2008 International Lubricants and Waxes Meeting NPRA International Lubricants and Waxes Meeting Session LW

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

PVC 2008 International Lubricants and Waxes Meeting 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.

PVC Compound 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 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 sub- grains which in turn are composed of primary particles with a diameter of approximately 1 micron 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 ) 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 2008 International Lubricants and Waxes Meeting Tensile Properties –Increase with increasing fusion Impact Properties –Peak at an intermediate level of fusion

Trial PVC Compound PVC Resin100 parts Stabilizer0.50 phr Wax1.30 phr Calcium Stearate0.65 phr Oxidized PE Wax0.15 phr Calcium Carbonate5.00 phr Titanium Dioxide0.50 phr 2008 International Lubricants and Waxes Meeting

100 grams of PVC Resin Assume primary particles are spheres Volume of a primary particle = 5.2x cm 3 Weight of a primary particle = 7.3x gms Number of primary particles per 100 grams of PVC resin = 1.4x International Lubricants and Waxes Meeting

1.3 grams of Paraffin Wax Assume molecular weight of 450 gm/mole # moles = moles # wax molecules = * 6.023x10 23 = 1.75x International Lubricants and Waxes Meeting

Wax Molecules Per PVC Primary Particle 1.4x10 14 PVC Primary Particles 1.75x10 21 Paraffin Wax Molecules Estimated 10,000,000 to 15,000,000 Wax Molecules per PVC PP 2008 International Lubricants and Waxes Meeting

PVC Resin100 parts Stabilizer0.50 phr Wax1.30 phr Calcium Stearate0.65 phr Oxidized PE Wax0.15 phr Calcium Carbonate5.00 phr Titanium Dioxide0.50 phr 2008 International Lubricants and Waxes Meeting Trial PVC Compound

Torque Rheometry - Classic Wax

Torque Rheometry - C32

Torque Rheometry – C26

Torque Rheometry – C40

Torque Rheometry – PE Wax

Test Results WaxFusion TimeFusion TorqueFusion TempEquil TorqueEquil Temp C26166 sec21.3 Nm179°CNone>195°C C32352 sec15.2 Nm183°C13.0 Nm188°C C402,120 sec10.1 Nm184°C12.4 Nm188°C Classic318 sec15.5 Nm183°C12.6 Nm188°C PE182 sec18.9 Nm182°CNone>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 C30 to C36 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 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 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 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 International Lubricants and Waxes Meeting