Composite ballistic resistant laminate

Abstract

An impact penetration resistant laminate comprises a plurality of alternating layers of (i) non-fibrous ultra-high molecular weight polyethylene monolayers and (ii) a thermoplastic adhesive, the adhesive having a basis weight of no greater than 5 gsm and a zero-shear-rate viscosity, determined from an oscillating disc rheometer in a frequency sweep between 0.1 rad/s and 100 rad/s, conducted per ASTM D 4440 at 125° C., and calculated from fitting to a Carrea-Yasuda four parameter model, of at least 1500 Pa-s, wherein (a) at least 90 percent of the monolayers are arranged such that the orientation of one monolayer is offset with respect to the orientation of an adjacent monolayer, and (b) the modulus of elasticity through the thickness of the laminate is at least 3 GPa.

What is claimed is: 
     
         1 . A method of making an impact penetration resistant laminate comprising the steps of
 (i) providing a plurality of cross-plied non-fibrous ultra-high molecular weight polyethylene sheets wherein the polyethylene sheet comprises two monolayers of polyethylene oriented film separated by an adhesive arranged such that the orientation of one monolayer in the sheet is offset with respect to the orientation of the other monolayer in the sheet, wherein the adhesive has a basis weight of no greater than 5 gsm and a zero-shear-rate viscosity, determined from an oscillating disc rheometer in a frequency sweep between 0.1 rad/s and 100 rad/s, conducted per ASTM D 4440 at 125° C., and calculated from fitting to a Carrea-Yasuda four parameter model, of at least 1500 Pa-s,   (ii) assembling a stack comprising a plurality of UHMWPE sheets of step (i) in an arrangement wherein at least 90 percent of the sheets are positioned such that the orientation of a monolayer of one sheet is offset with respect to the orientation of the closest monolayer of an adjacent sheet and the combined weight of polyethylene sheets and adhesive in the stack is from 0.6-600 kg/m 2 ,   (iii) subjecting the stack of step (ii) to a pressure of from 10 to 400 bar and a temperature of from 70 to 150 degrees C. for between 5 and 60 minutes, and   (iv) cooling the laminate to a temperature of 50 degrees C. or less.   
     
     
         2 . The method of  claim 1  wherein the adhesive has a zero-shear-rate viscosity of at least 10,000 Pa-s. 
     
     
         3 . The method of  claim 1  wherein the adhesive further comprises a thixotrope. 
     
     
         4 . The method of  claim 2  wherein the adhesive has a zero-shear-rate viscosity of at least 100,000 Pa-s. 
     
     
         5 . The method of  claim 3  wherein the thixotrope is an organic dendritic or inorganic particle. 
     
     
         6 . The method of  claim 4  wherein the adhesive has a zero-shear-rate viscosity of at least 1,000,000 Pa-s. 
     
     
         7 . A test method for assessing whether a consolidated stack of cross-plied non-fibrous ultra-high molecular weight polyethylene sheets will or will not suffer a pressure loss greater than 35 bar within the first two minutes and greater than 70 bar within the first 5 minutes when subjected to a compaction at a pressure of 255 Bar and a temperature of 132 degrees C. comprises the steps of
 (i) providing a plurality of cross-plied non-fibrous ultra-high molecular weight polyethylene sheets wherein the polyethylene sheet comprises two monolayers of polyethylene oriented film separated by an adhesive arranged such that the orientation of one monolayer in the sheet is offset with respect to the orientation of the other monolayer in the sheet, wherein the adhesive has a basis weight of no greater than 5 gsm and a zero-shear-rate viscosity, determined from an oscillating disc rheometer in a frequency sweep between 0.1 rad/s and 100 rad/s, conducted per ASTM D 4440 at 125° C., and calculated from fitting to a Carrea-Yasuda four parameter model, of at least 1500 Pa-s, and   (ii) assembling a stack comprising a plurality of UHMWPE sheets of step (i) in an arrangement wherein at least 90 percent of the sheets are positioned such that the orientation of a monolayer of one sheet is offset with respect to the orientation of the closest monolayer of an adjacent sheet and the combined weight of polyethylene sheets and adhesive in the stack is 660+/−50 gsm,   (iii) subjecting the stack of step (ii) to a pressure of 255 bar and a temperature of 132 degrees C., and   (iv) measuring the pressure loss after 2 and/or 5 minutes.