Abstract:
Thermally deformable face seals and respirators including such face seals. The thermally deformable face seal structures comprise composite phase change materials that mold to the face of a user to provide a personalized but one-size-fits-all facial fit having excellent shape retention after use and long term durability. The phase change material is applied onto a base component to cover all or substantially all of the surface area of the base component and adapts to the face of the user to provide a secure, leak-free seal.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a Continuation-In-Part of co-pending U.S. patent application Ser. No. 14/852,986 filed Sep. 14, 2015, which is a Continuation of International Patent Application No. PCT/US2014/028153 filed Mar. 14, 2014, which claims priority from U.S. Provisional Application No. 61/781,464, filed Mar. 14, 2013, U.S. Provisional Application No. 61/794,054, filed Mar. 15, 2013, and U.S. Provisional Application No. 61/794,226, filed Mar. 15, 2013. All of the aforementioned applications are incorporated herein by reference to the extent consistent with the present disclosure. 
     
    
     BACKGROUND 
       [0002]    Technical Field 
         [0003]    The disclosure relates to thermally deformable face seals and respirators including such face seals. More particularly, the disclosure pertains to thermally deformable face seal structures comprising composite phase change materials that mold to the face of a user to provide a personalized but one-size-fits-all facial fit. 
         [0004]    Description of the Related Art 
         [0005]    Respiratory protective devices are conventionally used in the workplace and by consumers to provide protection from respiratory inhalation hazards including particulates, gases and vapors. Typical respirator masks include a protective shell that covers the nose and mouth of the wearer with an incorporated filter that prevents contaminants in the air from being inhaled by the wearer. The effectiveness of respiratory protective devices to be used in a workplace in the U.S. is classified by the Occupational Safety and Health Administration (OSHA) by a value referred to as the assigned protection factor, or APF. The APF of a respiratory protective device is the workplace level of respiratory protection that a respirator or class of respirators is expected to provide to employees when the employer implements a continuing, effective respiratory protection program. A primary factor that influences the APF rating of a respiratory protective device is the facial fit of the facepiece. In this regard, improper facial fit is a primary source of leakage for respiratory protective devices utilizing face seals, such as half facepieces, full facepieces, tight fitting powered air-purifying respirator (PAPR) facepieces and filtering facepiece respirators. No matter how efficient the respirator filter, if a facepiece does not fit properly then gaps between the mask and the face will allow particulate impurities to enter the breathing zone of the wearer. 
         [0006]    Conventional respirators are most typically held in place by adjustable straps, elastic bands and nose clips that are adjusted to form a tight seal about the wearer&#39;s face. However, the tight fit often makes the respirator uncomfortable to wear and the respirator often will not maintain a consistent seal about the face during facial movement such as during speech or a change of facial expression. In addition, with the great variations in face shapes and sizes among potential users, attempts at designing a comfortable, one-size-fits-all respirator that can achieve a perfect face seal for all users have been generally ineffective. 
         [0007]    For example, U.S. Pat. No. 4,454,881 teaches a filtering face piece respirator including a strap member and a mask body that incorporates a filtering material and an injection molded rubber edge bead element attached around a periphery of the mask. The strap holds the mask body against the face and the edge bead provides a seal between the mask and the user&#39;s face. An inwardly extending membrane component is also provided to improve the seal and reduce air leak around the nose and cheekbones of the wearer. However, the injection molded seal is weak and susceptible to detachment from the mask body after extensive use. 
         [0008]    U.S. pre-grant publication 2012/0125341 teaches a filtering face-piece respirator having an overmolded face seal. The respirator includes a mask body and a harness, with the mask body including a support structure, a filtering structure and a face seal element. The face seal element is overmolded onto a portion of the perimeter of the support structure and is alleged to avoid the seal detachment risk of the seal taught in U.S. Pat. No. 4,454,881. However, their seal is formed from materials that are molded into a specifically defined shape that is not adaptable to the varied shapes and sizes of varied users, and are not suitable for a one-size-fits-all respirator. In this regard, analogous to the inwardly extending membrane portion of U.S. Pat. No. 4,454,881, the face seal of U.S. 2012/0125341 requires the addition of a very thin (less than 1 mm thick), inwardly extending flange portion to that can conform to the wearer&#39;s face to further provide for a snug fit. This flange must too be molded into a specific face-fitting configuration and is susceptible to fatigue induced degradation resulting from repeated flexing as the mask is repeatedly put on and taken off by the wearer. 
         [0009]    Accordingly, there remains a need in the art for a respiratory protective device having an effective and comfortable face seal that can adapt to faces having nearly any shape and size, with improved shape retention after use and improved long term durability. The present disclosure provides a solution to that need. 
       SUMMARY 
       [0010]    The present disclosure provides respirators utilizing phase change materials in a new face seal construction that provides a unique adaptive seal, wherein the face seal includes two distinct components, i.e., a seal component that includes a phase change material and a base component that does not include a phase change material. 
         [0011]    Particularly, the disclosure provides a respirator comprising a face seal member configured to surround at least the nasal and oral regions of a wearer, the face seal member including a base component having an interior surface area positioned proximal to the face of a potential wearer, and a seal component at least partially covering said interior surface area of the base component, the seal component being configured to engage a facial surface of the wearer, wherein the seal component comprises a phase change material and wherein the base component comprises a non-phase change material, and the base component having a greater thickness than the seal component. 
         [0012]    The disclosure also provides a respirator comprising: 
         [0013]    a) a frame; and 
         [0014]    b) a face seal member mounted to the frame, the face seal member configured to surround at least the nasal and oral regions of a wearer, the face seal member including a base component having an interior surface area positioned proximal to the face of a potential wearer, and a seal component at least partially covering said interior surface area of the base component, the seal component being configured to engage a facial surface of the wearer, wherein the seal component comprises a phase change material and wherein the base component comprises a non-phase change material, and wherein a ratio of the thickness of the base component to the thickness of the seal component is at least about 2:1. 
