Patent Publication Number: US-2022234803-A1

Title: Formable films, laminate structures, and related methods

Description:
TECHNICAL FIELD 
     The present specification generally relates to laminate structures having formable films and more specifically to a blister package having a laminate structure that is heat-sealable to a lacquer layer on strain-hardened aluminum foil. 
     BACKGROUND 
     Blister packages are well-known for packaging of food products, medicinal products, and other industrial goods. Blister packages are formed from laminate structures having one or more formable films. The laminate structures are sealed to a lid layer after the product is stored within wells formed therein. The lid layer is typically formed from strain-hardened aluminum foil and a sealing surface of the lid is coated with a lacquer layer for enhancing the bond between the lid layer and the laminate structure. 
     The bonding performance of the lacquer layer on the sealing surface of the lid layer varies widely depending on the nature and composition of the formable films used in the laminate structure. In some cases, an outer layer of the laminate structure may have an additional coating layer such as Vinoyl 15/45M manufactured by Wacker Polymers to improve bonding performance. But such an additional coating layer incurs increased manufacturing complexity, cost and can cause poorer performance of the blister package. In other cases, when the formable films are made of thermoplastic materials such as uncoated polyethylene terephthalate (PET), biaxially oriented Nylon (BON), polypropylene and similar materials, the laminate structures do not bond well with the lid layer. 
     SUMMARY 
     Embodiments of the disclosure relate to a blister package having a laminate structure that is heat-sealable to a lacquer layer on strain-hardened aluminum foil. In one embodiment, a multilayer film includes a first formable layer of a thermoplastic material and a sealing layer of a copolyester material. The sealing layer overlies the first formable layer and has an outer surface opposite the first formable layer. The sealing layer has a crystallinity from 5% to 20% as measured by differential scanning calorimetry (DSC) which is a technique well known to those skilled in the art. 
     In another embodiment, a blister package for packaging a product is disclosed. The blister package includes a lid layer comprising a strain-hardened aluminum foil, a lacquer layer on a sealing surface of the strain-hardened aluminum foil and a laminate structure sealed directly to the lacquer layer. The laminate structure includes a multilayer film and a plurality of wells formed therethrough. The multilayer film includes a first formable layer of a thermoplastic material and a sealing layer of a copolyester material. The sealing layer overlies the first formable layer and has an outer surface opposite the first formable layer. The sealing layer has a crystallinity from 5% to 20% as measured by differential scanning calorimetry (DSC). The outer surface of the sealing layer is sealed directly against the lacquer layer of the foil lid. 
     In yet another embodiment, a method of preparing a blister package is disclosed. The method includes the step of laminating a lid layer and a multilayer laminate structure under pressure to form the blister package. The lid layer includes a strain-hardened aluminum foil having a lacquer layer on a sealing surface of the strain-hardened aluminum foil. The laminate structure includes a multilayer film having a first formable layer of a thermoplastic material and a sealing layer of a copolyester material. The sealing layer overlies the first formable layer and has an outer surface opposite the first formable layer. The sealing layer has a crystallinity from 5% to 20% as measured by differential scanning calorimetry (DSC). During the step of lamination, the outer surface of the sealing layer is contacted directly against the lacquer layer of the lid. 
     These and additional features provided by the embodiments described herein will be more fully understood in view of the following detailed description, in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments set forth in the drawings are illustrative and exemplary in nature and not intended to limit the subject matter defined by the claims. The following detailed description of the illustrative embodiments can be understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which: 
         FIGS. 1A, 1B, and 1C  are schematic diagrams of three exemplary multilayer films having layers of formable films, according to one or more embodiments shown and described herein; 
         FIG. 2  is a schematic diagram of a lamination process of forming an exemplary laminate structure with any of the exemplary multilayer films of  FIGS. 1A -IC, according to one or more embodiments shown and described herein; 
         FIG. 3A  is a schematic diagram of a sealing process of bonding a lid layer with the exemplary laminate structure of  FIG. 2 , according to one or more embodiments shown and described herein; and 
         FIG. 3B  is a schematic diagram of forming a blister pack after sealing the exemplary laminate structure of  FIG. 2  with the lid layer, according to one or more embodiments shown and described herein. 
     
