Mechanical Recyclability of TPS/PVA Blends and Their Comparison with Other Bioplastics

Thermoplastic starch-PVA blends currently present great potential since they show stable mechanical performance along with the advantage of compostability and self-biodegradability in the marine environment. However, one step further could be attained if this ocean-friendly compound could be mechanically recycled and then promote circular economy applications before its final composting. The main goal of this work is to study, for the first time, the mechanical recyclability of TPS/PVA compounds up to ten cycles, using blends based on potato, wheat, and cassava starch. Furthermore, the results are compared to those obtained by reprocessing commercial PLA and PHB compounds. As the mechanical reprocessing cycles proceed, all TPS/PVA compounds retain the mechanical performance after ten cycles, and especially toughness is also maintained. At the same time, there is evidence of some chain scission in starch, observed in earlier cycles for cassava-based compounds, although it is ultimately superior in a potato mixture. Interestingly, the starch syneresis progress as well as some chain scission allows a stable melt-flow index, up to cycle 10. In addition, wheat compounds could have the highest recycling potential, with less chain scission and syneresis, being able to redistribute the plasticizer in the starch-rich phase, improving its plasticization. Regarding commercial biopolymers, PLA loses toughness dramatically from cycle 4 and PHB from cycle 1, and the melt-flow index increases sharply, denoting a significant polymer degradation and poor recyclability potential.