         [0015]    The disclosure further provides a respirator comprising: 
         [0016]    a) a frame having an exposed outer side and an enclosed inner side, the frame defining an opening therethrough; 
         [0017]    b) a filter layer mounted to the frame and covering the opening of the frame, the filter layer configured to prohibit permeation of aerosol contaminants therethrough; and 
         [0018]    c) a face seal member configured to surround at least the nasal and oral regions of a wearer, the face seal member configured to surround at least the nasal and oral regions of a wearer, the face seal member including a base component having an interior surface area positioned proximal to the face of a potential wearer, and a seal component at least partially covering said interior surface area of the base component, the seal component being configured to engage a facial surface of the wearer, wherein the seal component comprises a phase change material and wherein the base component comprises a non-phase change material, wherein a ratio of the thickness of the base component to the thickness of the seal component is at least about 2:1. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is a front perspective view schematic representation of a user wearing a respirator of the disclosure including a face seal. 
           [0020]      FIG. 2  is a perspective view schematic representation of a user wearing the respirator of  FIG. 1  with a partial cut-away showing the filter layer. 
           [0021]      FIG. 3  is a perspective view schematic representation of a user wearing another respirator of the disclosure including a face seal. 
           [0022]      FIG. 4  is a perspective view schematic representation of a user wearing the respirator of  FIG. 3  with a partial cut-away showing the filter layer. 
           [0023]      FIG. 5  is a perspective view schematic representation of an interior portion of a respirator according to another embodiment of the disclosure. 
           [0024]      FIG. 6  is a perspective view schematic representation of an interior portion of a respirator according to another embodiment of the disclosure. 
           [0025]      FIG. 7  is a front perspective view schematic representation of a user wearing another respirator of the disclosure including a face seal. 
           [0026]      FIG. 8  is a rear perspective view schematic representation of a user wearing the respirator of  FIG. 7 . 
           [0027]      FIG. 9  is a front perspective view schematic representation of the respirator shown in  FIG. 7  having an open exhalation door. 
           [0028]      FIG. 10  is a perspective view schematic representation showing the interior of the respirator of  FIG. 7 . 
           [0029]      FIG. 11  is a perspective view schematic representation showing the interior of the face seal member of the respirator shown in  FIG. 7 . 
           [0030]      FIG. 12  is a front perspective view schematic representation of a user wearing another respirator of the disclosure including a face seal. 
           [0031]      FIG. 13  is a partial cross-section view schematic representation of the interface between a face seal member and a shield of the respirator illustrated in  FIG. 12 . 
           [0032]      FIG. 14  is a rear perspective view schematic representation of the respirator shown in  FIG. 12 . 
           [0033]      FIG. 15  is a side view schematic representation of a respirator according to another embodiment of the disclosure. 
           [0034]      FIG. 16  is a partial deconstructed view schematic representation of the respirator shown in  FIG. 15 ; 
           [0035]      FIG. 17  is a perspective view schematic representation of a user wearing another respirator of the disclosure including a face seal. 
           [0036]      FIGS. 18A-18C  illustrate various steps for disposing the respirator shown in  FIG. 17  according to an example disposal process of the disclosure. 
           [0037]      FIG. 19  is a front perspective view schematic representation of another respirator of the disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0038]    The present disclosure provides an improved face seal member to be used with respirators disclosed in parent application Ser. No. 14/852,986. As shown in the Figures, the disclosure provides a respirator comprising a face seal member that is configured to surround at least the nasal and oral regions of a wearer. The face seal member includes a non-phase change base component that provides structural support and a seal component covering all or substantially all the surface area of the base component. The seal component comprises the phase change material and is configured to engage a facial surface of the wearer. It has been unexpectedly found that face seals formed with a discrete base component having no phase change material and which is separate from the seal component, rather than a single bi-modal face seal combining both a phase change material and a non-phase change material, unexpectedly achieves enhanced shape retention after use and unexpectedly achieves essentially universal adaptability to substantially all user face shapes and sizes. Additionally, only a small amount of the phase change material is needed to achieve these benefits, requiring as little as a 10 μm thick application of the seal component onto the base component. 
         [0039]    A “phase change material” (“PCM”) is conventionally known as a substance with a high heat of fusion that melts and solidifies at a certain temperature and is capable of storing and releasing large amounts of energy. PCM&#39;s have reversible thermal properties, meaning that the materials may reversibly transition between states, e.g., solid and liquid, with the application or removal of heat without causing permanent phase changes. 
         [0040]    The phase change material may be of any known phase change material chemistry including a variety of organic and inorganic substances and mixtures thereof. Suitable phase change materials non-exclusively include hydrocarbons (e.g., straight chain alkanes or paraffinic hydrocarbons (paraffins), branched-chain alkanes, unsaturated hydrocarbons, halogenated hydrocarbons, and alicyclic hydrocarbons), hydrated salts (e.g., calcium chloride hexahydrate, calcium bromide hexahydrate, magnesium nitrate hexahydrate, lithium nitrate trihydrate, potassium fluoride tetrahydrate, ammonium alum, magnesium chloride hexahydrate, sodium carbonate decahydrate, disodium phosphate dodecahydrate, sodium sulfate decahydrate, and sodium acetate trihydrate), waxes, oils, fatty acids, fatty acid esters, dibasic acids, dibasic esters, 1-halides, primary alcohols, aromatic compounds, clathrates, semi-clathrates, gas clathrates, anhydrides (e.g., stearic anhydride), ethylene carbonate, polyhydric alcohols (e.g., 2,2-dimethyl-1,3-propanediol, 2-hydroxymethyl-2-methyl-1,3-propanediol, ethylene glycol, polyethylene glycol, pentaerythritol, dipentaerythrital, pentaglycerine, tetramethylol ethane, neopentyl glycol, tetramethylol propane, 2-amino-2-methyl-1,3-propanediol, monoaminopentaerythritol, diaminopentaerythritol and tris(hydroxymethyl)acetic acid), polymers (e.g., polyethylene, polyethylene glycol, polyethylene oxide, polypropylene, polypropylene glycol, polytetramethylene glycol, polypropylene malonate, polyneopentyl glycol sebacate, polypentane glutarate, polyvinyl myristate, polyvinyl stearate, polyvinyl laurate, polyhexadecyl methacrylate, polyoctadecyl methacrylate, polyesters produced by polycondensation of glycols (or their derivatives) with diacids (or their derivatives), and copolymers, such as polyacrylate or poly(meth)acrylate with alkyl hydrocarbon side chain or with polyethylene glycol side chain and copolymers including polyethylene, polyethylene glycol, polyethylene oxide, polypropylene, polypropylene glycol, or polytetramethylene glycol), and mixtures thereof. 