    
    
     DETAILED DESCRIPTION 
     The details of one or more embodiments of the presently-disclosed subject matter are set forth in this document. Modifications to embodiments described in this document, and other embodiments, will be evident to those of ordinary skill in the art after a study of the information provided in this document. The information provided in this document, and particularly the specific details of the described exemplary embodiments, is provided primarily for clearness of understanding and no unnecessary limitations are to be understood therefrom. In case of conflict, the specification of this document, including definitions, will control. 
     Unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art to which the invention(s) belong. All patents, patent applications, published applications and publications, databases, websites and other published materials referred to throughout the entire disclosure herein, unless noted otherwise, are incorporated by reference in their entirety. In the event that there is a plurality of definitions for terms herein, those in this section prevail. Where reference is made to a URL or other such identifier or address, it understood that such identifiers can change and particular information on the internet can come and go, but equivalent information can be found by searching the internet. Reference thereto evidences the availability and public dissemination of such information. 
     Although any methods, devices, and materials similar or equivalent to those described herein can be used in the practice or testing of the presently-disclosed subject matter, representative methods, devices, and materials are now described. 
     Following long-standing patent law convention, the terms “a,” “an,” and “the” refer to “one or more” when used in this application, including the claims. Thus, for example, reference to “a layer” includes a plurality of such layers, and so forth, unless indicated otherwise. 
     Furthermore, unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in this specification and claims are approximations that can vary depending upon the desired properties sought to be obtained by the presently-disclosed subject matter. 
     As used herein, the term “about,” when referring to a value or to an amount of mass, weight, time, volume, concentration or percentage is meant to encompass variations of in some embodiments ±20%, in some embodiments ±10%, in some embodiments ±5%, in some embodiments ±1%, in some embodiments ±0.5%, and in some embodiments ±0.1% from the specified amount, as such variations are appropriate to perform the disclosed method. 
     As used herein, ranges can be expressed as from “about” one particular value, and/or to “about” another particular value. It is also understood that there are a number of values disclosed herein, and that each value is also herein disclosed as “about” that particular value in addition to the value itself. For example, if the value “10” is disclosed, then “about 10” is also disclosed. It is also understood that each unit between two particular units are also disclosed. For example, if 10 and 15 are disclosed, then 11, 12, 13, and 14 are also disclosed. 
     Embodiments described herein are directed to a blister package having a laminate structure that is heat-sealable to a lacquer layer on a strain-hardened aluminum foil. The laminate structure includes a sealing layer overlying one or more layers of formable films. The sealing layer is made of a copolyester material and can be co-extruded with layers of formable films to form the laminate structure. Accordingly, the inventors have discovered, an additional coating layer on the outer surface of the laminate structure is not necessary for bonding the laminate structure to a lid layer of strain-hardened aluminum foil. This reduces cost and complexity in the manufacturing process while also improving the overall construction of the blister package formed from the laminate structure. 
     Referring now to  FIGS. 1A, 1B, and 1C , schematic diagrams of three exemplary multilayer films  100  having layers of formable films  120   1  are depicted. Each of the embodiments in  FIGS. 1A-1C  include a multilayer film  100  of A/B/B structure having a sealing layer  110  overlying a first formable layer  120   1  and a second formable layer  120   2 , where the first formable layer  120   1  is interposed between the sealing layer  110  and the second formable layer  120   2 . While the embodiments shown in  FIGS. 1A-1C  show only two formable layers  120   1  and  120   2 , the multilayer film  100  is not restricted as such and may contain one or multiple formable layers  120   1 ,  120   2 ,  120   3 ,  120   4 , . . . ,  120   n  depending on the particular application. 
