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3 Table of Contents Chapter 1 Polymer Properties and Terminology 1 Chapter 2 Feeding Systems to Gearboxes 27 Chapter 3 Extruder Screws and Set-up 41 Chapter 4 Temperature Controllers to Screen Changers 63 Chapter 5 Blown Film Dies 77 Chapter 6 Bubble Cooling 105 Chapter 7 Bubble Collapsing 131 Chapter 8 Post Extrusion Operations 141 Chapter 9 Troubleshooting Techniques 177 Film Defects Troubleshooting Guide 183 Roll Defects Troubleshooting Guide 200 Glossary of Terminology 213

4 About the Author Paul Waller, P.Eng., MBA, Cert.P.P. President Plastics Touchpoint Group, Inc. Website: Phone: (001) Skype: paul_waller1 Plastics Touchpoint Group, Inc. was established to meet the growing demand for expertise in the flexible packaging industry. The company focus is on blown and cast film extrusion and film conversion operations. Plastics Touchpoint has worked with clients throughout North America, South America, the Middle East, Africa, Australia and Asia. Clients include raw material suppliers, processors, end users, educational institutions and industry associations. Paul Waller is a frequent presenter and trainer at conventions and professional functions as well as a prolific writer. He designed and delivered the Blown Film Technology Program for the Canadian Plastics Training Centre in Toronto, Canada and SENAI in Brazil. Mr. Waller has provided intensive in-house training to more than 1,000 operators, technicians and engineers. He has taught film troubleshooting seminars on five continents and is the first candidate to be awarded the Certified Plastics Practitioner designation for Blown Film Extrusion by the Canadian Plastics Sector Council. Mr. Waller is a Professional Engineer licensed in the province of Ontario, Canada. He is an Honored Service Member of the Society of Plastics Engineers (SPE), past President and Councilor of the Ontario section of SPE, Chair of the Flexible Packaging division of SPE, co-chair of the Canadian Plastics Sector Council, a member of the Canadian Plastics Industry Association and the Canadian Plastics Pioneers.

5 Chapter 1 Polymer Properties and Terminology Four Strategies to Improve Profitability Blown Film Property Relationships Typical Layout for Blown Film Line Monomers, Homopolymers and Copolymers Polymerization Techniques Addition Polymerization Condensation Polymerization Molecular Weight and Molecular Weight Distribution Affect of Molecular Weight and Molecular Weight Distribution Amorphous and Semi-Crystalline Polymers Melting Characteristics of Amorphous Polymers Melting Characteristics of Semi-Cystalline Polymers Types of Polyethylene Low Density Polyethylene (LDPE) Linear Low Density Polyethylene (LLDPE) Affect of Comonomer on LLDPE Characteristics Metallocene Linear Low Density Polyethylene (mlldpe) Polymerization of mlldpe Medium Density Polyethylene (MDPE) Very Low Density Polyethylene (VLDPE) High Density Polyethylene (HDPE) Polypropylene (PP) Ethylene Copolymers Ethylene (Vinyl Acetate) - EVA Ethylene Vinyl Alcohol - EVOH Polyamide Nylon (PA) Polyamide Nylon Polyamide Nylon 6, Polyamide Nylon MXD, Cyclic Olefin Copolymer (COC) Chlorinated Polymers Poly (Vinyl Chloride) - PVC Poly (Vinylidene Chloride) Saran - PVdC Ionomers Biodegradable Polymers Hydro-biodegradable Polymers Polylactic Acid (PLA) Oxo-biodegradable Polymers Effect of Chain Branching Short Chain Branching Long Chain Branching Common Applications for Film Grade Polymers Additives Migration of Slip Additive Effect of Erucamide Concentration on COF of LDPE Film Effect of Slip/Antiblock Concentration on LDPE Film COF 21

6 1.23 Deformation of Molten Polymers Viscosity versus Deformation Rate Shear Viscosity Curve Melt Flow Index (MFI) Limitations of Melt Flow Index (MFI) Extensional Viscosity Curve Factors Affecting Polymer Degradation Polymer Degradation Mechanisms Chain Scission Degradation Cross-linking 25 Chapter 2 Feeding Systems to Gearboxes Blown Film Terminology Transverse Direction Orientation Blow-up Ratio Machine Direction Orientation Draw-down Ratio Take-up Ratio Frost Line Height Melt Strength Affects Bubble Shape Process Time Grooved Feed Throat vs. Smooth Bore Extruders Bulk Conveying System Fundamentals Bulk Conveying Venturi Effect Dust from Bulk Conveying Systems Misconceptions about Bulk Conveying Systems Fluff and Angle Hair Streamers or Snake Skin Volumetric Blenders Gravimetric Blenders Gravimetric Feeding Principles Batch (Gain-in-Weight) Gravimetric Blenders Continuous (Loss-in-Weight) Gravimetric Blenders Gravimetric Feeding Modes Weight Throughput Monitor Weight Throughput Control Length Throughput and Weight Monitor Weight and Length Throughput Control Common Blender Problems Blender Usage and Inventory Do Not Match Inconsistent Feeding Trips Blender Alarm Wrong Formulation or Contamination Improper Flow in the Hopper Recycling Systems Hopper Magnets Motors and Drives Gear Reducers (Gearboxes) and Thrust Bearings 37

