MULTILAYERED CARBONATE SHEETS
An extruded polycarbonate multi-walled sheet structure includes at least two and in some cases seven or more generally parallel spaced apart walls and a plurality of ribs extending the length of the sheet in a direction of extrusion and separating adjacent walls. The sheet structure has a total thickness greater than 40 mm and the polycarbonate has a melt viscosity ratio greater than about 4.5 measured at 260° C. wherein the melt viscosity ratio is a ratio of the viscosity at a shear rate of 100 s −1 to the viscosity at a shear rate of 0.1 s −1 .
1 . An extruded polycarbonate multi-walled sheet structure comprising:
a. at least two generally parallel spaced apart walls; and
b. a plurality of ribs extending the length of the sheet in a direction of extrusion and separating adjacent walls;
wherein the sheet has a total thickness greater than 40 mm and the polycarbonate has a melt viscosity ratio greater than about 4.5 measured at 260° C. wherein the melt viscosity ratio is a ratio of the viscosity at a shear rate of 100 s −1 to the viscosity at a shear rate of 0.1 s −1 .
2 . The structure of claim 1 wherein the polycarbonate has a melt viscosity greater than 10,000 Pas at a shear rate of 0.1 s −1 and at 260° C.
3 . The structure of claim 1 wherein the polycarbonate has a weight average molecular weight between 35,000 and 40,000 as measured using gel permeation chromatography.
4 . The structure of claim 1 comprising at least seven walls.
5 . The structure of claim 4 wherein the sheet has a total thickness of 40 mm or greater.
6 . The structure of claim 1 wherein the sheet is extruded at a line speed of at least 0.8 mm/min.
7 . A method of making a multi-walled structure comprising:
a. preparing a polycarbonate having a melt viscosity ratio greater than about 4.5 measured at 260° C. wherein the melt viscosity ratio is a ratio of the viscosity at a shear rate of 100 s −1 to the viscosity at a shear rate of 0.1 s −1 ; and
b. extruding the polycarbonate at a melt temperature of about 260° C. and a line speed greater than about 0.8 mm/min to form a sheet having at least two generally parallel spaced apart walls separated from one another by ribs extending the length of the sheet in the direction of extrusion.
8 . The method of claim 7 wherein the polycarbonate has a viscosity greater than 10,000 Pas at a shear rate of 0.1 s −1 and at 260° C.
9 . The method of claim 7 wherein the polycarbonate has a weight average molecular weight between 35,000 and 40,000 as measured using gel permeation chromatography.
10 . The method of claim 7 wherein the sheet has at least seven walls.
11 . The method of claim 9 wherein the sheet has a total thickness of 40 mm or greater.
12 . The structure of claim 1 comprising at least nine walls.
13 . The structure of claim 1 comprising at least ten walls.
14 . The method of claim 7 wherein the sheet has at least ten walls.