Improved Optical Interlayer Systems Show Bond Stability at High Temperatures, High Humidity 911136
Tempered glass, once the optimum material for aircraft vision systems, is now being replaced by high-strength, lightweight plastics. Specially designed acrylic, glass, and polycarbonate laminates offer weight savings that give them a distinct advantage in weight-critical aerospace applications. Like tempered glass, laminates must withstand the impact of low-altitude debris and bird-strike as well as the shock of rapid temperature, humidity, and pressure changes. The laminating adhesive must be strong enough to withstand impact and must provide stress relief for the different substrates, which often have very different thermal coefficients of expansion.
Liquid and sheet silicone interlayer adhesives have been developed that provide the clarity, adhesion, and performance characteristics required by aircraft windshield and canopy designs. These adhesives have hydrolytic bond stability and high-temperature adhesion that are substantially greater than those of nonsilicone adhesives. This means that windshield replacement due to delamination is less frequent, significantly decreasing the costs of grounded craft and the maintenance required.
This paper gives new data on the high-temperature adhesion and hydrolytic bond stability of sheet silicone interlayer adhesives. Adhesion to acrylic was tested from -50°C to 125°C; adhesion to polycarbonate was tested from -50°C to 150°C; adhesion to glass was tested from -50°C to 250°C. Hydrolytic bond stability was tested at 100% relative humidity at various temperatures and compared to results with polyvinylbutyral and polyurethane adhesives.