Selective laser sintering of asymmetric particles

Abstract

A polymeric article of high ductility is produced by rapid prototyping or selective laser sintering. The article includes a plurality of layers of a fused thermoplastic powder, the thermoplastic powder including asymmetric fibrous particles having a mean length L and a mean width W, wherein L>2W. Within each of the layers, the mean length L of the asymmetric fibrous particles is preferentially oriented in a plane parallel to the layer. The polymeric article may have a microtextured surface, and a stress-strain curve such that ultimate strength is reached at a strain of 10% to 20%, and breaking stress is reached at >30% strain. The article includes a network of bonded fibers formed by the asymmetric fibrous particles, where the network of bonded fibers may create porosity in the polymeric article

What is claimed is: 
     
         1 . A polymeric article produced by rapid prototyping, the article comprising a plurality of layers of a fused thermoplastic powder, the thermoplastic powder comprising a majority of asymmetric fibrous particles characterized by a mean length L and a mean width W, wherein L>2W;
 wherein the polymeric article has a microtextured surface;   wherein each layer in the plurality of layers is characterized in that the asymmetric fibrous particles are preferentially oriented in a plane parallel to said each layer.   
     
     
         2 . The polymeric article of  claim 1 , where the polymeric article is a medical implant. 
     
     
         3 . The polymeric article of  claim 2 , where the medical implant is a spinal fusion cage. 
     
     
         4 . The polymeric article of  claim 2 , where the medical implant is a replacement for a bone or a tooth. 
     
     
         5 . The polymeric article of  claim 4 , where the medical implant is a replacement for a bone selected from the group consisting of a craniomaxillofacial bone, a mandible bone; a long bone in an arm or a leg; a replacement rib, and a replacement sternum. 
     
     
         6 . The polymeric article of  claim 1 , wherein the thermoplastic powder is a thermoplastic polyester, a thermoplastic polyolefin, a polyamide, a polycarbonate, an acrylic polymer, or a styrenic block copolymer. 
     
     
         7 . The polymeric article of  claim 6 , wherein the thermoplastic polyester is a polylactone, polyglycolic acid, or a polylactic acid. 
     
     
         8 . The polymeric article of  claim 6 , wherein the thermoplastic polyolefin is a polymer or copolymer of ethylene, propylene, n-butylene, or isobutylene. 
     
     
         9 . The polymeric article of  claim 6 , wherein the polyamide is polyamide 11, polyamide 12, polyamide 6, polyamide 4,6, polyamide 6,6, a copolymer thereof, or a mixture thereof. 
     
     
         10 . The polymeric article of  claim 1 , wherein the polymeric article has a stress-strain curve such that ultimate strength is reached at a strain of 10% to 20%, and breaking stress is reached at >20% strain. 
     
     
         11 . A method of creating a polymeric article with a microtextured surface by selective laser sintering, comprising:
 a. depositing a first layer of thermoplastic powder comprising asymmetric fibrous particles on a bed of a 3D printer, the asymmetric fibrous particles being preferentially oriented in a first plane parallel to the bed, wherein the asymmetric fibrous particles have a mean length L and a mean width W, wherein L>2W;   b. fusing the thermoplastic powder with a laser in selected portions of the layer to produce an initial cross section of the polymeric article;   c. depositing a further layer of the thermoplastic powder comprising the asymmetric fibrous particles on the first layer, the asymmetric fibrous particles in the further layer being preferentially oriented in a further plane parallel to the bed;   d. fusing the asymmetric fibrous powder with a laser in selected portions of the further layer to produce a further cross section of the polymeric article, bonded with the initial cross section; and   e. repeating step (c) and step (d) until the polymeric article is complete.   
     
     
         12 . The method of  claim 11 , where the polymeric article is a medical implant. 
     
     
         13 . The method of  claim 12 , where the medical implant is:
 a spinal fusion cage;   a replacement for a tooth; or   a replacement for a bone selected from the group consisting of a craniomaxillofacial bone, a mandible bone; a long bone in an arm or a leg; a replacement rib, and a replacement sternum.   
     
     
         14 . The method of  claim 10 , wherein the thermoplastic powder is a thermoplastic polyester, a thermoplastic polyolefin, a thermoplastic polyurethane, a polycarbonate-based urethane, a cyanate ester resin, a polyamide, a polycarbonate, an acrylic polymer, or a styrenic block copolymer. 
     
     
         15 . A polymeric article of high ductility produced by the method of  claim 10 , wherein the polymeric article has a stress-strain curve such that ultimate strength is reached at a strain of 10% to 20%, and breaking stress is reached at >20% strain. 
     
     
         16 . A porous polymeric article produced by rapid prototyping, the article comprising a plurality of layers of a fused thermoplastic powder, the thermoplastic powder comprising a majority of asymmetric fibrous particles characterized by a mean length L and a mean width W, wherein L>2W;
 wherein:
 each layer in the plurality of layers is characterized in that the asymmetric fibrous particles are preferentially oriented in a plane parallel to said each layer; 
 the asymmetric fibrous particles create a network of bonded fibers; and 
 the network of bonded fibers creates porosity in the porous polymeric article. 
   
     
     
         17 . The porous polymeric article of  claim 16 , wherein the porous polymeric article has a surface; and at least some of the asymmetric fibrous particles extend beyond the surface of the porous polymeric article, causing the surface of the porous polymeric article to be microtextured. 
     
     
         18 . The porous polymeric article of  claim 16 , wherein the porous polymeric article is a medical implant. 
     
     
         19 . The porous polymeric article of  claim 18 , wherein the porosity created by the network of bonded fibers is configured to promote tissue ingrowth. 
     
     
         20 . The porous polymeric article of  claim 17 , wherein the porous polymeric article is a medical implant; and the microtextured surface is configured to promote tissue ingrowth.