7 Types of Gear Reducers Gear Reducer Cooling Systems Symptoms of Gearbox Wear Direct Drive (Gearless) Extruders Energy Consumption in Blown Film Lines 39 Chapter 3 Extruder Screws and Set-up Screw Requirements Grooved Feed Throat Extruders Smooth Bore Extruders Critical Screw Parameters Solids Conveying in the Feed Zone Effect of Friction in Feed Zone Effect of Temperature in Grooved Feed Zone Effect of Temperature in Smooth Bore Feed Zone Melting and Conveying in Transition Zone Effect of Friction and Conduction on Melting Rate Melting Progression in Transition Zone Solids Bed Ratio Determining Screw Output in the Metering Zone Drag Flow Pressure Flow Effect of Drag and Pressure Flow on Velocity Profile Leakage Flow Net Melt Conveying Flow (Total Flow) Pressure Profile along the Barrel Summary of Grooved Feed vs. Smooth Bore Extruders Grooved Feed Throat Characteristics Smooth Bore Feed Throat Characteristics Barrier Screw Designs Comparison of Conventional versus Barrier Screws Temperature Profile across Screw Channel Effect of Increasing Screw Speed Mixing Mechanisms Distributive Mixing Cavity Transfer Mixer Mixing Pins Dispersive Mixing Blister Ring Mixer Maddock (Fluted) Mixer Spiral Fluted Mixer Optimizing Extruder Barrel Temperature Profiles Strategies to Optimize Barrel Temperature Profiles Design of Experiment (DOE) Dynamic Optimization (DO) One-at-a-Time Experiment (OTE) Extruder Temperature Profiles Gradually Increasing (Ramped) Barrel Temperature Profile 57

8 Reverse Barrel Temperature Profile Humped Barrel Temperature Profile Flat Barrel Temperature Profile Materials of Barrel and Screw Construction Screw and Barrel Wear Nominal Screw and Barrel Clearance Symptoms of Screw Wear Short Term Strategies to Compensate for Screw Wear Effect of Screw and Barrel Wear Long Term Strategies to Compensate for Screw Wear 62 Chapter 4 Temperature Controllers to Screen Changers Barrel Heating and Cooling Systems Air Cooled Systems Mica or Ceramic Heaters Finned Aluminum Heaters Infrared Heaters Liquid Cooled Systems Liquid Cooled Barrel Heater Liquid Cooled Barrel Circuit Principles of Process Control Controller Terminology Set Point Measured Value Control Error Alignment On/Off Control Mode PID Controllers PID Control Functions Proportional (How Much) Integral (How Often) Derivative (How Fast) Barrel Exit Components Rupture Disk Breaker Plate and Screens Non-Continuous Screen Changers Pressure Cycle Continuous Screen Changers Mixing Devices Dynamic Mixers Static Mixers Process Instabilities (Surging) Strategies to Avoid Very Slow Speed Instabilities Feeding Related Surging Solids Conveying Variations in Feed Zone Strategies to Avoid Solids Conveying Variations in Feed Zone Solids Bed Wedging in Transition Zone Symptoms of Solids Bed Wedging in Transition Zone 73

