Volume 8, Issue 2 - February 2007

Face Off

Which one is right for your product: reactive back-bedding technologies or hot-melt sealants? Find out the advantages of each with the help of two industry leaders, Jim Doell, the business leader for Industrial Products Division at Tremco Inc. in Beachwood, Ohio, and Ken Rubis, the fenestration technical specialist for Dow Corning Corp. headquartered in Midland, Mich. 

The Advantages of Reactive Back-Bedding Technologies
by Jim Doell

In May 2002, Tremco’s Residential Glazing Division conducted a customer survey regarding back-bedding products, including sealants and tape materials. The purpose of the survey was to determine customer satisfaction and needs related to back-bedding technologies. 

Customers rated the following items of primary importance when making a decision on back-bedding products: cost of material, cost of equipment, labor intensity, product performance, user friendliness and ability to deglaze.

When asked to rate the importance of various performance related attributes, customers overwhelmingly requested quicker setting and overall faster curing technologies. Along with quick cure characteristics, the following items were considered primary motivators in the decision process of choosing a back-bedding technology. 
• High green-strength;
• Adhesion to the window substrate;
• Compatibility to various window components, including sash, IG sealants and setting blocks; and
• Ability to be used over a wide range of material substrates, and, as an impact-glazing product. 

High green-strength development can best be described as the rate of development of rubber-like properties in a sealant material. For the purposes of the survey, it was more accurately described by participants as how quickly the door or window product could be moved following material application. Of primary importance was the ability to transport/handle large (picture windows and patio door), sash without distortion of the rails. 

Manufacturers indicated that, although quick green-strength was important, they were not willing to pay significantly more per lineal-foot for this benefit, nor were they willing to invest significant capitol on equipment. They seemed to be interested in a quick setting, cost-effective product that exhibited physical properties similar or better than traditional silicones, with easy de-glazability and the ability to be used with their existing equipment. 

In summary, customers wanted a back-bedding technology that did not add a lot of material cost to their existing glazing system, (no more than 10 percent); exhibited quick green-strength development (within five to ten minutes); was economically adaptable to existing equipment or required a minimum investment to upgrade; and could be utilized over their entire product offering, including impact glazing.

Over the course of the last two to three years several sealant manufacturers have attempted to address these requests by offering reactive back-bedding sealants. Each of these products has advantages and disadvantages. 

The primary benefits of all of these reactive technologies include:
• Reduced turn-around due to improvements in green-strength development;
• Elimination of squeeze-out and subsequent clean up of sash and glass;
• Reduction in floor space, as units can be immediately transported;
• Ability of the sealant to be utilized for the entire product offering, including impact glazing; and
• Ability to meet performance specifications, including AAMA 802.3-92, Type 1.

Bottom line, the leading concern to the manufacturer is that the product offers these performance and design advantages while maintaining or reducing the labor, material and equipment cost criteria identified in our customer survey. Some do a better job of addressing these criteria than others. 

Productivity Cost Savings of Hot Melt Sealants
by Ken Rubis

Manufacturers share the same goals: To increase employee productivity, boost the speed of production and achieve cost efficiencies. As demand for improved manufacturing processes grows, door and window manufacturers can choose from multiple sealing technology options. 

Tapes, for example, can have consistency and quality issues that require time for reworking. Wet sealants need time to cure–ranging from eight to 24 hours—which requires that manufacturers set aside time and space for the sealant to develop sufficient strength before moving the units. Additionally, wet sealants can need a clean-up step caused by squeeze-out when glass is pressed into the frame.

Hot-melt sealants offer instant bonding and high viscosity that helps eliminate squeeze-out. High viscosity hot-melts applied at room temperature by automated dispensing equipment create a uniform seal for window-to-window consistency, minimize sealant waste and clean up and substantially reduce labor costs. 

Hot-melt sealants combine the benefits of traditional wet sealants with that of glazing tapes, offering superior initial bonding consistency and uniformity. This helps manufacturing companies keep pace with growing demand. Companies that adopt this innovative technology are better able to address their business challenges because of the combination of improved adhesion performance and increased efficiency from reduced manufacturing time, material and labor costs. 

Hot-melt sealant technology is available in both organic and silicone forms to meet varying manufacturing requirements. Silicone hot-melt sealants offer clear advantages over organics. Once cured, hot-melt silicone sealants remain flexible below zero degrees Fahrenheit, where as organics may become brittle and crack. Additionally, silicone hot-melt’s higher movement capacity minimizes stress on the insulating glass unit. 

Silicone hot-melts offer longer performance against environmental factors due to their resistance to long term direct and indirect ultraviolet exposure. Silicone hot-melts demonstrate excellent performance in both high and low temperature conditions. They also meet environmental low volatile organic compound standards. 

Additionally, silicone hot-melts do not require priming or surface activation and are suitable for most common substrates, including glass, PVC, aluminum, wood and fiberglass. They are designed for easy processing with automatic equipment, and offer a long pot life and reasonable working time to allow for adjustment after glass is set in a frame. 

Hot-melt sealants are making a tremendous impact on productivity for door and window customers. Regardless of formulation, hot-melt sealants provide a single solution by combining the benefits of wet-applied sealants and traditional tapes. Taken a step further, silicone hot-melts differentiate themselves from their organic counterparts by offering long term durability and flexibility. 


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