Question

For the production of pipe one should use

• A. Calendering
• B. Extrusion
• C. Compression moulding
• D. Injection moulding

Hint:

PVC and HDPE pipes are commonly manufactured using extrusion.

Answer 1

The Correct Option is B

Step 1: Understanding pipe manufacturing.
Pipes require continuous hollow shapes with uniform cross-section along their length. This demands a process that can continuously form such shapes.
Step 2: Role of extrusion.
Extrusion involves forcing molten polymer through a die to produce long, continuous products like pipes, tubes, and rods with constant cross-section.
Step 3: Analysis of options.
(A) Calendering: Used for sheets and films, not pipes.
(B) Extrusion: Correct — Ideal for producing pipes and tubes.
(C) Compression moulding: Used for solid shapes, not hollow continuous products.
(D) Injection moulding: Used for discrete items, not continuous pipes.
Step 4: Conclusion.
Extrusion is the appropriate process for pipe production, making option (B) correct.

Answer 2

Pipe manufacturing requires a continuous hollow product of constant cross-section and theoretically unlimited length, so the right process must be one that can run continuously rather than one that makes discrete, individual parts.

1. Calendering: Passes softened polymer between a series of rotating rollers to form flat continuous sheets or films of defined thickness. It creates a continuous flat product, not a continuous hollow tube, so it is not the process used for pipes.
2. Extrusion: Forces molten polymer continuously through a shaped die (an annular die for pipes) using a screw, producing a never-ending profile of constant cross-section that is then cooled, sized, and cut to length. This continuous-forming, constant-cross-section nature is exactly what pipe manufacturing needs.
3. Compression moulding: A fixed charge of polymer is placed in an open mould cavity and compressed under heat and pressure into one discrete solid part per cycle; it cannot produce a continuous hollow tube.
4. Injection moulding: Molten polymer is injected into a closed mould cavity to form one discrete part per shot, ideal for complex shaped parts of finite size, but not suited to a continuous, indefinitely long hollow profile like pipe.

Only extrusion offers the continuous, constant-cross-section forming needed for pipe.

Therefore, the correct answer is Extrusion.