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NPRA International Lubricants and Waxes Meeting

NPRA International Lubricants and Waxes Meeting. Session LW-08-106. Function and Performance of Hydrocarbon Waxes in Rigid PVC. By: Thomas C. Pedersen Rheogistics LLC Picayune, MS USA. PVC . PVC resin is a free flowing, granular solid with a bulk density of 0.50 to 0.60 gm/ml.

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NPRA International Lubricants and Waxes Meeting

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  1. NPRA International Lubricants and Waxes Meeting Session LW-08-106 2008 International Lubricants and Waxes Meeting

  2. Function and Performance of Hydrocarbon Waxes in Rigid PVC • By: Thomas C. Pedersen Rheogistics LLC Picayune, MS USA 2008 International Lubricants and Waxes Meeting

  3. PVC • PVC resin is a free flowing, granular solid with a bulk density of 0.50 to 0.60 gm/ml. • PVC resin contains 57% chlorine, 38% carbon, and 5% hydrogen. 2008 International Lubricants and Waxes Meeting

  4. PVC Compound 2008 International Lubricants and Waxes Meeting

  5. PVC Compound 2008 International Lubricants and Waxes Meeting

  6. Vinyl Siding Vinyl Siding PVC Fence PVC Products

  7. PVC Pipe

  8. PVC • Rigid PVC has great properties • Typical 7000+ psi tensile strength • Excellent stiffness • Excellent impact strength • Good weatherability • Excellent cost performance

  9. Rigid PVC • Most rigid PVC properties are affected in one way or another by the lubricant system. • Getting things right is a constant balancing act. • Customer quote: “Its always the wax,” VP of manufacturing of a leading building products manufacturer, 1980

  10. PVC Resin • PVC resin grains are approximately 100 microns in diameter. The large grains are composed of 2 to 10 micron sub-grains which in turn are composed of primary particles with a diameter of approximately 1 micron. 2008 International Lubricants and Waxes Meeting

  11. PVC Resin 2008 International Lubricants and Waxes Meeting

  12. PVC Processing • The 1 micron PVC primary particles are thought to be the primary flow units during rigid PVC processing 2008 International Lubricants and Waxes Meeting

  13. Processing Rigid PVC • Rigid PVC products are formed by heating and compressing PVC compounds into desired shapes. • The compound is compressed from a bulk density of approximately 0.50 gm/ml to a product density of approximately 1.40 gm/ml • PVC is heated to ca. 400°F by mechanical shear and heat transfer. • During processing, PVC is exposed to pressures of 2000 to 4000 psi.

  14. Processing Rigid PVC • The function of lubricants in rigid PVC is to manage the fusion process while preventing the polymer from sticking to the processing equipment.

  15. PVC Lubrication • Paraffin and hydrocarbon waxes are used in conjunction with calcium stearate as primary lubricants • Ca(C18H35O2)2 2008 International Lubricants and Waxes Meeting

  16. Behavior of Lubricants • The calcium atom or polar end of calcium stearate is attracted to the machine and PVC resin surfaces • Paraffin wax is thought to act as a slip agent between the exposed tails of calcium stearate 2008 International Lubricants and Waxes Meeting

  17. Fusion Mechanism for Rigid PVC • C – Compaction • D – Densification • F – Fusion • E – Elongation • Chemical/Plasticizing Effects

  18. Rigid PVC Fusion in Extrusion

  19. Fusion Characterization in the Lab • Torque Rheometer • Fixed volume heated chamber • Work imparted into PVC compound by mixing blades • Measure torque required to turn the blades and melt temperature

  20. Torque Rheometer 2008 International Lubricants and Waxes Meeting

  21. Torque Rheometer Rotors 2008 International Lubricants and Waxes Meeting

  22. Torque Rheometry Energy Balance 2008 International Lubricants and Waxes Meeting

  23. Extruder Energy Balance 2008 International Lubricants and Waxes Meeting

  24. Effects of Fusion Levels on Physical Properties • Tensile Properties • Increase with increasing fusion • Impact Properties • Peak at an intermediate level of fusion 2008 International Lubricants and Waxes Meeting

  25. Trial PVC Compound • PVC Resin 100 parts • Stabilizer 0.50 phr • Wax 1.30 phr • Calcium Stearate 0.65 phr • Oxidized PE Wax 0.15 phr • Calcium Carbonate 5.00 phr • Titanium Dioxide 0.50 phr 2008 International Lubricants and Waxes Meeting

  26. 100 grams of PVC Resin Assume primary particles are spheres Volume of a primary particle = 5.2x10-13 cm3 Weight of a primary particle = 7.3x10-13 gms Number of primary particles per 100 grams of PVC resin = 1.4x1014 2008 International Lubricants and Waxes Meeting

  27. 1.3 grams of Paraffin Wax Assume molecular weight of 450 gm/mole # moles = 0.0029 moles # wax molecules = 0.0029 * 6.023x1023 = 1.75x1021 2008 International Lubricants and Waxes Meeting

  28. Wax Molecules Per PVC Primary Particle • 1.4x1014 PVC Primary Particles • 1.75x1021 Paraffin Wax Molecules • Estimated 10,000,000 to 15,000,000 Wax Molecules per PVC PP 2008 International Lubricants and Waxes Meeting

  29. Trial PVC Compound • PVC Resin 100 parts • Stabilizer 0.50 phr • Wax 1.30 phr • Calcium Stearate 0.65 phr • Oxidized PE Wax 0.15 phr • Calcium Carbonate 5.00 phr • Titanium Dioxide 0.50 phr 2008 International Lubricants and Waxes Meeting

  30. Torque Rheometry - Classic Wax

  31. Torque Rheometry - C32

  32. Torque Rheometry – C26

  33. Torque Rheometry – C40

  34. Torque Rheometry – PE Wax

  35. Test Results 2008 International Lubricants and Waxes Meeting

  36. Conclusions • The PVC Industry is a large application for paraffin and hydrocarbon waxes • Waxes with carbon numbers of C30 to C36 work best as primary PVC lubricants in North America’s tin stabilized formulations 2008 International Lubricants and Waxes Meeting

  37. Conclusions • The lubricant system is adjusted to tune the formulation to the heating and shearing characteristics of the customer’s processing equipment. • Changes in any material or any piece of equipment in a customer’s plant results in the need for a lubricant adjustment. 2008 International Lubricants and Waxes Meeting

  38. Conclusions • Understanding and managing lubricant performance in rigid PVC is complex • “Its always the wax.” The PVC industry requires in-depth technical support and service. 2008 International Lubricants and Waxes Meeting

  39. References • T. C. Pedersen, “Process and Material Considerations in the Industrial Application of Lubricants in Rigid PVC Extrusion”, Journal of Vinyl Technology, 6, 104 (1984) 2008 International Lubricants and Waxes Meeting

  40. References • J. W. Summers, “Lubrication Mechanism in Poly (Vinyl Chloride) Compounds: Understanding the Three Distinct Roles of Lubricants” Antec 2006, Society of Plastics Engineers. 2008 International Lubricants and Waxes Meeting

  41. References • P. Benjamin, “The Influence of Processing on the Properties of PVC Pipe”, International Conference on PVC Processing, 6 & 7 April 1978, The Plastics and Rubber Institute. 2008 International Lubricants and Waxes Meeting

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