Substrates: Building a better material sandwich

by all | 23 March 2017 10:30 am

By Peter Saunders
Many popular substrates for the sign and graphics industry are not simply base materials, but rather ‘sandwiches’ that combine multiple layers of different materials to create new composites. Over time, these materials have continued to be customized for signmakers’ changing needs.

Stained glass via foamboard
By way of example, when artist Calley O’Neill of Waimea, Hawaii, designed a new 15.8-m (52-ft) long forest-inspired stained glass mosaic mural for Maui’s Pukalani Elementary School, she decided to experiment with a new process she had developed with fellow artist Lamar Yoakum, using a heavy-duty graphic display board.

Titled ‘Na Wao A’O Pi’liani’ (The Life Giving Forests Of Maui), the mural was commissioned by the Hawaii State Foundation on Culture and the Arts, as part of its Art in Public Places collection, for installation on an exterior wall of the school. Measuring 4.3 m (14 ft) tall at its peak, the mural would involve the work of nearly 260 Pukalani community members, including teachers and some 185 students from the school’s Grade 4 and 5 classes.

O’Neill and Yoakum turned to a composite material consisting of polystyrene (PS) foam bonded between two layers of a wood-fibre veneer laminate, both to create a detailed mosaic pattern and to work on with the glass pieces. Three full-sized cartoons of O’Neill’s master plan were printed. The first of these numbered clear pencil line drawings was preserved as a blueprint and base pattern, upon which to place the actual mural each time it was fitted to a floor. The second was adhered to 12.7-mm (0.5-in.) thick white panels of the graphic display board and jigsaw-cut into a puzzle of 75 segments, which were sandwiched with light cement-based building panels and complemented with an additional 95 graphic board segments for the border. Finally, the third—printed on thin polyester sheets—was hand-cut with pattern shears into 3,350 pieces to guide the glass cutting, leaving 3.2-mm (0.13-in.) spaces between the pieces.

“This way, we were able to create the design and check it on the school’s gym floor twice before installation,” O’Neill explains. “While the 3,350 completed stained glass pieces on the cement building panels were heavy, we were able to construct the design on the foamboard panels, which are very light, rigid and water-resistant, so we could easily carry these pieces around our shop and to the wall. We’re very happy with the results and the technique we developed.”

After the stained glass pieces were shipped from O’Neill’s studio by truck and barge to the school, they were covered with mosaic tape, lifted and installed into thin-set mortar on the wall. The installation was completed in one week by a four-person team, directed by Isaac Homza of Higher Standard Tile and Stone.

A process of evolution
Specifically, the school mural used Gatorfoam boards from 3A Composites, which also manufactures Dibond aluminum composite materials (ACMs), Fome-Cor clay-coated paper-faced foamboards, Sintra polyvinyl chloride (PVC) boards and Smart-X recyclable foamboards, which combine an expanded PS (EPS) core with two layers of high-impact PS (HIPS).

“We have batch processes that allow us to take dissimilar materials and sandwich them together,” explains Douglas A. Twitchell, 3A’s vice-president (VP) of marketing for the Americas. “We closely monitor product developments by wide-format printer manufacturers, so whenever new models become available, we’re ready with tried and tested materials that are compatible with them.”

When new inks are formulated, for example, it is important for substrates to be able to receive those inks effectively, which may call for a composite approach.

“You want a bright white substrate to ensure colours ‘pop,’ but it can be difficult to make the surface more ink-receptive while maintaining that white point,” says Twitchell. “Beyond the core material, it’s a question of which coatings you add to the surface. Some ultraviolet-resistant (UV-resistant) coatings, for instance, will add a yellow cast, reducing the whiteness of the surface. The goal is to provide the highest-quality printing surface possible.”

For the sign shop, meanwhile, the choice among various composite substrates will depend on the intended application and its environment. A foam core with paper faces may be appropriate for temporary indoor signs and point-of-purchase (POP) displays, while rigid boards with a wood-fibre veneer skin offer a wider variety of thicknesses and levels of durability.