     In some embodiments, the sealing layer  110  is made from a copolyester material and has a thickness from about 1.5 microns to about 4 microns. The material chosen for the sealing layer  110  is required to be compatible with both the material of the formable layers  120   1 ,  120   2  and a multilayer extrusion process of forming the multilayer film  100 . In some embodiments, the sealing layer  110  is formed from a copolyester material such as, but not limited to, copolyesters of isophthalic acid, copolyesters of ethylene glycol, copolyesters of diethylene glycol (DEG), copolyesters of triethylene glycol (TEG), copolyesters of cyclohexanedimethanol (CHDM)-modified PET, copolyesters of n-propylene glycol, and copolyesters of n-butylene glycol. 
     In example embodiments, the copolyester material is formed by a catalyzed polycondensation reaction between one or more glycol components and one or more diacid components. In non-limiting examples, the glycol components may be ethylene glycol, DEG, TEG, CHDM, n-propylene glycol, n-butylene glycol and similar linear and branched diols. In non-limiting examples, the diacid components may be purified terephthalic acid (PTA), commoners of adipic acid, sebacic acid, succinic acid and similar linear and branched diacids. 
     In some embodiments, the copolyester material forming the sealing layer  110  has physical properties (e.g. intrinsic viscosity) that render heat-sealable characteristics to the copolyester material and improves interfacial compatibility with the material of the formable layers  120   1 ,  120   2  such that the sealing layer  110  can be co-extruded at a high temperature. In some embodiments, the copolyester material has an intrinsic viscosity from about 0.5 deciliters/gram to about 1.0 deciliters/gram, preferably from about 0.6 deciliters/gram to about 0.7 deciliters/gram. Intrinsic viscosity (IV) of a polymer reflects the property of a polymer in solution to increase the viscosity of the solution. Intrinsic viscosity is defined as the ratio of the solution&#39;s specific viscosity (the relative viscosity of the polymer solution of known concentration minus one) to the concentration of the solute extrapolated to zero concentration. Thus, the intrinsic viscosity is the limiting value of the ratio of specific viscosity and concentration at zero concentration. Intrinsic viscosity can be determined by measuring the relative viscosity of the solution at several different concentrations and then extrapolating the specific viscosity at zero concentration. 
     Intrinsic viscosity can also be determined by measuring the inherent viscosity at infinite dilution of the polymer, where inherent viscosity is the ratio between the natural logarithm of relative viscosity (ratio of the viscosities of the polymer solution and the pure solvent at the same temperature) and the concentration. Inherent viscosity can be measured using a method outlined in ASTM D 4603 (Standard Test Method for Determining Inherent Viscosity of Polyethylene Terephthalate (PET) by Glass Capillary Viscometer). 
     In some embodiments, the copolyester material has crystallinity from 1% to 25%, such as from 5% to 20%, from 5% to 15%, from 5% to 10%, or from 10% to 20%, for example, as measured by differential scanning calorimetry (DSC). If the copolyester material has a higher crystallinity, then it may often be heated and quenched quickly in a commercial coextrusion process such that the crystallinity is reduced to be within the range noted above. 
     DSC provides a known analytical technique for determining polymer crystallinity (and other morphological characteristics) based on the heat required to melt the polymer. As a polymer sample is heated and cooled over a period of time within a predetermined range of temperatures, the differential heat flow into or out of the polymer is measured using sensors and plotted. As a polymer is initially heated, the heat capacity of the polymer increases linearly as it passes the glass transition temperature (T g ). Subsequently, when the polymer is heated beyond the glass transition temperature T g , the polymer molecules gain more and more energy until they form ordered crystalline structures. Increase in crystallinity allows the polymer to release extra heat (ΔHc) such that the temperature drops to the polymer&#39;s cold crystalline temperature (T). Further application of heat however, begins to break down the ordered crystalline structures and the polymer gradually moves onto an amorphous phase and eventually melts at a melting temperature (T m ) upon absorbing sufficient heat (ΔHm). The data plotted by DSC enables the measurement of specific heat capacity, heat of transition, the temperature of phase changes and the rate of heat flow into or out of a polymer material both as a function of time and temperature. The percent crystallinity of a polymer is measured using the following equation: 
     
