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3M VHB Tape Durability
TM
TM
Technical Bulletin
Summary
August, 2018
This bulletin addresses the long-term durability of 3M™ VHB™ Tapes and
their ability to perform in certain types of demanding environments. This
will be addressed from a variety of view-points including chemical
composition, resistance to harsh environments, 3M and independent tests
for product durability, and certain applications where 3M™ VHB™ Tape
products have demonstrated excellent ability to perform in demanding
applications. Test results on moisture resistance, UL durability,
accelerated weathering, outdoor weathering, thermal cycling and fatigue
resistance will be discussed.
3M is a technological leader in acrylate pressure sensitive adhesive (PSA)
technology. 3M™ VHB™ Tapes represent examples of 3M’s proprietary,
state-of-the-art chemistry. The long-term aging resistance lies in the
polymer comprising 3M™ VHB™ Tapes. The chemical bonds that make up
the polymer chains consist of carbon-carbon single bonds that are highly
resistant to energy in the form of heat or ultraviolet light, as well as
chemical attack. In less durable foams or adhesives, such conditions could
lead to cleaving of the polymer backbone and thus a weakening of
mechanical properties. In the case of acrylic adhesives and foams,
however, additional crosslinking is chemically favored over chain scission
(cleavage). This means that, rather than undergoing a process of
decomposition, the acrylate materials will tend to build modulus very
slightly over extended exposures. This translates to a stronger, long lasting
bond.
Temperature Exposure
Because of the demanding and diverse applications users have for
3M™ VHB™ Tapes, durability has always been a key interest in the
performance of these products. One of the first issues for tapes is
retention of tack and adhesion after exposure to elevated
temperatures. Bonds made with 3M™ VHB™ Tapes can tolerate
periodic, short- term exposures to temperatures up to 300°F (150°C)
for most Foam Tapes.
Composition
Durability Testing
Technical Bulletin
TM
TM
3M VHB Tape Durability
Accelerated
Weathering
Certain other accelerated aging tests have been conducted in
weatherometers which subject a bond to heat, humidity and concentrated
ultraviolet light exposure. These tests were performed in dynamic shear by
making a stainless-steel overlap bond with 3M™ VHB™ Tape 4950 and
then subjecting the samples to cycling heat, humidity and carbon and arc
lamp exposure. Small samples provided an increased amount of edge
exposure to UV radiation. Figure 1 indicates that the bond strength does not
deteriorate below its original performance level, even after exposure of
7000 hours in the weatherometer under these tests.
Figure 1
Weatherometer Testing of 4950 VHB Tape
200
% Strength Retention
150
100
50
0
0
2000
4000
7000
Hours of Exposure
Outdoor Weathering
Outdoor weathering decks in Arizona, Florida and other locations around
the world are also used to collect data on the long-term performance of
the 3M™ VHB™ tape family. These tests typically demonstrate about
100% bond strength retention in certain 3M™ VHB™ Tapes after 2 to 5
years aging cycles in the hot, humid climate of Florida, the hot, dry and
very sunny climate of Arizona and the cold to hot extremes of Minnesota
on bonds to aluminum, glass, PVC and painted metal. Figure 2 shows the
constant performance of 3M™ VHB™ Tapes 4950, 4951 and 4952 after 5
years of outdoor aging in Minnesota. Similar results have been obtained in
5 year tests conducted in Japan on 3M™ VHB™ Tapes.
Figure 2
VHB™ Tape (5 Year Outdoor Aging, Minnesota)
150
% Strength Retention: Tensile
100
0 Yr
1 Yr
2 Yr
5 Yr
50
0
4950
4951
4952
VHB™ Tape
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Technical Bulletin
TM
TM
3M VHB Tape Durability
Moisture and
Solvent Resistance
Adhesion tests have been performed on 3M™ VHB™ Tape 4945 bonds of
aluminum to aluminum that were subjected to over 10 years of submersion
in 5% salt water and ordinary tap water. After testing, bright clean
aluminum surfaces were observed underneath the adhesive bond. A
combination of adhesive and cohesive failure modes was observed when
the bond was broken, indicating very high performance levels. Long-term
exposure to high humidity or water submersion can have the effect of
making a polymer more resilient and tolerant of high elongation. A
subsequent lowering in peak force is also measured after many days of
exposure, usually on the order of 40%. This effect is typical as it parallels
the increase in resilience and is the same trend often seen with structural
silicone materials which are also recognized for their durability. Drying of
the 3M™ VHB™ Tape bond, which occurs in a normal environmental cycle,
will show that this effect is reversible and that the bond will return to the
original dry strength.