         [0041]    The phase change material may have a high heat of fusion such that the material is capable of storing and releasing large amounts of energy. The phase change material may be selected or modified in order for the phase change material to change phase at a temperature or range of temperatures that includes or is proximate to the air temperature of the air exhaled by the wearer and/or the body temperature of the wearer, particularly the temperature at the facial surface of the wearer. For example, the exhalation air temperature may be around 34° C. and the body temperature of the wearer may be around 37° C. Accordingly, the phase change material may be configured to change phase (for example, by absorbing or releasing latent heat) at a temperature of from about 30° C. to about 40° C., and more preferably from about 33° C. to about 38° C. In some embodiments the phase change material will change between solid and liquid states within these temperature ranges, but in other embodiments using other phase change materials the phase change may be between liquid and gaseous states. 
         [0042]    As the phase change material absorbs heat and changes from a solid state toward a liquid state, the rigidity of the seal component changes and, if engaging a face of a wearer, will deform sufficiently to adapt and conform to the contours of the face of any user. In this regard, the rigidity of the seal component can be characterized in terms of its Shore A Hardness, which may be measured by the testing procedures of ASTM D2240. In a typical respirator embodiment of the disclosure, the seal component has a Shore A Hardness of from about 40 to about 90 at ambient temperature, but upon heat absorption, such as when the seal component is engaging the face of a wearer, the Shore A Hardness is reduced to a value of from about 10 to about 60, whereby the shape of the seal component changes to form a seal about the nasal and oral regions of the wearer. Upon removal from the thermal energy source, such as the removal of the seal component from the face of the wearer, the seal component will revert back to its original shape. In this regard, the seal component has a compression set, i.e. the degree of permanent deformation remaining when an applied force is removed, of less than 25% as determined by ASTM D395 when the seal component is removed from contact with the facial surface of the wearer. More preferably, the seal component has a compression set of less than 20%, still more preferably less than 15%, still more preferably less than 10%, still more preferably has a compression set of less than 5% as determined by ASTM D395, and most preferably has zero compression set when the seal component is removed from contact with the facial surface of the wearer. This unexpected result has led to the achievement of a one-size-fits-all respirator apparatus that can achieve a secure, leak-free seal for virtually any user. 
         [0043]    The phase change material may be incorporated in the seal component of the face seal in free, raw form such that it is not encapsulated, e.g., not micro-encapsulated, and wherein it is not contained within a containment structure as is known in the art. The phase change material in the raw form can be provided as a solid in a variety of forms (e.g., bulk form, powders, pellets, granules, flakes, etc.) or as a liquid in a variety of forms (e.g., molten form, dissolved in a solvent, etc.). The raw phase change material may or may not be dispersed within a polymeric matrix material or polymeric dispersing material. When the raw phase change material is not dispersed within a polymeric matrix/dispersing material, the seal component consists or consists essentially of the phase change material. When the raw phase change material is dispersed within a polymeric matrix/dispersing material, the seal component comprises, consists of or consists essentially of the phase change material and the matrix/dispersing material. In such an embodiment, the phase change material may be uniformly or non-uniformly dispersed within the matrix/dispersing material. If non-uniformly dispersed, it is most preferred that the greatest concentration of the phase change material is within the innermost portion of the seal component that will engage the face of the wearer. 
         [0044]    Alternatively, the phase change material may be contained within a containment structure that encapsulates, contains, surrounds or absorbs the phase change material. The primary purpose of a containment structure is to reduce or prevent leakage of the phase change material from the article or part of an article incorporating it. In one embodiment, the phase change material is contained within microcapsules that are uniformly, or non-uniformly, dispersed within a matrix/dispersing material. The microcapsules can be formed as hollow shells enclosing the phase change material and can include individual microcapsules formed in a variety of regular or irregular shapes (e.g., spherical, ellipsoidal, etc.) and sizes. The individual microcapsules can have the same or different shapes or sizes but typically have a maximum linear dimension (e.g., diameter) of from about 0.01 μm to about 100 μm. In one embodiment, the microcapsules can have a generally spherical shape and a diameter of from about 0.5 μm to about 10 μm, more preferably from about 0.5 μm to about 3 μm. Other examples of a containment structure include particulate materials or other absorbent materials that are impregnated with the phase change material. Such containment structures non-exclusively include silica particles (such as precipitated silica particles, fumed silica particles, and mixtures thereof), zeolite particles, carbon particles (such as graphite particles, activated carbon particles, and mixtures thereof), and absorbent materials (such as absorbent polymeric materials, superabsorbent materials, cellulosic materials, poly(meth)acrylate materials, metal salts of poly(meth)acrylate materials, and mixtures thereof). 
         [0045]    Whether the phase change material is in a raw or contained form, suitable matrix/dispersing materials within which the phase change material may be dispersed non-exclusively include one or more thermoset elastomers or one or more thermoplastic elastomers, including combinations of materials. Particularly preferred matrix/dispersing materials non-exclusively include polyamides (e.g., nylon 6, nylon 6/6, nylon 12, polyaspartic acid, polyglutamic acid, etc.), polyamines, polyimides, polyacrylics (e.g., polyacrylamide, polyacrylonitrile, esters of methacrylic acid and acrylic acid, etc.), polycarbonates (e.g., polybisphenol A carbonate, polypropylene carbonate, etc.), polydienes (e.g., polybutadiene, polyisoprene, polynorbornene, etc.), halogenated butyl rubber, polyepoxides, polyesters (e.g., polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polycaprolactone, polyglycolide, polylactide, polyhydroxybutyrate, polyhydroxyvalerate, polyethylene adipate, polybutylene adipate, polypropylene succinate, etc.), polyethers (e.g., polyethylene glycol, polybutylene glycol, polypropylene oxide, polyoxymethylene (paraformaldehyde), polytetramethylene ether (polytetrahydrofuran), polyepichlorohydrin, etc.), polyflourocarbons, formaldehyde polymers (e.g., urea-formaldehyde, melamine-formaldehyde, phenol formaldehyde, etc.), natural polymers (e.g., cellulosics, chitosans, lignins, waxes, etc.), polyolefins (e.g., polyethylene, polypropylene, polybutylene, polybutene, polyoctene, etc.), polyphenylenes (e.g., polyphenylene oxide, polyphenylene sulfide, polyphenylene ether sulfone, etc.), silicon containing polymers (e.g., silicone, polydimethyl siloxane, polycarbomethyl silane, etc.), polyurethanes, polyvinyls (e.g., polyvinyl butryal, polyvinyl alcohol, polyvinyl acetate, polystyrene, polymethylstyrene, polyvinyl chloride, polyvinyl pryrrolidone, polymethyl vinyl ether, polyethyl vinyl ether, polyvinyl methyl ketone, etc.), polyacetals, polyarylates, copolymers (e.g., polyethylene-co-vinyl acetate, polyethylene-co-acrylic acid, polybutylene terphthalate-co-polytetramethylene terephthalate, polylauryllactam-block-polytetrahydrofuran, and etc.), and mixtures thereof. Most preferably, the matrix/dispersing material consists of or consists essentially of a non-phase change polymer. 