       
         
           
             
               
                 
                   
                     
                       % 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       crystallinity 
                     
                     = 
                     
                       
                         [ 
                         
                           
                             Δ 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             Hm 
                           
                           - 
                           
                             Δ 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             Hc 
                           
                         
                         ] 
                       
                       * 
                       100 
                       ⁢ 
                       
                         % 
                         / 
                         Δ 
                       
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       Hm° 
                     
                   
                   , 
                 
               
               
                 
                   ( 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                   
                   ) 
                 
               
             
           
         
       
     
     where:
         ΔHm=heat of melting (measured in Joules/gram)   ΔHc=heat of cold crystallization (measured in Joules/gram)   ΔHm°=heat of melting of a fully crystalline polymer (measured in Joules/gram and is a reference value commonly known for different polymers)       

     It is believed that a crystallinity from 5% to 20% as measured by DSC provides the copolyester material of the sealing layer  110  an ability to seal directly to a lacquer layer on strain-hardened aluminum foil, by application of heat and pressure alone, without the need for an additional coating or adhesive layer. The seal strength of the sealing layer  110  thus formed has been experimentally verified, as described in Example A below. 
     In some embodiments, the sealing layer  110  may further contain silica, alumina, or a combination thereof mixed in with the copolyester material. Dry particles of silica, alumina, or a combination thereof are blended with one or more layers of the copolyester material having low viscosity and subsequently polymerized together to form the blended sealing layer  110 . 
     The sealing layer  110  has an outer surface  112  that is opposite to an inner surface  114  facing the first formable layer  120   1 . The outer surface  112  of the sealing layer  110  is heat-sealable directly to a lacquer layer  354  coated on a strain-hardened aluminum foil  352  (shown in  FIG. 3A ). In some embodiments, the sealability between the sealing layer  110  and the lacquer layer  354  can be observed starting at a temperature of about 85° C. 
     In some embodiments, one or more of the formable layers  120   1  is formed from a thermoplastic material capable of thermoforming or cold-forming such as, but not limited to, polyethylene, polypropylene, nylon, polystyrene, polyethylene terephthalate (PET), polylactic acid, and polyvinyl chloride (PVC). In some embodiments, one or more of the formable layers  120   1  is formed from a biaxially-oriented PET layer having a metaphase evidenced by a metaphase transition at about 180° C. to about 200° C. as measured by DSC upon a first heating and a molded volume of greater than or equal to about 200%. In one example, the first formable layer  120   1  may be formed from a biaxially-oriented PET layer having a metaphase evidenced by a metaphase transition at about 180° C. to about 200° C. as measured by DSC upon a first heating and a molded volume of greater than or equal to about 200%. In another example, the second formable layer  120   2  may be, additionally or alternatively, formed from a biaxially-oriented PET layer having a metaphase evidenced by a metaphase transition at about 180° C. to about 200° C. as measured by DSC upon a first heating and a molded volume of greater than or equal to about 200%. 
     In this context, and as used herein, the term “metaphase” refers to an amorphous phase induced in a formable film that renders it excellent formability (e.g., thermoformability) and tensile strength, and which is not found in standard biaxially-oriented PET films. Such a metaphase can be induced and the resulting properties obtained by orienting the biaxially-oriented PET film layer at reduced temperatures and draw ratios, and subsequently allowing the biaxially-orienting PET film layer to relax to a greater extent than is done in the production of other thermoformable films. The metaphase is readily observed in the DSC profile of the formable films of biaxially-oriented PET as a deflection point in the heat-flow curves at approximately 180° C. to about 200° C. (e.g., 190° C.) upon first heating experiments. Being a metastable phase, second heating or annealing experiments then will not reveal this phase as the metaphase will be squelched. 
     Not wishing to be bound by any particular theories, it is believed that the metaphase is a quasi-stable phase intermediate in composition between that of the crystalline and amorphous materials typical of a semi-crystalline thermoplastic material. In particular, it is believed that the phase is a tied amorphous phase associated with the crystalline structure within the film. This tied amorphous phase has additional latent elongation properties and thus allows for significantly higher formability within the formable films of biaxially-oriented PET. 
