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Understanding Plastic Properties and Fabrication Methods

Learn about physical properties and processing methods of plastics in this informative module. Explore injection molding, extrusion, welding, bonding, mechanical properties, and testing organizations.

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Understanding Plastic Properties and Fabrication Methods

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  1. How Plastics are Made Understanding the Physical Properties of Plastics Prepared by the IAPD Education Committee (Module 1) Presented courtesy of Modern Plastics, Inc. The IAPD Plastics Primer, Module 1

  2. Processing • Hand (or spray) lay up • Laminating • Filament winding • Polymer orientation • Injection molding • Extrusion • Ram extrusion • Screw extrusion • Coextrusion • Casting • Compression molding • Rotational molding • Transfer molding • Calendering The IAPD Plastics Primer, Module 1

  3. Injection Molding The IAPD Plastics Primer, Module 1

  4. Extrusion • Ram • Screw • Coextrusion The IAPD Plastics Primer, Module 1

  5. Casting Base Material Reactive Additive Oven Casting Mold The IAPD Plastics Primer, Module 1

  6. Mold Lid Mold Resin Compression Molding • Sheet and block molding • Parts molding The IAPD Plastics Primer, Module 1

  7. Rotational Molding • Low cost • Low pressure • Used in many markets • Easily adapted for short production runs The IAPD Plastics Primer, Module 1

  8. Transfer Molding Widely used in the semiconductor industry The IAPD Plastics Primer, Module 1

  9. Calendering The IAPD Plastics Primer, Module 1

  10. Hand (or Spray) Lay Up • Used to make large parts • Used to produce fiberglass boats and camper shells The IAPD Plastics Primer, Module 1

  11. Laminating Resin Binder Reinforcing Substrate Heat and pressure applied to the top and bottom of the material The IAPD Plastics Primer, Module 1

  12. Filament Winding • Used to make containers and tubes • Items used for transportation of liquids or gasses The IAPD Plastics Primer, Module 1

  13. Polymer Orientation Used to manufacture polymer fibers, strapping, webbing, film, sheet and profiles The IAPD Plastics Primer, Module 1

  14. Plastics Fabrication • CNC machining centers • CNC lathes • Cutting and drilling • Profiling • Routing and milling • Thermoforming • Forging • Milling • Welding • Bending • Bonding The IAPD Plastics Primer, Module 1

  15. Thermoforming • Single station thermoforming • Rotary station thermoformers • Pressure forming • Twin sheet thermoforming The IAPD Plastics Primer, Module 1

  16. Welding • Extrusion welding • Hot gas welding • Butt welding • Spin welding • Solvent welding The IAPD Plastics Primer, Module 1

  17. Bonding The union of materials by adhesives; to unite materials by means of an adhesive The IAPD Plastics Primer, Module 1

  18. The Performance of a Plastic Part is Affected By: • Type of load • Size and application of load • Frequency of application of load • Speed of load • Temperature the part will see, and for how long • Use and environment of load The IAPD Plastics Primer, Module 1

  19. Mechanical Properties • Torsional strength • Modulus • Impact strength • Specific gravity • Water absorbtion • Coefficient of Friction (COF) • Tensile strength • Elongation • Compressive strength • Creep • Shear strength • Flexural strength The IAPD Plastics Primer, Module 1

  20. Testing Organizations • AFNOR - Association Francaise de Normalisation (France) • BSI - British Standards Institution (UK) • IEC - International Electrotechnical Commission • JIS - Japanese Industrial Standards The IAPD Plastics Primer, Module 1

  21. Tensile Strength The IAPD Plastics Primer, Module 1

  22. Elongation The IAPD Plastics Primer, Module 1

  23. Compressive Strength • Measured in pounds per square inch (PSI) • Higher PSI = harder to compress The IAPD Plastics Primer, Module 1

  24. Creep • Associated with compressive strength • Creep at room temperature is called “cold flow” The IAPD Plastics Primer, Module 1

