E-Grow used a 3-D computer-assisted manufacturing file to CNC mill individual mold plugs from wax blocks. Each plug was created with all surface texture and design details. The plugs were then used to cast the large gypsum-based mold tools that were used for the hand lay-up process.
“For the Disney project, we generally started with wax positives from which we would cast glass fiber reinforced gypsum (GFRG) negatives and assemble them to make very large gypsum molds with highly detailed textures,” says Lee. It then cast composite panels from these large GFRG molds.
An additional benefit of this process is that the wax plugs could be melted down and reused after parts were produced. Because the wax is recycled, the fabricator was able to cost effectively create large numbers of custom GFRP parts with minimal waste.
However, cost wasn’t the biggest challenge the project faced. The composite products had to meet stringent fire requirements. Every GFRP component in the park had to meet both Disney’s fire standards, as well as the Chinese B1 “reaction to fire” classification for fully assembled composite parts, as stipulated and tested by the Chinese National Inspection and Testing Centre for Building and Engineering Materials.
“FRP is only fire-rated B1 in China and, although the regulations allow FRP to be used on facades under 50 meters in height, it is still not easy to convince clients to agree to using FRP on facades,” says Philip Vernon, project manager for E-Grow. Fortunately, he adds, Disney had worked with FRP for decades and already had a good understanding of the materials.
Disney’s toughest requirement was that both the resin and gel coat, together as an assembly, had to be fire-rated B1, rather than simply the resin alone. “We went through entrusted fire-testing at laboratories in Shanghai, and only Scott Bader’s products reached those requirements,” Vernon says.
E-Grow ultimately incorporated a number of Scott Bader’s fire-resistant products, including Crestapol® 1212 high-performance aluminum trihydrate (ATH) filled urethane acrylate resin. Reinforcements included 450 gsm chopped strand mat and 450 gsm woven rovings. Vernon notes that Scott Bader adjusted its resin formula “to make it easier to hand-lay with the fibers, despite the high-loading of ATH.”
Disney added another wrinkle to meeting fire requirements when it insisted that all fire-resistant gel coats match the paint system so that in the event of any damage to the paint surface the part would maintain its color. To meet this demand, Scott Bader provided E-Grow with eight custom colors of its Crystic® 967 FR fire-retardant, pre-accelerated, ISO-NPG polyester gel coat.