Evaluating Myths about Metal Composite Material (MCM)

by Jonathan McGaha | June 12, 2013 12:00 am

Sean Walker Headshot

The goal of this article is to address a handful of these myths, including:

Myth #1: All MCMs are manufact ured using a continuous process with a polyethylene core.

False.

Perhaps the biggest misconception is that all MCMs are produced by the same method using the same core material. This is simply not true. According to the 2012 International Building Code, Section 1402, metal composite material is defined as: “… a factory manufactured panel consisting of metal skins bonded to both faces of a plastic core.”

So by definition, there are three common physical components to every metal composite panel- regardless of manufacturer:

Currently, there are two different industry methods (using those three components) being utilized to manufacture MCM:

While there are differences in the resulting composites, both types of manufacturing processes produce high-quality products and satisfy the parameters set forth in the definition of an MCM. Conclusion: Not all MCMs use a continuous production method with a polyethylene core. In fact, a batch process offers several distinct benefits (see Myth #4).

Myth #2: No adhesives are used in the manufacture of MCMs.

False.

Referring back to the IBC definition, MCMs contain a bond that combines the aluminum and the plastic components into a unified assembly. By looking at ASTM D907, we can determine this bond is comprised of an adhesive and the component to which it adheres. The resulting layer is called a bondline.

The two most common types (or forms) of adhesive used to create the bondline are:

It is important to note that some manufacturers use different terminology to refer to their adhesive (i.e., tie layer), or simply do not refer to it at all. However, regardless of what it is called, a bond that contains some form of adhesive is present for all MCMs.

As a result, every quality MCM manufacturer submits their products for testing and publishes a value for ASTM D1781: Standard Test Method for Climbing Drum Peel for Adhesives. This test provides an objectively quantifiable result that can be used for evaluating the quality of the bondline, as well as the overall composite assembly.

Evaluation of the published data from major MCM manufacturers further confirms that both types (dry film and liquid) produce equally strong results for an architecturally implemented product.

Conclusion: All MCMs (both continuous-process and batch-process manufacturing methods) use high-performing adhesives.

Myth #3: The use of adhesives implies inferiority.

False.

The key word is performance. The use of adhesives in composite cladding has nearly 50 years of proven performance in the architectural community (beginning with Panel 15 in 1968). Continually improving since that time, the bonding agents utilized in the production of today’s MCM requires strict adherence to time, temperature, pressure and component condition in a controlled environment.

These products are manufactured by ISO 9000 registered companies with decades of experience in composite technology. It is this level of quality assurance that allows each manufacturer to submit our composites to third-party labs for testing under ASTM D1781 guidelines with confidence.

Conclusion: Testing concludes and proven performance affirms that adhesives are a viable component in the built environment. Not only for MCMs, but countless other engineered products as well.

Myth #4: Continuous process production is better than batch production.

False.

Occasionally, architects will limit the number of products being considered with specification language with wording such as: “formed in a continuous process using no glues or adhesives between dissimilar materials.”

Unfortunately, this verbiage is misleading (see Myth #2). As we have established (and independent testing labs confirm), all MCMs have some type of adhesive bond. Further, it clouds the issue by specifying a production process rather than a product. Performance is (and should be) key. Both of the main types of production
(continuous process and batch) are time tested, as well as capable of producing consistent, reliable products.

Both also have inherent advantages and disadvantages: continuous-run production:

So when the architect limits the products considered to just those using a continuous process, they are missing out on potential advantages offered by those composites produced using a batch process.

Conclusion: Quality MCMs are manufactured using both methods of production. Evaluate and specify performance, not process.

Myth #5: Fire-resistant (FR) cores are required above 40 feet

True and False.

Some code bodies indicate that if MCM is to be used 40 feet above grade, that certain requirements must be met.

For manufacturers that utilize a polyethylene (PE) core, this means that the standard product must be substituted with a fire-resistant (FR) core. This results in increased costs, less flexibility and heavier weight.

