polyethylene the miracle plastic that is used for milk cartons buckets holding tanks gas cans cutting boards marine accessories and a multitude of other applications you can often recognize polyethylene by this recycle symbol and the letters HDPE or LDPE why is polyethylene able to do all this because it is impervious to water chemicals and even gasoline virtually nothing affects it however that has made repairing it difficult because no glue could stick to it until now now with tap poly weld adhesive it is possible to repair polyethylene and even build products for outdoor use with seaboard this polyethylene tank has been repaired with poly weld and we can't peel it off these two pieces of seaboard won't break even with this kind of force this video segment will show you how to get these results Polly weld is a two-part epoxy adhesive it comes in two sizes the 30 milliliters size dispenses like this and the resin and hardener are dispensed in equal amounts onto a smooth surface such as a butter dish lid and mixed thoroughly for larger jobs use the fifty seven grams eyes attach the mixing tube place the plunger on the gun then insert the glue container and mixing tube when assembled the Polly bonder is automatically mixed and dispensed through the mixing tube for easy application the key to Polly welds strength is in the preparation be sure to read the directions carefully all polyethylene must be flame treated here is how using a propane torch with either a pencil tip or a flame spreader observe where the flame turns yellow you may need to do this in a darkened room to see this part of the flame using that yellow portion wave the flame back and forth over the area to be glued four or five times for a total exposure of two to three seconds make sure you do it to both pieces this process makes the polyethylene molecules receptive to the glue it is important to do it exactly as described and not to melt the plastic please note this process should not be used on fuel tanks due to the risk of explosion to tell if the flame treatment is effective dab some water on the treated area we have dyed the water green to make it easier for the camera to see water applied to untreated polyethylene beads up as you can see here the properly treated surface will allow the water to sheet or flatten without beating if the water beads treat the surface again this step is essential for bond strength note that water will not impair the bond let's demonstrate repairing a polyethylene tank polyethylene tanks are you for hundreds of applications because they can hold everything from drinking water to gasoline we will demonstrate on this small tank first we will clean the surface using acetone and a clean paper towel acetone is highly flammable prior to flame treating make sure all acetone has evaporated from the cleaned area close the acetone container and properly dispose of rags second we flame treat and test the surface since this is a small repair we will use the 30 milliliter tube dispensed equal amounts of resin and hardener onto a hard non-porous surface and mix thoroughly for two full minutes even though it looks mixed sooner once mixed you have 10 to 15 minutes of working time simply smear the poly weld onto the tank and you are done for more structural strength you can embed fiberglass fabric as you see here to smooth out the repair put a piece of wax paper on the uncured poly weld and use your finger to shape it in a few hours the glue will be cured enough to peel off the wax paper poly weld reaches 90% strength in 24 hours what about building with polyethylene we will demonstrate with seaboard which is an exterior grade of polyethylene the technique is very similar to repairing tanks the surface to be bonded must be flame treated remember to treat both surfaces using the dispensing gun and the mixing tubes is convenient for this type of use dispense the glue along the edges to be joined when using the mixing tube and gun discard the first two to three inches of mixture to establish a good accurate flow in the mixing tube for best adhesion apply the poly weld to both pieces before putting them together when putting the pieces together it is possible to squeeze out so much glue that the joint is weak this is especially true if you are using clamps this can be Illustrated using to clear pieces of plastic you can see the glue being squeezed out so that very little remains this will produce a weak bond therefore it is important that the glue remains at least 5 thousandths of an inch thick in the joint to provide maximum strength but how do you measure 5 thousandths here are two simple methods you will think of others both heavyweight typing paper or copy paper and 2 pound fishing line or about 5 thousandths of an inch thick after you apply the glue put a few small pieces of fishing line or strips of paper in the glue joint these will create the perfect gap for maximum bond strength there is no need for clamping wipe off the excess glue and allow it to cure polyworld reaches 90% strength in 24 hours and continues to cure for 7 days since only the glued areas were flame treated any excess glue which was squeezed out can usually be easily removed with a sharp knife one last safety note Polly weld has not been approved for food or drinking water contact and remember never heat treat a fuel tank due to the risk of explosion now with tap Polly weld adhesive you can tackle tasks you never before thought possible and it works with other plastics too down to plastics the fantastic plastic place