Plastic Welding course transitions you from traditional metal-joining mindsets to the world of polymers. Unlike metal, plastic has a narrow "melt window" and no visible color change when it gets hot, making temperature control and "molecular agitation" the keys to a strong bond.

Day 1: Material Identification & Hot Air Welding

Day one is about chemistry and manual dexterity. If you try to weld Polyethylene (PE) with a Polypropylene (PP) rod, the bond will fail instantly.

• Polymer Identification: Learning the "Burn and Sniff" test and using resin codes to match welding rods to base materials.

• The "Melt Window": Understanding the specific temperature ranges for common plastics (e.g., $280\text{°C}$ for PVC vs. $300\text{°C}$ for PP).

• Hot Air Hand Welding: * Pendulum Welding: Moving the torch in a steady rhythm to heat both the rod and the groove.

  • Speed Tip Welding: Using a specialized nozzle that feeds the rod and applies pressure simultaneously.

• Joint Preparation: Using scrapers to remove the "oxidation layer" (UV-damaged skin) which prevents a true molecular bond.

Day 2: Extrusion Welding & Butt Fusion

Day two moves into heavy-duty industrial applications, such as chemical tanks and geomembranes, where hand welding isn't strong enough.

• Extrusion Welding: Using a "portable extruder" that grinds plastic rod, melts it internally, and pumps out a molten bead. This is essential for thick materials ($6\text{ mm}$ to $30\text{ mm}$).

• Butt Fusion (Pipe Welding): * The 4 Phases: Heating, Change-over, Joining, and Cooling.

  • Bead Interpretation: Learning how the shape of the rolled-over "bead" indicates if the pressure and heat were correct.

• Electrofusion: Joining HDPE pipes using internal electrical heating coils and a computerized processor.

• Quality Control: Performing "Spark Testing" (High Voltage) to find pinhole leaks in a weld and "Peel Decohesion" tests to verify strength.