     In some embodiments, the formable films of biaxially-oriented PET can be described as having a metastable phase having a phase transition temperature less than the crystalline melting point of the film as measured by DSC. In some embodiments, the phase transition temperature is about 40° C. less, about 45° C. less, about 50° C. less, about 55° C. less, about 60° C. less, or about 65° C. less than the crystalline melting point of the film as measured by DSC. 
     The phrase “molded volume” refers to the amount of increase in the volume exhibited by a particular film layer before breakage occurs. In this regard, molded volume is typically measured by making use of heat and reduced pressure experiments by which thin film materials are placed over a cavity mold and, under heat and reduced pressure, molded into a half-moon shape. Generally, such experimental procedures are optimized to produce the maximum molded volume before breakage occurs. The relative volume measured before breakage occurs is then normalized to a traditionally manufactured biaxially-oriented PET film that would give 100% normalized volume under optimal conditions. 
     As an effect of the metaphase transition present in the formable films of biaxially-oriented PET, the molded volume of any well that is formed therein becomes greater than 200% due to an increase in diameter of the well. The increase in volume can be measured by comparing the amount of water or other liquid required to completely fill the well before and after the metaphase transition is achieved by the formable film. 
     In some embodiments, one or more of the formable layers  120   i  may further include silica, alumina, or a combination thereof mixed in with the thermoplastic material. In one example, the first formable layer  120   1  may contain silica, alumina, or a combination thereof mixed in with the thermoplastic material. In another example, the second formable layer  120   2  may, additionally or alternatively, contain silica, alumina, or a combination thereof mixed in with the thermoplastic material. The process of blending dry particles of silica, alumina, or a combination thereof in the thermoplastic material is substantially similar to the process of blending the same within copolyester material of the sealing layer  110 , as described above. 
     In some embodiments, the one or more formable layers  120   i  are prepared through the use of conventional sequential biaxial orientation machines having a single-screw mainline extrusion train and a twin-screw sub-extrusion process. Other modifications to the standard machine set-ups are also possible and well known to those skilled in the art. In this regard, in some embodiments, standard PET pellets having a desired intrinsic viscosity can be fed into the main extrusion line, while pellets of another composition can be fed into a sub-extrusion process. For instance, a blend of standard PET pellets and silica-filled PET pellets can be fed in to the sub-extrusion process. The materials can then be melted separately and laminated together in a feed-block to produce a desired multilayer molten structure (e.g., an A/B/A molten structure) in an extrusion die. The laminated PET layers emerging from the extrusion die are then quenched on a chilled casting drum to produce a thick, amorphous film structure having a thickness of about 9 μm, about 12 μm, about 15 μm, about 20 μm, about 23 μm, about 25 μm, about 30 μm, about 35 μm, about 36 μm, about 40 m, about 45 μm, or about 50 m. 
       FIG. 2  is a schematic diagram of a lamination process of forming an exemplary laminate structure  200  with any of the exemplary multilayer films  100  of  FIGS. 1A-1C . In embodiments, a laminate structure  200  may include multilayer film  100  laminated to a core structure. The core structure may include at least one layer exhibiting a metaphasic transition such as, for example, a layer of metaphasic PET. In embodiments, the core structure may include, for example, a trilayer metaphasic structure  250 . In the laminate structure  200 , additional layers may be interposed between the multilayer film  100  and the core structure such as the trilayer metaphasic structure  250 . For example, an intermediate layer  230  may be interposed between the multilayer film  100  and the core structure such as the trilayer metaphasic structure  250 . In example embodiments, the intermediate layer  230  may be a soft metal foil such as a soft aluminum foil. The intermediate layer  230  may be adhered to the multilayer film  100  by a first adhesive layer  220  between the intermediate layer  230  and the multilayer film  100 . The intermediate layer  230  may be adhered to the core structure such as the trilayer metaphasic structure  250 , for example, by a second adhesive layer  240  between the intermediate layer  230  and the core structure. Exemplary lamination processes for forming the laminate structure  200  will now be described. 
     As shown in  FIG. 2 , the laminate structure  200  is formed over Lamination Step A and Lamination Step B. During Lamination Step A, the multilayer film  100  is laminated to an intermediate layer  230  with a first adhesive layer  220  such that the first adhesive layer  220  is between the second formable layer  120   2  and the intermediate layer  230 . In some embodiments, the intermediate layer  230  is formed from a soft aluminum foil. In some embodiments, the first adhesive layer  220  is ADCOTE® 811A+COREACTANT F, produced by Rohm and Haas Chemicals LLC, Philadelphia, Pa. In other embodiments, adhesives based on reactions of polyols and urethane prepolymers may be used. 
