NPRA International Lubricants and Waxes Meeting Session LW08

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

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

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

PVC Compound 2008 International Lubricants and Waxes Meeting

PVC Products Vinyl Siding PVC Fence

PVC Pipe

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

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

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

PVC Resin 2008 International Lubricants and Waxes Meeting

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

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.

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.

PVC Lubrication • Paraffin and hydrocarbon waxes are used in conjunction with calcium stearate as primary lubricants • Ca(C 18 H 35 O 2)2 2008 International Lubricants and Waxes Meeting

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

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

Rigid PVC Fusion in Extrusion

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

Torque Rheometer 2008 International Lubricants and Waxes Meeting

Torque Rheometer Rotors 2008 International Lubricants and Waxes Meeting

Torque Rheometry Energy Balance 2008 International Lubricants and Waxes Meeting

Extruder Energy Balance 2008 International Lubricants and Waxes Meeting

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

Trial PVC Compound • • PVC Resin Stabilizer Wax Calcium Stearate Oxidized PE Wax Calcium Carbonate Titanium Dioxide 100 parts 0. 50 phr 1. 30 phr 0. 65 phr 0. 15 phr 5. 00 phr 0. 50 phr 2008 International Lubricants and Waxes Meeting

100 grams of PVC Resin Assume primary particles are spheres Volume of a primary particle = 5. 2 x 10 -13 cm 3 Weight of a primary particle = 7. 3 x 10 -13 gms Number of primary particles per 100 grams of PVC resin = 1. 4 x 1014 2008 International Lubricants and Waxes Meeting

1. 3 grams of Paraffin Wax Assume molecular weight of 450 gm/mole # moles = 0. 0029 moles # wax molecules = 0. 0029 * 6. 023 x 1023 = 1. 75 x 1021 2008 International Lubricants and Waxes Meeting

Wax Molecules Per PVC Primary Particle • 1. 4 x 1014 PVC Primary Particles • 1. 75 x 1021 Paraffin Wax Molecules • Estimated 10, 000 to 15, 000 Wax Molecules per PVC PP 2008 International Lubricants and Waxes Meeting

Trial PVC Compound • • PVC Resin Stabilizer Wax Calcium Stearate Oxidized PE Wax Calcium Carbonate Titanium Dioxide 100 parts 0. 50 phr 1. 30 phr 0. 65 phr 0. 15 phr 5. 00 phr 0. 50 phr 2008 International Lubricants and Waxes Meeting

Torque Rheometry - Classic Wax

Torque Rheometry - C 32

Torque Rheometry – C 26

Torque Rheometry – C 40

Torque Rheometry – PE Wax

Test Results Wax Fusion Time Fusion Torque Fusion Temp Equil Torque Equil Temp C 26 166 sec 21. 3 Nm 179°C None >195°C C 32 352 sec 15. 2 Nm 183°C 13. 0 Nm 188°C C 40 2, 120 sec 10. 1 Nm 184°C 12. 4 Nm 188°C Classic 318 sec 15. 5 Nm 183°C 12. 6 Nm 188°C PE 182 sec 18. 9 Nm 182°C None >195°C 2008 International Lubricants and Waxes Meeting

Conclusions • The PVC Industry is a large application for paraffin and hydrocarbon waxes • Waxes with carbon numbers of C 30 to C 36 work best as primary PVC lubricants in North America’s tin stabilized formulations 2008 International Lubricants and Waxes Meeting

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

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

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

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

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