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Reactive Material to Heat Up the Sealant Industry?
by Kelly Charbonneau and Ross Noel
A breakthrough in silicone sealant technology is
causing a fundamental change in the window and door industry. A new reactive
hot-melt material from our company—the InstantGlaze window assembly sealant,
allows fabricators to manufacture high-quality silicone-glazed units at two to
four times of that of current speeds using fewer workers. This combination of
higher quality, faster output and lower costs delivers a significant competitive
advantage to manufacturers of PVC, wood and aluminum windows.
Silicone sealants have long been the gold standard in
glazing performance. They are the sealants of choice in high-end windows and
doors because they deliver the best durability, flexibility and longevity. They
resist ultraviolet degradation and remain flexible across a wide range of
temperatures. Silicone remains elastic enough to handle the different thermal
expansion rates of various window components, even vinyl, which can expand nine
times more than glass. For in-field repairs, it is much easier to de-glaze a
unit sealed with silicone than one sealed with an organic sealant such as
polyurethane, which hardens over time.
For the window fabricator, though, silicone
performance has come at a price. Silicone takes time to cure, so lines must move
more slowly while the sealant achieves green strength. Uncured sealant can be
squeezed out when the glass is placed and pressure applied. This excess sealant
must be cleaned from the glass and sash components, wasting material and adding
labor costs. If too much sealant squeezes out, the remaining bead may be too
thin, reducing the gap between the sash and glass, possibly compromising the
seal. Even after the unit is
fabricated successfully, it often must be held until sufficient green strength
Many shops sidestep these challenges by using
pressure-sensitive foam tape to adhere glass to the sash. Tape has the advantage
of instant green strength, but it, too, has disadvantages. Tape must be cut
precisely to size and applied without gaps, overlaps or folds to avoid leaky
corners. Tape also makes rework difficult, as it must be pulled out and all
residue scraped away before it can be reapplied.
“Tape is very labor-intensive and the failure rate
is high,” said Anthony Ferrera, director of manufacturing for Graham
Architectural Products. “Tape typically fails at the corners, causing leaky
units and requires extra backsealing.”
A breakthrough in silicone sealant technology has
created a third alternative that speeds production significantly, reduces labor
costs and delivers the quality performance of silicone. This unique, patented
formulation is a reactive hot-melt silicone material designed specifically to
take full advantage of automated backbedding technology. It has instant green
strength so windows can be handled immediately without risking the integrity of
the seal or distorting the sash, offering major productivity improvements.
It works like this: the solid silicone is loaded into
a pump. A heated plate presses it down and melts it, forcing it into a metering
device. A perfectly formed, seamless sealant bead is applied to the frame on an
X-Y glazing table. All these operations are controlled by a micro-processor,
reducing the need for scarce skilled labor.
Here the advantages of the pressure-sensitive
hot-melt silicone become clear. The material has a pot life of 24 hours and an
open time of up to 15 minutes. This compensates for variability in line speed
and reduces downtime.
“The material’s long open time allows for glass
positioning adjustments to be made before the material fully cures,” said John
Hannan, senior manufacturing engineer for Eagle Window & Door Inc.
The sealant delivers immediate aggressive adhesion to
vinyl, wood, glass, aluminum, and painted or treated wood, high-performance
paint and fiberglass. Within 30 seconds of application, the shear strength of
the material exceeds that of tape. The unit can be turned over immediately for
work on the second side. Units can be shipped as quickly as they are fabricated,
improving delivery times dramatically and reducing warehousing space and
The quality of the finished unit is enhanced for two
reasons. First is the well-known performance and longevity of silicone sealants.
Second is the viscosity and uniform bead size of the reactive hot melt. The bead
holds its shape well, even while glass is being pressed onto it. There is no
squeeze out, little material waste and no contamination of the sash. The
consistent bead ensures proper spacing between glass and frame. Ferrera also
likes the fact that the sealant is clear, so it never distracts from the
aesthetics of the window.
This unique neutral-moisture cure material forms a
100-percent silicone sealant. Additionally, the volatile organic compounds (VOC)
content is low enough to be exempt from California VOC regulations, the
strictest in the nation. The sealant is non-hazardous, odorless and
The development of a reactive hot-melt silicone sealant puts the advantages of automated glazing within reach of any window and door fabricator performing manual tape operations. Our company and its preferred equipment suppliers work with customers to supply pre-engineered pump, dispensing and X-Y glazing table combinations. With this equipment, fabricators can increase output two to four times while reducing labor hours. The following chart shows an example of the labor savings and increased production that can be realized by a manufacturer switching from five tape glazing lines to automated glazing, working one eight-hour shift per day, five days per week.
of Manual Versus Automated Glazing Systems
|Productivity||Manual Tape Glazing||Automated Glazing with Reactive Hot-Melt Silicone|
|Labor hours||48,000 hours||29,000 hours|
|Number of operators||25||15|
|Units produced per hour||750||1,000|
|Annual capacity||1,224M window units||1,632M window units|
|Cost savings||Manual Tape Glazing||Automated Glazing|
|Tape/sealant cost per year||$600M||$649M|
|Labor cost per year||$720M||$432M|
|Cost of waste per year||$30M (5%)||$16.2M (2.5%)|
|Cost of window rejects/scrap per year||$450M (0.5%)||Negligible|
|Total annual glazing operations costs||$1,800M||$1,097M|
|New equipment investment||N/A||$500M|
|Estimated payback||N/A||0.71 year|
this example shows, the equipment investment pays for itself in less than nine
months, so increased profits begin to accrue during the first year of operation.
product is designed specifically to
enhance the efficiency and cost benefits of both sealant and equipment.
sealant advances window assembly and quality to a new level. The ability to
increase production speed while producing better products is a technology sought
by all manufacturing processes,” said Don McLane, president of the adhesive
systems group at Nordson Corp., a pump manufacturer. “Utilizing InstantGlaze
sealant in conjunction with Nordson dispensing technology delivers a reliable
production process with a consistent, high-quality window.”
dispensing equipment also improves quality by applying a sealant of uniform
diameter, no matter what the line speed. According to Jerry Wells, outside sales
for equipment manufacturer Erdman Automation, this optimizes the efficient
application of InstantGlaze.
both instant stick and long range performance benefits. I think they really have
good material here,” he said.
While fabricators switching from glazing tape to this product will realize the greatest gains, those already using automated technology also can increase productivity because of the fast cure and reduced assembly time the sealant allows.
is clear we have reduced the post-glazing labor that used to be spent on
clean-up and adjusting prior to shipping,” said Ferrera. “The sealant also
eliminates the 24-hour cure period. Since we have been testing this material,
I’ve embraced it. It’s a wonderful product, not only in production, but for
its performance as well. We have three lines using it now and I am planning to
convert the entire building by the end of the year.”
Oliva, vice president for equipment manufacturer Besten Inc., confirms that the
sealant optimizes the performance of automated X-Y glazing tables.
speeds process time by reducing the time required for assembly. This increases
throughput. We’re pretty impressed with it,” he said.
hot-melt silicone technology puts the advantages of silicone performance and
automated glazing operations within reach of fabricators of all sizes.
“This product is still new, but it appears to solve an issue many of our customers have – getting the long-term benefits of silicone with the immediate benefits of double-sided tape,” said Oliva. “It satisfies both. As a table manufacturer, we see that as meeting a need in the industry. ”
Kelly Charbonneau serves as window industry analyst at Dow Corning Corp. and Ross Noel serves as senior technical specialist.