Make Your Own Plastic "Epoxy" Adhesive

[sequoiaranger]

I kinda discovered this the hard way a long time ago---parts of some of my models dissolved when I spilled some Lacquer thinner on them and didn't wipe it up right away.

To help fix my box-spar to the wing of my whif-project Avro Avatar, and to add some adhesive area, I used my "plastic epoxy" to good effect. I took an old photo film canister (remember when they had those?), put in a small handful of plastic sprue bits, then poured in lacquer thinner (make sure it's LACQUER thinner---regular paint thinner won't work) until I had covered the parts. Then sealed the canister up to let the parts "soak" up the thinner. Then wait. Maybe hours. With trial-and-error, you can vary the consistency of the "putty" from tarry to gooey to runny by how long you let the thinner work, and the proportions of volume of thinner to plastic. If you only need a small bit of putty, use a 1/2-inch piece of sprue and a thimble-full of thinner. My stuff "dried" out and solidified overnight, but all I had to do was add more thinner and wait to get it to working consistency again.

The stuff will smear on with a craft stick, but it will dissolve, and bond with, adjacent plastic like a weld. When "dry", it behaves just like the plastic it is--its file-able, sand-able, and paint-able. It will stay pliable for a long time, but slowly will harden to "real" plastic.

You can shove it into holes and have it wrap around the lip, making a nice inside "grip" for whatever you stick in the hole. Probably not too good on very thin pieces (again, trial and error) or vac-forms. For those, you can use PVC cement and small pieces of PVC to get a putty.

You can do the same with MEK or other plastic solvent-glues, but lacquer thinner is so much cheaper, just takes a little longer.

EDIT: The pic below has two cast-off model pieces (gray) held together with a gob of "plastic epoxy" (green?). The gob was soft for about a day, getting harder by the hour, but when it became solid I couldn't pull the pieces apart with two pliers--I mean this is SOLID!!

[Hobbes]

IIRC this used to be pretty common in the old days, before decent cements were available. Some people use lacquer thinner to glue long straight seams (e.g. fuselage halves) through capillary action: hold the fuselage halves together, and drip some thinner on the inside.