SE-381 EVA Interlayer Application Bulletin

APPLICATION BULLETI
ArgoBond®
SE-381 EVA Interlayer
For Laminated Switchable and Decorative Glass Applications
INTRODUCTION
Optical interlayers have been
employed to laminate layers of
glass into clear composites since
the 1930’s. Typically made from
polyvinyl butyral (PVB), these
interlayers have performed well
in a wide variety of glass-to-glass
applications, particularly curved
automotive windshields. Through
the evolution of security glass –
like glass-to-polycarbonate used
in today’s bullet resistant constructions, thermoplastic polyurethane
(TPU) interlayer materials evolved
as the material of choice for those
applications due to its ability to
accommodate the varying rates
of thermal expansion and contraction between such dissimilar
substrates.
Now with the growth of decorative and switchable glass markets over the past several years,
thermoset ethylene vinyl acetate
(EVA) interlayers have gained
importance based on their key
properties, including high transparency, good strength, long term
reliability (heat, humidity and
UV durability), low temperature
lamination and broad compatibility
with other materials and decorative media.
In the late 1970’s, interlayers
made from thermoset ethylene vinyl acetate (EVA) were introduced
as encapsulants to laminate
photovoltaic panels, comprising
glass laminates containing solar
cells. SWM International (formerly
Argotec) has been producing
ArgoBond® thermoset EVA optical
interlayers since 2007.
The purpose of this application
bulletin is to provide the prospective user with guidelines on selection, handling and design considerations for ArgoBond SE-381
thermoset EVA optical interlayer
film.
Switchable Glass Laminate:
Glass/Thermoset EVA Interlayer/Switchable Film/Thermoset
EVA Interlayer /Glass (see fig. 1)
Outer Glass Substrate
EVA Interlayer
PET
END USES
Thermoset EVA optical interlayers
find applications wherever high
transparency, good strength, long
term reliability (heat, humidity and
UV durability), low temperature
lamination and broad compatibility
with other materials and decorative media are required, like:
■ Switchable glass laminates
■ Decorative glass laminates
The low melting point allows
the thermoset EVA interlayers to
be laminated and simultaneously
cured at temperatures which accommodate the low temperature
limitations of the switchable film
laminates. Uncured or thermoplastic EVA can undergo creep/
cold flow in a laminated glass
structure at temperatures as low
as 35 to 40°C, depending on the
vinyl acetate content. Creep/Cold
Flow is noted by movement of one
glass substrate in respect to the
other due to outside forces, i.e.
gravity. Thermoset EVA, properly
cured during lamination, will not
suffer from creep/cold flow at
elevated use temperatures.
LAMINATE DESIGNS/
CONSTRUCTIONS
The following constructions are
recommended for switchable and
decorative laminated glass configurations:
PDLC
PET
EVA Interlayer
Inner Glass Substrate
Fig. 1. Switchable glass laminate structure
Recommendations: Use a minimum
of 0.015” (0.38 mm) thermoset EVA
interlayer between the glass and
switchable film on both the front and
back. There are no substrate min/
max thickness requirements.
Decorative Glass Laminate:
Glass/Thermoset EVA Interlayer/Decorative Media/Thermoset
EVA Interlayer /Glass (see fig. 2)
Outer Glass Substrate
EVA Interlayer
EVA Interlayer
Inner Glass Substrate
Decorative media
Fig. 2. Decorative glass laminate structure
Recommendations: Use a minimum of 0.015” (0.38 mm) thermoset EVA interlayer between
the glass and decorative media
interfaces. If using a thick decorative media that exceeds 0.015”
(0.38 mm) thickness but less than
0.030” (0.76 mm), then the 0.030”
(0.76 mm) should be used. In all
cases, the EVA layer thickness
should be greater than the decorative media being encapsulated
or laminated.
OTHER DESIGN
CONSIDERATIONS
Additional factors can impact an
optical interlayer’s ability to bond
to a substrate. For instance, there
are different types of glass (chemically strengthened, tempered,
float, etc.). These may also have
additives or coatings that can affect adhesion and performance of
the interlayer. Engineered plastic
sheet can have varying coatings
(i.e., UV-absorbers, coated one or
both sides) that can also impact
interlayer performance.
