The main objective of this research was to evaluate the properties of sheet containing mechanically recycled post-consumer polylactic acid (PLA) bottle flakes blended with virgin PLA resin. PLA bottles were flaked, cleaned, blended with virgin resin and then extruded and thermoformed into trays. The molecular weight, physical, optical, thermal and mechanical properties of sheet containing 0, 20, 40, 60, 80 and 100 wt.-% recycled content were evaluated. Cleaning conditions were evaluated using response surface methodology, and conditions of 15 min, 85°C, 1 wt.-% NaOH, and 0.3 wt.-% surfactant were adopted for cleaning the PLA flake. Virgin PLA sheet possessed superior properties to recycled sheet with statistically significant differences at α=0.05. PLA sheets were darker and absorbed more UV light in the 260 to 285 nm range when 20% or more recycled content was added. At 40% recycled content, the sheet had increased blue and red tones and the mechanical properties in the cross-machine direction decreased. At 60% recycled content or above, reduction of weight average molecular weight (M w), tensile strength and tensile strength at yield in the machine direction (MD) were found. At 80% recycled content, the melting temperature and modulus of elasticity in the MD decreased. All of the sheet samples were successfully thermoformed into trays.
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