More about Polycaprolactone


PCL pellets, before and after melting

[Edit: Updated to add PLA and ABS to the list of compatible materials]

Polycaprolactone or PCL is a white plastic that is very hard and slick at room temperature, but melts to a putty-like consistency when heated under very hot water. Make Magazine has an excellent article summarizing some of PCL’s many uses, and in fact that article is where I first learned of it.

PCL is very useful as a clay-like molding material, and as I discuss in a previous post, as a material for Reversible, semi-permanent PVC glue joints and custom fittings.

Two PVC pipes joined with Polycaprolactone

Compatibility with other plastics

Depending on your application, PCL’s tendency to stick to other plastics may or may not be desirable. I compiled this table of compatibility based on my own experiments:

Material Type Common Uses Result Notes
PLA (Polylactic Acid) 3d printing sticks very well Be careful not to overheat and distort PLA
ABS (acrylonitrile butadiene styrene) 3d printing, Lego sticks very well Custom Lego!!!
PVC (Polyvinyl Chloride) white plastic pipe sticks very well preheat pieces for best bond
CPVC (Cross-linked Poly Vinyl Chloride) yellowish plastic pipe sticks very well preheat pieces for best bond
Polycarbonate (aka Lexan) very strong glass substitute sticks very well preheat pieces for best bond
PEX flexible water pipe does not stick
PET / PETG soda bottles does not stick
Metals copper, steel, aluminum does not stick


Polycaprolactone is sold under  a number of  brand names including InstaMorph, Shapelock, Friendly Plastic, Missing Link plastic, etc.

As far as I can tell they are nearly identical products, with the exception of Missing Link — they sell a “flow formula” that is a bit less viscous when melted, which may be useful for some applications.

Where to buy

      Make Magazine’s Maker Shed sells Shapelock brand



        Amazon sells various brands and sizes for prices mostly in the $10-20 range. I found that the best way to find all your options on Amazon is to

search for polycaprolactone

        rather than any particular brand.


Buying through my Amazon links has the added benefit of modestly subsidizing my experimentation, for which I thank you.