     During Lamination Step B, a trilayer metaphasic structure  250  is laminated to the intermediate layer  230  with a second adhesive layer  240 , substantially similar to the first adhesive layer  220 , such that the second adhesive layer  240  is between the intermediate layer  230  and the trilayer metaphasic structure  250 . In some embodiments, the trilayer metaphasic structure  250  has an A-B-A structure including a first PET layer  252 , a second PET layer  256  and a silica-containing PET layer  254  interposed between the first PET layer  252  and the second PET layer  256 . Thus, the intermediate layer  230  is placed between the second formable layer  120   2  and the first PET layer  252 . In some embodiments, the first PET layer  252  and the second PET layer  256  are formed from a biaxially-oriented PET layer having a metaphase evidenced by a metaphase transition present at about 180° C. to about 200° C. as measured by DSC upon a first heating and a molded volume of greater than or equal to about 200%. 
     In some embodiments, one or more layers of thermoplastic material such as, but not limited to, polyethylene, polypropylene, nylon, polystyrene, PET, polylactic acid, and PVC may be disposed in addition to or instead of the trilayer metaphasic structure  250 . Such additional layers may be incorporated through additional lamination steps. The lamination process shown in  FIG. 2  yields an exemplary laminate structure  200  that can be used for preparing a blister package  300 , as described below. 
       FIGS. 3A-3B  depict the formation of a blister package  300  from the exemplary laminate structure  200 . In particular,  FIG. 3A  depicts a schematic diagram of a sealing process of bonding a lid layer  350  with the exemplary laminate structure  200  to prepare the blister package  300 , while  FIG. 3B  depicts a schematic diagram of forming a blister pack  360  after sealing the exemplary laminate structure  200  with the lid layer  350 . As shown in  FIG. 3A , the lid layer  350  comprises the strain-hardened aluminum foil layer  352  having a sealing surface  353 . Strain-hardened aluminum foil is typically brittle and can be punctured easily to retrieve contents of the blister package  300 . The sealing surface  353  is coated with the lacquer layer  354 . During the sealing process, the outer surface  112  of the sealing layer  110  is directly pressed against a bottom surface  355  of the lacquer layer  354  and heated to a temperature above 85° C. to form the blister package  300 . Accordingly the lid layer  350  is laminated with the multilayer laminate structure  200  under heat and pressure to form the blister package  300 . 
     As shown in  FIG. 3B , the laminate structure  200  rolled around an unwinder  310  is passed through a die to make a plurality of wells  320  by applying pressure, typically between 4 and 6 kg/cm 2 . The plurality of wells  320  are formed by a well-forming part (not shown) at a speed between about 20 to about 30 blisters per minute. A product  330  is then inserted in each of the plurality of wells  320 . The product  330  may be a food product, a medicinal product, or another commercial product. The lid layer  350  rolled around a spindle  340  is pressed against the laminate structure  200  and heat-sealed to form the blister package  300 , as described above. Finally, individual blister packs  360  are punched off from the blister package  300 . 
     The apparatuses and methods described herein can be advantageously used for preparing a laminate structure of formable films that can be easily heat-sealable to a lid layer of strain-hardened aluminum foil to form a blister package, without requiring additional coatings for enhancing bonding between the laminate structure and the lid layer. When additional coatings are used, the laminate structure must be processed through the laminating machine a second time to add the additional coating. However, since additional coatings are no longer needed by virtue of the co-extruded sealing layer in the laminate structure, the laminating machine need only be used once. This results in significant savings in manufacturing cost and time, while improving the overall construction of the blister package at the same time. 
     The following specific but non-limiting example, Example A demonstrates the seal strength of the sealing layer in the laminate structure through experimentally-verified data. 
     Example A—Measurement of Seal Strength of the Sealing Layer 
     The seal strength of the sealing layer described in the present disclosure was examined using a first specimen of the sealing layer partially heat-sealed on one surface to a strain-hardened aluminum foil layer coated with a lacquer layer on the sealing surface and a second specimen of the sealing layer partially heat-sealed on both surfaces to strain-hardened aluminum foil layers coated with lacquer layers on the sealing surfaces. The test measured the force needed to separate the sealing layer from the strain-hardened aluminum foil layer(s) by gripping the unsealed portions of the strain-hardened aluminum foil layer(s) in the movable jaws of a tensile tester and then moving the jaws of the tensile tester with a constant strain rate to pull the sealed portions of the strain-hardened aluminum foil layer(s) apart. 
     Conditions of testing were followed per standardized guidelines of ASTM D 882 and ASTM F 88. The force applied and displacement on the sealing layer was continuously measured. The seal strength was measured as the amount of force needed (in grams) per 25 mm of width of the specimen to separate the sealing layer from the strain-hardened aluminum foil layer(s). For each specimen, the minimum, maximum, and average force needed to break the seal was measured at different temperatures (100° C., 110° C., 120° C., 130° C., 140° C., 150° C., 160° C., 170° C., 180° C., 190° C., 200° C., and 210° C.) and compared against a benchmark desired seal strength of greater than 500 g/25 mm. The data from the test is shown in Table 1 below and demonstrates high seal strength in all cases. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Seal Strength data from tensile tester 
               
