Modified fibers for use in the formation of thermoplastic fiber-reinforced composite articles and process

Abstract

A surface-modified fibrous material is provided for incorporation in a thermoplastic matrix to form a fiber-reinforced composite article. Good binding between the fibrous material and the thermoplastic matrix is achieved through the presence of finely roughened surfaces on the fibers of nanoparticles of an inorganic material. Such nanoparticles are provided from an alkaline aqueous size composition containing the nanoparticles dispersed therein (as described). The fibrous material may be provided in continuous or discontinuous form. In a preferred embodiment glass fibers are initially provided in continuous form followed by cutting into discontinuous lengths and drying with the retention of the nanoparticles on the surfaces of the fibers. The surface-roughened fibrous material is incorporated in a thermoplastic matrix as fibrous reinforcement with the application of heat whereby the thermoplastic matrix is rendered melt processable. In preferred embodiments injection or compression molding is utilized. Improved long-fiber thermoplastics also may be formed to advantage.

1 . A process for forming modified fibers having roughened surfaces suitable for incorporation in a thermoplastic matrix to form a fiber-reinforced composite article comprising:
 (a) applying as a coating to the surface of the fibrous material an alkaline aqueous size composition comprising a dispersion of nanoparticles of an inorganic material, and   (b) drying said coating present on said fibrous material to provide a roughened surface on said fibrous material as the result of the presence of said nanoparticles of said inorganic material.   
   
   
       2 . The process of  claim 1 , wherein said fibrous material comprises glass fibers. 
   
   
       3 . The process of  claim 1 , wherein said fibrous material comprises mineral fibers. 
   
   
       4 . The process of  claim 1 , wherein said fibrous material is in the form of a multifilamentary roving. 
   
   
       5 . The process of  claim 1 , wherein said alkaline aqueous dispersion of nanoparticles of an inorganic material possesses a pH of approximately 7.5 to 13. 
   
   
       6 . The process of  claim 1 , wherein said nanoparticles of an inorganic material possess an average particle size of approximately 3 to 40 nm. 
   
   
       7 . The process of  claim 1 , wherein said nanoparticles of an inorganic material possess an average particle size of approximately 3 to 10 nm. 
   
   
       8 . The process of  claim 1 , wherein said nanoparticles of an inorganic material are silica. 
   
   
       9 . A surface-modified fibrous material suitable for incorporation in a thermoplastic matrix to form a fiber-reinforced composite article having surface roughening created by the presence of adhering nanoparticles of an inorganic material formed by the process of  claim 1 . 
   
   
       10 . A process for forming discontinuous modified glass fibers suitable for incorporation in a thermoplastic matrix and the formation of a fiber-reinforced composite article by injection or compression molding which displays an enhanced mechanical property comprising:
 (a) adhering nanoparticles of an inorganic material that are dispersed in an alkaline aqueous size composition to the surfaces of glass fibers which are present in continuous form to provide finely roughened surfaces on said continuous glass fibers as the result of the presence of said nanoparticles of said inorganic material, and   (b) cutting said continuous glass fibers into discontinuous lengths while retaining said roughened surfaces on said glass fibers as the result of the presence of said nanoparticles of said inorganic material.   
   
   
       11 . The process for forming discontinuous glass fibers suitable for incorporation in a thermoplastic matrix according to  claim 10 , wherein said continuous glass fibers of step (a) are selected from the group consisting of E-glass, C-glass, A-glass, AR-glass, D-glass, R-glass, S-glass, and mixtures of the foregoing, and possess a diameter of approximately 2 to 50 microns. 
   
   
       12 . The process for forming discontinuous glass fibers suitable for incorporation in a thermoplastic matrix according to  claim 10 , wherein said continuous glass fibers of step (a) are E-glass, and possess a diameter of approximately 7 to 30 microns. 
   
   
       13 . The process for forming discontinuous glass fibers suitable for incorporation in a thermoplastic matrix according to  claim 10 , wherein said alkaline aqueous dispersion possesses a pH of approximately 8 to 11. 
   