  25. Shear Strength The IAPD Plastics Primer, Module 1

  26. Flexural Strength The IAPD Plastics Primer, Module 1

  27. Torsional Strength The IAPD Plastics Primer, Module 1

  28. Modulus • Also referred to as “stiffness” • Used in conjunction with strengths (flexural modulus, tensile modulus, etc.) • Higher modulus = stiffer material • Measured in PSI The IAPD Plastics Primer, Module 1

  29. Izod Impact Tensile Impact Gardner Impact Impact Strength The IAPD Plastics Primer, Module 1

  30. Specific Gravity • Related to the density of material • Can be used to determine the weight of material • Specific gravity of less than 1.0 will float in water The IAPD Plastics Primer, Module 1

  31. Water Absorption • Measured by the percentage of swell • Think of a sponge as having high percentage absorption The IAPD Plastics Primer, Module 1

  32. Coefficient of Friction (COF) • Resistance to sliding (slickness) • Low COF = more slippery (think of “wet ice” as having lowest COF) • Static COF refers to initial movement from rest • Dynamic COF refers to being already in motion The IAPD Plastics Primer, Module 1

  33. Thermal Properties • Coefficient of thermal expansion • Heat deflection temperature • Continuous service temperature • Melting point • Thermal conductivity The IAPD Plastics Primer, Module 1

  34. Coefficient of Thermal Expansion (CTE) • Change in size as temperature changes • Lower value = less change with temperature The IAPD Plastics Primer, Module 1

  35. Heat Deflection Temperature (HDT) • Temperature up to which a material can perform, under load, without distorting • Measured in degrees Fahrenheit, usually under 264 PSI • Used most widely to predict performance The IAPD Plastics Primer, Module 1

  36. Continuous Service Temperature (CST) • Highest temperature a material can withstand and still retain at least 50% of its properties • Measured in degrees Fahrenheit, in air • In high temperatures, both CST and HDT must be considered The IAPD Plastics Primer, Module 1

  37. Melting Point Temperature at which a crystalline thermoplastic changes from solid to liquid The IAPD Plastics Primer, Module 1

  38. Thermal Conductivity • How much heat a material will conduct • Most plastics are good “insulators” (do not conduct heat well) • Higher value = more heat conducted • Thermal conductivity of plastics is 300 to 2,500 times less than most metals The IAPD Plastics Primer, Module 1

  39. Electrical Properties • Volume resistivity • Surface resistivity • Dielectric constant • Dielectric strength • Dissipation factor • Arc resistance • Flammability The IAPD Plastics Primer, Module 1

  40. Volume Resistivity • Ability of electricity to flow through a material • Measured in ohms/cm • Lower value = more easily current flows • Higher value = better resistor or insulator The IAPD Plastics Primer, Module 1

  41. Surface Resistivity • Ability of electricity to flow over the surface of a material • Same measurements as volume resistivity • Used to evaluate material when static discharge characteristics are critical The IAPD Plastics Primer, Module 1

  42. Surface Resistivity Insulative Range Conductive Range Static Dissipative Range 20 9 10 11 12 1 2 3 4 5 1 10 10 10 10 10 10 10 10 10 10 Shielding Range 6 7 8 10 10 10 106 to 108 Critical Range for ESD Control The IAPD Plastics Primer, Module 1

  43. Dielectric Constant That property of a dielectric that determines the electrostatic energy stored per unit volume for unit potential gradient The IAPD Plastics Primer, Module 1

  44. Dielectric Strength • Effectiveness of material as an insulator • Measured in volts/.001 thickness • Higher value = better insulator • Voltage is increased until material arcs, showing a breakdown The IAPD Plastics Primer, Module 1

  45. Dissipation Factor Tangent of the loss angle of the insulating material The IAPD Plastics Primer, Module 1

  46. Arc Resistance Time required for an arc to establish a conductive path on the surface of an organic material The IAPD Plastics Primer, Module 1

  47. Flammability • Measured by UL94 ratings • Most favorable ratings are given to materials that extinguish themselves rapidly, and do not drip flaming particles • Scale from highest burn rate => most flame retardant is HB, V-2, V-1, V-0, 5V The IAPD Plastics Primer, Module 1

  48. The IAPD Plastics Primer, Module 1

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