Multiwall polymer sheet, and methods for making and articles using the same
View Patent ↗In one embodiment, a multiwall sheet comprises: non-intersecting polymer walls comprising outer layers and transverse layers. The transverse layers intersect the walls to form cells. The multiwall sheet has a non-uniform cell density. In another embodiment, a multiwall sheet can comprise: non-intersecting polymer walls comprising outer layers and a transverse layer and/or a divider. The transverse layer and/or the divider extends from one of the polymer walls to another of the polymer walls to form cells. The multiwall sheet has a non-uniform cell density. In yet another embodiment, a multiwall sheet comprises: non-intersecting polymer walls comprising outer layers and transverse layers. The transverse layers intersect the walls to form cells. The multiwall sheet has a different number of inner layers, transverse layers, and/or dividers, in different portions of the sheet. The multiwall sheets can be used, for example, in a naturally light structure.
1. A multiwall sheet, comprising:
non-intersecting polymer walls comprising outer layers; and
transverse layers, wherein the transverse layers extend perpendicular and intersect the polymer walls, wherein only the transverse layers and polymer walls define cells;
wherein the multiwall sheet has a non-uniform cell density; and
a U-value of less than or equal to about 1.2 W/m 2 K at a nominal volume density of less than or equal to about 180.
2. The multiwall sheet of claim 1 , wherein the U-value is less than or equal to about 1.0 W/m 2 K.
3. The multiwall sheet of claim 1 , wherein the cell density in a middle of the sheet is about 10% to about 60% of a cell density adjacent the outer layers.
4. The multiwall sheet of claim 3 , wherein the cell density in a middle of the sheet is about 15% to about 50% of the cell density adjacent the outer layers.
5. The multiwall sheet of claim 4 , wherein the cell density in a middle of the sheet is about 20% to about 40% of the cell density adjacent the outer layers.
6. The multiwall sheet of claim 1 , further comprising a cell size gradient such that the cell size increases toward a center of the multiwall sheet.
7. The multiwall sheet of claim 6 , wherein the cells have a decreasing size from the middle to toward the ends of the sheet.
8. The multiwall sheet of claim 6 , wherein the cells have a decreasing size from the middle to toward the outer layers.
9. The multiwall sheet of claim 1 , wherein the transverse layers have a thickness of about 0.1 mm to about 1 mm.
10. The multiwall sheet of claim 1 , wherein the polymer walls comprise micro-features and/or nano-features.
11. The multiwall sheet of claim 1 , wherein the transverse layers comprise micro-features and/or nano-features.
12. The multiwall sheet of claim 1 , wherein the cells have a length and/or width of less than or equal to about 2 mm.
13. A multiwall sheet, comprising:
non-intersecting polymer walls comprising outer layers; and
transverse layers, wherein the transverse layers extend perpendicular and intersect the polymer walls, wherein only the transverse layers and polymer walls define to form cells; and
wherein the multiwall sheet has a non-uniform cell density and comprises a stiffness of greater than or equal to about 4,000 N/mm.
14. The multiwall sheet of claim 13 , wherein the stiffness is greater than or equal to about 5,000 N/mm.