'SINGLE-SITE' CATALYZED POLYOLEFIN FOR FRESH-CUT PRODUCE PACKAGING - A COMPARISON BETWEEN MONOEXTRUDED BLENDS AND COEXTRUDED FILM

摘要

Single-site and Metallocene catalyzed polymers, such as polyolefin plastomers (POPs) are unique due to their narrow molecular weight distribution (MWD) and comonomer distribution (CD). These factors can dramatically enhance the properties such as toughness, clarity, sealability and oxygen transmission rate. While linear low-density polyethylene (LLDPE) exhibits excellent physical properties and drawdown capability, the combination of both resins via blending or coextrusion provides a mix of film properties very difficult to achieve with individual components. This study examines the performance of monoextruded blown film made from blends of POP1 (0.9038 gm/cc density) and POP2 (0.8996 gm/cc density) with LLDPE (0.922 gm/cc), versus coextruded film made of POP1 40 % (1.0 mil) / LLDPE 60 % (1.5 mil). In addition, a bimodal resin (0.9175 gm/cc) was also compared with the above materials for the fresh-cut produce packaging application. Both monoextruded and coextruded films can be used for modified atmosphere packaging (MAP) of fresh-cut produce. Coextruded film is the best option for low respiration products because of its excellent sealing performance over other monoextruded films. The end use requirements at the reduced cost are better satisfied by bimodal resin film compared to monoextruded films made of POP1 and POP2 with higher LLDPE contents. Monoextruded blends of POPs with lower LLDPE content (< 40 %_w) exhibit most of the property requirements of moderate to high respiration rate fresh-cut produce.