PPG Aerospace is introducing new materials for improved aircraft windshields and windows. For the Airbus A320 family of airliners, the French company has developed a new windshield featuring two new PRC sealants used to improve moisture resistance: PR-2060 polyurethane, which has a low moisture vapor transmission rate, has been added as an internal sealant behind the Z-retainer (a part that holds plies together); and PR-1425CF chromate-free sealant has replaced PR-1425 as the outboard moisture seal for the windshields it has a faster cure rate and is less environmentally harmful.
To defend against delamination, S-123 urethane bonds the outboard and middle glass plies, in lieu of a urethane-vinyl-urethane sandwich. According to PPG, the material maintains elasticity better even when cold. It also prevents cold chipping and resists moisture damage.
Brent Wright, PPG’s global platform director for transparencies, told AIN that the company has sold more than 500 retrofit shipsets for the new Airbus windshields.
A source familiar with the transparency market explained to AIN that airframers generally qualify two sources. One source is for original equipment; the other, qualified for retrofit, can have to wait years until it sells its first replacement windows. Sometimes the two sources are qualified for original production, as is the case with the A320.
The design of a windshield or cockpit window usually is based on three glass plies such as PPG’s Herculite II. Ply thickness is usually eight millimeters (for two of them) and three millimeters. Intermediate layers–often made of polyurethane or PVB–play a strengthening role. Metal films also function as de-ice/defog heater films. They can reflect solar (infrared) light for comfort. In addition, nonmetallic exterior coatings are used for rain shedding and window durability, protecting against environmental degradation.
A major challenge is optical quality. “It should be better than for a car windshield because you should avoid any form of optical distortion during critical flight phases, such as landing,” the company said. It is all the more difficult as plies are thicker in aviation applications. Moreover, heating is part of the equation.
In passenger cabin windows (a less high-tech product), PPG (Stand E108) claims its Opticor plastic is more craze resistant. Opticor is the first new transparent plastic developed in more than 50 years for aerospace applications, according to Anthony Stone, PPG’s global director for new business development and innovations for transparencies. “We expect it to replace stretched acrylic for passenger-cabin windows because it weighs less and has better craze and fire resistance,” he said.
Stone said Opticor is approximately 5 percent lighter than acrylic and presents possible weight savings of 660 pounds for a large transport aircraft.
Gulfstream has selected the new material for the outboard surface of the G650 business jet’s passenger windows. The plastic is laminated to stretched acrylic for increased stiffness. It is then assembled with an inboard coated glass panel that can be heated for antifogging.
Opticor also is expected to be used in cockpit windows (as one of the plies) because it is “an excellent substrate” for metallic and nonmetallic coatings. In addition to large civil aircraft, it may have a significant potential in general aviation. There, “its durability will be a significant benefit compared to the currently used as-cast acrylic,” Wright said.