Basic differences between common plastics

Understanding DIY Plastics

Plastics are everywhere in modern homes, from plumbing pipes to picture frame glazing. However, they are not all the same. Treating acrylic the same way you treat PVC will almost certainly result in ruined material.

Here are the four most common plastics you will encounter and how to handle them.

1. Acrylic (Plexiglass, Perspex)

Acrylic is a transparent plastic often used as a cheaper, safer alternative to glass in sheds, picture frames, and secondary glazing.

• Properties: It is stiff and scratches easily. More importantly, it is extremely brittle.
• Working with it: If you drill it with a standard wood drill bit, the bit will grab the plastic as it breaks through the back, shattering the sheet instantly. Always use a specialised plastic drill bit or a blunt twist bit, and drill slowly with a piece of scrap wood pressed firmly against the back.
• Cutting: Thin sheets can be scored deeply with a sharp utility knife and snapped over a sharp edge.

2. Polycarbonate (Lexan, Makrolon)

Polycarbonate looks exactly like acrylic but behaves entirely differently. It is often used for conservatory roofs or safety visors.

• Properties: It is virtually unbreakable and highly impact-resistant. You can hit a sheet of polycarbonate with a hammer, and it will bounce off.
• Working with it: It can be drilled easily with standard bits and cut with standard woodworking saws without shattering. However, it scratches very easily and degrades in sunlight if not treated with a UV-resistant coating.

3. PVC (Polyvinyl Chloride)

PVC is the standard material for modern drain pipes, gutters, and UPVC window frames.

• Properties: It is rigid, highly weather-resistant, and relatively easy to cut.
• Gluing: PVC is very difficult to glue with standard adhesives like epoxy or superglue. To join PVC pipes, you must use a specialised solvent cement that actually melts the surface of the plastic, fusing the two pieces together chemically.

4. ABS (Acrylonitrile Butadiene Styrene)

ABS is an impact-resistant, tough plastic used for 3D printing, Lego bricks, car interior trims, and some black plumbing pipes.

• Properties: It is tougher than PVC and handles wide temperature swings better.
• Working with it: It sands well and can be glued successfully with cyanoacrylate (superglue) or specific ABS solvent cements.

Safety Note

When cutting or sanding plastic by machine, the friction generates heat. If you go too fast, the plastic will melt rather than cut, gumming up your saw blade or sandpaper and releasing toxic fumes. Always use low speeds and wear a mask so you do not inhale plastic dust.