   
       14 . The process for forming discontinuous glass fibers suitable for incorporation in a thermoplastic matrix according to  claim 10 , wherein said nanoparticles of an inorganic material possess an average particle size of approximately 3 to 40 nm. 
   
   
       15 . The process for forming discontinuous glass fibers suitable for incorporation in a thermoplastic matrix according to  claim 10 , wherein said nanoparticles of an inorganic material possess an average particle size of approximately 3 to 10 nm. 
   
   
       16 . The process for forming discontinuous glass fibers suitable for incorporation in a thermoplastic matrix according to  claim 10 , wherein said nanoparticles of an inorganic material are selected from the group consisting of silica, clay, glass, metals, titanium dioxide, zinc oxide, barium oxide, cerium gadolinium oxide, iron ferrite, aluminum polyphosphate, nanodiamonds, and mixtures of the foregoing. 
   
   
       17 . The process for forming discontinuous glass fibers according to  claim 10 , wherein said nanoparticles of an inorganic material are silica. 
   
   
       18 . The process for forming discontinuous glass fibers according to  claim 10 , wherein said alkaline size composition of step (a) additionally includes silane, surfactant, and polymeric film-former. 
   
   
       19 . The process for forming discontinuous glass fibers according to  claim 10 , wherein in step (a) the nanoparticles of said inorganic material are caused to adhere to said continuous glass fibers by initially coating said alkaline aqueous size composition on the surfaces of said glass fibers followed by removal of volatile components. 
   
   
       20 . The process for forming discontinuous glass fibers according to  claim 10 , wherein in step (b) said continuous glass fibers are cut into discontinuous lengths of approximately 2 to 100 mm. 
   
   
       21 . The process for forming discontinuous glass fibers according to  claim 10 , wherein in step (b) said continuous glass fibers are cut into discontinuous lengths of approximately 3 to 50 mm. 
   
   
       22 . Surface-modified discontinuous glass fibers suitable for incorporation in a thermoplastic matrix and the formation of a fiber-reinforced composite article by injection or compression molding which displays an enhanced mechanical property as the result of surface roughening created by the presence of adhering nanoparticles of an inorganic material formed by the process of  claim 10 . 
   
   
       23 . A process for forming a fiber-reinforced thermoplastic composite article comprising:
 (a) applying as a coating to the surface of a fibrous material an alkaline aqueous size composition comprising a dispersion of nanoparticles of an inorganic material,   (b) drying said coating present on said fibrous material to provide a roughened surface on said fibrous material as the result of the presence of said nanoparticles of said inorganic material, and   (c) incorporating said fibrous material bearing said roughened surface in a thermoplastic matrix as fibrous reinforcement with the application of heat whereby said thermoplastic matrix is rendered melt processable.   
   
   
       24 . The process according to  claim 23 , wherein said fibrous material is provided in discontinuous lengths and injection or compression molding is utilized in step (c). 
   
   
       25 . The process according to  claim 23 , wherein step (c) forms a long-fiber-reinforced thermoplastic composite article. 
   
   
       26 . A process for forming a discontinuous glass fiber-reinforced thermoplastic composite article comprising:
 (a) adhering nanoparticles of an inorganic material that are dispersed in an alkaline aqueous size composition to the surfaces of glass fibers which are present in continuous form to provide finely roughened surfaces on said continuous glass fibers as the result of the presence of said nanoparticles of said inorganic material,   (b) cutting said continuous glass fibers into discontinuous lengths while retaining said roughened surfaces on said glass fibers as the result of the presence of said nanoparticles of said inorganic material,   (c) extruding the discontinuous glass fibers having said finely roughened surfaces together with a thermoplastic wherein the surface-attached nanoparticles of inorganic material serve to promote the secure bonding of the discontinuous glass fibers within said thermoplastic matrix to form a material suitable for molding, and   (d) injection or compression molding said material incorporating said discontinuous glass fibers having said finely roughened surfaces to form a fiber-reinforced composite article which displays an enhanced mechanical property.   
   
