Glass Laminators Shouldn’t Cut Corners When it Comes to Quality

By Sam Barnes

Laminated glass serves a vital, functional purpose: life safety. While the end product can and should appear seamless and devoid of optical flaws, getting to that point is a complex, multi-step process whereby a variety of factors can impact quality negatively.

That’s why an optimal environment must be created for the highly sensitive polyvinyl butyral (PVB) laminate material—one of the most common interlayers used in high-volume applications—to avoid the intrusion of foreign particulates and other factors that could hinder the process. It’s all necessary to achieve the desired aesthetic with unparalleled optical clarity, superior adhesion, strength and flexibility.

This is not always easy to do, as the complexity of this fabrication process can vary considerably depending on several factors. These include the type of product, the region where it’s being fabricated and production volume.

Laminated Glass Production 101

According to Julia Schimmelpenningh, industry technical leader/customer applications and support lab manager for Eastman Chemical Co., there are six essential steps in the glass laminating process: glass prep and washing; interlayer sizing; component assembly; de-airing; finalization; and quality assessment.

“Consistency, tracking and quality control testing are fundamental. Each step needs to be the highest quality raw materials and proper preparation; glass washing needs to be complete and uniform, as does the drying of glass panels,” she says. “The interlayer should be from a quality supplier, stored and handled in accordance with the manufacturer’s instructions and kept clean and dry. Assembly needs to ensure flatness of all components as well as alignment of edges and flush trim of the interlayer to prevent damage. The air needs to be drawn out from between the layers in a uniform and complete manner without tracking or pockets that may form by inconsistent heating or pressure. The autoclave or finalization cycle needs to ensure proper flow, optics and adhesion.”

She adds, “Knowing what is put out there by doing appropriate quality control with looping to production, participating in laminate testing services as provided by interlayer suppliers and certification of impact testing in-house and by independent third party laboratories is highly recommended.”

Start with Clean Glass

When it comes to fabricating high quality laminated glass, cleanliness is essential. Vaughn Schauss, manager, technical consultancy Americas at Kuraray America Inc., says production of quality laminated glass starts with the cleanliness of the glass and the proper storage of the interlayer.

“Dirty wash water and/or improper interlayer storage may produce blemishes such as bubbles, encapsulated fibers and dirt and even delamination,” he says.

Chris Mammen, board member and co-owner of M3 Glass Technologies in Irving, Texas, agrees that the highest quality laminated glass begins with the highest quality glass.

“All of the standard operating procedures in glass processing become twice as important when you are laminating two (or more) lites together. Avoiding scratches and tempering defects lead the list, but edge work quality and holding dimensional tolerances are also important prerequisites to making the best laminated glass,” he says.

“All of these initial steps, and the ensuing quality control, must be done right before you even begin to laminate the glass.”

Schauss adds a number of other considerations.

“If using heat-treated glass, flatness is always a critical issue for lamination. Effective de-airing, whether by nip roll or vacuum, is another step that requires monitoring. Insufficient removal of the air may lead to bubbles and poor heat stability.”

For companies working with structural interlayer material, the quality control considerations are similar to those of PVB. Schauss adds that exposed edges are one additional consideration, noting that “care must be taken to ensure proper alignment of the glass edges. Trimming some types of structural interlayer material, such as ionoplast, flush while still warm after the nip roller will produce a good quality edge.”

No Cutting Corners

When it comes to quality, a clean work environment is essential. For fabricators producing PVB-laminated glass, having what’s known as the clean room is a critical part of the process. This is a climate-controlled room used for PVB/interlayer storage and making clean lay-ups before entering the oven. These rooms are designed to prevent contamination among interlayers during fabrication, as well as eliminate unwanted surface debris during additional processes, such as digital ink printing.

Mammen adds that cleaning the glass properly and removing any static electricity are the first quality steps in the actual laminating.

