Method for forming a cast elastomer

Abstract

One variation of a method for directly casting a thin layer onto a substrate includes: combining a prepolymer, a solvent, and a curing agent to define a viscous material; advancing a substrate from a roll across a surface continuously at a first speed; depositing the viscous material at a viscosity through a deposition head onto the substrate, the viscous material flowing laterally across the substrate to form a thin layer of substantially uniform thickness over the substrate over a period of time while the substrate advances along the surface; and, at a distance from the deposition head depositing the viscous material onto the substrate corresponding to a duration of time for the viscous material to flow laterally across the substrate, heating the viscous material to evaporate solvent and to induce reaction between the curing agent and the prepolymer to cure the viscous material to form a layer.

I claim: 
     
         1 . A tactile layer comprising:
 a substrate;   a first layer exhibiting a first relaxation time for recovery from deformation, the first layer cast onto the substrate by:
 combining a first prepolymer, a first solvent, and a first curing agent to define a first viscous material; 
 depositing the first viscous material onto the substrate, the first viscous material flowing across the substrate to form the first layer of substantially uniform thickness; and 
 heating the first layer to drive off the solvent and induce reaction between the first curing agent and the prepolymer to form the first layer defined by physically and chemically cross-linked polymer chains; 
   a second layer cast over the first layer opposite the substrate and defining a touch surface, the second layer exhibiting a second relaxation time for recovery from deformation.   
     
     
         2 . The tactile layer of  claim 1 , wherein the second layer is cast onto the first layer by:
 combining a second prepolymer, a second solvent, and a second curing agent to define a second viscous material;   depositing the second viscous material onto the first layer, the second viscous material flowing across the first layer to form the second layer of uniform thickness; and   heating the second layer to drive off the solvent and induce reaction between the second curing agent and the second prepolymer to cure the second layer defined by physically and chemically cross-linked polymer chains.   
     
     
         3 . The tactile layer of  claim 1 , wherein the first layer is cast onto the substrate by:
 combining the first prepolymer and the first solvent, the first prepolymer to define a first solution comprising a TDI-terminated polyester prepolymer, the first solvent comprising methyl ethyl ketone;   combining a catalyst, a chain extender, and a cross-linking agent to define the first curing agent, the catalyst comprising dibutyltin dilaurate, the chain extender comprising an aromatic diamine curative for polyurethane, and a cross-linking agent comprising ditrimethylolpropane; and   combining the first solution and the first curing agent to define the first viscous material.   
     
     
         4 . The tactile layer of  claim 1 , wherein the second layer exhibits the second relaxation time within a threshold offset from the first relaxation time, the second layer cooperating with the first layer to recover the touch surface to a pre-deformation state within a period defined by a slower of the first relaxation time and the second relaxation time in response to deformation of the first layer and the second layer.