A new method based on application of cyclic strain to evaluate the durability of pressure sensitive adhesives

Abstract

The development of PSAs suitable for speci c applications requires an optimization of the two most essential properties: suf cient bond strength and clean removability. The latter is conveniently obtained by controlling the mode of debonding to an interfacial failure, yet the issue of bond strength is challenging since the optimum bond strength must be available in the same failure mode. More complication arises from the fact that the methods, such as peel and creep tests, used to evaluate the bond strength are often qualitative and the results obtained may not accurately reveal the effects of various PSA design parameters. In the present study, a new method, named cyclic strain application (CSA) test, is devised to evaluate the durability of PSAs. A key feature of this test is that by applying a controlled cyclic strain on a PSA / substrate interface we can quantitatively monitor the temporal stress variation as well as the time for interfacial failure (t f ). As a result, the effects of various PSA design parameters, such as molar mass, blending with low molar mass fractions, adhesion promoters, and the level of crosslinking on PSA durability can be clearly seen. Other factors being equal, higher molar mass samples showed greater t f , while, blending with low molar mass fractions led to a reduced t f . The use of a strong adhesion promoter, as anticipated, increased t f . However, it should be noted that excessive bond strength may lead to a cohesive failure, which is detrimental in the design of good PSAs. From a comparison of t f with peel strength, it was clearly shown that t f , the key parameter obtained from the CSA test, had a strong correlation with peel strength. In addition, some other information, such as the detailed in uences of the level of crosslinking and molar mass on PSA durability was also obtained from the CSA test. Lastly, some important PSA design concepts and other examples utilizing the CSA test are presented.

Structure and application of polarizer film for thin-film-transistor liquid crystal displays

“…It is used to attach the polarizer film to a LCD panel. It is also used as bonding material among the other layers in the polarizer film [37][38][39]. The sufficient bond strength and clean removability are two essential factors to optimize PSA property.…”

Cyclic magnetic actuation technique for thin film interfacial fatigue crack propagation

“…These peel tests are generally performed using displacement controlled actuators, which pull on the film at a constant rate while measuring the reaction force. Consequently, any FCP study to date that has utilized a peel-typetest has been conducted under constant displacement amplitude loading [16,17].…”