Pressure polished extruded polycarbonate sheet
US3937863A · kind A · utility
Inventor
Key dates
| Filing date | Dec 6, 1974 |
| Grant date | Feb 10, 1976 |
| Priority date | — |
| Expiry date | Dec 6, 1994 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10T428/315
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
Pressure polished transparent unfilled polycarbonate sheet substantially free of ripples, wiggles, extrusion die lines, and stresses and having a light transmittance greater than, a percentage haze lower than and a distortion lower than the as extruded sheet so that the polished sheet can be mechanically or thermoformed into such articles as airplane windshields, canopies, protective headgears and see-through enclosures. The sheet is made by polishing it between mirror finish plates using a sequence of preheating the as extruded sheet to the heat distortion temperature at zero or minimal pressure, heating to higher temperatures while rapidly increasing the pressure so as to transfer the mirror finish from the plates to the sheet surfaces, and cooling the sheet while decreasing the pressure to fix the mirror finish in the sheet surfaces as the sheet contracts and solidifies.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.