1: Thermoplastic Classifications

Introduction to Thermoplastic Classifications

• Thermoplastics dominate the plastics market, comprising approximately 85% of total usage.
• Classification of thermoplastics:
  • Commodity Thermoplastics: Common, low-cost materials.
  • Engineering Thermoplastics: Higher performance materials with advanced properties and costs.

Thermoplastics Classification Pyramid

• Two main categories:
  • Amorphous Thermoplastics
  • Semi-crystalline Thermoplastics

Characteristics of Amorphous vs Semi-crystalline Thermoplastics

• Semi-crystalline thermoplastics:

  • Exhibit a sharp melting point and specific melt behavior.
  • Difficult to thermoform.
  • Generally opaque or translucent.

• Amorphous thermoplastics:

  • Soften over a broad temperature range.
  • Easier to thermoform.
  • Tend to be clear or semi-transparent.

Properties Comparison

• Amorphous Plastics have:

  • Superior adhesive bonding characteristics.
  • Prone to stress cracking and have poor fatigue resistance.
  • Generally lower chemical resistance compared to semi-crystalline plastics.

• Semi-crystalline Plastics have:

  • Better fatigue and chemical resistance.
  • Lower coefficients of friction.

Commodity Thermoplastics Categories

• Amorphous Thermoplastics:

  • Polystyrene
  • Polyvinyl Chloride (PVC)
  • Glycol Modified PET (PETG)
  • Acrylonitrile Butadiene Styrene (ABS)
  • PMMA (Plexiglass)
  • Cellulosic (Cellulose Acetate Butyrate)

• Semi-crystalline Thermoplastics:

  • High Density Polyethylene (HDPE)
  • Low Density Polyethylene (LDPE)
  • Ultra High Molecular Weight Polyethylene (UHMWPE)
  • Polypropylene (PP)

Engineering Thermoplastics

• Amorphous Engineering Thermoplastics:

  • Polycarbonate (e.g., Lexan)

• Semi-crystalline Engineering Thermoplastics:

  • Nylons (Polyamides)
  • Polyethylene Terephthalate (PET)
  • Polybutylene Terephthalate (PBT)
  • Polyoxymethylene (POM/Acetyls) (e.g., Delrin)

High Performance Engineering Thermoplastics

• Amorphous High Performance Thermoplastics:

  • Polysulfone (PSU) (e.g., Udel)
  • Polyetherimide (PEI) (e.g., Altem)

• Semi-crystalline High Performance Thermoplastics:

  • Fluoropolymers (e.g., Teflon, PTFE)
  • Other Fluorinated Polymers (e.g., FEP, PFA, PVDF)
  • Polyphenylene Sulfide (PPS)
  • Polyether Ketone (PEEK)

Imidized Polymers

• Polyimides:
  • Examples include:
  • Vespel
  • Kapton
  • Modified Polyimide (Polyamide Imide) (e.g., Torlon)
  • Combines properties of polyamides and polyimides.

Conclusion

• Upcoming lectures will delve deeper into the characteristics of highlighted thermoplastic families, enhancing understanding and preparation for applications in material selection.

• Thanks for listening!