         [0046]    All of the above matrix/dispersing materials are also suitable materials for the base component, but most preferably the base component consists of or consists essentially of a non-phase change polymer. Most preferably the base component comprises silicone, polyisoprene, halo-butyl rubber, a thermoplastic elastomer, or a combination thereof. 
         [0047]    The base component may be formed by any conventionally known molding method, such as injection molding. The seal component is then applied directly onto the base component by any suitable deposition means in the art permitting the seal component to at least partially, and preferably substantially or fully cover the interior surface area of the base component in areas positioned proximal to where the face seal will contact the face of a potential wearer. In this regard, the “interior surface area” includes all of the surface area of the base component that will in contact with the facial surface of the wearer while the respirator is in use (see seal contact area  114  below in  FIGS. 2-6 ), as well as any additional surfaces of the face seal that are not exposed to the outer environment. This typically will include at least 50% of the total surface area of the base component as measured from the interior of the respirator (see, for example, interior  124  of the respirator  100  in  FIGS. 5-6 ) toward the opposite, outside facing external surface of the respirator. In some embodiments the seal component will substantially or fully cover all of the surface area of the base component, including areas in the rear of the face seal that will not contact the face of the wearer. Useful deposition methods for applying the seal component directly onto the base component non-exclusively include coating, co-molding and over-molding. As used herein, “over-molding” means molding one component over another already formed component or onto another already formed component. In the context of the present disclosure, this means molding the seal component onto an already formed base component. As used herein, “co-molding” (also referred to in the art as co-injection molding, double-shot, double-shot molding, dual-injection molding and insert molding, inter alia , is a process of molding a polymeric material around a preformed insert (typically also polymeric). Each of these methods (coating, co-molding and over-molding) forms a very strong bond between the seal component and base component without the need for intermediate adhesives. Each also permits the simple fabrication of face seals having any desired shape. 
         [0048]    Regardless of the fabrication technique used, the seal component should be applied onto or co-formed with the base component such that the ratio of the thickness of the base component to the thickness of the seal component is at least about 2:1, more preferably at least about 2:1 to about 10:1 and most preferably from about 2:1 to about 4:1. In the preferred embodiments, the seal component has a thickness of from about 10 μm to about 5.0 mm, more preferably from about 100 μm about 2.0 mm, still more preferably from about 0.5 mm about 1.5 mm and most preferably from about 0.5 mm to about 1.0 mm. In the preferred embodiments, the base component has a thickness of at least about 1.0 mm, preferably from about 1.0 mm to 10.0 mm, more preferably from about 1.0 mm to about 4.0 mm, still more preferably from about 1.0 mm to about 3.0 mm, and most preferably from about 1.0 mm to about 2.0 mm. 
         [0049]    With particular reference to the figures,  FIG. 1  is perspective view of a respirator  100  of this disclosure. The respirator  100  includes a frame  102 , a filter layer  104 , and a face seal member  106 . In every embodiment of this disclosure, the face seal member  106  includes a base component having a surface area and a seal component substantially covering the surface area of the base component, the seal component being configured to engage a facial surface of the wearer, wherein the seal component comprises a phase change material and wherein the base component comprises a non-phase change polymer, and the base component having a greater thickness than the seal component. 
         [0050]      FIG. 2  illustrates the respirator  100  shown in  FIG. 1  showing a partially cut-away filter layer  104 . As illustrated in both  FIGS. 1 and 2 , the respirator  100  may be a mask worn by a person, referred to herein as either a wearer or a user. The respirator  100  may be configured to protect the wearer from harmful contaminants, such as particulates, fumes, vapors, gases, and/or splattered liquids in the environment around the wearer by shielding the nose and mouth of the wearer to prohibit the wearer from inhaling or ingesting the harmful contaminants. The air supplied through the respirator  100  to the wearer may be filtered and at least partially purified by the respirator  100  prior to inhalation. The respirator  100  shown in  FIGS. 1 and 2  is a half-face mask, such that the respirator  100  covers the nasal and oral regions of the wearer while exposing other portions of the face, such as the eyes, ears, and other facial surfaces of the wearer. Although at least some of the embodiments shown and described herein are directed to a half-face respirator, in other embodiments, the respirator  100  may be or may be used in a full-face respirator that covers at least most of the face and/or the head. For example, the respirator  100  may be an inner mask component of a full face piece or hood respirator assembly. 
         [0051]    In one or more embodiments, the respirator  100  may be disposable or semi-disposable. A disposable respirator is configured to be disposed in its entirety after one or more uses by a wearer. A semi-disposable respirator may be at least partially disassembled or deconstructed, and at least some parts of the respirator may be disposed and other parts of the respirator may be sterilized or decontaminated before being reassembled with one or more new disposable parts for a subsequent use by a wearer. 
