Low Crystallinity Susceptor Films

Abstract

A microwave energy interactive structure includes a polymer film having a crystallinity of from about 1% to about 50% (as derived from density measurements) prior to being exposed to microwave energy, and a layer of microwave energy interactive material on the polymer film. The layer of microwave energy interactive material is operative for converting at least a portion of impinging microwave energy into thermal energy.

What is claimed is: 
     
         1 . A microwave energy interactive structure, comprising:
 a polymer film having a crystallinity of from about 1% to about 50% prior to being exposed to microwave energy, wherein the crystallinity of the polymer film is determined using density measurements; and   a layer of microwave energy interactive material on the polymer film, the layer of microwave energy interactive material being operative for converting at least a portion of impinging microwave energy into thermal energy.   
     
     
         2 . The microwave energy interactive structure of  claim 1 , wherein the polymer film has a crystallinity of from about 1% to about 25% prior to being exposed to microwave energy. 
     
     
         3 . The microwave energy interactive structure of  claim 1 , wherein the polymer film has a crystallinity of from about 1% to about 10% prior to being exposed to microwave energy. 
     
     
         4 . The microwave energy interactive structure of  claim 1 , wherein the polymer film has a crystallinity of from about 1% to about 7% prior to being exposed to microwave energy. 
     
     
         5 . The microwave energy interactive structure of  claim 1 , wherein the polymer film has a crystallinity of about 4% prior to being exposed to microwave energy. 
     
     
         6 . The microwave energy interactive structure of  claim 1 , wherein the polymer film comprises polyethylene terephthalate. 
     
     
         7 . The microwave energy interactive structure of  claim 1 , wherein the polymer film comprises nylon. 
     
     
         8 . The microwave energy interactive structure of  claim 1 , wherein the polymer film is unoriented. 
     
     
         9 . The microwave energy interactive structure of  claim 1 , wherein the polymer film is substantially unoriented. 
     
     
         10 . The microwave energy interactive structure of  claim 1 , further comprising an additive for enhancing the strength of the polymer film. 
     
     
         11 . The microwave energy interactive structure of  claim 10 , wherein the additive is present in an amount up to about 10% by weight of the polymer film. 
     
     
         12 . The microwave energy interactive structure of  claim 10 , wherein the additive is present in an amount up to about 5% by weight of the polymer film. 
     
     
         13 . The microwave energy interactive structure of  claim 10 , wherein the additive comprises at least one of an ethylene methyl acrylate copolymer and an ethylene-octene copolymer. 
     
     
         14 . The microwave energy interactive structure of  claim 1 , wherein the polymer film is a multilayer polymer film. 
     
     
         15 . The microwave energy interactive structure of  claim 14 , wherein the multilayer film includes
 a layer comprising polyethylene terephthalate, and   at least one of a layer of nylon, a layer of nylon 6,6, a layer of olefin, and a layer of ethylene vinyl alcohol.   
     
     
         16 . The microwave energy interactive structure of  claim 14 , wherein the multilayer film includes
 a layer comprising at least one of nylon and nylon 6,6, and   at least one of a layer of polyethylene terephthalate, a layer of olefin, and a layer of ethylene vinyl alcohol.   
     
     
         17 . The microwave energy interactive structure of  claim 1 , further comprising a support layer joined to the layer of microwave energy interactive material such that the layer of microwave energy interactive material is disposed between the polymer film and the support layer. 
     
     
         18 . The microwave energy interactive structure of  claim 17 , wherein the support layer comprises paper, paperboard, or any combination thereof. 
     
     
         19 . The microwave energy interactive structure of  claim 17 , wherein the support layer is joined to the layer of microwave energy interactive material by an adhesive. 
     
     
         20 . The microwave energy interactive structure of  claim 1 , comprising at least a portion of a microwave heating construct for heating, browning, and/or crisping a food item in a microwave oven. 
     
     
         21 . A microwave energy interactive structure, comprising:
 a polymer film having a crystallinity of from about 1% to about 50% prior to being exposed to microwave energy; and   a layer of microwave energy interactive material on the polymer film, the layer of microwave energy interactive material being operative so that the microwave energy interactive structure is operative for absorbing a fractional portion of microwave energy,   wherein the structure is operative for absorbing at least 40% of impinging microwave energy after exposure to microwave energy for 60 seconds.   
     
     
         22 . A microwave energy interactive structure, comprising:
 a polymer film having a crystallinity of from about 1% to about 50% prior to being exposed to microwave energy; and   a layer of microwave energy interactive material on the polymer film, the layer of microwave energy interactive material being operative for converting at least a portion of impinging microwave energy into thermal energy,   wherein after exposing the microwave energy interactive structure to microwave energy for 60 seconds, the microwave energy interactive structure exhibits a ratio of a craze perimeter to field area of less than 1.