Evaluation of Injection-moldable PLA- and PHA-based Biocomposites for Horticultural Application: Processing, Properties, and Performance

Replacement of petroleum-based materials with renewable materials for plant pots (containers) is a priority for the horticulture industry, and the majority of containers that are used in horticulture are injection molded.  The goals of our research were to develop and characterize the processing, properties, and performance of six injection-moldable biocomposites made with base resins of polylactic acid (PLA) or polyhydroxyalkanoate (PHA) and evaluated for use in the model application of sustainable horticulture containers.  Resins of PLA or PHA were combined with fillers of soy protein, distillers dry grains with solubles (DDGS), lignin, BioRes™, or selected combinations of these fillers and were evaluated for their processability on common injection molding equipment and for their suitability to fulfill the functional requirements of the model application.  We conclude that, with proper management of material moisture content and thermal processing profiles, all six biocomposites are suitable for processing on standard compounding equipment and molding on standard injection-molding machines.  Results from mechanical testing and application trials indicate that all of the materials fulfill the functional requirements for horticultural production of common greenhouse crops, and two of the materials, PLA-Lignin (90/10) and PHA-DDGS (80/20), should be sufficiently durable for culture of long-cycle nursery crops.