Solvent-welding plastic involves using a solvent to partially liquefy plastic along the joint and allowing the joint to solidify causing a permanent chemical weld

Solvent-welding plastic involves using a solvent to partially liquefy plastic along the joint and allowing the joint to solidify causing a permanent chemical weld. It is similar in end result to heat welding metal or thermoplastic. Welded joints have an advantage over other adhesives in that there is no third material creating the joint. Joints are also airtight when created properly. Thus, for example, PVC/ABS cement is my preferred method for attaching vinyl tubing (flexible PVC) to air tanks (made from ABS) when simply connecting existing tubing is not possible or practical.

The process of solvent welding is simple. Apply solvent to the pieces you want to adhere, push the pieces together (not necessarily in that order), and then wait for the solvent (they are all very volatile) to evaporate into the environment and the polymer strands of the plastic to solidify. The most difficult part is thus finding solvents that will dissolve the plastic in question.

Safety Warning: most of these solvents are toxic. Do not inhale them, especially deliberately. Use in a very well ventilated area. They are also highly volatile and thus flammable. Keep away from open flames. Do not smoke while applying solvents.

On solubility

The following is an incomplete list of the most common plastics used in Nerf and their compatibility with common solvents. A "Y" indicates that the solvent will dissolve the plastic in question. A "N" indicates that the solvent is not recommended for use with that plastic. Either it does not dissolve the plastic at all or does so poorly.

Polymethyl methacrylate (Acrylic)- 1,2 Dichloroethane: Y- Acetone: Y- Cyclohexanone: Y- Dichloromethane: Y- MEK: Y- Methyl benzene: Y- Tetrahydrofuran: Y

Acrylonitrile butadiene styrene (ABS)- 1,2 Dichloroethane: Y- Acetone: Y- Cyclohexanone: Y- Dichloromethane: N- MEK: Y- Methyl benzene: N- Tetrahydrofuran: N

Polyacetal (Delrin - POM)- 1,2 Dichloroethane: N- Acetone: N- Cyclohexanone: N- Dichloromethane: N- MEK: Y- Methyl benzene: Y- Tetrahydrofuran: N

Cellulose acetate butyrate (Butyrate)- 1,2 Dichloroethane: Y- Acetone: Y- Cyclohexanone: Y- Dichloromethane: Y- MEK: Y- Methyl benzene: Y- Tetrahydrofuran: Y

Cross-linked low density polyethylene (PEX)- 1,2 Dichloroethane: Y- Acetone: Y (at 100%)- Cyclohexanone: N- Dichloromethane: Y- MEK: N- Methyl benzene: Y- Tetrahydrofuran: Y

Low density polyethylene (LDPE)- 1,2 Dichloroethane: Y- Acetone: Y- Cyclohexanone: Y- Dichloromethane: Y- MEK: Y- Methyl benzene: N- Tetrahydrofuran: N

High density polyethylene (HDPE)- 1,2 Dichloroethane: Y- Acetone: Y- Cyclohexanone: N- Dichloromethane: N- MEK: Y- Methyl benzene: Y- Tetrahydrofuran: N

Ultra high molecular weight polyethylene (UHMW)- 1,2 Dichloroethane: N- Acetone: N- Cyclohexanone: N- Dichloromethane: Y- MEK: N- Methyl benzene: Y- Tetrahydrofuran: N

Nylon- 1,2 Dichloroethane: N- Acetone: N- Cyclohexanone: N- Dichloromethane: N- MEK: N- Methyl benzene: N- Tetrahydrofuran: N

Polycarbonate- 1,2 Dichloroethane: Y- Acetone: Y- Cyclohexanone: Y- Dichloromethane: Y- MEK: Y- Methyl benzene: Y- Tetrahydrofuran: Y

Polyester (Polyethylene terephthalate - PET)- 1,2 Dichloroethane: Y- Acetone: Y- Cyclohexanone: N- Dichloromethane: Y- MEK: N- Methyl benzene: N- Tetrahydrofuran: Y

Copolyester (Polyethylene terephthalate glycol - PETG)- 1,2 Dichloroethane: Y- Acetone: Y- Cyclohexanone: Y- Dichloromethane: Y- MEK: Y- Methyl benzene: Y- Tetrahydrofuran: Y

Polypropylene- 1,2 Dichloroethane: Y- Acetone: Y- Cyclohexanone: N- Dichloromethane: Y- MEK: N- Methyl benzene: Y- Tetrahydrofuran: N

Polystyrene- 1,2 Dichloroethane: Y- Acetone: Y- Cyclohexanone: Y- Dichloromethane: Y- MEK: Y- Methyl benzene: Y- Tetrahydrofuran: Y

Polyvinyl chloride (PVC)*- 1,2 Dichloroethane: Y- Acetone: Y- Cyclohexanone: Y- Dichloromethane: Y- MEK: Y- Methyl benzene: Y- Tetrahydrofuran: Y*Includes PVC in pipe and flexible tube, as well as CPVC as we use it, since our CPVC is simply Copper-sized PVC and not Chlorinated PVC.

Teflon (TFE)- 1,2 Dichloroethane: N- Acetone: N- Cyclohexanone: N- Dichloromethane: N- MEK: N- Methyl benzene: N- Tetrahydrofuran: N

On solvents

1,2 Dichloroethane: Also known as Ethylene dichloride. Found in paint removers.

Acetone: Found in small quantities in nail polish remover. Also found in various plastic cements. Also found in acrylic paint thinners and varnishes. Can be bought pure.

Cyclohexanone: Found in plastic cement, particularly ABS and PVC pipe cement.

Dichloromethane: Also known as Methylene chloride. Found primarily in paint stripper. Used as an industrial solvent. Banned in Europe.

Methyl ethyl ketone (MEK): Also known as Butanone. A large component of almost all plastic cements especially ABS and polystyrene cement. Can be bought pure.

Methyl benzene: Also known as Toluene. Used mostly as a paint thinner or paint remover. Found along with MEK in polystyrene model kit cement.

Tetrahydrofuran: Found almost exclusively in PVC cement. Can also be in some varnishes.

Plastic cement is generally comprised of a solvent (or mixture of solvents) along with dissolve plastic resin of the plastic in question. Thus PVC cement will contain dissolved PVC along with the solvents.Examples:Genova ABS cement is around 20% Acetone, 60% MEK, and 20% ABS resin.Oatey Green Transition cement is around 40% Tetrahydrofuran, 35% Acetone and MEK, 10% Cyclohexanone, and 15% PVC resin.Look either on the can or search for Material Safety Data Sheets for the ingredients and quantities, and then look up which plastics these will work with.

This post has been edited by Zorn's Lemma: 21 April 2010 - 07:17 PM