Metals and Plastics: Properties, Types, and Processing

Properties of Metals

• Electrical Conductivity
• Heat Conductivity
• Effort Resistance
• Toughness
• Ductility
• Malleability
• Solid at ambient temperature (except for mercury)
• Economical
• Heavy
• Some are magnetic
• High melting temperature

Types of Non-Ferrous Metals and Alloys

• Copper: Red, excellent thermal and electrical conductor, corrosion-resistant, easily welded, ductile, and malleable.
• Tin: Bluish-white, brilliant, soft steel.
• Zinc: White, very resistant to corrosion and oxidation.
• Aluminum: Brilliant white, light, non-toxic, corrosion-resistant, and less soft.
• Magnesium: Lightest, elevated cost, in liquid state it reacts violently with oxygen.
• Titanium: Very expensive, durable against corrosion, good mechanical resistance, and biocompatible.

Metalworking Processes

• Embossing: Metallic iron from a dune superimposed on a matrix, which is deformed by applying a skewer with great pressure.
• Punching: Consists of cutting metallic plate with precision using a skewer with sharp edges, moved by a press.
• Spot Welding: Joining metallic plates with a cordon of welded points throughout the area.
• Drilling: For holes in metal profiles, vertical drills are used.
• Cutting: Involves cutting metal profiles using a rotating disk.
• Milling and Turning: From a solid piece, material is removed using carved tooling.
• Computer-Assisted Manufacturing: The computer is integrated into the manufacturing process.

Properties of Plastics

• Plasticity
• Thermal and Electrical Insulation
• Good combustibility
• Mechanical Resistance
• Flexibility
• Lightweight

The molecules are long, repeated combinations of atoms that form a union of monomers, and it becomes a polymer (a process called polymerization).

Types of Plastics

• Thermoplastics

  Deform with heat and solidify when cooled. They can be recycled several times. Examples include Teflon, methacrylate, and polyethylene.

• Thermosets

  They are fragile. A treatment process is used. They are more rigid and resistant than thermoplastics. They are not recyclable. Examples include phenol, epoxy resins, and polystyrene.

• Elastomers

  Macromolecules contract and expand. They have high elasticity and a high fusion temperature. They are not recyclable. Examples include silicone and rubber wetsuits.

Plastic Processing Techniques

• Injection Molding
• Compression Molding
• Vacuum Forming
• Extrusion
• Spinning
• Laminating
• Foaming

Workshop Techniques for Plastics

• Marking: Soft pencil and ink marker
• Holding: Bench vise or table clamp

• Cutting

  • Soft and thin plastic: Scissors and cutter
  • Thick plates: Metal saw
  • Brittle plastic: Arc saw
  • Expanded plastic: Utility knife, metal saw, or metallic thread
• Drilling: Hand drill or drill press
• Sanding: Files or carbide sandpaper
• Bending or Curving: Hair dryer or electric heater

• Finishing

  Paint (apply a primer of white glue beforehand)

• Joining

  Cyanoacrylate glue, contact adhesive, impact adhesive, rubber latex, hot melt glue, and epoxy adhesive