In the present state of technology, there is substantial interest in the use of plastic materials for containers and package liners, as well as for food contact applications. Plastic materials have been accepted as being quite acceptable for disposable applications since the plastic materials are normally much less expensive than glass and metal, and, if properly designed, they are more readily disposable than metal. A substantial challenge to the wider use of plastic materials in the food packaging industry is that many polymeric food packaging applications require substantial barrier properties to prevent the transmission of gases, such as oxygen and carbon dioxide, and other chemicals, such as moisture. As mentioned above, one such food packaging application is as a package liner and/or food container. However, the plastic material must also meet certain performance criteria in order to be used for such an application. For example, it is important that the plastic liner and/or container exhibit sufficient resistance to transmission of gases such as oxygen. The liner material must be substantially free from imperfections and cracks which could permit gas transmission, and the liner should be free of pinholes, lacerations, scratches and nicks. The liner should also be free of blemishes and/or spots of discoloration to avoid the production of a commercially unacceptable package product. In order to assure a desirable food-packaging container, it is necessary to have a barrier against gas and moisture permeation through the package's wall to prevent spoilage. The desired degree of barrier can be obtained by coating a container plastic with a barrier layer which will provide a satisfactory barrier. An adhesion between the barrier material and the base material is also desired. Coating an aluminum foil base with a thin organic vapor barrier layer is one method of obtaining a barrier to gas and moisture transmission. Frequently, however, this coating is not satisfactory in practice because the coating tends to flake off. For example, the commonly used barrier film materials are polyvinylidene chloride ("PVDC") and acrylonitrile copolymers. A problem with both of these materials is that they generally have some detrimental properties, including reduced light transmission, brittleness and the tendency to absorb moisture. Other common coating materials are polyvinyl alcohol ("PVA"), polyvinyl chloride ("PVC") and polyethylene terephthalate ("PET"). However, PVA and PVC are not suitable for many applications because of their flammability. PET films are also not completely gas impermeable and may not be used in certain medical applications, since in certain uses certain drugs can be discolored or destroyed by PET. In order to avoid the problems associated with the use of the common coating materials, attempts have been made to improve the barrier properties of plastics by blending certain plastic materials with certain materials, such as epoxy resins, phenolics and/or inorganic oxides and/or salts. For example, U.S. Pat. Nos. 4,472,469 and 4,526,877 disclose certain blends of PET, ethylene vinyl alcohol and/or polyethylene terephthalate with an inorganic oxide filler to form a barrier layer for gas permeation. These blends were disclosed as being useful for containers and other articles of manufacture. However, the problem with the compositions of the above patents are that they do not have a good moisture barrier. In fact, moisture is actually transmitted through them. Also, it is often difficult to print on these blends. Furthermore, the barrier properties of these compositions may degrade over time at certain elevated temperatures. It would be desirable to have an improved composition which will exhibit sufficient gas barrier properties for use as a food package container and also have a low moisture transmission rate. Also, it would be desirable to have a barrier composition which can be coated onto a plastic substrate without flaking or delaminating and a barrier coating which can be processed or printed on relatively easily. Also, it would be desirable to have an improved barrier composition which could be formed into a container or film and which can be easily molded or extruded, yet, still exhibits sufficient barrier properties for commercial acceptance. It would also be desirable to have an improved barrier material which can be used to form a package having a hermetically sealed seam. Many of the problems associated with the prior art have been overcome with the barrier compositions and method of the present invention, which is described in detail below.