Foaming technology in long glass fiber filled materials

Abstract

A foamed part, includes: a long glass fiber filled polymeric material, wherein the long glass fibers have an initial length before molding of the foamed part and a final length after molding of the foamed part; wherein a post-molding length of the long glass fibers in the foamed part is greater than or equal to a post-molding length of long glass fibers in a similarly dimensioned foamed part made without a pressurized plasticizing unit.

What is claimed is: 
     
         1 . A method of making a foamed part, comprising:
 introducing a long glass fiber filled polymeric material to a hopper of an injection molding machine, wherein the long glass fibers have a pre-molding length;   melting the long glass fiber filled polymeric material to form a melt;   pressurizing a plasticizing unit of the injection molding machine with a blowing agent, wherein a seal is located between a rotating part and a fixed part of the plasticizing unit;   having a seal between the rotating and fixed parts of the plasticizing unit;   sealing the plasticizing unit with an airlock mounted between a barrel of the injection molding machine and the hopper;   increasing a pressure of the blowing agent and increasing a back pressure of the injection molding machine to homogenize the melt and the blowing agent; and   forming the foamed part;   wherein a post-molding length of the long glass fibers in the foamed part is greater than or equal to a post-molding length of long glass fibers in a similarly dimensioned foamed part made without the pressurized plasticizing unit.   
     
     
         2 . The method of  claim 1 , wherein the post-molding length of the long glass fibers in the foamed part is greater than or equal to a post-molding length of long glass fibers in a similarly dimensioned non-foamed part. 
     
     
         3 . The method of  claim 1 , wherein the blowing agent is a gaseous blowing agent. 
     
     
         4 . The method of  claim 3 , wherein the blowing agent is at least one from carbon dioxide, sodium bicarbonate, azide compounds, ammonium carbonate, ammonium nitrite, monosodium citrate, light metals which evolve hydrogen upon reaction with water, chlorinated hydrocarbons, chlorofluorocarbons, azodicarbonamide, N,N′dinitrosopentamethylenetetramine, trichloromonofluoromethane, trichlorotrifluoroethane, methylene chloride, organic carboxylic acids (such as formic acid, acetic acid, oxalic acid, ricinoleic acid, and so forth), pentane, butane, ethanol, acetone, oxygen gas, nitrogen gas, ammonia gas, and combinations comprising at least one of the foregoing. 
     
     
         5 . The method of  claim 4 , wherein the blowing agent is at least one from nitrogen gas, oxygen gas, carbon dioxide gas, and a combination comprising at least one of the foregoing. 
     
     
         6 . The method of  claim 1 , wherein a weight of the foamed part is reduced by greater than or equal to 5% as compared to a similarly dimensioned non-foamed part including long glass fibers. 
     
     
         7 . The method of  claim 1 , wherein a foamed injected plaque has 10% less thickness shrinkage as compared to non-foamed injected plaque. 
     
     
         8 . The method of  claim 1 , wherein the blowing agent pressure and the back pressure of the injection molding machine differ by greater than or equal to 0 megaPascals. 
     
     
         9 . The method of  claim 1 , wherein the blowing agent pressure or the back pressure of the injection molding machine is 0 to 10 MegaPascals. 
     
     
         10 . The method of  claim 1 , wherein the difference between back pressure and the blowing agent pressure of the injection molding machine is 0 to 5 MegaPascals. 
     
     
         11 . The method of  claim 1 , wherein the polymeric material is at least one from polycarbonate, polypropylene, polyarylate, polyester, polyphenylene ether, polystyrene, acrylonitrile butadiene styrene, polyether, polyimide, polyetherimide, polysulfone, polyether ketone, polyether ether ketone, poly(methyl methacrylate), polyvinyl chloride, polysiloxane, and combinations comprising at least one of the foregoing. 
     
     
         12 . The method of  claim 1 , wherein an injection pressure of the injection molding machine is greater than or equal to 10% less in making the foamed part as compared to the injection pressure when making a non-foamed part including long glass fibers. 
     
     
         13 . A polymeric part made by the method of  claim 1 . 
     
     
         14 . A foamed part, comprising:
 a long glass fiber filled polymeric material, wherein the long glass fibers have an initial length before molding of the foamed part and a final length after molding of the foamed part;   wherein a post-molding length of the long glass fibers in the foamed part is greater than or equal to a post-molding length of long glass fibers in a similarly dimensioned foamed part made without a pressurized plasticizing unit.   
     
     
         15 . The foamed part of  claim 14 , wherein the polymeric material is at least one from polycarbonate, polypropylene, polyarylate, polyester, polyphenylene ether, polystyrene, acrylonitrile butadiene styrene, polyether, polyimide, polyetherimide, polysulfone, polyether ketone, polyether ether ketone, poly(methyl methacrylate), polyvinyl chloride, polysiloxane, and combinations comprising at least one of the foregoing. 
     
     
         16 . The foamed part of  claim 14 , wherein the final length of the long glass fibers in the foamed part is increased as compared to a similarly dimensioned non-foamed part including long glass fibers. 
     
     
         17 . The foamed part of  claim 14 , wherein a weight of the foamed part is reduced by greater than or equal to 5% as compared to a similarly dimensioned non-foamed part including long glass fibers. 
     
     
         18 . The foamed part of  claim 14 , wherein a foamed injected plaque has 10% less thickness shrinkage as compared to a non-foamed injected plaque. 
     
     
         19 . The foamed part of  claim 14 , wherein the foamed part has a number of long glass fibers that is greater than or equal to a number of long glass fibers in a similarly dimensioned non-foamed part including long glass fibers. 
     
     
         20 . The foamed part of  claim 14 , wherein a thickness of the foamed part is increased greater than or equal 50% a thickness of a non-foamed part including long glass fibers.