         [0052]    The frame  102  may have an enclosed, inner side  108  and an exposed, outer side  110 , with an opening  112  that extends through the frame  102  between the inner and outer sides  108 ,  110 . The terms “inner” and “outer” are defined relative to the facial surface of the wearer when the respirator is engaged with the face of a wearer such that the inner side  108  of the frame  102  faces toward the wearer and is within the decontaminated facial area, while the outer side  110  faces away from the wearer and is exposed to the environment. The frame  102  may be configured to provide structure and some rigidity to the respirator  100  to allow the respirator  100  to retain a defined shape. In one embodiment, the frame  102  may be at least partially convex, such that the frame  102  slopes or bulges outward away from the wearer. The opening  112  of the frame  102  may optionally occupy a majority of the area of the frame  102 , such that the frame  102  itself forms a border around the opening  112 . 
         [0053]    The filter layer  104  may be mounted to the frame  102  such that the filter layer  104  covers the opening  112 . In one embodiment, the filter layer  104  is mounted to the outer side  110  of the frame  102 . The filter layer  104  seals to the frame  102  such that no gaps extend between the filter layer  104  and the frame  104  around the perimeter of the filter layer  104 , and any air that enters the respirator  100  through the opening  112  in the frame  102  must permeate through the filter layer  104 . The filter layer  104  may be semi-permeable and configured to allow some permeation of air therethrough while prohibiting permeation of aerosol contaminants with the air. As such, the filter layer  104  filters the air that permeates through the filter layer  104 . 
         [0054]    The face seal member  106  may be mounted to the frame  102 . For example, the face seal member  106  may be mounted to the inner side  108  of the frame  102  while the filter layer  104  is mounted to the outer side  110 . The face seal member  106  is designed to surround at least both the nasal and oral regions (i.e., oronasal regions) of the wearer. The face seal member  106  includes a seal contact area  114  that is configured to engage a facial surface of the wearer. For example, the seal contact area  114  may extend along a perimeter of the face seal member  106 . The seal contact area  114  may contact the cheeks, the chin, and the nose of the wearer when the respirator  100  is worn by the wearer. The seal contact area  114  is configured to seal to the facial surfaces of the wearer to prohibit the passage of air between the face seal member  106  and the face of the wearer, as such air may be un-filtered and include harmful contaminants. 
         [0055]    The respirator  100  may also include a harness assembly  116 . The harness assembly  116  includes one or more straps  118  configured to removably mount the respirator  100  to a head of the wearer. The one or more straps  118  may be coupled to the frame  102  and/or the face seal member  106 . The one or more straps  118  provide tension to hold the face seal member  106  in contact with the facial surface of the wearer to seal the respirator  100  to the wearer. The one or more straps  118  may be stretchable and/or include one or more adjustable straps to allow for a customized fit of the respirator  100  on the wearer. Optionally, the harness assembly  116  may include a harness cradle  160  (shown in  FIG. 14 ) that couples two straps  118  together along the sides or the back of the head of the wearer and provides a preset spacing between the two straps  118 . 
         [0056]    As noted above, in a preferred embodiment, the phase change material may be micro-encapsulated in a polymer coating prior to being incorporated into a component of the respirator  100 . After micro-encapsulation, the phase change material may be co-molded with one or more of the components of the respirator  100  to form the respective component(s). 
         [0057]    The phase change material of the seal component is configured to provide thermoregulation at the boundary of contact between the wearer&#39;s face and at the boundary of contact between the wearer&#39;s face and the respirator  100 . For example, the phase change material may provide localized cooling for the wearer by absorbing heat emitted by the wearer. The heat may be direct conductive heat emitted by a skin surface of the wearer directly into a component of the respirator  100  that engages the skin surface or convective heat that is absorbed from air exhaled from the wearer into the respirator  100 . The phase change material may be configured to absorb heat without exhibiting a substantial increase in temperature by undergoing a phase change. For example, the heat that is absorbed is used to change the phase of at least some of the phase change material from a solid to a liquid phase. Latent heat is used to change the phase of the material and does not increase the temperature of the material. The temperature at which the phase change material melts, or changes from a solid to a gel or to a liquid, depends on the properties of the phase change material. In an embodiment, the phase change material that is incorporated into the respirator  100  melts at a temperature that is proximate to an exhalation air temperature of the wearer and/or a body temperature of the wearer. 
         [0058]    As the phase change material absorbs heat and changes state, the facial surfaces and/or air proximate to the phase change material is cooled as the heat is dissipated away from the facial surfaces and/or air in the respirator  100 . Thus, the incorporation of the phase change material may improve comfort of the wearer while wearing the respirator  100 . Increased comfort of the wearer while wearing the respirator  100  reduces the urge or tendency of the wearer to remove the respirator  100  (or not even put on the respirator  100  in the first place) out of discomfort. 
         [0059]    As stated above, the phase change material provides thermoregulation, and not only cooling. Thus, the phase change material may also provide heating to the air within the respirator  100  and/or the skin, surfaces of the wearer based on the thermal conditions of the wearer and the ambient environment. For example, the phase change material may be in a liquid or gel state after absorbing heat emitted from the wearer. However, if the wearer enters an environment that is below a certain temperature, the phase change material may begin to undergo a reverse phase change process that causes the melted phase change material to return to a solid state. As the phase change material solidifies, heat is released from the phase change material, and the heat may be absorbed by the skin surfaces of the wearer and/or the air in the respirator  100  to provide localized heating. The release of heat may provide comfort to a wearer who is working outside, for example, in freezing or at least low temperatures. Thus, although one or more embodiments described herein are directed to the ability of the phase change material to provide cooling, it is recognized that the phase change material may also be used in each embodiment to provide heating. The phase change material provides thermal regulation by absorbing heat from the wearer upon melting to cool the wearer when the wearer is hot, and releasing the absorbed heat to the wearer upon solidifying to heat the wearer when the environment is cold. 
         [0060]      FIG. 3  is a perspective view of the respirator  100  in accordance with another embodiment. The respirator  100  shown in  FIG. 3  may be similar to the embodiment of the respirator  100  shown in  FIG. 1 , although the respirator  100  shown in  FIG. 3  includes an exhalation valve  120  on the filter layer  104 .  FIG. 4  illustrates the respirator  100  shown in  FIG. 3  with the filter layer  104  partially cut-away for descriptive purposes. 