After splashes or incidental contact with solvents such as fuels, alcohols,
adhesive removers like MEK, and even weak acids or bases, no affect is
measured on the bond performance. Only after continuous submersion in
harsh fuels or solvents is softening of the adhesive/foam experienced.
Note: While 3M™ VHB™ Tape products may withstand occasional contact
with these types of chemicals, continuous exposure is not recommended.
UL Listing and
Durability Testing
3M™ VHB™ Tape carries UL 746C listings which involve stringent
qualification tests and periodic monitoring by Underwriter’s Laboratories.
Qualification for this listing requires high-strength retention after extended
exposure to high temperatures, humidity, cold, and cyclic conditions. The
table below details 3M™ VHB™ Tapes with the UL 746C listing, and
substrate combinations, as well as the minimum and maximum listed
temperature for each combination.
3M™ VHB™ Tapes
UL746C Listings - File MH 17478
Category QOQW2 Component - Polymeric Adhesive Systems, Electrical Equipment
3M™ VHB™ Tapes/
Product Families
4919F, 4926, 4936,
4936F, 4941, 4941F,
4947F, 4956, 4956F,
4979F
Ceramic
Substrates
Temperature Rating
Minimum
-35°C
-35°C
Maximum
110°C
90°C
Aluminum, Galvanized Steel, Stainless Steel, Enameled Steel, Nickel Coated ABS, Glass (with or
without Silane Coating) PVC, Glass/Epoxy, PBT, Polycarbonate, Acrylic/Polyurethane Paint,
Polyester Paint
ABS
-35°C
-35°
75°C
90°C
4991
5915, 5915P, 5915WF
5925, 5925P, 5925WF,
5930, 5030P, 5930WF,
5952, 5952P, 5952WF,
5962, 5962P, 5962WF
5952, 5952P, 5952WF
RP16
Polycarbonate, Aluminum, Acrylic/
Polyurethane Paint, Polyester Paint
Polycarbonate, Primer 94 Coated Polycarbonate, Aluminum, Acrylic/ Polyurethane Paint,
Galvanized Steel, Polyester Paint, Epoxy Paint, Silane Coated Glass, Uncoated Glass, Stainless
Steel, Enameled Steel, Glass Epoxy, Polybutylene Terephthalate, Nylon, Polyphenelene Ether
(PPE), Acrylic
Rigid PVC, ABS
Cellulose Acetate Butyrate
Aluminum, Silane Coated Glass
PVC, ABS
-35°C
90°C
-35°C
-35°C
-35°C
-35°C
-35°C
75°C
90°C
90°C
75°C
90°C
RP16, RP25, RP32,
RP45, RP62
RP62
Galvanized Steel, Enameled Steel, Nylon, Polycarbonate, Glass Epoxy, Phenolic, PPE/PS Blend,
PBT, Epoxy Paint, Polyester Paint, Adhesion Promoter 111 Coated Epoxy Paint, Promoter 111
Coated Polyester Paint, Acrylic Urethane Paint, Epoxy/ Polyester Paint
Stainless Steel, Glass, Acrylic
PVC, ABS
-35°C
-35°C
90°C
75°C
Current listings of all 3M VHB Tapes can be found at www.ul.com
Technical Bulletin
TM
TM
3M VHB Tape Durability
Clarity
Since the introduction of the clear 3M™ VHB™ Tapes 4910 and 4905, the
additional issue of long-term clarity and appearance consistency is
commonly asked. Tests have been run for 3000 hours in an accelerated
weathering machine which exposes bonds to high temperatures and
intense ultraviolet (UV) light. To measure clarity, 3 mm float glass plates
were bonded together with 3M™ VHB™ Tape 4910, a 0.040" thick,
transparent foam tape. The percent transmittance was monitored
periodically during the exposure cycle, beginning at 88.2% and finishing at
87.3%. After this long, harsh exposure, only a 1% change in transmittance
was observed. In high humidity environments, however, 3M™ VHB™
Tapes 4910 and 4905 may take on a hazy appearance due to slight
absorption of water molecules. Because the same acrylic polymers are
used throughout 3M™ VHB™ Tape, these results suggest inherent stability
of the whole family.
