Blazing sun, driving rain, baking heat and excessive cold? Just a typical day in the laboratory as Rohm and Haas designs and improves innovative water-based pressure sensitive adhesive (PSA) systems. As these adhesives become tougher, more versatile and able to endure more stress, performance testing necessarily gets more severe. Company scientists creatively design tests and equipment that strain adhesives to their limits and provide valuable data for modifying and improving polymer design. It’s a grueling job to devise new adhesive punishments, but the route to dependability – from coating through storage through years of use – travels right through some very uncomfortable environments.

Building Better Adhesives
Rohm and Haas continues to enhance all four areas of water-based performance: adhesion/cohesion balance, resistance properties, aesthetics and processability. The company custom-designs different combinations of these properties for specific applications, and the resulting systems are grabbing market share from solvent-based adhesive strongholds: auto-interiors, trim mounting, outdoor graphics and industrial tapes, to name a few. “We are quickly narrowing the performance gap between aqueous systems and solvent-based choices,” adds Chris Urheim, marketing manager, Pressure Sensitive Adhesives, North America.

As Rohm and Haas’ water-based systems continue their upward trajectory both in performance and in the marketplace, aqueous PSAs bond in increasingly variable and difficult environments. Once applied to the substrate, systems in any application must endure shipping, storage and end-use. “A system may encounter very disparate environments: for example, a hot warehouse followed by dry, wintry conditions in use,” Urheim explains. “Continued use may expose the same system to ultraviolet light, heat and humidity. That adhesive must handle them all equally well to succeed for our customer.”

If It Bonds Here, It Should Adhere Anywhere
Rohm and Haas tests adhesives with sophisticated equipment and methodology that most companies can’t equal. These protocols simulate – and often go beyond – what the adhesive system will confront during its lifetime. Data gathered during these arduous protocols may be used to aid research and development, evaluate specific customer applications, modify adhesive properties such as cohesive strength or polymer design, or benchmark against competitive water-based products and solvent-based adhesives.

During testing, the company may employ state-of-the-art equipment like the “torture chamber” – a nickname the company’s scientists bestowed. Built to Rohm and Haas’ exacting specifications, this large, walk-in chamber mimics widely varying environments, from extremely hot and humid through very dry, sub-freezing temperatures.

“Because of its size, we have great flexibility for designing and conducting tests,” notes Sekhar Sundaram, project team leader. “We can stack and store completed laminations under different conditions for lengths of time, for example. The room also accommodates loaded shear bars, allowing us to evaluate shear strength in varying extreme environments for long periods.” An unusual tool that most in the industry can’t match, the chamber is the next best thing to real customer storage and use. It separates the finest systems from among the good candidates, and generates valuable data that guides future polymer design.

When the Rain Won’t Stop Rohm and Haas also employs another innovative apparatus called a rain chamber, which stresses the adhesive beyond just humid conditions. This device simulates water impinging forcefully and directly onto the surface of the adhesive – a much harsher situation than the system likely encounters in actual use as a laminated structure. “But it’s an additional comfort level for our customers that our adhesives can succeed beyond the standard challenges,” adds Urheim.

Additionally, scientists use more standard industry equipment such as ovens to evaluate shrinkage, a particular issue for PVC film adhesives in graphic arts applications. They also employ weatherometers. A much more compact version of the “torture chamber,” this apparatus cycles adhesives through heat up to 60 degrees C, humidity to rain conditions, and ultraviolet light that simulates sun exposure. “About 1,000 hours in a weatherometer simulates about a year of exposure,” explains Bill Griffith, project team leader. “We often run tests simulating multiple years.”

The Architect of a Better Adhesive
Data from tests like these enable Rohm and Haas to develop water-based PSA systems that perform more and more like their solvent-based cousins. The company invests in state-of-the-art testing technology and employs very experienced scientists to put these products through veritable adhesive obstacle courses. “The marketplace is realizing that Rohm and Haas’ aqueous systems are providing higher performance and that our technology continues to move to higher levels,” Urheim summarizes.