         [0061]    As illustrated in  FIG. 3  and  FIG. 4 , the frame  102  of the respirator  102  may be formed of a plastic material. For example, the frame  102  may be formed by a molding process. Depending on the plastic material, the frame  102  may be flexible, semi-rigid, or rigid to provide structure to the respirator  102 . The frame  102  optionally may be a five-sided structure. One or more support beams  168  (shown in  FIG. 17 ) may extend across the opening  112  of the frame  102  to provide support for the filter layer  104  or a shield mounted to the frame  102 . 
         [0062]    The exhalation valve  120  of the frame  102  provides a port for the air that is exhaled from the wearer to exit the respirator  100 . The exhalation valve  120  may be integral to the frame  102 . Alternatively, the valve may be a snap-in valve. Optionally, the valve  120  may include an associated plenum that directs the air through a channel before or after flowing through the valve  120 . The exhalation valve  120  may include filter media to prohibit outside air from entering the respirator  100  through the valve  120 . Optionally, the exhalation valve  120  may be biased to open at a lower flow rate that is consistent with regular, non-elevated breathing rates (such as experienced by a healthcare worker). Resistance may be lower to ensure that a majority of the exhaled air exits through the exhalation valve instead of through inhalation filter media portions (for example, the filter layer  104 ) of the respirator  100 . The exhalation filter media may have a targeted efficiency for filtering out larger biological contaminants (as compared to inhalation filter media used in an inhalation portion) in order to achieve the lower resistance. The exhalation filter media may also have a lower particulate loading capacity which is commensurate with the lower loading of biological particulate matter exhaled from the respirator  100  as compared to the higher biological particulate loading in the ambient environment. 
         [0063]    The filter layer  104  may include particulate filter media that is oriented into a textile or sheet. The filter layer  104  may include pleated or non-pleated electrostatic or synthetic membrane filter media. Synthetic membrane material may be re-usable due to being able to undergo common sterilization techniques. The filter layer  104  may be mounted to the outer side  110  of the frame  102  by insert molding, heat staking, ultrasonic welding, or the like. Optionally, the filter layer  104  may include an opening  122  at the exhalation valve  120  to allow the exhaled air to be discharged from the respirator  100 . In one or more alternative embodiments, the outer layer of the respirator  100  may be a non-permeable or semi-permeable plastic shield instead of a filter layer  104 , as described further herein. 
         [0064]    The face seal member  106  may be molded such that the seal contact area  114  conforms around the nasal and oral regions of the wearer. The face seal member  106  optionally may be molded in a convex or c-shaped structure that bulges outward away from the wearer. Upon assembly of the respirator  100 , the frame  102  and mounted filter layer  104  may be received over the face seal member  106 . In an optional embodiment, the seal face member  106  may include one or more inhalation valves  152  (shown in  FIG. 11 ) to regulate airflow into the respirator  100 . 
         [0065]    Optionally, the respirator  110  may be semi-disposable, wherein the face seal member  106  is removably mounted to the frame  102  and filter layer  104  to allow for disposal of the frame  102  and filter layer  104  and sterilization of the face seal member  106  and harness assembly  116 . For example, the face seal member  106  may have integrated strap loops that are configured to receive the straps  118  of the harness assembly  116  therethrough. In another semi-disposable embodiment, the frame  102  and harness assembly  116  may be dismantled for sterilization while the filter layer  104  and face seal member  106  are disposed. In an alternative embodiment in which the respirator  100  is fully disposable, the face seal member  106  may incorporate the filter layer  104  and the combined material may be bonded to the frame  102 , such as by heat staking, to construct the disposable respirator  100 . 
         [0066]    The one or more straps  118  of the harness assembly  116  may be formed at least partially of a stretchable material, such as neoprene, elastic, or the like. In other embodiments, the one or more straps  118  may not stretch, but may be coupled to adjustable coupling devices that allow the wearer to adjust the length of the one or more straps  118 . For example, plastic buckles, hook and loop patches, “push to snap” butterfly clips, and other coupling devices may be located along the one or more straps  118 . In one embodiment, the coupling device is located along the back of the neck of the wearer. In another embodiment, the harness assembly  116  may have a single strap  118  that loops twice around the head of the wearer, once along the bottom of the head or neck and again along the top of the head. The one or more straps  118  may have a single or double point attachment to the respirator  100 . The one or more straps  118  optionally may include pads that provide padding for the wearer, and the pads may be formed of silicone, a thermoplastic elastomer, or the like. Optionally, the harness assembly  116  may include a harness cradle  160 , as described further herein with reference to  FIG. 14 . 
         [0067]      FIG. 5  and  FIG. 6  illustrate views of the interior  124  of the respirator  100  according to two alternative embodiments of the disclosure. As illustrated in these figures, the interior  124  of the respirator  100  shows the respirator  100  from the perspective of the wearer. Each of the respirators  100  shown in  FIGS. 5 and 6  include a single strap  118  that is looped through the face seal member  106  at two points, one point on each side of the seal contact area  114 . The strap  118  has a buckle  126  that is used to removably couple the two ends of the strap  118 . The length of the strap  118  may be adjustable using the buckle  126 . The inner region of the seal contact area  114  is open to allow the nose and mouth of the wearer to extend into the respirator  110  through the face seal member  106 . The frame  102  and/or filter layer  104  may be at least partially convex and curved or bulged away from the face seal member  106  such that a cavity  128  is formed between the filter layer  104 /frame  102  and the face seal member  106 . The cavity  128  includes air that is to be inhaled by the wearer as well as air that is exhaled from the wearer. In an alternative embodiment, the frame  102  and/or filter layer  104  may not be convex but may be disposed a distance from the face seal member  106  such that the cavity  128  is formed. 
         [0068]    The face seal member  106  shown in  FIG. 5  includes an upper portion  130  and an opposing lower portion  132  that are separated by a horizontal slot  134 . The upper and lower portions  130 ,  132  are pulled apart in opposing upward and downward directions to form the seal contact area  114 . The face seal member  106  shown in  FIG. 6  includes a one-piece molded seal contact area  114 . The one-piece molded seal contact area  114  includes a narrow nasal area  136  that receives the bridge of the nose of the wearer and a wider oral area  138  that receives the mouth of the wearer. Although the face seal member  106  shown in  FIG. 5  is not contoured to the facial features of the wearer like the face seal member  106  shown in  FIG. 6 , one or both of the face seal members  106  may include a formable nasal member  140  that allows for some customization of the fit between the seal contact area  114  and the nasal region of the wearer. As shown in  FIG. 5 , the nasal member  140  may be bendable or heat-treatable in order to provide a structure that conforms to the nasal region of the wearer and provides a better seal between the respirator  100  and the facial surfaces of the wearer. 
