Nitrile rubber (NBR) is an oil-resistant synthetic rubber and a copolymer. The monomers used to produce nitrile are acrylonitrile and butadiene. Nitrile is often used in gaskets, hoses and applications which require oil-resistant properties. Common exposure to gas, oil and other typically harmful liquids and chemicals, make nitrile a hard to glue material, in most instances. This difficulty is compounded when you factor in the low surface energy of the nitrile substrate. Low surface energy materials are extremely difficult to glue. Their low surface energy results in an extremely slick surface. Glues function by forming a superficial glue join, between each substrate. Glue joins have nothing to stick to, on extremely low surface energy slick surfaces. Even if it did, this glue join is exposed to the elements, including oil, water, etc. These elements break down the join. Glue joins will not flex and will become brittle and break, when bent. Nitrile is flexible. All of these issues, make nitrile a problem substrate for many.
It is imperative that the adhesive used to bond nitrile rubber needs to a) work beneath the surface, b) have oil, gas and chemical resistance and c) be flexible. Fortunately our Surface Insensitive Molecular Bonding Agent and Bonding Poly Process (Process) does just that. Our Process uses the laws of chemistry and the principles of Physics to create bonds. With elastomers, pressure effectively increases the surface area area available to bond. With the added pressure, the Process will bond Nitrile to itself, to any other polymer and/or to any other substrate quickly, easily and permanently. The steps of the Process are outlined later down the page.
Nitrile rubber is a polymer. Conventional wisdom dictates that you can not glue polymers, especially nitrile rubber….for all the reasons we discussed. Since we developed our Polymer Bonding Process, we have learned a lot about bonding polymers. One discovered fact is that nitrile rubber is a very difficult polymer to glue. It is not just getting nitrile rubber to stick to something, the challenge is to get nitrile rubber to adhere with strength.
Why is nitrile rubber so difficult to glue? Fundamentally, the difficulty is that nitrile rubber is an elastomer. From trial and error, we have learned that, with elastomers, pressure is needed to create a bond to any surface. Greater pressure than with polymers like nylon, HDPE, polypropylene, etc. The key to bonding any type of nitrile is applying extra firm pressure for fifteen seconds, when the two surfaces are brought together. When this technique is used in conjunction with the Bonding Poly Process, the nitrile will be covalently bonded.
The Secret to our patented Polymer Bonding Process
What’s the secret of the Polymer Bonding Process? It’s the chemical and molecular reaction created when we combine:
- a polymer-enhanced, Surface Insensitive Structural Adhesive;
- our standard Activator/Accelerator, (the chemistry)
- the Poly Prep (chemistry again)
- Heat (the molecular reaction part of the process.)
This molecular process we utilize conjoins the two surfaces together on a molecular level and not a purely superficial one, as is the problem with glues and nitrile. The result of this process is a bond that is often stronger than the material itself. Unlike glues or epoxy’s that work purely on a superficial level by being “sticky”, our molecular bonding process takes place beneath the surface. What the Process is, is the cohesion of the monomers and polymers of each material, whether they are similar or dissimilar. In regards to plastics, this process is called polymerization. One of the reasons our bonding process is so effective on poly’s, is that our system of bonding them, is similar to the system used to create them in the first place. Our Bonding Poly Process is a quick, simple way to permanently interlace two surfaces together on a molecular level. The end result is a covalent bond that is flexible, permanent and impervious to the elements, oil, gas, etc. This is essential, when attempting to successfully bond nitrile rubber.
The steps for bonding nitrile rubber to itself or to another poly surface.
- Use sandpaper or steel wool to rough the nitrile rubber or poly surfaces.
- Clean the surfaces with a cleaner that will not leave a residue.
- Wipe with a soft cloth.
- Saturate the nitrile rubber or poly surfaces with our Poly Prep, an adhesion promoter for polymers.
- Spray one of the nitrile rubber (poly) surfaces with our Activator/Accelerator (AA).
- Warm both poly surfaces with a hair dryer or heat gun. By touch, you want the nitrile/poly just to below hot. By temperature, about 120 degrees F.
- Apply an SI Structural Adhesive to the opposite surface from where you sprayed the AA. Make sure that the SI adhesive reaches the edges of the join.
- Very firmly Firmly press the two surfaces together for at least 15 seconds.
- Apply a bead of the SI Structural Adhesive to the seam between the surfaces.
- Spray the seam with the Activator/Accelerator.
As a result of this process, the two nitrile rubber surfaces will be bonded. Operational strength is achieved almost immediately, but the strength of the bond is directly proportional to the amount of time it is given to fully cure.
NOTE: We soon will have a how to video for every substrate. In the meantime, the process for bonding Silicone rubber as an elastomer, is identical to the process for bonding nitrile rubber. Below is the video for bonding Silicone rubber. The steps are the same.
To bond nitrile rubber to steel; to bond nitrile rubber to aluminum; to bond nitrile rubber to metal
- Rough the surface of nitrile rubber with sandpaper or steel wool.
- Sand the steel, aluminum or metal first with a coarse grade of sand paper.
- Then sand the steel, aluminum or and the metal with a low-grit (400 or 600) coarse sand paper. You want a near white finish or steel or polished surface for aluminum and other metals. It makes a difference.
- Clean all surfaces with a cleaner that will not leave a residue.
- Wipe with a clean soft cloth.
- Saturate the nitrile rubber surface with our Poly Prep, an adhesion promoter for polymers.
- Spray a solvent based Activator/Accelerator (AA) on either the nitrile rubber or metal.
- Warm the nitrile rubber surface with a hair dryer or heat gun. By touch, you want the nitrile/poly just to below hot. By temperature, about 120 degrees F.
- Apply an SI Structural Adhesive to the opposite surface from where the AA was sprayed.
- Firmly press the two surfaces together for a minimum of fifteen seconds.
As a result of this process, the nitrile rubber and metal surfaces are bonded. Operational strength is immediate, but the strength of the bond is directly proportional to the amount of time it is given to fully cure.
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Any of our Poly, Deluxe or Professional Kits will bond Delrin® to itself and any other substrate; except stainless steel and glass.
*If you have any questions, feel free to call 877-565-7225.