Thermoplastic polymer extrusion bending

Abstract

Methods for bending preformed thermoplastic extrusions having at least one cavity comprise filling at least one of the extrusion cavities with polymer foam and curing the foam within the filled cavity. An extrusion is heated to allow plastic deformation and then smoothly bent over a mandrill to impart a desired curved shape. Following cooling to below the extrusion's plastic deformation temperature on the mandrill, smoothly curved extrusions are removed for cooling to room temperature. Cured polymer foam within an extrusion cavity resists distortion of the cavity during the bending process.

1 . A method for bending a preformed thermoplastic polymer extrusion comprising at least one cavity to make a curved polymer extrusion, the method comprising: 
 filling at least one said cavity with polymer foam formed within said cavity;    curing said polymer foam within said at least one cavity;    heating said extrusion to a first temperature;    bending said heated extrusion on a curved mandrill;    cooling said extrusion to a second temperature on said mandrill to make a curved polymer extrusion; and    removing said cooled curved polymer extrusion from said mandrill.    
     
     
         2 . The method of  claim 1  wherein said polymer foam is polyisocyanate-based.  
     
     
         3 . The method of  claim 2  wherein said polymer foam is polyurethane foam.  
     
     
         4 . The method of  claim 3  wherein said polyurethane foam is rigid closed-cell foam, semi-rigid closed-cell/open-cell foam and flexible open-cell foam.  
     
     
         5 . The method of  claim 1  wherein said first temperature is the heat deflection temperature of the preformed polymer extrusion.  
     
     
         6 . The method of  claim 1  wherein said second temperature is at least about 10 degrees Celsius less than the heat deflection temperature of the preformed polymer extrusion.  
     
     
         7 . The method of  claim 1  wherein said polymer foam has a density of about 16 kg per cubic meter to about 320 kg per cubic meter.  
     
     
         8 . The method of  claim 1  wherein said extrusion is heated to said first temperature in a glycol bath.  
     
     
         9 . The method of  claim 1  wherein said extrusion is heated to said first temperature by infrared radiation.  
     
     
         10 . The method of  claim 1  wherein said extrusion is heated to said first temperature by heated air.  
     
     
         11 . The method of  claim 1  wherein said preformed extrusion comprises a vinyl polymer.  
     
     
         12 . The method of  claim 1  wherein each said cavity is filled with foam by injection from a mixing head of a plurality of ingredients comprising polyisocyanate, at least one active hydrogen-containing compound, and a blowing agent.  
     
     
         13 . The method of  claim 1  wherein each said cavity is filled with foam by hand pouring into each said cavity a plurality of ingredients comprising polyisocyanate, at least one active hydrogen-containing compound, and a blowing agent.  
     
     
         14 . A method for bending a preformed vinyl extrusion comprising at least one cavity to make a curved vinyl extrusion, the method comprising: 
 filling at least one said cavity with polyurethane foam formed within said cavity;    curing said polyurethane foam within said at least one cavity;    heating said extrusion to about 70 degrees Celsius;    bending said heated extrusion on a curved mandrill;    cooling said extrusion to a temperature less than about 60 degrees Celsius on said mandrill to make a curved polymer extrusion; and    removing said cooled curved polymer extrusion from said mandrill.    
     
     
         15 . The method of  claim 14  wherein said extrusion is heated by immersion in a glycol bath maintained at about 70 degrees Celsius.  
     
     
         16 . The method of  claim 14  wherein said extrusion is heated by infrared radiation.  
     
     
         17 . The method of  claim 16  wherein said cured polyurethane foam has a density of about 320 kg per cubic meter.  
     
     
         18 . A window frame comprising a curved polymer extrusion made by the method of  claim 14 .  
     
     
         19 . A window comprising the window frame of  claim 18 .  
     
     
         20 . The window of  claim 19  wherein said polyurethane foam is rigid closed-cell foam, semi-rigid closed-cell/open-cell foam and flexible open-cell foam.