         [0069]      FIGS. 7-18  show various alternative embodiments of the respirator  100  shown and described herein.  FIG. 7  is a front perspective view of the respirator  100  in accordance with a preferred embodiment of the disclosure. The frame  102  of the respirator  100  is or includes a shield  142 , and a filter layer  104  (shown in  FIG. 1 ) is not mounted to an outer side of the shield  142 . The shield  142  may be formed of a non-permeable plastic material that captures splatter and prohibits contaminants from permeating therethrough. The shield  142  optionally may be transparent or semi-transparent (for example, translucent) to facilitate speech comprehension by allowing a visual indication of facial features. The shield  142  may include an exhalation valve  120 . As shown in  FIG. 9 , the shield  142  has a door  146  that rotates open to allow exhaled air out of the valve  120  to be discharged through the shield  142  into the ambient environment. 
         [0070]      FIG. 8  is a rear perspective view of the respirator  100  shown in  FIG. 7 . The respirator  100  includes a rear-facing filter member  144 . The rear-facing filter member  144  includes a filter media configured to allow for air exchange through the respirator  100  while prohibiting permeation of aerosol contaminants across the filter member  144 . For example, the rear-facing filter member  144  may be an inhalation filter to allow filtered air into the respirator  100  for the wearer to breathe. The filter member  144  is rear-facing to avoid splash contamination directly onto the filter media and also to direct inhalation airflow to the wearer away from potential sources of aerosol hazards, such as patients with respiratory illnesses. Referring now to  FIG. 10 , which shows an interior of the respirator  100  shown in  FIG. 7 , the rear-facing filter member  144  may form at least part of the face seal member  106 . As such, the face seal member  106  may comprise a filter medium that is configured to prohibit the permeation of aerosol contaminants therethrough. The rear-facing filter member  144  may be disposed rearward of the frame  102  and extend between the frame  102  and the seal contact area  114  of the face seal member  106 . As shown in  FIG. 10 , the filter member  144  is disposed leftward and rightward of the seal contact area  114  from the perspective of the wearer. Optionally, the filter member  144  may also extend downward of the seal contact area  114  to allow air from around the neck and chin to be inhaled into the respirator  100  through the filter member  114 . 
         [0071]      FIG. 11  illustrates the interior of the face seal member  106  of the respirator  100  shown in  FIG. 7  according to another embodiment. The face seal member  106  may include mounting holes  148  configured to receive replaceable filter modules  150 . The filter modules  150  may include inhalation valves  152  to better control air exchange within the respirator  100 . The inhalation valves  152  may be used in addition to the exhalation valve  120  shown in  FIGS. 7 and 9  to filter the air coming into and discharging out of the respirator  100 . Like the rear-facing filter member  144  shown in  FIG. 8 , the filter modules  150  and incorporated inhalation valves  152  may be rear-facing to minimize capture of aerosol droplets and splatter from frontal facing work tasks. 
         [0072]      FIG. 12  is a front perspective view of the respirator  100  in accordance with another embodiment of the disclosure. The frame  102  of the respirator  100  shown in  FIG. 12  is or at least includes a shield  142 . The frame  102  may include or house a front-facing filter member  154 . The frame  102  may be mounted directly to the face seal member  106  along a perimeter edge  156  of the frame  102  as shown in  FIG. 13 , which illustrates a partial cross-section of the interface  158  between the face seal member  106  and the edge  156  of the frame  102  (for example, shield  142 ). 
         [0073]      FIG. 14  is a rear perspective view of the respirator  100  shown in  FIG. 12 . The harness assembly  116  of the respirator  100  includes a harness cradle  160 . The harness cradle  160  is coupled to an upper strap  118 A and a lower strap  118 B to provide a predefined spacing between the upper and lower straps  118 A,  118 B. The harness cradle  160  may include one or more coupling straps  162  or panels. For example, the cradle  160  shown in  FIG. 14  includes two coupling straps  162  and defines a space  164  therebetween. In another embodiment, the space  164  may be filled by a panel (not shown) which may have padding. 
         [0074]      FIG. 15  is a side view of the respirator  100  according to an alternative embodiment of the disclosure.  FIG. 16  is a partial deconstructed view of the respirator  100  shown in  FIG. 15 . The respirator  100  shown in  FIGS. 15 and 16  may be semi-disposable. For example, the face seal member  106  may be a shaped molded cup (for example, having a convex shape) that is configured to insert into the frame  102 . The frame  102  may be a semi-rigid plastic that has a dual function of supporting the face seal member  106  in constant engagement with the facial surface of the wearer as well as conforms at least slightly to the contours of the face of the wearer to provide a better seal. The frame  102  may include plural contact points with the straps  118  of the harness assembly  116  to provide a balanced pulling force on the face seal member  106 . 
         [0075]      FIG. 17  is a perspective view of the respirator  100  according to another embodiment of the disclosure. The frame  102  of the respirator  100  includes support beams  168  that span across the opening  112  of the frame  102  to provide support for the face seal member  106 . At least one support beam  168  includes an integrated handling tab  170  at a frontal end  172  of the respirator  100  that is located away from the head of the wearer. The tab  170  may be positioned in the center of the frame  102 . The harness assembly  116  includes two butterfly clips  174 . The respirator  100  optionally may be fully disposable and  FIGS. 18A-18C  show various steps for disposing the respirator  100  as shown in  FIG. 17  according to an exemplary disposal process. In operation, once the wearer is finished wearing the respirator  100  and wants to discard the respirator  100  in a sanitary process, the wearer holds onto the frame  102  using the handling tab  170  (see  FIG. 18A ), and with the other hand snaps both butterfly clips  174  open, allowing the respirator  100  to be released from the head of the wearer. As the individual continues to hold the respirator  100  via the handling tab  170 , with the other hand, the wearer starts to remove a disposable glove  176  (see  FIG. 18B ) from the hand holding the handling tab  170  and pulls the glove  176  over the respirator  100  and envelops the respirator  100  (see  FIG. 18C ). Once the respirator  100  has been covered by the glove  176 , the respirator  100  is disposed. 
