Foam gasket and bonding tape based on polyurethane dispersions

Abstract

A polymer sheet includes a polyurethane core. The polyurethane core has a first major surface and a second major surface opposite the first major surface. The polymer sheet can have at least one functional layer overlying a major surface. The polymer sheet has a thickness t PS . The polyurethane core has a thickness t PC . In embodiments t PC can be at least 0.3 t PS . The polyurethane core can have at least one of the following property: (i) a Scratch Resistance Rating, as further described herein, of not greater than about 10 wt %, (ii) an elongation at break of at least 200%, (iii) a tensile strength at break of at least 0.3 MPa, (iv) a loss of tensile strength of not greater than about 30% when exposed to UV light according to standard SAE J1960 (Rev. August 2003). The polymer sheet can be used for gaskets or bonding tapes.

1 . A polymer sheet comprising:
 a polyurethane core, having a first major surface and a second major surface opposite the first major surface; and   at least one functional layer, wherein the polymer sheet has a thickness tPS and the polyurethane core has a thickness tPC, wherein tPC is at least 0.3 tPS,   
       wherein the polyurethane core comprises polyurethane polymer, wherein the polyurethane core has at least one of the following property:
 (i) an elongation at break of at least 200%, 
 (ii) a tensile strength at break of at least 0.3 MPa. 
 
     
     
         2 . The polymer sheet according to  claim 1 , wherein the polymer sheet has a primary aspect ratio of at least about 400. 
     
     
         3 . The polymer sheet according to  claim 1 , wherein the functional layer is selected from the group of a permanent liner, a release liner, a topcoat, an adhesive, or any combination thereof. 
     
     
         4 . The polymer sheet according to  claim 3 , wherein the permanent liner includes a thermoplastic selected from polyethylene, polyester, polyimide, or any combination thereof. 
     
     
         5 . The polymer sheet according to  claim 4 , wherein the polyethylene includes ultra-high molecular weight polyethylene. 
     
     
         6 . The polymer sheet according to  claim 3 , wherein the permanent liner, the release liner, or the adhesive layer has a thickness of in a range of about 0.01 mm to about 0.1 mm. 
     
     
         7 . The polymer sheet according to  claim 3 , wherein the release liner includes a polyester, polyethylene, polypropylene, paper, or any combination thereof. 
     
     
         8 . The polymer sheet according to  claim 3 , wherein the topcoat as thickness in a range of from 0.001 mm to about 0.01 mm. 
     
     
         9 . The polymer sheet according to  claim 3 , wherein the adhesive is a pressure sensitive adhesive selected from an acrylic adhesive, a silicon adhesive, a rubber hot melt adhesive, an acrylic copolymer, a rubber acrylic copolymer, or any combination thereof. 
     
     
         10 . The polymer sheet according to  claim 1 , wherein the polymer sheet is in form of a roll. 
     
     
         11 . The polymer sheet according to  claim 1 , wherein the polyurethane core has a thickness in a range of about 0.2 mm to about 3.0 mm. 
     
     
         12 . The polymer sheet according to  claim 1 , wherein the loss of tensile strength when exposed to UV light according to standard SAE J1960 (Rev. August 2003) is not greater than about 25%. 
     
     
         13 . The polymer sheet according to  claim 1 , wherein the polyurethane core has at least one of the following performance data:
 (i) a compression force deflection at 25% compression of at least 3 kPa;   (ii) a force to compress at 25% compression of at least 6 kPa and;   (iii) a recovery time of not greater than 5 seconds according to ASTM D3574   (iv) a compression set of not greater than 10% after compression of 50% at room temperature for 22 hours according to ASTM D3574.   
     
     
         14 . The polymer sheet according to  claim 1 , wherein the polyurethane core has a discoloration ΔE of not greater than 4.0. 
     
     
         15 . The polymer sheet according to  claim 1 , wherein the polyurethane core has a yellowing Δb of not greater than 2. 
     
     
         16 . The polymer sheet according to  claim 1 , wherein the polyurethane core is essentially free of pigment. 
     
     
         17 . The polymer sheet according to  claim 1 , wherein the polyurethane core has an elongation at break of at least 200%. 
     
     
         18 . The polymer sheet according to  claim 1 , wherein the polyurethane core has a tensile strength at break of at least 0.3 MPa. 
     
     
         19 . An assembly comprising:
 a first member and a second member; and   a gasket compressed between the first member and the second member, wherein the gasket includes a polyurethane core, having a first major surface and a second major surface opposite the first major surface; and   the gasket is compressed between the first and the second member at a compression of at least about 10%,   
       wherein the polyurethane core comprises polyurethane polymer, wherein the polyurethane core has at least one of the following property:
 (i) an elongation at break of at least 200%, 
 (ii) a tensile strength at break of at least 0.3 MPa. 
 
     
     
         20 . The assembly according to  claim 19 , wherein the assembly is an electronic device and the first member and the second member are components of the electronic device.