Assessing the Potential of Farm Dairy Effluent as a Filler in Novel PLA Biocomposites

The migration from the concept of waste streams to untapped side streams has meant that by-products from industrial processes are being investigated as sustainable resources. As a side stream containing cellulosic fibre, the influence of integrating farm dairy effluent (FDE) in polylactic acid (PLA) was investigated and compared with wood sander dust (SD). The mechanical and thermal properties of injection moulded specimens were evaluated as a function of filler type. The investigation indicated that FDE had similar density to SD but a lower stiffness attributed to the presence of proteins and the lesser amount of cellulose. The Young's moduli of the FDE composites were higher than the neat PLA, however, the tensile strength generally decreased but remained comparable to those filled with SD. Thermo-mechanical analysis indicated an improvement in the storage modulus of all composites containing 40 wt% of either filler above the glass transition temperature of PLA. Tensile testing of specimens that were exposed to accelerated weathering indicated a faster decrease in properties for the FDE composites compared to those filled with SD. The FDE composites degraded at least twice as fast as neat PLA and SD composites, which was tentatively attributed to the acids (e.g. fatty and amino-acids) contained in FDE and not present in SD. These findings revealed that using extrusion and injection moulding processes, FDE has potential as a composite filler from an improved stiffness and UV accelerated degradation perspectives.