         [0076]      FIG. 19  is a front perspective view of the respirator  100  according to another alternative embodiment of the disclosure. The respirator  100  may be (or may be part of) a full face piece and/or a hood respirator assembly. The respirator  100  includes the frame  102 , the face seal member  106  which forms an inner face seal, a lens  178 , an outer sealing member  180 , the harness assembly  116 , and a filter member (not shown). The frame  102  may provide structure to the respirator  100 . The frame  102  may include a speech diaphragm  186 , an exhalation valve assembly  188 , and at least one inhalation valve assembly  190 . The lens  178  is mounted to the frame  102 . The lens  178  is configured to cover at least the eyes of the wearer and may be transparent or clear to allow the wearer to see through the lens  178 . The lens  178  optionally may fully cover the full frontal facial region of the wearer. 
         [0077]    The outer sealing member  180  is mounted to the frame  102 . The outer sealing member  180  may be formed from any of the materials suitable for fabrication of the base component. Most preferably, the outer sealing member  180  comprises silicone, polyisoprene, halo-butyl, a thermoplastic elastomer, or a combination thereof. The outer sealing member  180  includes a seal contact area  182  that is configured to engage a facial surface of the wearer. For example, the seal contact area  182  may contact a perimeter the face of the wearer, including but not limited to the forehead, cheeks, chin, and neck areas. The face seal member  106  is mounted to the frame  102  and/or the outer sealing member  180 . The face seal member  106  is configured to surround and engage the nasal and oral regions of the wearer. The harness assembly  116  has one or more straps coupled to at least one of the frame  102 , the lens  178 , or the outer sealing member  180 . The filter member (not shown) may be mounted within a defined opening in the frame  102  and/or the lens  178 . For example, the filter member may be mounted within the inhalation valve assembly  190  and/or the exhalation valve assembly  188 . The filter member may be a filter layer or a filter cartridge, depending on the placement and application. The filter member  184  is configured to prohibit permeation of aerosol, gas, and/or vapor contaminants therethrough. 
         [0078]    In accordance with one or more embodiments described herein, a respirator is provided that affords, among other technical effects, the technical effect of providing thermoregulation of areas in and on the respirator to provide comfort for the wearer of the respirator. One or more embodiments provide a technical effect of absorbing heat emitted by a facial surface of the wearer to provide cooling for the wearer. A technical effect may also include releasing heat onto a facial surface of the wearer and/or into air within the respirator when the ambient temperature is low to provide heating for the wearer. A technical effect of the respirator providing cooling and/or heating for the wearer is that the wearer will be more comfortable wearing the respirator, and will be more inclined to wear the respirator while exposed to aerosol, gas, and/or vapor contaminants in the air. A further effect of wearing the respirator will be that the wearer is less likely to be harmed by the contaminants in the air. 
         [0079]    While various spatial and directional terms, such as front, back, left, right, lower, upper, horizontal, vertical, and the like may be used to describe embodiments of the present disclosure, it is understood that such terms are merely used with respect to the orientations shown in the drawings. The orientations may be inverted, rotated, or otherwise changed, such that an upper portion is a lower portion, and vice versa, horizontal becomes vertical, and the like. 
         [0080]    It should also be understood that any or all of the materials disclosed herein may further include one or more additives that are well known in the art, such as surfactants, dispersants, anti-foam agents (e.g., silicone containing compounds and flourine containing compounds), antioxidants (e.g., hindered phenols and phosphites), thermal stabilizers (e.g., phosphites, organophosphorous compounds, metal salts of organic carboxylic acids, and phenolic compounds), light or UV stabilizers (e.g., hydroxy benzoates, hindered hydroxy benzoates, and hindered amines), light or UV absorbing additives (e.g., ceramic particles of Group IV transition metal carbides and oxides), lubricants, processing aids, fire retardants (e.g., halogenated compounds, phosphorous compounds, organophosphates, organobromides, alumina trihydrate, melamine derivatives, magnesium hydroxide, antimony compounds, antimony oxide, and boron compounds), anti-blocking additives (e.g., silica, talc, zeolites, metal carbonates, and organic polymers), anti-fogging additives (e.g., non-ionic surfactants, glycerol esters, polyglycerol esters, sorbitan esters and their ethoxylates, nonyl phenyl ethoxylates, and alcohol ethyoxylates), anti-static additives (e.g., non-ionics such as fatty acid esters, ethoxylated alkylamines, diethanolamides, and ethoxylated alcohol; anionics such as alkylsulfonates and alkylphosphates; cationics such as metal salts of chlorides, methosulfates or nitrates, and quaternary ammonium compounds; and amphoterics such as alkylbetaines), anti-microbials (e.g., arsenic compounds, sulfur, copper compounds, isothiazolins phthalamides, carbamates, silver base inorganic agents, silver zinc zeolites, silver copper zeolites, silver zeolites, metal oxides, and silicates), crosslinking agents, controlled degradation agents (e.g., peroxides, azo compounds, and silanes), colorants, pigments, dyes, fluorescent whitening agents or optical brighteners (e.g., bis-benzoxazoles, phenylcoumarins, and bis-(styryl)biphenyls), fillers (e.g., natural minerals and metals such as oxides, hydroxides, carbonates, sulfates, and silicates; talc; clay; wollastonite; graphite; carbon black; carbon fibers; glass fibers and beads; ceramic fibers and beads; metal fibers and beads; flours; and fibers of natural or synthetic origin such as fibers of wood, starch, or cellulose flours), coupling agents (e.g., silanes, titanates, zirconates, fatty acid salts, anhydrides, epoxies, and unsaturated polymeric acids), reinforcement agents, crystallization or nucleation agents (e.g., any material which increases or improves the crystallinity in a polymer, such as to improve rate/kinetics of crystal growth, number of crystals grown, or type of crystals grown), etc. 
         [0081]    While the present invention has been particularly shown and described with reference to preferred embodiments, it will be readily appreciated by those of ordinary skill in the art that various changes and modifications may be made without departing from the spirit and scope of the invention. It is intended that the claims be interpreted to cover the disclosed embodiment, those alternatives which have been discussed above and all equivalents thereto.