Structural adhesives are strong enough for many applications, but aren't they more costly?

Structural adhesives are replacing mechanical fasteners in many applications. They form strong bonds, are aesthetically pleasing, reduce weight, and can withstand harsh environments. In addition, when compared to welding, screwing, and bolting, they are generally more cost effective.

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  • Craig McClenachan

    Craig McClenachan

    Vice President Fabrication and Assembly Business Unit FABRICO To read Craig's opening, click here
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    1. As more design engineers investigate structural adhesives and liquid adhesives to take advantage of all the benefits you have mentioned, an experienced converter can play a critical role. Working from the design phase, a converter can bring both materials and adhesives expertise to bear on a project. In addition, beyond just recommending materials and adhesives, a converter like Fabrico can also provide capabilities for testing how different materials and adhesives work together to meet the design engineer’s requirements. Finally, a converter can ensure that design-for-manufacturability is considered from the earliest design phase. Why use adhesives to replace mechanical fasteners? Cost savings, improved structural strength, and aesthetics are just some of the advantages adhesives can offer. From the standpoint of the design engineer, we also see that adhesives allow them to work with designs that include hard-to-bond and dissimilar substrates, thereby increasing their design options and leading to more innovative designs.

  • Thomas Buckley

    Thomas Buckley

    Structural Adhesive Engineer Henkel/Loctite To read Thomas's opening, click here
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    1. There are many benefits to using adhesives instead of mechanical fastening methods, including: joining dissimilar substrates; distributing stress evenly; filling large gaps between substrates; sealing joints to protect from corrosion; providing a neat and aesthetically pleasing appearance; the process can be easily automated. Another main reason to use adhesives is to save on cost. Adhesives are more cost effective and provide stronger bonds than many competing mechanical fastening technologies, including welding.

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14 Responses Below

  1. How do structural adhesives perform with metal bonded to composites? Will some composite/adhesive matches fail at the bond joint? How can I avoid this?

    by Greg on May 15, 2012 at: 1:36 pm
    • There are a number of structural adhesives that can bond metals to composites quite effectively. If your application requires varying temperature, you may want to consider a flexible epoxy or urethane, which will allow for some “give” in case the composite and the urethane have large swings in coefficients of thermal expansion. Quite often, metals expand and contract at a greater rate than composites.
      You will also want to determine whether there are low surface energy components within the composite that would require a primer, or an acrylic adhesive to promote better bond stregth to difficult substrates. Any of our design engineers or technical reps would be happy to further assist you with adhesive selection and product testing.

      by Craig McClenachan on May 22, 2012 at: 2:55 pm
  2. Are there high temperature limits for structural adhesive bonded joints?

    by Sara on May 15, 2012 at: 1:30 pm
    • All substances, adhesives, paints, plastics, and metals, will soften as temperatures increase. In most applications, there is not an upper limit for temperatures on structural adhesives, but there are extremes where they can no longer adequately perform. If your application requires a short term bake cycle as part of assembly, often that exposure to heat will actually help adhesives cure at a better rate than they would have at room temperature. If you are talking about prolonged exposures above 500 F, then you may find that the adhesive softens to a point that it no longer performs adequately. We recommend testing each product at the extremes of your application requirements.

      by Craig McClenachan on May 22, 2012 at: 3:37 pm
  3. Fabrico is developing a series of videos to support our customers’ needs for technical information on structural bonding adhesives. Do you have an application we can feature or would like discussed in one of our videos? Let us know by posting.

    by Craig C. McClenachan on April 19, 2012 at: 5:29 pm
  4. I want to place metal wear feet on the bottom of Rubbermaid tm trash cans. How do I determine the correct adhesive — better yet, what is the correct adhesive to do this. I have tried many adhesives and many stick to the metal but none stick very long to the trash cans. Thanks.

    by R D Moore on November 17, 2011 at: 12:19 pm
    • The majority of Rubbermaid trashcans are made of LDPE (low density Polyethelyne) or PP (Polypropylene), the LDPE are the softer flexible trash cans, while the PP are the more rigid. These are both very inexpensive plastics yet highly durable and perfectly suited for their purpose. Most people who visit this site need a high performing bond for a difficult application. In this case since temperature, weather and stresses are not a factor, most rubber based adhesives would work for this. Pick up an inexpensive roll of scotch mounting tape or squares from your hardware store, should be a few dollars. Make sure you pick up the products that say “high strength” or “permanent”, this most likely indicates it is a rubber based product. The more expensive “outdoor” and “removable” products are acrylic and will not perform well to the plastic.

      by jeremy cooler on November 18, 2011 at: 11:58 am
  5. Are there available structural adhesives that meet food grade and/or food contact requirements?

    by Jim Schroeder on November 3, 2011 at: 12:18 pm
    • Jim-

      Thank you for your question. To fully answer however I would need a better understanding of the actual application. Many of my experiences in the past with gaining NSF or other governing body approvals usually always requires testing. Any “approved” products are approved for specific applications. Typically in these situations we leverage our relationships with our manufacturers technical teams, who have been involved in similar projects and can suggest materials that their customers have been able to get approval for with similar substrates and similar food contact requirements. Please feel free to contact me direct…..jcooler@fabrico.com and we can discuss more in detail and examine some options.

      by jeremy cooler on November 3, 2011 at: 3:14 pm
  6. There is a critical shortage of informative articles like this.

    by Jacey on October 31, 2011 at: 11:35 pm
    • Thank you for your note. We at Fabrico are working to try and provide the design community with a site that will offer good technical resources for solving application problems. Please keep checking back for updates and additional topics.

      by Craig McClenachan on November 4, 2011 at: 9:54 am
  7. Can structural adhesives bond metals to plastics, or are they only appropriate in metal to metal applications?

    by Adam on October 20, 2011 at: 8:40 pm
    • Structural adhesives are often used on plastic to metal applications. Not only is the bond strong but, in many cases, the adhesive bond is superior to other fastening alternatives. For instance, it can allow for the different rates of expansion and contraction where a mechanical faster would not. It can create a waterproof seal as well as absorb stress along the entire bond line instead of just at the spots where they would be mechanically fastened. There are also structural adhesive options out there to bond to the harder to stick to plastics like, Polyethelyene, Polypropylene, and TPO to virtually any other substrate.

      by Jeremy Cooler on October 21, 2011 at: 4:02 pm
    • Structural adhesives can absolutely bond plastic to metal, in fact structural adhesives can virtually bond any substrates together. Many times using a structural adhesives to bond different substrates is superior to using mechanical fasteners. For example, different substrates expand and contract at different rates when exposed to different temperatures. With a mechanical fastener this could put stress on the fastener causing a mechanical failure or damage, i.e. cracking or warping to one or more of the substrates. A flexible structural adhesive can allow for the different coefficients of expansion/contraction. A flexible adhesive can also absorb shock or impact and spread it over the entire bondline. A mechanical fastener will take the abuse at the point of attachment and potentially fail. We would be happy to answer any specific bonding questions you might have, feel free to post your application details, or click the ask an engineer button on the top of the page to get a an answer and product suggestions/ samples for your specific application.

      by jeremy cooler on October 27, 2011 at: 11:57 am