High-temperature resistant PVC welding

Plastic hot-melt welding is a process in which the plastic joint surface is melted by heating and then cooled and solidified under pressure to form a strong connection. The following is a detailed description of this technology:

1. Process principle

Heating and melting: By using heat sources such as hot plates, hot air, lasers or ultrasonic waves, the plastic joint area is heated to a molten state (usually reaching 10-30℃ above the material's melting point).

Pressure fusion: Apply pressure (0.2-1.0MPa) in a molten state to cause the molecular chains to diffuse with each other.

Cooling and setting: Maintain the pressure until it cools and solidifies, forming a weld seam with a strength close to that of the base material.

2. Applicable materials

Thermoplastics: PP, PE, PVC, ABS, PC, PA (nylon), PVDF, etc.

Not applicable materials: Thermosetting plastics (such as epoxy resin), some high-temperature resistant special engineering plastics (such as PEEK, which requires special processes).

3. Comparison of welding methods

Method: Temperature range (℃), applicable thickness (mm), characteristics

Hot plate welding 200-400 2-20 is suitable for large flat joints and has low energy consumption

Ultrasonic welding features a local instantaneous high temperature of 0.5 to 5 seconds and a fast speed (0.1 to 1 second), making it suitable for precision parts

Rotary friction welding 180-300 5-50 is suitable for circular cross-sections and has high strength

Laser transmission welding features precise temperature control from 1 to 10 degrees Celsius without contact, making it suitable for transparent and semi-transparent materials

4. Key process parameters

Temperature control: It needs to be precisely adjusted according to the melting point of the material (for example, HDPE is usually 190-230℃).

Pressure time

Heating time: 10-60 seconds (depending on thickness)

Holding pressure time: Usually 1.5 to 2 times the heating time

Bevel design: V-shaped (60-90°) or lap joint (overlap ≥3 times the wall thickness)

5. Quality inspection standards

Non-destructive testing

Air pressure test (0.2-0.5MPa for 5 minutes)

Ultrasonic C-scan (for detecting internal pores)

Destructive testing

Tensile strength (should reach more than 80% of the base material)

Bending test (no cracking)

Industry standard

ISO 12176 (Welding of Polyethylene Pipes)

AWS G1.10M (Plastic Welding Specification)

6. Typical application scenarios

Piping system: Welding of plastic pressure pipes with diameters ranging from DN20 to DN1200

Automotive parts: Fuel tank (HDPE), intake manifold (PA66) welding

Medical devices: IV infusion bottles, dialysis filter housings

Packaging industry: Plastic drum sealing and welding, IBC ton box seams

7. Advantages and Limitations

Advantages

No adhesive contamination (compliant with FDA/USP Class VI requirements)

Weldable dissimilar plastics (such as ABS and PC)

The energy consumption is only 1/3 to 1/5 of that of metal welding

Limitation

Not applicable to workpieces with a wall thickness greater than 50mm

Hygroscopic materials (such as PA) need to be pre-dried

8. Latest technological advancements

Infrared preheating + vibration friction hybrid welding (30% efficiency boost)

Real-time temperature field control system based on machine learning

Low-temperature welding process for degradable PLA materials (< 150℃)

Note: Specific parameters need to be adjusted according to the welding process Card (WPS) provided by the material supplier. Especially for modified plastics with glass fiber reinforcement, the welding pressure should be increased by 10-15%.