   
       27 . The process for forming a discontinuous glass fiber-reinforced thermoplastic composite article according to  claim 26 , wherein said continuous glass fibers of step (a) are selected from the group consisting of E-glass, C-glass, A-glass, AR-glass, D-glass, R-glass, S-glass, and mixture of the foregoing, and possess a diameter of approximately 2 to 50 microns. 
   
   
       28 . The process for forming a discontinuous glass fiber-reinforced thermoplastic composite article according to  claim 26 , wherein said continuous glass fibers of step (a) are E-glass, and possess a diameter of approximately 7 to 30 microns. 
   
   
       29 . The process for forming a discontinuous glass fiber-reinforced thermoplastic composite article according to  claim 26 , wherein said alkaline aqueous dispersion possesses a pH of approximately 8 to 11. 
   
   
       30 . The process for forming a discontinuous glass fiber-reinforced thermoplastic composite article according to  claim 26 , wherein said nanoparticles of an inorganic material possess an average particle size of approximately 3 to 40 nm. 
   
   
       31 . The process for forming a discontinuous glass fiber-reinforced thermoplastic composite article according to  claim 26 , wherein said nanoparticles of an inorganic material possess an average particle size of approximately 3 to 10 nm. 
   
   
       32 . The process for forming a discontinuous glass fiber-reinforced thermoplastic composite article according to  claim 26 , wherein said nanoparticles of an inorganic material are selected from the group consisting of silica, clay, glass, metals, titanium dioxide, zinc oxide, barium oxide, cerium gadolinium oxide, iron ferrite, aluminum polyphosphate, nanodiamonds, and mixtures of the foregoing. 
   
   
       33 . The process for forming a discontinuous glass fiber-reinforced thermoplastic composite article according to  claim 26 , wherein said nanoparticles of an inorganic material are silica. 
   
   
       34 . The process for forming a discontinuous glass fiber-reinforced thermoplastic composite article according to  claim 26 , wherein said alkaline size composition of step (a) additionally includes silane, surfactant, and polymeric film-former. 
   
   
       35 . The process for forming a discontinuous glass fiber-reinforced thermoplastic composite article according to  claim 26 , wherein in step (a) the nanoparticles of said inorganic material are caused to adhere to said continuous glass fibers by initially coating said alkaline aqueous size composition on the surfaces of said glass fibers followed by removal of volatile materials. 
   
   
       36 . The process for forming a discontinuous glass fiber-reinforced thermoplastic composite article according to  claim 26 , wherein in step (b) said continuous glass fibers are cut into discontinuous lengths of approximately 2 to 100 mm. 
   
   
       37 . The process for forming a discontinuous glass fiber-reinforced thermoplastic composite article according to  claim 26 , wherein in step (b) said continuous glass fibers are cut into discontinuous lengths of approximately 3 to 50 mm. 
   
   
       38 . The process for forming a discontinuous glass fiber-reinforced thermoplastic composite article according to  claim 26 , wherein said thermoplastic of step (c) is selected from the group consisting of polyolefins, polyesters, polyamides, polycarbonates, polyethers, liquid crystal polymers, polyethersulfones, polyphenylene oxide, polyphenylene sulfide, polybenzimidazoles, thermoplastic polyurethanes, and blends of the foregoing. 
   
   
       39 . The process for forming a discontinuous glass fiber-reinforced thermoplastic composite article according to  claim 26 , wherein said thermoplastic is polypropylene. 
   
   
       40 . A discontinuous glass fiber-reinforced thermoplastic composite article formed by the process of  claim 26 , which displays an enhanced mechanical property following injection or compression molding containing discontinuous glass fiber reinforcement having finely roughened surfaces as the result of the presence of adhering nanoparticles of an inorganic material.