Japan's Shiga Prefectural Shigaraki Ceramic Research Institute has developed an ultralight plastic-ceramic hybrid that is lighter than wood, rivaling plastics for many weight-sensitive applications. The new material, which can float on water, is produced by mixing tiny gas-filled plastic microballoons with clay. When the mixture is fired in a kiln, the gas in the microballoons ignites and the combustion process leaves tiny pores in the ceramic.
Conventional ceramic materials weigh 2.3 times as much as an equal volume of water. By adjusting the ratio of the tiny plastic spheres to clay, specific gravity of the resulting material can be lowered to as little as 0.5, half the density of water.
The Shigaraki-based research institute has applied for patents on the process, according to chief engineer Kazushi Kawasami. The microballoons are produced in Sweden by Expancel, a unit of the Nobel Group in Sweden, and are supplied by Nihon Fillite KK in Osaka, Japan.
The plastic material used is a copolymer of vinyl chloride and acrylonitrile and the gas is isobutane.
Each microballoon is 50 microns in diameter, so the tiny pores detract little from the strength of the material.
Many of the applications foreseen by the developers of the material are products that had been the exclusive domain of ceramics but now are made predominately of plastics.
Roofing tiles are an attractive application, because most Japanese homes are roofed with traditional ceramic tiles that are extremely heavy and add to earthquake damage. In the southwestern United States, where most Spanish-style roofing materials are no longer made of ceramics, the new material could reverse the trend. The same is true of flowerpots and building materials.
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