How we make it
Hot Vulcanized Seams: How We Make Every Gum Rubber Boot
Every AG Rubber Company boot starts as one flat sheet of pure gum rubber with dovetail puzzle pieces cut on each end. We roll it to your size, lock the puzzle pieces together, seal the joint and hot vulcanize it, then lay rubber-to-rubber vulcanizing tape over the seam full length and cure it a second time. The finished boot is one continuous piece of rubber with no glue line to peel.
What happens at each step
Sheet
We cut pure gum rubber sheet, tan, 40 durometer, to a flat pattern for your size. For a straight boot it is as wide as the circumference of your inside diameter; for a tapered boot it is cut as a curved sector so it rolls into a cone. One end gets a row of dovetail puzzle tabs and the other end the matching sockets.
Roll
The sheet rolls into a straight or tapered boot. The tabs on one end drop into the sockets on the other, so the joint is locked together before any heat touches it.
Seal and first cure
Vulcanizing seal goes on the puzzle-piece joint and the seam is hot vulcanized under heat and pressure. The rubber on both sides of the joint cures together into one piece.
Tape and second cure
A strip of rubber-to-rubber vulcanizing tape goes over the outside of the seam along its full length, and the boot is cured a second time. That second cure is what we mean by double hot vulcanized.
Finished
The finished boot is one continuous piece of rubber with no glue line anywhere to peel, ready to clamp onto your spout, chute or pipe.
Why not just glue the seam?
Because glue is where boots fail. A cold-bonded seam is two layers of rubber held together by adhesive, and heat, vibration and a clamp band work that glue line loose until the seam walks apart. A hot vulcanized seam has no glue line at all: the rubber on both sides of the joint cures into one piece. On our boots that happens twice, once at the puzzle-piece joint and again under the tape.
Cold bonded
Two layers held together by adhesive. It is the number one failure point on cheap boots.
Double hot vulcanized
The dovetail joint cured into one piece of rubber, then taped over full length and cured again.
What we make this way
Every part we sell gets the same double hot vulcanized seam, whatever it is called on your plant: gum rubber boots and sleeves in any size, tapered rubber boots for transitions between two diameters, rubber flex connectors for spouting and conveyors, and silo bands between a cone and a bin activator. See the industries we build for for the common sizes in each.
Sizes, walls and materials
Any inside diameter from 1 inch up, with 60 inches the largest we list. Walls of 1/8, 3/16, 1/4, 3/8 or 1/2 inch. Straight or tapered, from 4 inches long, and past 48 inches on request. Pure gum rubber, tan, 40 durometer, or EPDM, and no minimum order: one boot is a normal order.
Working from an old part number? Put it in the notes on the quote form and we will match the dimensions. The gum rubber boot FAQ covers measuring a pipe or spout.
How fast can you quote it?
Send the inside diameter, wall thickness and length, and we quote within 24 hours. Local plants can call ahead for will-call pickup in Englewood, Colorado, where most standard boots are ready the same week.
Have your measurements?
ID, wall, length. That is all we need to quote it.
Will-call pickup
Pick up your order in Englewood
AG Rubber Company2780 S Raritan St
Englewood, CO 80110
303-339-1240
Will-call hours: Monday to Friday, 7:00 AM to 4:00 PM
Local plants: call ahead and most standard boots are ready for same-week pickup.