            
           
           
               
               
            
               
                   
                 Seal Strength (g/25 mm) 
               
            
           
           
               
               
               
            
               
                   
                 Without Support 
                 With Support of Al/Alu Laminate 
               
               
                   
                 Pressure 
                 Pressure 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Sr. 
                 Temp 
                 3.0 kg 
                 4.0 kg 
                 5.0 kg 
                 4.0 kg 
                 5.0 kg 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 No. 
                 (° C.) 
                 Min 
                 Max 
                 Avg 
                 Min 
                 Max 
                 Avg 
                 Min 
                 Max 
                 Avg 
                 Min 
                 Max 
                 Avg 
                 Min 
                 Max 
                 Avg 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 1 
                 100 
                 430 
                 720 
                 575 
                 375 
                 800 
                 590 
                 560 
                 740 
                 650 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 2 
                 110 
                 845 
                 1180 
                 1015 
                 830 
                 1100 
                 965 
                 775 
                 1150 
                 965 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 3 
                 120 
                 760 
                 1065 
                 915 
                 325 
                 920 
                 620 
                 905 
                 960 
                 930 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 4 
                 130 
                 610 
                 670 
                 640 
                 445 
                 915 
                 680 
                 380 
                 675 
                 530 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 5 
                 140 
                 510 
                 690 
                 600 
                 360 
                 790 
                 575 
                 435 
                 780 
                 605 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 6 
                 150 
                 500 
                 565 
                 535 
                 565 
                 915 
                 740 
                 565 
                 895 
                 730 
                 695 
                 710 
                 700 
                 565 
                 660 
                 610 
               
               
                 7 
                 160 
                 500 
                 760 
                 630 
                 575 
                 750 
                 660 
                 830 
                 715 
                 770 
                 555 
                 800 
                 675 
                 400 
                 760 
                 580 
               
               
                 8 
                 170 
                 510 
                 720 
                 615 
                 565 
                 610 
                 585 
                 750 
                 785 
                 770 
                 480 
                 950 
                 715 
                 595 
                 1000 
                 800 
               
               
                 9 
                 180 
                 595 
                 955 
                 775 
                 610 
                 885 
                 750 
                 645 
                 1155 
                 900 
                 645 
                 710 
                 680 
                 460 
                 925 
                 695 
               
               
                 10 
                 190 
                 290 
                 420 
                 355 
                 365 
                 680 
                 520 
                 465 
                 680 
                 570 
                 430 
                 945 
                 690 
                 535 
                 885 
                 710 
               
               
                 11 
                 200 
                 425 
                 740 
                 585 
                 490 
                 535 
                 515 
                 345 
                 1035 
                 690 
                 520 
                 850 
                 685 
                 355 
                 565 
                 460 
               
               
                 12 
                 210 
                 495 
                 620 
                 555 
                 350 
                 625 
                 490 
                 360 
                 770 
                 565 
                 770 
                 875 
                 820 
                 645 
                 810 
                 730 
               
               
                   
               
            
           
         
       
     
     It is noted that the terms “substantially” and “about” may be utilized herein to include the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. These terms are also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function and intended scope of the subject matter at issue. 
     While particular embodiments have been illustrated and described herein, it should be understood that various other changes and modifications may be made without departing from the spirit and scope of the claimed subject matter. Moreover, although various aspects of the claimed subject matter have been described herein, such aspects need not be utilized in combination. It is therefore intended that the appended claims cover all such changes and modifications that are within the scope of the claimed subject matter.