9 Strategies to Avoid Solids Bed Wedging in Transition Zone Solids Bed Breakup in Transition Zone Symptoms of Solids Bed Breakup in Transition Zone Strategies to Avoid Solids Bed Breakup in Transition Zone Strategies to Avoid Melt Conveying Surging in Metering Zone Test to Detect Surging 76 Chapter 5 Blown Film Dies Die Specific Output Formulas Die Carts Stationary Die Carts Rotating Die Carts Oscillating Die Carts Limitations in Gauge Randomization with Die Carts Melt Channeling Die Design Concepts Function of the Die Spiral Mandrel Distribution System Function of Spiral Channels Port Splitting Distributors Effect of Number of Spirals on Flow Variation Effect of Spiral Angle on Flow Variation Die Lip Configurations Effect of Viscosity on TD Gauge Variation at Die Lips Die Bolt Designs for Blown Film Dies Die Bolt Adjustment Procedure for Blown Film Dies Coextrusion Die Technology Nested Spiral (Concentric Annuli) Design Blown Film Dies Nested Spiral Co-extrusion Die Design Limitations Stacked (Modular) Spiral Die Designs Limitations of Stacked Die Designs Surface Imperfections Melt Fracture Strategies to Prevent Shark Skin and Melt Fracture Polymer Processing Aids (PPA) Die Plating Die Gap Interfacial Instability Zig Zag Pattern Interfacial Instability Short Wave Pattern Interfacial Instability Effect of Changing Layer Ratios Long Wave Pattern Interfacial Instability Effect of Adjusting Melt Temperature Strategies to Prevent Interfacial Instability Test to Distinguish Melt Fracture from Interfacial Instability Gels Unmelted Gels (Applesauce, Unmelts) Causes and Solutions for Unmelted Gels 98

10 5.6.2 Lens or Hollow Gels Solutions for Lens (Hollow) Gels Arrowhead, Chevron, V or J type, Chevron, Platelet and Disc Gels Solutions for Arrowhead, Chevron, V, J, Platelet, Disc Gels Discolored or Cross-linked Gels Symptoms of Overheating Degradation Symptoms of Chain Scission Degradation Symptoms of Oxidative Degradation Symptoms of Cross Linking Degradation Solutions for Discolored or Cross-linked Gels Purging Techniques Preventative Maintenance Purging Controlled Shutdown Technique Start-Up Procedure Process Interruption Purging Stable Scouring Chemical Purge Mechanical Purge Cyclical Scouring (Disco Purge) Disassembly and Cleaning 104 Chapter 6 Bubble Cooling Bubble Cooling Systems Principles of Air Ring Design Air Ring Adjustment Principles Air Ring Adjustment Rules Air Ring Control (Locking) Points Manipulation of Air Ring Control (Locking) Points Windmöeller and Höelscher Single Lip Air Ring Future Design Genie Perforated Chimney Dual Lip Air Ring Macro Engineering Dual Lip Air Ring with Stabilizer Rings Gloucester Engineering Polycool Dual Lip Air Ring with Iris Air Ring Chamber Designs to Minimize Vortex Air Flow Davis Standard Westjet Dual Lip Air Ring Diffuser Effect of Air Ring Sealing Systems on TD Gauge Bands HDPE Air Ring Setup Controls Film Properties Enhanced Bubble Cooling Techniques Stacked Air Rings Macro Engineering Binary Cooling System Chilled Bubble Mandrels Internal Bubble Cooling (IBC) Comparison of Common IBC Control Systems D.R. Joseph IBC System with Layflat Control Function of IBC Valves Reserve Factor and Bubble Inflation Time Advanced IBC Control Systems Pancake Style IBC Air Diffuser Nested Spiral Dies TD Gauge Variation in Non-IBC versus IBC Dies 115

11 Pancake Style Air Diffuser for IBC Stack with Stacked Dies Waller s Rule of Melt Temperature Typical Die Specific Output Rates Bubble Stabilizers Rod Stabilizers Radial versus Iris Cage Designs Radial versus Iris Cage Designs Bubble Instability Common Causes of Bubble Instability Types of Bubble Instability Draw Resonance Adjustments to Eliminate Draw Resonance Helical Instability Adjustments to Eliminate Helical Instability Bubble Breathing Slow Bubble Breathing Effect of Improper IBC Sensor Position Effect of Leaking IBC Air Plenums Adjustments to Eliminate Slow Bubble Breathing Fast Bubble Breathing Adjustments to Eliminate Fast Bubble Breathing Bubble Sag Adjustments to Eliminate Bubble Sag Bubble Tear Adjustments to Eliminate Bubble Tear Bubble Flutter Adjustments to Eliminate Bubble Flutter Automatic Gauge Control Systems Standard Deviation Automatic Gauge Control Techniques Air Ring Melt Temperature Die Gap IBC On-Line Sensor Systems for Automatic Gauge Controllers 129 Chapter 7 Bubble Collapsing Collapsing the Bubble Optimizing the Collapsing Frame Angle Formation of Horizontal Wrinkles Collapsing Frame Surfaces Gusseters and Side Stabilizers Primary Nips (Haul-Offs) Effect of Oscillating Nips on Gauge Randomization Oscillating Nip Designs Central Pivot Horizontal Oscillating Nip Stacked Ring Horizontal Oscillating Nip Vertical Oscillating Nip 137