The 3M™ VHB™ Tapes have also performed well in tests, similar to
MILSTD 883, which are commonly used to qualify durable products for the
electronics industry. Under this testing, protocol bonds are subjected to
1000 hours at 150°C, 1000 hours at 85°C and 85% relative humidity, and
1000 hours of thermal shock which cycles hourly from -50°C to 150°C.
Figure 3 shows the excellent performance of the 3M™ VHB™ Adhesive
Transfer Tape F-9460PC in similar testing which involved bonding
polyimide to aluminum. Typically, the bond strength increases with time
due to the high-performance PSA’s more complete wet out of the surfaces.
Figure 3
MIL STD 883 Exposure Tests
VHB™ Tape F-9460 PC: Polyimide to Aluminum
15
*Thermal shock: -50°C to 150°C hourly
Thermal Shock
Peel Adhesion (lbs/inch)
10
5
0
Control: 72 hr RT
1000 @ 90°F/90% RH
1000 T. Shock
1000 @ 150°C
Exposure Time (hours) and Condition
Fatigue
Another durability issue is fatigue resistance. Many types of adhesive
tests are run in a short-term peel, shear or tensile mode where the
sample is broken in a matter of a few seconds. These tests are
convenient for quick characterization of the peak force holding
capability, but do not offer any information about a product’s ability to
tolerate vibration or repetitive strains. Because users have used 3M™
VHB™ Tapes in many applications which require fatigue resistance, such
as trucks or trailers, signs and building panels, a test has been designed
by 3M to characterize this property.
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3M VHB Tape Durability
TM
TM
Technical Bulletin
Fatigue
(continued)
In a constant stress machine, tension samples were cyclically loaded over
a range of stresses. The loads were chosen so that bond failures would
occur over a broad range of times. As the load decreases, the specimens
will survive more and more cycles; this trend can be plotted semi-log as in
Figure 4. The semi-log plot yields a straight line which can be used to help
predict longer term performance at lower stresses not practical to
measure. Given a product lifetime estimate for cyclic loading, the data can
be extrapolated to estimate the maximum tolerable design stress. For
3M™ VHB™ Tapes , this is typically about 20 psi for one million cycles of
full reversal loading. These tapes tend to perform well in these types of
tests because of their inherent viscoelasticity. The acrylic foam and
adhesive absorb energy and relax stresses internally, thus helping protect
the adhesive bond on the substrate.
Figure 4
Dynamic Tension Fatigue VHB™ Tape 4950
10
6
Cycles to Failure
10
5
10
4
10
3
10
2
15
25
35
45
55
65
Load (PSI)
Application Examples
of Durability
While positive test results are always encouraging, some of the best
examples of 3M™ VHB™ Tape’s durability are existing applications in the
field. 3M™ VHB™ Tapes have been used in applications dating back to
1980.
One of the oldest and most visible applications for the 3M™ VHB™ Foam
Tapes is on ambulance bodies. The aluminum panels comprising the body
of an ambulance can be bonded onto the frame with 3M™ VHB™ Tape.
These applications require durability in harsh conditions on rugged
vehicles that are in service for many years.
Another example of durable applications with excellent performance have
been curtain wall constructions such as the Singapore Treasury Building.
Here the exterior panels are stiffened against wind loads by attaching
unseen stiffeners to the inner surface. These bonds must sustain wind
loads, daily thermal expansion and contraction cycles, and elevated
temperatures. Similar curtain wall and facade applications exist around the
world such as the Walt Disney Concert Hall in Los Angeles, California and
composite ceiling panels in the O’Hare Airport in Chicago, Illinois.
Architectural signs and traffic signs using 3M™ VHB™ Tapes have also
been standing up to constant weathering, buffering winds, and occasional
storms since the early 1980’s.
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stm32/stm8
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