INTERLAYER SELECTION
Interlayer materials should be
matched to the specific application
based on:
■Adhesion
■ Coefficient of thermal expansion and contraction
■ Light transmission
■ Ultraviolet resistance
■ Color (clear, non-yellowing)
■Haze
■ Impact resistance
■Strength
■ Operating temperature range
INTERLAYER MATERIAL
COMPARISON
PVB: Polyvinyl butyral works
well in glass-to-glass and curved
interlayer applications. However,
it contains plasticizers that can
migrate, embrittle and cause
fogging around the edges of
the composite. Plasticizers can
cause variability in optical properties and adhesion. Because they
are sensitive to water and other
chemicals, PVB interlayers may
require an edge seal to preserve
the integrity of the laminate. PVB
also requires refrigerated storage
to prevent blocking. It does not
bond well to plastic substrates.
Finally, PVB interlayers can degas
and cause bubbles between the
substrates.
2
TPU: The base TPU polymer
is 100% solids and contains no
plasticizers. TPU interlayers exhibit excellent adhesion to glass,
polycarbonate and polyester (up
to 150 pli/26.3 kN/m), as well as
the thermal expansion/contraction
properties needed for bonding
dissimilar materials to glass. TPU
has good light transmission, low
haze, and possesses high tensile strength (up to 6000 psi/41.4
MPa) for high-impact applications.
No distortion (birefringence) is observed on bent-glass laminations.
TPU interlayers are interleafed, so
no refrigeration is needed during
storage or processing.
■ Layup (stacking of the layers)
■ Deaeration or evacuation of air
lamination is typically carried
out by vacuum bag / autoclave
or by vacuum lamination. During lamination, the substrate
preparation is critical to the
successful bonding of the layers into a single composite, as
is careful control of the process
conditions:
■ Preheat temperature ramp-up
■Pressure
■ Cure time, temperature and
pressure
■ Ramp-down time (reduction of
temperature and pressure)
EVA: Thermoset EVA works well
in low temperature lamination applications with low melt viscosity
and contains no plasticizers. The
high vinyl acetate content of EVA
copolymer resins afford a combination of beneficial properties
including: good optical clarity and
no distortion, low haze, and low
melting points. The low melting
point allows the thermoset EVA
interlayers to be laminated and
cured (crosslinked) as low 105°C
(221°F), which accommodates
the low processing temperature
limitations of the switchable film
laminates. The low melt viscosity
allows for ease of bubble-free or
void-free lamination of complex
decorative media. The thermoset
EVA interlayers bond aggressively
to glass, PET and many other
substrates. Roll storage is at room
temperature; however, direct sunlight should be avoided.
Note:The key temperature reading
is at the core of the EVA interlayer and needs to be tracked
throughout each cycle.
LAMINATION PROCESSES
Lamination is typically carried
out by vacuum bag / autoclave
or by vacuum lamination. During
lamination, the substrate preparation is critical to the successful
bonding of the layers into a single
composite, as is careful control of
the process conditions:
A core coupon (see fig. 3) is a
laminate of the same configuration
that is placed centrally in the laminating chamber. It has a thermocouple placed in the center of the
thickest configuration in the core
of the laminate, with the thermocouple passed through the wall of
the laminating chamber to a device
that will allow constant monitoring
of the core temperature.
GLASS
GLASS
Fig. 3. Core coupon
THERMOCOUPLE
EVA INTERLAYER
GENERAL TEMPERATURE/
PRESSURE/TIME GUIDELINES
■ Temperature/pressure/time are
composition dependent.
■ As glass thickness increases,
the lamination cycle time is
increased.
■ The lamination cycle should
be verified by adhesion testing
to ensure that proper cure has
been achieved. Poor adhesion
is an indication of insufficient
cure during lamination.
■ EVA interlayers should be
quench cooled as rapidly as
possible to minimize haze formation. Although the EVA cannot
be remelted, haze levels can be
reduced by heating the laminate
to 90°C (194°F) and then cooling the laminate rapidly.
■ The lamination cycle should
be verified by adhesion testing
to ensure that proper cure has
been achieved. Poor adhesion
is an indication of insufficient
cure during lamination.
