The Science of Strength in Adhesives

It would be simpler if all that was needed to create a permanent impervious seal for insulating glass panels was a strong adhesive, but that isn’t how it works. In fact, too much “strength” can work against the requirements of a permanent glass adhesive. One way an adhesive strength is measured is its hardness via a scientific test called the Shore hardness test which generates a number called Shore A hardness. While this measure to some degree indicates the shear strength of a product it can be deceiving and can lead to misunderstanding how such an adhesive needs to work.

Of course strength is critical to a strong bond on insulated glass but it’s far from the only concern of assembly. Where other adhesives can become tired after years Delchem D-2000 presses on.

Overall what we’re all seeking is the strongest solution that seals in the gas, seals out the moisture and holds everything together. So we have the list for you.

Shear strength (aka sheer strength) is specifically how much effort it takes to directly break either a material itself or it’s bond to other materials, wether mechanical or chemical. While this is a trait of adhesives it can not be confused as a direct measure of effectiveness. The problem as we’ll review, is that it functions as a direct balance to elasticity which is VERY critical of any adhesive and extremely critical for handling weather and insulating glass panels. The durometer used to determine hardness is a Shore A Durometer. D-2000 has a Shore A hardness of 35 immediately after application, and 45 at full cure. The urethane “reactive hot melt” sealants all demonstrate a much higher Shore A hardness after full cure; 55 and higher. This relates, however to the previously discussed topic (elastomeric traits). The harder the sealant, the less “forgiving” it is as the glass of an IG unit “flexes” during temperature and pressure changes. Once again, excessive hardness (lack of elasticity) places severe stress on the adhesive bond line, leading to premature failure of the bondline, hence, failure of the IG unit! This is why not only is shear strength not the best measurement, but will also adversely affect real-world performance.

Meanwhile, one good mention here that can be a bottom line benefit to you is that while it can take other sealants orders of magnitude in additional time to reach their full strength and often should not be handled while hardeing your D-2000 seal sets to a workable hardness in minutes. As an example we know of a use-case where large (8′ x 11′) IG panels, once assembled, are being lifted by an overhead suction cup crane 90 seconds after assembly. That is a normal practice, time-tested.

While “strength” as a measure of overall performance isn’t the key factor, it’s a serious benefit to production when your product strength is stable and workable this quickly. If you’re in the process of evaluating adhesives you know that strength is one measure but actually not even the most critical one. When it comes to being the best sealant adhesive available we’ve done all the testing and determined that without fail, D-2000 is the industry leader in the measures that count the most. To learn more please contact us and our agents will help you arrange your own test so you can see the superior properties of Delchem D-2000 directly as they help with your operations and products.