Methods and systems for the preparation of molded plastic articles having a structural barrier layer

A method of co-extruding a plurality of polymeric plastic material streams to produce a resulting molded plastic article, the method comprising the steps of:

• forming in an injection nozzle a three-layer combined polymeric plastic stream, the combined stream comprising an interior core stream of a first polymeric material encased by an inner stream of a second polymeric material and an outer stream of the second polymeric material;
• injecting the combined stream into a mold cavity configured to form a resulting molded plastic article having a sidewall portion;
• and
• adjusting a volumetric flow ratio of the inner stream to the outer stream during injection of the combined stream into the mold cavity a plurality of times to intentionally form a plurality of cohesion members from the interior core stream that structurally interlock an interior layer of the resulting molded plastic article formed from the interior core stream with an inner layer of the resulting molded plastic article formed from the inner stream, with an outer layer of the resulting molded plastic article formed from the outer stream, or with both, the plurality of cohesion members disposed in the sidewall portion of the resulting molded plastic article away from a leading edge and a trailing edge of the interior layer,
• wherein each of the plurality of cohesion members is a structural element in the resulting molded plastic article having a first interior layer segment that overlaps a second interior layer segment or a protrusion extending from the interior layer into the inner layer, the outer layer, or both.