How to properly use a epoxy cartridge system

Through our experiences we have developed the following recommendations for successful epoxy cartridge applications.

1. Remove the the tip(s) of the cartridge(s) to expose the epoxy. Position the mixing nozzle over the tip(s). Place the retaining nut over the mixing nozzle and screw and tighten the retaining nut until secure.






2. Clip the tip of the mixing nozzle to the desired thickness of bead if needed (just like caulking tubes). For knifegrade material you may need to clip the tip back most of the way back.






3. Dispense the first 25ml (or 3-4 inches) of the mixed product onto a spare piece of cardboard. After the first 3 or 4 inches, the product should be fully mixed when it exists the mixing nozzle. Check for thoroughly mixed color at this point and then start dispensing as needed into the crack or hole.


4. When you are finished with the application you first should take the mixing nozzle off and wipe tip of cartridges with a cloth. Try not to drag A product into B hole. Wipe down when holes are horizontal.

5. Fill tip(s) with plug(s) to store product. Note: Do not put product plug A in product B cartridge hole.

3 Things NOT to do When Using Epoxies

OK, you've decided your project deserves the very best, and you've opted for a high-quality two component structural epoxy adhesive to assure the highest strength for your assembly. Now, how do you make sure it's used correctly (either by you or someone else), so you can get the maximum performance expected? Here are 3 things NOT TO DO--doing these will definitely compromise the cure of the adhesive and reduce the strength and durability:

1. Not using the correct mix ratio. For instance: if the mix instructions call for a 2:1 mix (that is, 2 parts of "A" with 1 part of "B"), DO NOT vary from this ratio! Some people are under the misconception that "if a little "B" is good, a little more is better". Not at all! Epoxies are formulated for a specific mix ratio, and that mix ratio needs to be maintained to ensure that the proper chemical reaction occurs between the two parts. Adding more "B" (a common mistake) may seem to make the cure progress faster, but at the expense of ultimate cured properties. Don't do it.

2. Not mixing the two parts thoroughly. Many people begin their fabricating careers with the unsaturated polyesters, then advance to the stronger and more versatile epoxies as they learn more about the relative performance capabilities of the two different chemistries. But, while it is somewhat OK to mix the polyester and cream hardener "with a lick and a promise" (the cure will still progress adequately, albeit slower), this cavalier attitude towards mixing will definitely NOT work with the epoxies: the "A" and "B" MUST be thoroughly mixed, again to ensure that the appropriate chemicals are in intimate contact to carry out the necessary cure reaction. Thorough mixing for 30-60 seconds, occasionally scraping the sides if the container, is usually sufficient. (Be careful, however, not to stir so vigorously that you whip sir bubbles into the adhesive).

3. Not following application instructions regarding limitations of the product, such as surface preparation, temperature issues, moisture concerns, etc. The data sheet lists specifics that must be complied with if proper performance of the adhesive is to be expected. A common issue is temperature: for instance, if the data sheet says to not use below 50 degrees F, then don't use the adhesive if the temperature is 35 degrees! The adhesive simply will not cure.

Pay attention to these 3 ways to abuse an epoxy and you’ll eliminate a lot of headaches!

Suggestions for Handling Epoxies

Proper mixing and handling epoxies eases the application process and allows for the best possible performance of an adhesive.

• Refer to MSDS for all your products and review all safety handling information
• Select and wear proper gloves for your operation
• Use protective creams ONLY as supplements to, NOT as replacement for, gloves
• Practice good housekeeping and personal cleanliness at all times
• Change clothing if it comes in contact with epoxy
• Keep tools and clothes clean
• Follow proper procedures to dispose of empty drums and containers
• Read container labels for special instructions

Measure and Mix for a Better Bond

So now we have touched on what epoxies & polyesters are and their differences, you are all set and ready for gluing. So, you slap a little of the Part A into a cup, put in some of the Part B, stir, and you're off, right?

Is that all there is to it? Are you confident you've achieved the best that the adhesive is capa­ble of delivering? You may be surprised...let's touch upon: mix ratio, and mixing thoroughness.

If you remember in our previous posts, we mentioned one main important difference in epoxies and polyesters is the mix ratio. In a typical polyester system usage is extremely simple: squirt some of the catalyst into the polyester, give it a "lick-­and-a-promise" stir, and you're off! Mix ratios are not critical—use a little catalyst, it cures slowly; use a lot, it cures faster. And the catalyst does not need to be thoroughly mixed in with the polyester; a sloppy stir, and it will still cure just fine.

Epoxies are completely different, however. As is usual when working with a superior product, a little more care is required to achieve the ultimate designed properties. Here, the Part A and Part B MUST be combined in the exact mix ratio specified. Any deviation will adversely affect the ultimate cured properties. Don't be fooled into adding more Part B than recommended to try to speed the cure: it will indeed cure somewhat faster, but the result will be an inferior cure and poor adhesion and strength. And be sure to mix the Part A and B very thoroughly together—the only way to assure complete and proper cure is to be sure the two parts are mixed homogenously. A sloppy stir will result in sloppy cure, producing soft spots as well as "over-cured" and extremely brittle spots.

So pay attention to proper mix ratios and thorough mixing, and you will be rewarded with knowing your epoxy is performing as scientifically engineered to give you a tenacious adhesive bond and long term strength and durability.