On the other hand, MCMs with a thermoset phenolic core (such as Envelope 2000 from Indianapolis-based Citadel Architectural Products) requires no special composition or core substitution to meet code guidelines. Further, the phenolic core meets or exceeds the ignition temperature (as tested by ASTM D1929) of most other manufacturer’s FR core.

This allows one product to be consistently utilized throughout the project with no expensive core upgrades.

Conclusion: Only some (not all) manufacturers are required to switch core material to satisfy certain code requirements.

Myth #6: All MCM manufacturers offer only panels, not instalation systems.

False.

Most MCM manufacturers produce the flat sheet and test their performance accordingly. However, design and testing of the fabricated system is typically performed by the fabricator.

As one exception to that rule, Citadel not only manufactures the panel, but also has designed and tested the systems (e.g., Rout
& Return, Rain- Screen, Reveal and Deep-Reveal) it offers. If a fabricated system is selected, the panel is still shipped flat from our facility. However, the specifier has the option at that point to select a system that the fabricator provides or one Citadel has designed.

This means that if a Citadel system is selected, the CAD drawings and testing data found in our collateral will be the system that gets installed on the project. This small benefit provides extra confidence that what is actually going on the wall will perform as intended.

Conclusion: Some MCM manufacturers not only produce (and test) the panels, but also leverage that expertise in designing, testing, and offering the corresponding attachment systems.

Myth #7: Shop-fabricated systems are the only option for installation.

False.

When most people consider MCM, they tend to think the only option for installation is a fabricated system. While this may be the only type of system supplied by some fabricators, there are other options available.

Field-assembled systems (such as Envelope 2000 Reveal and Deep-Reveal) have grown in awareness and popularity over the last few decades. These systems are installed using perimeter moldings and flat sheets. Systems such as these have been designed to create a similar look to that of a fabricated system. However, they significantly reduce lead time, eliminate shop fabrication (as they are cut-to-size in the field), and lower overall job cost.

Further, these systems utilize the exact same panel that is found in the fabricated options so all of the same panel benefits are still present. While these systems offer lower costs, quality is not sacrificed-they offer many of the same tests (i.e., ASTM E330, 331, 283) as the fabricated systems.

There are certainly times and applications when only a fabricated system will do. All MCM manufacturers can supply panels for such a system. However, if budget and time are a concern, fieldassembled systems are a very attractive option.

Conclusion: MCMs can also be installed using field-assembled methods saving time, labor and money.

Myth #8: Anodized finishes are not suitable for MCM.

False.

Anodized finishes have long been a standard in the glazing industry. As a natural carryover, an anodized look is often desired on the exterior cladding as well.

The industry addresses this demand in two different ways. Some manufacturers cannot produce a true anodized finish and instead offer an ‘anodic look’ by utilizing a paint system designed to simulate an anodized finish.

Other manufacturers offer an actual anodized aluminum. This finish is transparent and is integral to the base aluminum induced by electricity and chemicals. This ‘true integral’ anodized finish more closely matches storefronts and window extrusions because it is produced using the same basic process, making it a popular option.

In fact, the popularity of this finish has been proven with countless jobs (both field-assembled systems as well as fabricated systems) across the nation over the past several decades.

But this finish is not only popular, it is warranted. In Citadel’s case for example, it carries a 20-year standard warranty with all of the performance parameters found in most paint warranties (even for fabricated systems).

It is worth noting that anodized finishes are lotspecific. However, this is no different than any mica or metallic paint-which are also lot-specific.

Conclusion: A proven track record confirms that anodized finishes are a very viable (and popular) finish option for MCM.

Summary

Architects have several manufacturers from which to choose when specifying metal composite material. And although these companies may utilize different production methods and produce slightly different products, the results are similar-high performing composites designed for longevity with an aesthetic to match.

Be informed about the product selection and the options available in the industry. Doing so will help filter out the myths and misconceptions found within the industry and develop a decision based upon the characteristics and performance best suited for the application.

Sean Walker is the marketing manager for Indianapolis- based Citadel Architectural Products Inc. For more information, visit www.citadelap.com.

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