Energy absorbing blends

Abstract

A composite material which is elastic, which exhibits a resistive load under deformation which increases with the rate of deformation, which is unfoamed or foamed, comminuted or uncomminuted and which comprises i) a first polymer-based elastic material and ii) a second polymer-based material, different from i), which exhibits dilatancy in the absence of i) wherein ii) is entrapped in a solid matrix of i), the composite material being unfoamed or, when foamed, preparable by incorporating ii) with i) prior to foaming.

1 . A composite material which is elastic, which exhibits a resistive load under deformation which increases with the rate of deformation, which is comminuted or uncomminuted and which comprises i) a first polymer-based elastic material and ii) a second polymer-based material, different from i), which exhibits dilatanoy in the absence of i) wherein ii) is entrapped in a solid matrix of i), the composite material being unfoamed or, when foamed, preparable by incorporating ii) with i) prior to foaming, the first material i) and second material ii) being in intimate admixture.  
   
   
       2 . A composite material according to  claim 1  wherein the admixture is attainable by blending i) and ii) together.  
   
   
       3 . A composite material according to  claim 1  or  2  wherein the polymer comprising the first material i) comprises EVA or an olefin polymer, for example polypropylene or an ethylene polymer such as high pressure polyethylene (LDPE), LLDPE or HDPE.  
   
   
       4 . A composite material according  claim 1  or  2  wherein the polymer comprising the first material i) comprises an elastomer.  
   
   
       5 . A composite material according to  claim 4  wherein the elastomer is a natural elastomer, such as latex rubber.  
   
   
       6 . A composite material according to  claim 4  wherein the elastomer is a synthetic elastomer.  
   
   
       7 . A composite material according to  claim 6  wherein the synthetic elastomer is a silicone rubber, a polyurethane or an EP rubber such as EPDM.  
   
   
       8 . A composite material according to  claim 6  wherein the synthetic elastomer is a thermoplastic elastomer.  
   
   
       9 . A composite material according to  claim 8  wherein the thermoplastic elastomer comprises a polyester.  
   
   
       10 . A composite material according to any one of the preceding claims wherein the polymer comprising the second material ii) is selected from silicone polymers exhibiting dilatant properties.  
   
   
       11 . A composite material according to  claim 10  wherein the silicone polymer is selected from borated siloxane polymers.  
   
   
       12 . A composite material according to  claim 11  wherein the silicone polymer is selected from filled polyborodimethylsiloxanes.  
   
   
       13 . A composite material according to any one of the preceding claims which is comminuted.  
   
   
       14 . A process for the preparation of a composite material according to  claim 1 , which process comprises: 
 a) melting the polymer intended to comprise the first material i); and    b) blending the polymeric dilatant intended to comprise the second material ii) therewith.    
   
   
       15 . A process according to  claim 14  wherein the polymer intended to comprise the first material i) is defined in any one of  claims 3  to  9  and/or the polymeric dilatant intended to comprise the second material ii) is defined in any one of  claims 10  to  12 .  
   
   
       16 . A process according to  claim 14  or  15  wherein the polymeric dilatant is melted prior to and/or during the blending step (b).  
   
   
       17 . A process according to  claim 14 ,  15  or  16  wherein, after blending and cooling, the composite material so formed is c) comminuted.  
   
   
       18 . A composite material prepared by the process of any one of claims  14  to  17 .  
   
   
       19 . A composite material according to any one of  claims 1  to  13  and  18  which has subsequently been foamed.  
   
   
       20 . A composite material according to  claim 19  wherein the foam is a closed cell foam.  
   
   
       21 . A composite material according to  claim 19  or  20  wherein at least part of the polymeric dilatant ii) is included within cell walls of the foam.  
   
   
       22 . A composite material according to  claim 19 ,  20  or  21  wherein the cells include, as pneumatogen, a gas.  
   
   
       23 . A composite material according to  claim 22  wherein the gas comprises nitrogen.  
   
   
       24 . A process for the preparation of a composite material according to any one of  claims 19  to  23 , which process comprises: 
 d) incorporating an unfoamed composite material, or a mixture of i) and ii), as defined in any one of  claims 1  to  13  or  18 , in the barrel of an injection moulding machine including means for supplying a pneumatogen thereinto;    e) bringing the material defined in d) to an elevated temperature and an elevated pressure such that it is in molten form;    f) supplying a pneumatogen to the barrel; and    g) reducing the pressure of the heated composite material thereby causing foaming of the composite material.    
   
   
       25 . A process according to  claim 24  wherein the pressure is reduced in step g) by injecting the composite material into a mould or extruding the composite material.  
   
   
       26 . A process for the preparation of a composite material according to any one of  claims 19  to  23 , which process comprises: 
 h) incorporating an unfoamed composite material, or a mixture of i) and ii), as defined in any of  claims 1  to  13  or  18  into a hermetic container including means for supplying a pneumatogen thereinto;    j) bringing the composite material to an elevated temperature and an elevated pressure; and    k) injecting pneumatogen into the hermetic container; and    l) reducing the pressure of the heated composite material thereby causing foaming of the composite material.    
   
   
       27 . A process according to  claim 26  wherein the interior of the container is formed as a mould.  
   
   
       28 . A process for the preparation of a composite material according to  claims 19  to  23 , which process comprises: 
 m) incorporating with an unfoamed composite material, or with one or both components of a mixture of i) and ii), as defined in any one of  claims 1  to  13  or  18  microspheres comprising a plastic shell which hermetically encapsulates a gas or vapour;    n) bringing the material defined in m) to an elevated temperature and pressure; and    o) reducing the pressure of the heated composite material thereby causing the expansion of the microspheres and foaming of the composite material.    
   
   
       29 . A process according to  claim 28  operated on a continuous basis.  
   
   
       30 . A foamed composite material prepared by the process of any one of  claims 24  to  29 .  
   
   
       31 . A shaped article comprising a composite material according to any one of  claims 1  to  13 ,  18 ,  19  to  23  and  30 .  
   
   
       32 . A shaped article as claimed in  claim 31  in the form of a sheet, film, filament or fibre.  
   
   
       33 . A shaped article according to  claim 32  in the form of a fibre.  
   
   
       34 . A fibre according to  claim 33  wherein the core is hollow.  
   
   
       35 . A fibre according to  claim 33  or  34  wherein the first material i) is defined in any one of  claims 3  to  9  and/or the second material ii) is defined in any one of  claims 10  to  12 .  
   
   
       36 . A textile or web including filaments or fibres as claimed in any one of  claims 32  to  35 .  
   
   
       37 . An impact protection system including a composite material as claimed in any one of  claims 1  to  13 ,  18 ,  19  to  23  and  30 ; a shaped article as claimed in any one of  claims 31  to  35  or a textile or web as claimed in  claim 36 .  
   
   
       38 . An impact protection system according to  claim 37  associated with a rigid or semi-rigid component.  
   
   
       39 . An impact protection system according to  claim 37  or  38  associated with a textile layer.  
   
   
       40 . An impact protection system, for example footwear, according to any one of  claims 37  to  39  wherein the composite material is as claimed in  claim 30  when dependent from claims  28  or  20  which is self-moulding in service.