RECOMMENDED STARTING POINT
LAMINATION CYCLES FOR EVA GLASS INTERLAYERS
Switchable Glass Lamination
SILICONE SEALANT
COMPATIBILITY WITH
ARGOBOND® SE-381
THERMOSET EVA INTERLAYER
Silicone sealants are frequently
used on glass laminates constructed with ArgoBond SE-381
thermoset EVA interlayer. Certain
types of silicone sealants can
react with the EVA interlayer and
cause the interlayer to rapidly
discolor. Typically, neutral cure
or platinum cure silicone sealants are found to be compatible.
Acetoxy cure silicone sealants
in general react with the EVA
causing rapid discoloration of the
interlayer. Verification of a silicone
sealant’s compatibility with the
EVA interlayer is recommended.
Switchable Glass Lamination
SWM’S ARGOBOND® SE-381
THERMOSET EVA INTERLAYER
ArgoBond SE-381 thermoset
EVA interlayer is a great choice
for switchable glass and decorative glass laminates. SE-381 is
Starting Point Parameters – Vacuum Bag and Autoclave Lamination:
Interlayer Temperature and Autoclave Pressure Vs. Time
Time Interval
Temperature
Pressure
Pull vacuum
Process
15 minutes
Room temperature
Atmospheric
Ramp temperature
30 minutes
Room temp to
90°C / 194°F
Pressurize to
10.5 bars
Melt EVA
90 minutes
90°C / 194°F
10.5 bars
Ramp temperature
15 minutes
110°C / 230°F
10.5 bars
Cure EVA
250 minutes
110°C / 230°F
10.5 bars
Cool EVA
Quench cool
110°C / 230°F to ambient
10.5 bars
Decorative Glass Lamination
Starting Point Parameters – Vacuum Bag and Autoclave Lamination: Interlayer
Temperature and Autoclave Pressure Vs. Time
Time Interval
Temperature
Pressure
Pull vacuum
Process
15 minutes
Room temperature
Atmospheric
Ramp temperature
30 minutes
Room temp to
90°C / 194°F
Pressurize
to 2 bars
Melt EVA
90 minutes
90°C / 194°F
2 bars
Ramp temperature
15 minutes
130°C / 266°F
2 bars
Cure EVA
50 minutes
130°C / 266°F
2 bars
Cool EVA
Quench cool
130°C / 266°F to ambient
2 bars
Starting Point Parameters – Dual Chamber Vacuum Lamination:
Interlayer Temperature and Chamber Pressure Vs. Time
Time
Description
0 minutes
Deaerate the laminate by loading it to the bottom chamber of the laminator, then evacuate the air from the top and bottom chambers at room
temperature.
15 minutes
Initiate temperature ramp to 90°C / 194°F while maintaining full vacuum
in both chambers.
60 minutes
Melt the EVA under vacuum to remove any volatiles while equilibrating
the EVA/laminate temperature to 90°C / 194°F.
Table continues on next page.
3
extruded in a clean environment
with each extrusion line housed
in its own ISO Class-7 soft-walled
clean room.
Camera systems provide 100%
in-line inspection of SE-381 that
can detect contamination or
inclusions, pin holes, voids, gels,
wrinkles and streaks as small as
0.3 mm (0.012 in.). The result is
the cleanest, most optically clear
EVA interlayer film in the industry.
INTERLAYER SIZES
■ Roll lengths (by gauge & width):
125 minutes
Ramp the EVA/laminate temperature to 110°C / 230°F while simultaneously releasing the top chamber’s vacuum returning to 760 mm/1
atmosphere pressure.
135 minutes
Begin the crosslinking/curing of the EVA at 110°C / 230°F for 215
minutes under full vacuum in the bottom chamber, the top chamber
remains pressurized.
400 minutes
Cure is complete, begin quench cooling the laminate to room temperature, simultaneously releasing the top chamber’s vacuum returning to
760 mm/1 atmosphere pressure.
Note:
The laminate may be removed hot from the laminator to facilitate
quench cooling. Rapid/quench cooling is necessary to reduce haze
formation. Be sure to handle the laminate with care to avoid disrupting
the bonded surfaces.
