3M VHB Technical Bulletin

March, 2001
3
Technical Bulletin
3MTMVHBTMDurability
Durability of 3M™VHB™Tapes
Summary
This bulletin addresses the long-term durability of VHB™ Acrylic Foam and Adhesive Transfer Tape products 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 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.
Composition
3M has been a technological leader in acrylate pressure sensitive adhesive (PSA) technology for over 35 years. The VHB™ Acrylic Foam and Adhesive Transfer Tapes represent examples of 3M’s proprietary state-of-the-art in this durable chemistry. The long-term aging resistance lies in the polymer comprising VHB™ Adhesive Transfer and Foam 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.
Durability Testing
Temperature Exposure
Because of the demanding and diverse applications users have for 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. The VHB™ Adhesive Transfer Tape F-9473PC yielded 92% retention of peel adhesion after the roll was aged for more than 5 years at 150°F (65°C). The initial tack and liner release properties were still excellent. The difference in peel values suggests that a roll of this tape is relatively unaffected by long-term exposure to elevated temperatures. Bonds made with VHB™ Tapes can tolerate periodic, short­term exposures to temperatures up to 300°F (150°C) for most Foam Tapes and 500°F (260°C) for Adhesive Transfer Tapes.
Technical Bulletin
3MTMVHBTMTape 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 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.
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Figure 1
Weatherometer Testing of 4950 VHB Tape
Hours of Exposure
% Strength Retention
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 VHB™ tape family. These tests typically demonstrate about 100% bond strength retention in certain 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 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 the VHB™ tapes.
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Figure 2
VHB™ Tape (5 Year Outdoor Aging, Minnesota)
% Strength Retention: Tensile
0 Yr 1 Yr 2 Yr 5 Yr
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VHB™ Tape
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