n creasi n g Flow rate Melt Instabili t y

27. I M MOLD F I L L I NG & S R P V T AC C ES S ORY Partial Filling Complete Filling Simulations for Mold Filling Phase PVT Test Mold Cavity Molded Part Complete Mold Filling is critical to the process

28. I M MOLD F I L L I NG& SR T C AC C ES S ORY TC Test Molded Part Heat Conduction through the material Mold Cavity is critical to get a perfectly molded part

29. BLOW MOLDING/FILM BLOWING & SR STRETCHING UNIT Polymer Melt Extrudate Air Hose Stretching

30. TH A NK Y O U FOR Y O U R TIME!