the most direct ways to increase the gas barrier characteristics of a pet container are a to increase the wall thickness of the container or b to put a barrier coating on the container.1. to the inside&mdashif approved for foodcontact.2. to the outside of the finished bottle.3. in a process which remains precommercial, to the preform itself before it is stretchblown.a barrier coating can also provide two additional benefits 1 it may help to resist creep in a container for carbonated products and 2 with certain sensitive products such as wine, an internal siox coating would assure a totally inert glass contact surface. a potentially more costeffective and flexible solution currently being proposed is to increase the gas barrier properties of the pet resin itself by taking advantage of the chemically active nature of the oxygen molecule, and using a &ldquoscavenger&rdquo molecule preblended into the pet resin, to entrap &ldquooxidize&rdquo the oxygen within the bottle wall before it reaches packaged product. 
