Synthesis and Thermomechanical Properties of Polyurethanes and Biocomposites Derived from Macauba Oil and Coconut Husk Fibers

Abstract

This work reports on a very effective route to produce bio-based polyurethanes (PUs) and composites with high content of renewable carbon sources. The PUs are prepared with polyols synthesized from macauba oil (Acrocomia aculeata) and methylene diphenyl diisocyanate, at different [NCO]/[OH] molar ratios. Later, biocomposites are prepared with the as-obtained PUs reinforced with coconut husk fibers. The successful synthesis of natural oil-based polyols is ascribed to the hydroxylation and consumption of carbon-carbon double bonds in the fatty acid chains of the original starting oil as attested by FTIR spectroscopy. According to different thermal analysis techniques (TG, DTG, and DTA), the increase in the [NCO]/[OH] molar ratio improves the thermal stability of PUs, likely due to an increase of crosslinks. Dynamic mechanical analysis evidences the reinforcement effect of coconut husk fibers in bio-based PUs. The present PUs and composites are of low-cost and environmentally friendly materials for structural applications.

Omniphobic polyurethane – superabsorbent polymer – fluoropolymer surface coating on cotton fabric for chemical protection and thermal comfort

“…34 The extra peaks at 2954 cm À1 and 2845 cm À1 correspond to the asymmetric and the symmetric stretching of methylene (-CH 2 -) groups. 35 The -NH and -CH 2 vibrations were detected by the peaks at 1448 and 1260 cm À1 , respectively. 36 The broadening in the band between 3200 cm À1 to 3600 cm À1 corresponding to OHstretching of cotton fibre (Figures 3(a) and (b)) indicates the formation of H-bond between hydroxyl groups (-OH) of cellulose polymer and carbonyl groups (>C = O) of PU.…”

Thermosetting polymers from renewable sources

“…Such polyols react with diisocyanates to give bio‐based polyurethanes. Polyols from SOY, LIN, sunflower, canola, COR, 85 castor, 86,87 passion fruit, 88 and macauba oils have been polymerized with methylene diphenyl diisocyanate to give polyurethanes 89 . In order to increase the mechanical properties of SOY‐based waterborne anionic polyurethane dispersions (PUDs), emulsion copolymerization of AESO with acrylic comonomers was performed, resulting in hybrid latexes with similar properties to polypropylene‐glycol‐based polyurethane/acrylic hybrid latex films 90,91 .…”

Flammability and mechanical behavior of cotton fiber polymeric composite laminate with polyurethane and alumina trihydrate

“…The use of raw materials, from renewable sources, for research involving green polymers as substitutes for petroleum-based polymers, and the manufacture of bio-composites, showed a great growth. 1–6 The main reason for these researches is to decrease the risk of environmental damage caused by petroleum-based polymers and synthetic fibers. 7–9…”