Structural Adhesives - PART 4, POLYURETHANE

Quick recap – structural adhesives are used in high strength, permanent applications and are able to withstand considerable distress and will not fail at the bonded joint. There are 3 main types: Epoxies, Polyesters and Polyurethanes. Epoxies are high strength and versatile. Unsaturated polyesters are used in the stone industry and are fast curing and low cost. Let us now discuss the third, Polyurethanes.

Polyurethane is any polymer consisting of a chain of organic units joined by urethane links. These polymers are formed through polymerization by reacting a monomer containing at least two isocyanate functional groups with another monomer containing at least two hydroxyl (alcohol) groups in the presence of a catalyst. Whew! In other words - it's a high-tech polymer formed by the reaction between two precursor materials. By adjusting the individual properties of the precursors, an almost limitless variety of polyurethanes can be produced. This flexibility in formulation allows one to custom-engineer the polyurethane to meet the unique demands of the project.

There is a large range of polyurethane adhesive products available. Different chemical combinations result in different properties in polyurethanes. The chemical make-up can be altered to produce different levels of stiffness, density and hardness. All this makes polyurethanes versatile over many industries, such as: automotive, aerospace, construction, textile, wood working, book binding and hardscapes. Out of the three: Polyester, Epoxy and Polyurethane – Polyurethanes are the most flexible (ie: least rigid). Polyurethane, as an adhesive, was first developed in 1985 and has gone through many changes to be the product it is today – especially in cure speed. They are available in one-part or two-part systems. The two part systems require a catalyst.

Benefits of Polyurethanes:

• Long open time
• Flexibility
• Resiliency

Specific uses can be:

• Aesthetic repairs to stone surfaces
• Retaining wall capping
• Subfloor construction
• PreFab or modular construction
• Book Binding
• Binding leather soles to leather and synthetic uppers (shoes)

So, what do you think of these structural adhesives? Which do you prefer to work with and why?

Structural Adhesives - Part 3, EPOXY

Let’s quickly recap – structural adhesives are used in high strength, permanent applications and able to withstand considerable magnitude and will not fail at the bonded joint. There are 3 main types Epoxies, Polyesters and Polyurethanes. Unsaturated polyesters are used in the stone industry and are fast curing and low cost.

Epoxy is a copolymer that is formed from two different chemicals - resin and hardener. When these are mixed together, the amine groups react with the epoxide groups to form a bond. This process is called "curing". A strict mix ratio is needed for full cure and cured property retention. If an epoxy is mixed with the incorrect ratio, it may fail.

Epoxies were first introduced commercially in 1946. These high-strength adhesives have a wide range of industry use, such as construction, automotive, aerospace and more. Epoxy adhesives are used where high strength bonds are required.

Epoxies are versatile - as they bond well to many substrates and can be easily modified and developed to suit almost any application. They can be used as adhesives for wood, metal, glass, stone, and some plastics. They can be made flexible or rigid, transparent or colored, fast setting or slow setting.

Epoxies are high strength and have less shrinkage and more chemical resistance than unsaturated polyesters. Epoxies are the structural adhesive that is used primarily in the exterior stone building industry.

Benefits of Epoxies:

• High strength
• Excellent durability
• Extremely versatile

Specific uses can be:

• Anchor Bolts
• Buildings – i.e. stone cladding or dimensional stone
• Boats construction
• Countertops
• Golf clubs
• Surfboards
  

So, do you use Epoxies in your company? Good or Bad - what are your thoughts? Please tell us your thoughts in the comments section, we'd love to hear from you! * * Stay tuned for the final part of our Structural Adhesives postings as we wrap up with Polyurethanes. * *

Structural Adhesives - Part 2, POLYESTER

Let’s begin with Polyester. Polyester is a polymer which contains the ester functional group in their main chain. Depending on the chemical structure polyester can be saturated (thermoplastic) and unsaturated (thermoset).

Translation #1 – saturated/thermoplastic turns to a liquid when heated and freezes to a very glassy state when cooled sufficiently. Saturated polyesters are primarily used in the paint industry for general industrial coating.

Translation #2 - unstaturated/thermoset is material that irreversibly cures. The cure may be done through heat or a chemical reaction. Unsaturated polyesters are used for castings, glass fiber laminates and adhesive systems. It's these adhesive systems that are used in the stone industry – primarily in the stone countertop segment. Unsaturated polyesters are two part systems consisting of a resin and peroxide based catalyst, a strict mix ratio is not required for cure. Unsaturated polyesters have greater shrinkage and less chemical resistance than epoxy adhesives.

Benefits of Unsaturated Polyesters:

• Fast curing
• Low cost
• Perfect for more porous stone, such as Marble

Specific uses with stone can be:

• Interior use
• Laminating Countertop Edges
• Rodding Thin Stone and Countertops
• Countertop Seaming

Have you used Polyesters? If so, what has been your experience with them. If not, why not? * * Stay tuned for the next part of our Structural Adhesives postings as we tackle Epoxy next. * *

Structural Adhesives - Part 1

According to McGraw-Hill Science & Technology Dictionary structural adhesives are capable of bearing loads of considerable magnitude. A structural adhesive will not fail when a bonded joint prepared from the thickness of metal, stone or other material typical for that industry is stressed to its yield point.Structural adhesives are adhesives that are used in high strength-permanent applications. Most often these adhesives are the primary means of attachment in structural applications.

There are many different types of structural adhesives, but, the three main types are Epoxies, Polyesters and Polyurethanes.

In our next few posts, we try to explain the chemical make up, uses, and benefits of these three types of structural adhesives.