Methods for altering the impact strength of noncellular thermoplastic materials

Abstract

Methods for reducing the density of thermoplastic materials and the articles made therefrom having similar or improved mechanical properties to the solid or noncellular material. Also disclosed are improvements to foaming methods and the cellular structures of the foams made therefrom, and methods for altering the impact strength of solid or noncellular thermoplastic materials and the shaping of the materials into useful articles.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
         1 . A method for altering the impact strength of a solid thermoplastic material, comprising:
 obtaining a solid thermoplastic material having an initial impact strength;   treating the material under pressure to cause the material to absorb a gas; and   treating the material at a lower pressure to allow desorption of gas from the material to produce a solid material having an impact strength altered from the initial impact strength of the solid thermoplastic material.   
     
     
         2 . The method of  claim 1 , wherein the thermoplastic material is an amorphous or semi-crystalline polymer. 
     
     
         3 . The method of  claim 1 , further comprising treating the thermoplastic material at a pressure of 1 MPa to 5 MPa. 
     
     
         4 . The method of  claim 1 , further comprising treating the thermoplastic material at a lower pressure in ambient atmospheric pressure. 
     
     
         5 . The method of  claim 1 , wherein the thermoplastic material is polyetherimide. 
     
     
         6 . The method of  claim 1 , further comprising shaping the thermoplastic material during treating the material at a lower pressure. 
     
     
         7 . The method of  claim 6 , wherein the thermoplastic material comprises absorbed gas during shaping. 
     
     
         8 . The method of  claim 1 , further comprising shaping the thermoplastic material after treating the material at a lower pressure. 
     
     
         9 . The method of  claim 8 , wherein the thermoplastic material is desorbed of gas during shaping. 
     
     
         10 . The method of  claim 1 , further comprising placing more than one thermoplastic material in a pressure vessel and interleaving a porous material between thermoplastic materials. 
     
     
         11 . The method of  claim 1 , further comprising assembling the solid thermoplastic material with altered impact strength into an article. 
     
     
         12 . The method of  claim 1 , wherein the thermoplastic material is a thermoplastic urethane, thermoplastic elastomer, polyethylene naphthalate, polyetherimide, polyetheretherketone, polyphenylene, sulfone, polyamide-imide, polysulfone, polyphenylsulfone, polyethersulfone, polyphthalamide, polyarylamide, polyphenylene sulfide, cyclic olefin copolymer, polyphthalate carbonate, polycarbonate, polyvinylidene chloride, polyurethane, polyphenylene oxide, poly (acrylonitrile-butadiene-styrene), polymethylmethacrylate, crosslinked polyethylene, polystyrene, styrene acrylonitrile, polyvinyl chloride, polybutylene terephthalate, polyethylene terephthalate, polyoxymethylene, polyacetal, polyamide, polyolefin, polyethylene, polypropylene. 
     
     
         13 . The method of  claim 1 , wherein the impact strength is greater than the initial impact strength. 
     
     
         14 . The method of  claim 1 , wherein the impact strength is less than the initial impact strength. 
     
     
         15 . A method for altering the impact strength of a solid thermoplastic material without substantially changing the density of the solid thermoplastic material, comprising:
 obtaining a solid thermoplastic material having an initial impact strength and initial density;   treating the material under pressure to cause the material to absorb a gas; and   treating the material at a lower pressure to allow desorption of gas from the material to produce a solid material having an impact strength altered from the initial impact strength and a density substantially the same as the initial density of the solid thermoplastic material.   
     
     
         16 . The method of  claim 15 , wherein the thermoplastic material is an amorphous or semi-crystalline polymer. 
     
     
         17 . The method of  claim 15 , further comprising treating the thermoplastic material at a pressure of 1 MPa to 5 MPa. 
     
     
         18 . The method of  claim 15 , further comprising treating the thermoplastic material at a lower pressure in ambient atmospheric pressure. 
     
     
         19 . The method of  claim 15 , wherein the thermoplastic material is polyetherimide. 
     
     
         20 . The method of  claim 15 , further comprising shaping the thermoplastic material during treating the material at a lower pressure. 
     
     
         21 . The method of  claim 20 , wherein the thermoplastic material comprises absorbed gas during shaping. 
     
     
         22 . The method of  claim 15 , further comprising shaping the thermoplastic material after treating the material at a lower pressure. 
     
     
         23 . The method of  claim 22 , wherein the thermoplastic material is desorbed of gas during shaping. 
     
     
         24 . The method of  claim 15 , further comprising placing more than one thermoplastic material in a pressure vessel and interleaving a porous material between thermoplastic materials. 
     
     
         25 . The method of  claim 15 , further comprising assembling the solid thermoplastic material with higher impact strength into an article. 
     
     
         26 . The method of  claim 15 , wherein the thermoplastic material is a thermoplastic urethane, thermoplastic elastomer, polyethylene naphthalate, polyetherimide, polyetheretherketone, polyphenylene, sulfone, polyamide-imide, polysulfone, polyphenylsulfone, polyethersulfone, polyphthalamide, polyarylamide, polyphenylene sulfide, cyclic olefin copolymer, polyphthalate carbonate, polycarbonate, polyvinylidene chloride, polyurethane, polyphenylene oxide, poly (acrylonitrile-butadiene-styrene), polymethylmethacrylate, crosslinked polyethylene, polystyrene, styrene acrylonitrile, polyvinyl chloride, polybutylene terephthalate, polyethylene terephthalate, polyoxymethylene, polyacetal, polyamide, polyolefin, polyethylene, polypropylene. 
     
     
         27 . The method of  claim 15 , wherein the impact strength is greater than the initial impact strength. 
     
     
         28 . The method of  claim 15 , wherein the impact strength is less than the initial impact strength.