Starch is a renewable natural biopolymer; it can be converted into thermoplastic starch (TPS). TPS has been investigated in detail in the recent decades for the plastic usage. It is renewable and biodegradable, but pure TPS has limited utility due to poor processability and mechanical properties; Polyethylene (PE) is the most common polymer for manufacturing flexible packaging films today, but it is made from fossil resources and not renewable. Recently, a new type of renewable polyethylene became commercially available; it is made from bio-ethylene from bioethanol through fermentation of sugarcane sucrose from sugarcane.   The bio-based PE (Bio-PE) is renewable and has similar properties and processability of petroleum-derived PE.To enlarge the processing window of TPS, PE and Bio-PE were applied in this study to blend with TPS. The structure-property relationship of different PE/TPS blend systems will be discussed in this presentation. Different film performance was revealed for these two different blend systems-PE/TPS and Bio-PE/TPS.To improve the dispersion of TPS phase and obtain high performance blend films, TPS was processed into masterbatch (TPSM) first, and then blend with PE or Bio-PE. These new blend systems (PE/TPSM and Bio-PE/TPSM) led to improved mechanical properties of the final films.  Due to the large difference in polarity between TPS and PE, these two biopolymers are not compatible. Without compatibilizer, the film quality of the Bio-PE/TPS films was poor due to severe incompatibility and phase separation. The effect of different compatibilizers on the film quality and mechanical properties were also compared and discussed for PE/TPS and Bio-PE/TPS blend systems.In summary, multiple blend systems of TPS, TPSM, PE, and Bio-PE with and without compatibilizers were processed into films, their mechanical properties were compared and studied related to phase structure. The morphology of these blend systems was investigated by scanning electron microscopy (SEM).

New innovations in renewable thermoplastic starch based materials

247th National Meeting (2014)

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