Stormwater Chambers Thermoformed from Coextruded Sheet Material
A thermoformed storm water chamber has an exterior surface formed of first layer having an increased reflectance additive and an interior surface formed of a second layer. The increased reflectance additive is a pigment (other than a black pigment) or may be a mineral component. Optionally, a supplemental ultraviolet and/or antioxidant protection additive is also provided in the first layer. The thickness of the first layer is less than the thickness of the second layer, optionally in a 20%/80% of total thickness ratio. The two layers may be made from the same or different HDPE or blends thereof.
1 . A chamber comprising:
an arch-shaped plastic body formed from a vacuum-molded polyethylene sheet having an exterior surface and an interior surface;
the exterior surface of the body being a first layer comprising an increased reflectance coating; and
the interior surface of the body being a second layer;
wherein the first layer and the second layer are coextruded and each comprise a high density polyethylene (HDPE).
2 . The chamber of claim 1 , wherein the increased reflectance additive is a pigment other than a black pigment.
3 . The chamber of claim 1 , wherein the increased reflectance additive is a mineral component.
4 . The chamber of claim 1 , wherein the first layer has a supplemental ultraviolet and/or antioxidant protection additive.
5 . (canceled)
6 . The chamber of claim 1 , wherein the first layer has a thickness, and the second layer has a thickness, and the thickness of the first layer is less than the thickness of the second layer.
7 . The chamber of claim 6 , wherein the body has a thickness, and the thickness of the first layer is about 20% of the thickness of the body, and the thickness of the second layer is about 80% of the thickness of the body.
8 .- 9 . (canceled)
10 . The chamber of claim 1 , wherein the first layer and the second layer comprise different high density polyethylene resins.
11 . The chamber of claim 1 , wherein the first layer and the second layer each comprise a blend of high density polyethylene resins.
12 . The chamber of claim 11 , wherein the blend of high density polyethylene resins comprises a first resin having a tensile yield strength of approximately 28 MPa and a flexural modulus of approximately 1,378 MPa and a second resin has a tensile yield strength of approximately 25 MPa and a flexural modulus of approximately 1,200 MPa.
13 . The chamber of claim 1 , wherein the first layer and second layer are coextruded and the chamber is thermoformed in a vacuum mold.
14 . A method of manufacturing a chamber, comprising steps of:
extruding high density polyethylene resin pellets or a blend of different high density polyethylene resin pellets containing an increased reflectance additive from a die to form a continuous web of a first layer;
extruding high density polyethylene resin pellets or a blend of different high density polyethylene resin pellets from a die to form a continuous web of a second layer;
joining the first layer and second layer together to form a web;
cutting the web into sheets;
heating one of the sheets until the sheet is in a pliable plastic state for thermoforming;
thermoforming in a vacuum mold, whereby the first layer is located on an exterior surface of the chamber.
15 . The method of claim 14 , wherein the increased reflectance additive is a pigment other than a black pigment.
16 . The method of claim 14 , wherein the increased reflectance additive is a mineral component.
17 . The method of claim 14 , wherein a supplemental ultraviolet and/or antioxidant protection additive is added to the high density polyethylene resin pellets or a blend of different high density polyethylene resin pellets which form the first layer.
18 . The method of claim 14 , wherein the first layer has a thickness, and the second layer has a thickness, and the thickness of the first layer is less than the thickness of the second layer.
19 . The method of claim 18 , wherein the chamber has a thickness, and the thickness of the first layer is about 20% of the thickness of the chamber, and the thickness of the second layer is about 80% of the thickness of the chamber.
20 . The chamber of claim 14 , wherein the first layer and the second layer comprise a same high density polyethylene resin.
21 . The chamber of claim 14 , wherein the first layer and the second layer comprise different high density polyethylene resins.
22 . The chamber of claim 14 , wherein the first layer comprises a blend of high density polyethylene resins.
23 . The chamber of claim 22 , wherein the blend of high density polyethylene resins comprises a first resin having a tensile yield strength of approximately 28 MPa and a flexural modulus of approximately 1,378 MPa and a second resin has a tensile yield strength of approximately 25 MPa and a flexural modulus of approximately 1,200 MPa.
24 . The method of claim 14 , wherein the first layer is positioned against a molding surface of the vacuum mold and the second layer is positioned away from the molding surface.
25 . The chamber of claim 1 , wherein said second layer comprises a carbon black additive.
26 . A chamber comprising:
an arch-shaped plastic body formed from a vacuum-molded polyethylene sheet having an exterior surface and an interior surface;
the exterior surface of the body being a first layer comprising an increased reflectance coating; and
the interior surface of the body being a second layer;
wherein the first layer and the second layer are coextruded and each comprise a high density polyethylene (HDPE).
27 . The chamber of claim 26 , wherein the first layer comprises a blend of high density polyethylene resins.
28 . (canceled)