The most durable options are ACMs. Brushed finishes are available for interior use, but their primary applications are outdoors, including larger monument signs that must cope with wind loads. Similar materials are even used for cladding buildings.

“We can mix and match substrate cores and surfaces both for the architectural market and for signs and displays,” Twitchell says. “It’s a process of evolution for existing technologies.”

By way of example, 3A is developing lighter foamboards with balsam plywood veneer panels, as well as custom colour-matched panels for more visually creative fabrication projects.

The versatility of ACMs
There has also been a process of diversification specifically for ACMs, given their versatility across various industries.

“There can be very significant differences, depending on the type of skin on the product,” says Ted Isbell, a graphics specialist for Piedmont Plastics, which distributes sheet, rod, tube and film products across North America. “It can range anywhere from 0.08 to 0.5 mm (3 to 20 mil) in thickness.”

Piedmont’s most common option is a 0.2-mm (8-mil) skinned standard-grade ACM for flat sheet applications, but the company also recommends a 0.3-mm (12-mil) version for bending, three-dimensional (3-D) forming and V-grooving, as well as applications with wind loads.

“If you go as thin as 0.15 mm (6 mil), there will be durability issues, as the material will dent fairly easily and won’t stand up to a lot of abuse,” Isbell says. “There are also varying grades of aluminum. Some are harder than others. We test them in the field and gather customer feedback.”

As mentioned, one of the primary concerns for print service providers (PSPs) is ink adhesion. This has gotten much better, Isbell explains, with today’s flatbed printers processing ‘digital-grade’ matte-finish ACMs, which can support adhesion not only at the printing stage, but also through finishing, as the edges are engineered to prevent chipping during routing.

“Some sign shops will also laminate with UV stabilizers to protect the inks,” he says. “You don’t need to laminate against moisture, though, as the ACMs are already water-resistant.”

Beyond direct-print substrates, ACMs are also used as backings for other signs. Many signmakers use the 0.2-mm thick material on the backs of channel letters and the 0.3-mm version for sign cans.

“The edges are protected in the letters or cans, so there is not much threat of any impact or breakdown for these applications,” says Isbell. “They perform well in both hot and cold environments.”

In the future, he predicts, in addition to tweaking printer-friendly topcoatings and other types of finishes for ACMs, the sheets will likely be made available in larger sizes to meet sign shop requests—and thicker, for that matter, since the materials are already so much lighter than the plywood they have replaced in outdoor signage.

“A larger sheet might well need a thicker skin to mitigate the impact of handing,” says Isbell.

Maximizing metal
The main advantages of ACMs over plywood for exterior signs are their lower weight, which means easier handling for installers, and their stronger weatherability.

“In the U.S., ACMs have been approved by the Department of Transportation (DOT) for construction zone signs,” says Shaun Allen, a product manager for sign supply distributor Grimco. “They are less expensive than thicker-gauge aluminums, but also more rigid than thinner aluminums. So, you even have signs that would previously have been aluminum switching to ACMs.”

Grimco carries a variety of ACMs, from Nudo’s AlumaCorr, which sandwiches a corrugated/fluted polypropylene (PP) co-polymer between two aluminum faces, to Max Metal, whose polyethylene (PE) core can reportedly stand up to being hit with a hammer.

“An open-flute design is more subject to denting,” Allen explains. “The choice will depend on where the material will be used. Some sheets are designed for mounting vinyl graphics, but the majority have shifted toward flatbed direct printing. And some are intended more for architectural purposes, such as brushed silver canopies.”

As with Piedmont’s digital-grade ACMs, Grimco has recently tested Max Metal Digital with major printer manufacturers to optimize its ink adhesion.

“The world of digital printing has really changed ACMs,” says Allen. “The selection will continue to broaden for different applications.”

With files from 3A Composites, Piedmont Plastics and Grimco. For more information, visit www.graphicdisplay.com[6], www.piedmontplastics.com[7] and www.grimco.ca[8].

Source URL: https://www.signmedia.ca/substrates-building-a-better-material-sandwich/

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