12 7.9 Causes of Layflat Edge Movement Causes of Layflat Width Variation Collapsing Surface Adjustment Principles Summary of Sources of Layflat Width Variation 140 Chapter 8 Post Extrusion Operations Surface Treatment Fundamentals SI Units US Units Surface Tensions for Common Inks and Substrates Surface Treatment Mechanisms Watt Density Formula for Corona Treaters Effect of Additives on Watt Density Requirements Causes of Changes in Film Surface Tension Causes of Poor Surface Treatment Back side Surface Treatment Misaligned or Dirty Electrodes Loose Electrodes Causes of Static Build-up and Control Techniques Wrinkle Eliminators Fixed Bowed Spreader Rollers Spiral Grooved Spreader Rollers Elastic Expander Spreader Rollers Tension and Elastic Modulus Edge Variation Patterns Slitting Defects Slit Seal Defects Seal Cutter System Web Guides Wrinkles Wrinkle Patterns Causes of MD Wrinkles Causes of Diagonal Wrinkles Tension Control Fundamentals Tension Control Zones Load Cell Web Tension Controller Vertical Dancer Assembly Web Tension Controller Horizontal Dancer Assembly Web Tension Controller Winding Fundamentals Typical Web Tension Ranges Effect of Winding Tension of Coefficient of Friction Types of Winders Surface / Drum Winders Advantages Surface Winder Configuration Surface / Center Driven Winder Configuration Gap Surface Winder Configuration Center Driven Winders Advantages Air Shaft Capacity and Limitations 157

13 8.14 Roll Defects Starred or Spoked Rolls Solutions for Starred or Spoked Rolls Taper Tension Buckled Rolls Solutions for Buckled Rolls Tapered Rolls Solutions for Tapered Rolls Telescoped Rolls Solutions for Telescoping Rolls Ringed Rolls Solutions for Ringed Rolls Tin Canning Solutions for Tin Canning Bag Machines Fundamentals Bag Machines Accumulator Mechanism Sealing Head and Platen in Shuttle Bag Machine Bag Machine Blades Separators Causes of Low Heat Seal Strength Gauge Variation Basis Weight Measurement Technique Manual Measurement Techniques Mechanical Micrometer Calibration Techniques Cleaning and Recalibration Procedure Parallelism Test and Adjustment Procedure General Causes of Machine Direction Gauge Variation Causes of Transverse Direction Gauge Variation Equipment Problems Causing TD Gauge Variation Bench Top Gauge Profilers Fourier Series Analysis of Gauge Variation 174 Chapter 9 Troubleshooting Techniques Scientific Method for Troubleshooting Quality Control Strategies ISO Success Factors for Troubleshooting Minimum Sample Size Requirements for General Tests 178

14 Chapter 8 Post Extrusion Operations The following guide summarizes the troubleshooting tips described in the manual. The blown film line is split into several zones to remind operators which area of the line should be examined when problems occur. Each problem includes causes split into raw material, processing conditions and equipment. Recommendations for each cause are included. Blown Film Troubleshooting Guide 179 Film Defects Troubleshooting Guide Index 179 Roll Defects Troubleshooting Guide Index 180 Film Defects Troubleshooting Guide 183 Blocking 183 Die lines, weld lines (MD) 184 Gels -Apple sauce (very small gels) 184 Gels - Arrow heads, chevrons ( V or J ) 185 Gels - Discol-ored 186 Gels - Fisheye, platelet, disc 186 Gels Hollow or Void 187 Low gloss, high haze, low clarity 188 Low heat seal strength 188 MD gauge variation 189 Melt fracture and shark skin 191 Interfacial instability - short wave pattern 191 Interfacial instability - short and long wave patterns 192 Port lines 192 Poor surface treatment 192 Scratches (MD) 193 Splitty film (low MD tear strength) 193 Streaks in MD 194 Streaks in TD 194 TD gauge variation 195 Uneven film or sheet width 197 Uneven gussets 198 Weak edge folds 198 Wrong color

15 Chapter 8 Post Extrusion Operations Roll Defects Troubleshooting Guide 200 Baggy edges 200 Buckled rolls 200 Bumpy rolls (Tin Canning) 200 Folds, creases 201 Non uniform surface hardness 201 Ringed rolls (fuzzy edges) 201 Roll too hard 202 Roll too soft 202 Sag in film (soft in middle of roll) 202 Starred rolls or crushed cores 203 Tapered, convex or concave rolls 203 Telescoped rolls 204 Uneven roll width 204 Wrinkles in roll