Recycled Polymeric Composite Crossties and Methods of Manufacture

Abstract

A polymeric composite useful for producing large shaped articles such as railroad crossties comprises a filler component having minimal reinforcing/structural characteristics; and a polymer blend including at least one polymeric stiffening component, at least one polymeric density component, and at least one polymeric flexibility component. The polymer blend can include post-consumer recycled thermoplastic polymers. To produce the composite, a multistage extruder brings a blend of polymer and filler materials to an extrudable threshold without completely liquefying the polymer blend. The extruded blend is cooled within a mold to form a shaped article such as a recycled composite crosstie. Exemplary recycled composite mixtures may include composite polymer materials, such as, polypropylene, High Density Polyethylene (HDPE), High Molecular Weight Polyethylene (HMW), Low Density Polyethylene (LDPE), ABS, Ethylene Vinyl Acetate (EVA), Linear Low Density Polyethylene (LLDPE), and combinations of these polymers. The filler may include talc, fly ash, potash, and combinations of these or other mineral powder products.

1 - 35 . (canceled)  
     
     
         36 . A method comprising: 
 mixing filler material and polymer material to form a composite material;    heating the composite material to less than a melting temperature threshold;    extruding the composite material into at least one mold; and    compressing the composite material within said at least one mold.    
     
     
         37 . The method of  claim 36  wherein heating the composition material comprises staged heating within an extruder to a temperature less than a transition threshold of the composition material.  
     
     
         38 . The method of  claim 36  including extruding the composite material into the mold at a compression pressure between about 600 psi and about 3100 psi.  
     
     
         39 . The method of  claim 38  wherein the compression pressure within the mold from extrusion is between about 1700 psi and about 3000 psi.  
     
     
         40 . The method of  claim 36  wherein the mold dimensions comply with American Railroad Engineering and Maintenance of Way Association (AREMA) specifications for composite railroad ties.  
     
     
         41 . The method of  claim 36  including: 
 quenching an exterior portion of the composite material within the mold; and    removing the composite material from the mold prior to complete cooling/solidification.    
     
     
         42 . The method of  claim 36  wherein the polymer material is selected from the group consisting of polypropylene, High Density Polyethylene (HDPE), High Molecular Weight Polyethylene (HMW), Low Density Polyethylene (LDPE), ABS, Ethylene Vinyl Acetate (EVA), Linear Low Density Polyethylene (LLDPE), and combinations thereof.