FAQ > Urethane Adhesives

• I have a Volkswagen Beetle, when I called Phoenix Glass for a price on a new OEM replacement windshield, the customer service representative told me my VW called for the application of a different type of adhesive called high modulus urethane. I understand it's a form of urethane but how does it differ from the type normally used? The short answer is that your VW, along with many other German automobile manufacturers, such as Audi, BMW, Volvo and Mercedes, have mandated a rigidity requirement on the vehicles that they produce. In order to meet that engineering requirement and retain the structural integrity of the vehicle it is necessary to use a different type of urethane to bond the windshield, back glass and side windows to the vehicle. High Modulus urethane adhesives provide the extra strength to help the vehicle resist torsional twisting as well as help quiet and stabilize the vehicles ride. Another added plus that is built into High Modulus Urethane is that it preserves radio, cell phone, and global positioning system reception in an OEM antenna encapsulated windshield or rear back glass window.

The long answer is now that you have learned how important it is and how it all works together we're going to recap a bit as we get into why it's so important to not only make sure your new windshield is installed with a High Modulus adhesive but with the "right OEM type" of High Modulus Urethane. If you read multiple adhesive manufacturers literature to determine whether their urethane is high modulus, you will find different definitions of the term. Some manufacturers define their windshield adhesives as "modulus enough" or "high on the OEM specification for high modulus classification," but does that really mean that they can be classified as high modulus adhesives? To answer that question, first we must define what high modulus means. High modulus is a rigidity requirement of cured adhesive. It measures the ability of the adhesive to withstand a variety of stresses and still return to its original form. It must be able to withstand tension, compression, shear and torsion without adhesive or cohesive failure. High performance and luxury vehicle manufacturers specify and use adhesives like BETASEAL ONE because they can use it as a structural element to stabilize the vehicle which improves the ride and reduces rattles, vibrations and other vehicle noises. High modulus adhesives have a much higher resistance to stress. This characteristic enables high modulus adhesives to stiffen the vehicle body, improving handling and overall stability in vehicles designed to use this advanced technology. Vehicle designers place greater demands on high modulus adhesives. The adhesive bears much more of the pushes, pulls and twists associated with everyday driving. High modulus adhesives must have a higher elastic resistance than normal so they will not deform or rupture under the increased stress. So how do adhesive manufacturers know which property and specification should be met in order to be high modulus? To clarify, it must be understood that an adhesive is either high modulus or it is not. There is no in between modulus that is good enough for all vehicles.

According to Mercedes specifications, in order for an adhesive to be considered high modulus, it must meet 2.5 MPa. Dow Automotive's Betaseal One Urethane Adhesive passes the defining test to be called high modulus with a shear strength of 2.7 MPa at full cure. The Bottom Line A urethane manufacturer cannot claim to be "on the high end of the specification" and therefore be considered "modulus enough" for all vehicles. Any urethane manufacturer claiming to be high modulus should be able to provide supporting data, to include laboratory testing as well as technical data. • I’ve been reading your website about High Modulus Urethanes and it sounds like it would work better than the type used in my GM Vehicle. If I have a new windshield installed wouldn’t it be better to use it.

It does sound better but your vehicle isn’t designed for it. According to I-CAR, Using a high modulus adhesive when it's not specified or when it was not designed into the vehicle could alter the vehicle by making it stiffer than original design and cause other potential problems.

• What is Urethane Adhesive? Polyurethane better known as Urethane is an adhesive that is specially made for sealing and bonding a windshield, side window, quarter glass, and rear window back glass in the automotive industry. Even though Europe was already using urethane in some of it’s vehicles the first reported use in an American produced car was in a 1973 Oldsmobile windshield and rear back glass window. In 1974 it was used exclusively in all General Motors as well as American Motors vehicles. In later years GM also began using it to bond rubber gasket set windshields in GMC and Chevrolet pick up trucks.

In today’s foreign and domestic vehicles urethane is the only adhesive technology used in high performance auto glass bonding applications because urethane is capable of withstanding high levels of deformation with little loss of adhesive strength and performance. Urethanes are tough and and abrasion resistant. The Betaseal urethane adhesives we use here at Phoenix Glass are formulated to be durable enough to withstand long term weather exposure.