Due
to the depletion of fossil fuels, higher oil prices, and greenhouse
gas emissions, the scientific community has been conducting an ongoing
search for viable renewable alternatives to petroleum-based products,
with the anticipation of increased adaptation in the coming years.
New academic and industrial developments have encouraged the utilization
of renewable resources for the development of ecofriendly and sustainable
materials, and here, we focus on those advances that impact polyurethane
(PU) materials. Vegetable oils, algae oils, and polysaccharides are
included among the major renewable resources that have supported the
development of sustainable PU precursors to date. Renewable feedstocks
such as algae have the benefit of requiring only sunshine, carbon
dioxide, and trace minerals to generate a sustainable biomass source,
offering an improved carbon footprint to lessen environmental impacts.
Incorporation of renewable content into commercially viable polymer
materials, particularly PUs, has increasing and realistic potential.
Biobased polyols can currently be purchased, and the potential to
expand into new monomers offers exciting possibilities for new product
development. This Review highlights the latest developments in PU
chemistry from renewable raw materials, as well as the various biological
precursors being employed in the synthesis of thermoset and thermoplastic
PUs. We also provide an overview of literature reports that focus
on biobased polyols and isocyanates, the two major precursors to PUs.
To achieve sustainably-sourced polymers from algae, azelaic acid was prepared from an algae oil waste stream and converted into a flexible polyurethane foam. The heptanoic acid co-product was converted into both a flavoring and a renewable solvent.
In the transition to renewably sourced, biodegradable polymers, the preparation of low viscosity polyester‐polyols has posed a challenge for renewable polyurethane (PU) development. Low viscosity polyols not only reduce the requirement for high process temperatures but also decrease manufacturing time. In our efforts to incorporate increasing ratios of bio‐based monomers into renewable PUs, we mixed diacids such as even carbon sebacic acid and odd carbon azelaic acid along with a renewable diol. This provided library of 2000 g/mol molecular weight polyester‐polyols, and structures were established by 1H and 13C NMR analysis. The prepared polyester‐polyols offered lower viscosity and enable lower fabrication temperatures to make TPUs, and their structure and material metrics were evaluated. The formation of TPUs is ascertained from FTIR and NMR analysis. The final TPUs displayed good physical and mechanical properties. These TPUs exhibited Tg in the range of −56.5 to −39.7°C, corresponding to TPU soft block structure, and Tm between 98.3 and 105.1°C originating from the hard segment. Prepared TPUs exhibit excellent biodegradation under compost environmental conditions. These TPUs showed up to 57% decrease in molecular weight by GPC analysis after 9 weeks of biodegradation, and respirometer analysis displayed up to 97% biodegradation over 120 days.
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