| 摘要 |
<p>Rigid panels are made by pressing a layer of mineral fibers into a loaded stratum of hardenable resin, pressing another loaded stratum of hardenable resin into the mineral fiber stratum of the first pressing, the constitution or quantity of the third stratum differing from that of the first to provide equal mechanical properties at both faces of the sheet. The stratified sheet is then hardened and has density of load (particulate filler) increasing from the center toward the surfaces of the sheet. The sheet is preferably produced between outer pellicles of organic plastic, e.g. cellulosic, which can be removed before use. Such sheets serve as roofing and wall paneling and may be corrugated or otherwise shaped during manufacture.</p> |