“Positive air pressure, temperature control and humidity control are the mandatory basics for a laminating clean room, along with best practices for the team members laying-up the glass. These best practices include lint-free lab coats, hair nets, extensive cleaning protocols, and some sort of clean-entry procedure for the room,” he says. “Interlayers that are moisture-sensitive must be acclimated and stored in the appropriate humidity and
temperature conditions, as well.”

Mammen points out that, while many laminators take steps beyond these minimal requirements, those steps are often proprietary.

“One somewhat common step is vacuum-bagging individual laminated units for precise edge-alignment, hole-alignment, and for the best adhesion,” he says.

Additionally, many types of interlayer materials require specific moisture-control levels in both lay-up and storage. Uncontrolled moisture levels could affect lamination-adhesion qualities. Clean rooms must strictly adhere to specified temperature and humidity levels, while also maintaining a clean and dust free environment. If any of these variables is off target, quality could be diminished.

While the climate-controlled clean room is necessary for PVB, fabricators working with some other materials, such as EVA, don’t face the same requirements.

“When laminating with EVA it is not necessary to have a full clean room with climate control because [our company’s] EVA can withstand temperatures up to 80 degrees Fahrenheit and 60% humidity without any problems,” says Pete DeGorter, vice president of DeGorter Inc. which represents the Spanish company Hornos Industriales Pujol, a manufacturer of laminating ovens and EVA products, adding that not all EVA may be the same. “It is strongly recommended to have what we call a white room. This is an environment that is away from dirt and dust to prevent it from adhering to the laminate.”

Eric Gertken, a product specialist and owner with Salem Flat Glass & Mirror, which sells SWM’s Argotec EVA film, agrees that a clean work environment is a must.

“The reason is to control the dust, dirt, debris or any other contaminants from getting on the film or glass prior to lamination,” he says, adding that EVA does not need to be in a temperature controlled environment like PVB.

While many laminators have clean rooms, the quality of the rooms can vary significantly, says Todd Roshell, senior project manager at Joe’s Refrigeration Inc./Cleanroom Solutions in Stanley, Wis.

“The clean room should be designed properly,” Roshell adds. “We’ve seen some fabricators that have skimped on the clean room and suffered consequences down the road. You invest a lot of money in PVB storage, in its varieties of colors and thicknesses. Why would you risk losing all of that if something goes haywire with the clean room?”

But some fabricators, particularly small companies, aren’t always as thorough.

“We’ve seen it among some of the smaller companies,” says Steve Rodgers, glass solutions specialist at Billco Manufacturing in Zelienople, Pa., “Some of them don’t put a high priority on a proper clean room, or in the proper application of other pieces of equipment, such as their glass washing systems.”

When deciding to construct a fully functional glass clean room, fabricators should consider their exact processing needs to determine the level of room controls needed.

“When laminating, the crucial variables are air temperature and humidity,” Roshell says. “Ideally, you need 22 to 25 percent relative humidity. Otherwise, when you’re assembling the glass, the PVB starts to get a little bit soft when the humidity rises.”

Regional Considerations

The laminating process can be exacerbated by geography. A clean room in Florida, for example, will face different challenges in regards to humidity and refrigeration than a room in a drier climate such as southern Utah. Clean room companies can design and install a clean room that suits each unique situation.

“We’ll adapt the systems, whether through humidification or refrigeration, to maintain the necessary conditions,” Roshell says, adding that there are other variables to consider when creating an optimal design. “There are some questions to be asked, such as, ‘How many people are going to be using the clean room? What is the storage capacity of the room? What are the levels that we need to maintain?’”

Another potential obstacle to quality is improperly maintained clean rooms.

“I’ve been in rooms that I installed 15 years ago that looked better than rooms installed five years ago,” he adds. “It all depends on their preventative maintenance and protocol.”

Quality on the Front End

Often constructed with a layer of PVB sandwiched between two lites of glass, laminated glass can be used in a variety of architectural applications, but regardless of where it’s used, one essential fact remains: when laminated glass breaks, the interlayer holds everything together.

A logical and efficient production flow can be similarly beneficial to quality during the lamination process. In that regard, “overhead distribution” production lines and automation are quickly becoming popular, although they remain a bit costly to implement for the small fabricator.

