Economics of Coextruded Barrier Structures, 1990 Polymers, Laminations & Coatings Conference Proceedings

Metal and glass are traditional packaging materials which have been displaced in countless applications by plastics. Those applications still in metal and glass are generally ones, in which, no single plastic material has the necessary economics and performance properties. coextrusion, either for packaging (sheet) or containers (blowmolding), offers an alternative in that combinations of various structural properties unobtainable from a single resin.

With proper attention to process and tooling design details, high nitrile barrier resins (HNR’s) have been added to the list of coextrudable resins. Its use in coextruded structures combines the advantages of the AN/MA copolymer, such as excellent chemical resistance, gas barrier, formability, rigidity and optical clarity with those of the polyolefins such as moisture barrier and higher heat distortion temperature. With presently available technology, these coextrusions reduce costs: both by usage of lower cost resins and by recycling of trim and forming scrap.

This paper will describe the experience of BP Chemicals in the coextrusion of its high nitrile polymer family known as Barex resins. It will focus mainly on coextrusion blowmolding and its associated economics although the procedures are amenable to other forms of coextrusion such as sheet, pipe and film.