Investigation of mechanical and physical properties of chemically foamed Polylactic acid for the purpose of plant growth

This study was to investigate the mechanical and physical properties of chemically foamed Polylactic acid (PLA) for the purpose of plant growth in horticulture. PLA is a biodegradable polymer that shows promising suitability in varied fields by incorporating certain chemical foaming agents (CFA). For this study, we blended PLA with varied CFA concentrations using hot melt extrusion (HME) and then characterized the batches of PLA/CFA blends to optimise plant growth. The conducted studies (i.e., density, water holding content (WHC), foam expansion, porosity, and air-filled porosity (AFP) demonstrated that the addition of CFAcould improve the structural properties of PLAand support plant growth by enhancing water retention based on the porous structure in the finalized blends. In addition, a saturation point can be observed beyond which the additional CFA has no significant effect on the density, porosity, or water-holding capacity of the PLA matrix. Regarding the mechanical performance, a negative impact of CFA concentration can be seen, where the tensile strength reduced from 32.61MPa to 15MPa, and Young’s modulus decreased from 0.792GPa to 0.365GPa for the finalized blends. In addition, an elevated potential of Hydrogen (pH) value can be seen based on the increasing CFA concentrations, where a pH7 can be found in the 0wt% and a pH8.4 can be found in the 50wt% CFA. This high pH value decreases the mineral nutrients and, therefore, a growth inhibition can be seen. Overall, this study advances the understanding of foamed PLA as a potential alternative to peat as a growing media and lays a foundation in sustainable plant growth substrate, including a substituted foaming agent such as critical CO 2 extrusion and an addition of a controlled-release fertilizer to promote the effectiveness of PLA matrix. • Foamed PLA enhances water retention for plant growth. • Higher CFA levels reduce PLA density, aiding porosity. • Excess CFA lowers tensile strength, limiting structural use. • Optimal CFA level found for density without collapse. • Successful germination obtained from foamed PLA material.