Decorative Glass Lamination
Starting Point Parameters – Dual Chamber Vacuum Lamination:
Interlayer Temperature and Chamber Pressure Vs. Time
0.015” (0.38 mm) x
40-80” (1016–2032 mm) x
400’ (122 M) roll
0.030” (0.76 mm) x 40-80” (1016–2032 mm) x
200’ (61 M) roll
■ Available thicknesses:
0.150” (0.38 mm)
0.030” (0.76 mm)
INTERLAYER HANDLING
CONSIDERATIONS
Rolls are typically hermetically
sealed in a foil-lined pouch, suspended on end plates and individually boxed, then palletized, nine
rolls per pallet.
Time
Description
0 minutes
Deaerate the laminate by loading it to the bottom chamber of the laminator, then evacuate the air from the top and bottom chambers at room
temperature.
15 minutes
Initiate temperature ramp to 90°C /1 94° while maintaining full vacuum
in both chambers.
60 minutes
Melt the EVA under vacuum to remove any volatiles while equilibrating
the EVA/laminate temperature to 90°C / 194°.
125 minutes
Ramp the EVA/laminate temperature to 130°C / 266°F while simultaneously releasing the top chamber’s vacuum returning to 760 mm/1
atmosphere pressure.
■ Store unused material in the
original packaging, resealed.
135 minutes
Begin the crosslinking/curing of the EVA at 130°C / 266°F for 50 minutes
under full vacuum in the bottom chamber, top chamber remains pressurized.
■ Keep in a cool and dry warehouse.
185 minutes
Cure is complete, begin quench cooling the laminate to room temperature, simultaneously releasing the top chamber’s vacuum returning to
760 mm/1 atmosphere pressure.
■ Widths up to 80-inches (2 meters) depending on gauge.
■ It is best to unwind by pulling
the polyethylene interleaving.
■ Contact the local waste management company for disposal
of the interleaf.
■ Shelf-life is 6 months from the
date of manufacture, provided
the material remains uncompromised in its original packaging.
For more information on SE-381,
please visit our web site,
www.swmintl.com.
4
Note:
The laminate may be removed hot from the laminator to facilitate
quench cooling. Rapid/quench cooling is necessary to reduce haze
formation. Be sure to handle the laminate with care to avoid disrupting
the bonded surfaces.
Important: It should be noted that there can be considerable variability from
one lamination device to another. The above processing parameters serve
only as a guidance for designing the parameters that are best suited for your
laminate configuration and equipment. It is important to understand that the
temperature parameters are designed around the EVA interlayer temperature
Notes continue on next page.
and not the lamination device’s temperature. Validation of the lamination profile
is recommended using the core coupon configuration as previously depicted in
Figure 3.
The most critical factors for ensuring high quality laminates are deaeration,
interlayer cure time, interlayer cure temperature and cooling rate. As you dial
in your optimal processing parameters it is critical to ensure that the thermoset
EVA interlayer is fully cured. The time and temperature relationship is a logarithmic relationship and must be maintained in accordance with the time and
temperatures presented in Table 1 below.
Table 1 Minimum Soak Time as a Function of EVA Interlayer Cure Temperature
EVA Temperature
Minimum Soak Time @ Temperature
221ºF/105ºC
330 minutes
230ºF/110ºC
190 minutes
239ºF/115ºC
115 minutes
248ºF/120ºC
65 minutes
257ºF/125ºC
40 minutes
266ºF/130ºC
25 minutes
275ºF/135ºC
15 minutes
284ºF/140ºC
9 minutes
293ºF/145ºC
6.5 minutes
302ºF/150ºC
3.5 minutes
Date of publication: August 16, 2017
All statements, product characteristics, and performance data contained herein are believed to be reliable based on observation and
testing, but no representations, guarantees, or warranties of any kind are made as to accuracy, suitability for particular applications,
or the results to be obtained.
Nothing contained herein is to be considered to be permission or a recommendation to use any
proprietary process or technology without permission of the owner. No warranty of any kind, expressed or implied, is made or intended.
SWM INTL
53 Silvio O. Conte Drive
Greenfield, Massachusetts 01301 USA
tel: (413)772-2564 fax: (413)772-2565
web: www.swmintl.com e-mail: ams@swmintl.com
© 2017 Schweitzer-Mauduit International, Inc.
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