“Today, fabricators are becoming more automated, where the rolls of PVB are mounted on a mezzanine above the line, and the vinyl comes down and feeds onto the glass,” Roshell says, explaining that the distinctive layout reduces a fabricator’s dependence on storage and compensates for a limited workforce.

Automation has also enabled many fabricators to take a sizeable step toward improving quality in the lamination process. In addition, it can minimize the need for operator intervention.

“A lot of it is recipe controlled in the lamination line,” Rodgers says. “We’re plugging in all the recipes and all of the different scenarios in the laminating process, and it automatically sets itself for those predetermined recipes.”

He continues, “They simply select a button. The temperature, conveyor speed and entire scope of the line is set by that single press of a button.”

Even with automation, though, training is a big part of the process, as workers should be skilled in a variety of tasks, such as material handling, quality control, trimming the PVB and setting up the laminating line—all with the end goal of maximizing PVB yield.

Equipment suppliers can also incorporate a programmable logic controller (PLC) into the laminating machinery, thereby improving reliability and ease of programming.

“Once we set it for premium performance, it stays that way,” Rodgers
adds.

There are a number of other steps that fabricators can take for improving quality and efficiency. These include ensuring adequate lead times for materials and keeping equipment up-to-date and maintained. Washers should also be properly configured and maintained.

“Don’t put a 50-year-old washer in front of a new $500,000 printing machine,” Rodgers says.

Rodgers says Billco also works closely with its customers to determine throughput requirements and specific needs.

“Poor quality at any step of the way can give you a black eye,” he says. “Everyone needs to have a full understanding of everything that’s involved, including interlayer handling, proper clean room design, construction and maintenance, ensuring the washer is adequate and properly maintained, etc.”

The selection of the oven is also critical. “Today’s convection ovens allow a fabricator to maintain a very precise temperature,” Rodgers says. “That also creates an energy savings because the louvers aren’t opening and closing as often.”

Another Look: EVA and Poured Resin

Ensuring quality control during the lamination process is a challenge faced by all fabricators, whether they’re producing high-volume laminated products in an autoclave or custom-laminated, low-volume decorative glazings. American Insulated Glass internally produces custom-laminated glass at its Atlanta facility using Ethylene Vinyl Acetate (EVA) film and at its Charlotte and Pensacola facilities using UV-cured resin interlayers.

Supplied in roll form to fabricators, EVA is placed between one or more plies of glass and plastic, then exposed to heat and pressure to bond the components into an integral unit. The EVA process requires less floor space than PVB, as it’s performed in smaller convection or infrared lamination furnaces instead of an autoclave, and are generally used for specialty or decorative glass  projects. As with PVB, these processes must follow stringent safety glazing codes.

Likewise, the poured resin process begins with two lites of glass. They are separated by an edge tape, placed together on a horizontal vacuum table. The edge tape traps the resin in liquid form.

Resin is pumped through a nozzle into the cavity formed by the edge tape on a tilting table. The table tilts the glass until the resin has filled the space between the lites uniformly. The glass unit on the table is then moved underneath ultraviolet lights which cure the resin.

According to Clint Blair, AIG’s vice president of operations in Atlanta, EVA is a durable laminated glass solution that provides excellent edge quality and resistance to weathering conditions, while PVB is more vulnerable to water penetration around the edges because it has higher tendency to permeate water. While EVA and resin laminated glass offer high quality and visual clarity, the fabricator’s expertise and commitment to the process
are necessary for a successful outcome.

“The uneven surfaces prevent most textured, patterned glass types from being heat-treated or laminated with traditional PVB,” says Blair. “This is where producing laminated glass using EVA film or UV-cured resin offers us a tremendous advantage in servicing our customers.”

Quality standards are achieved through the strict adherence to a clean work environment. “The quality and clarity of EVA and resin laminated are excellent, but as with any fabricated product it’s a matter of expertise and quality control to ensure a successful outcome,” Blair adds.

Sam Barnes is a contributing writer for USGlass magazine.

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