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. 2023 Mar 22;15(6):1589.
doi: 10.3390/polym15061589.

Tailor-Made Bio-Based Non-Isocyanate Polyurethanes (NIPUs)

Juan Catalá  1 , Irene Guerra  1 , Jesús Manuel García-Vargas  1 , María Jesús Ramos  1 , María Teresa García  1 , Juan Francisco Rodríguez  1
Affiliations

Tailor-Made Bio-Based Non-Isocyanate Polyurethanes (NIPUs)

Juan Catalá et al. Polymers (Basel). .

Abstract

Non-isocyanate polyurethanes (NIPUs) based on biobased polyamines and polycarbonates are a sustainable alternative to conventional polyurethanes (PU). This article discloses a novel method to control the crosslinking density of fully biobased isocyanate-free polyurethanes, synthesized from triglycerides carbonated previously in scCO2 and different diamines, such as ethylenediamine (EDA), hexamethylenediamine (HMDA) and PriamineTM-1075 (derived from a dimerized fatty acid). As capping substances, water or bioalcohols are used in such a way that the crosslinking density can be adjusted to suit the requirements of the intended application. An optimization of the NIPU synthesis procedure is firstly carried out, establishing the polymerization kinetics and proposing optimal conditions set for the synthesis of the NIPUs. Then, the influence of the partial blocking of the active polymerization sites of the carbonated soybean oil (CSBO), using monofunctional amines, on the physical properties of the NIPUS is explored. Finally, the synthesis of fully biobased NIPUs with a targeted crosslinking density is achieved using hybrid NIPUs, employing partially carbonated oil and H2O or ethanol as blockers to achieve the desired physical properties in a very precise manner.

Keywords: CSBO; NIPU; crosslink; cyclic carbonate; priamine; tailor-made; vegetable oil.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Main synthesis routes for NIPU synthesis.
Scheme 1
Scheme 1
Polyaddition of carbonated triglycerides and diamines. Cyclic carbonate groups and derivatives are in red. Amine groups in green.
Figure 2
Figure 2
FT-IR NIPU spectra and carbonyl urethane/CC deconvolution (T = 100 °C, A/CC = 1, t = 30 min).
Figure 3
Figure 3
FT-IR integrated data for the development of the NIPU curing process. (T = 100 °C, A/CC = 1, t = 0–24 h).
Figure 4
Figure 4
A/CC molar ratio swelling index results within a 24 h curing time (T = 100 °C).
Figure 5
Figure 5
Temperature influence on swelling index results (A/CC = 1.1, t = 0–24 h).
Scheme 2
Scheme 2
Multistep modified-functionality NIPU synthesis mechanism (blocking method). Cyclic carbonate groups and derivatives are in red. Amine groups in green.
Figure 6
Figure 6
Swelling index results for the f′CC study.
Figure 7
Figure 7
TGA analysis results. (a) EDA, (b) HMDA, (c) Pr–1075, (d) Pr–1075–DBA.
Figure 8
Figure 8
DSC analysis results. (a) EDA, (b) HMDA, (c) Pr–1075, (d) Pr–1075–DBA.
Figure 9
Figure 9
Glass transition temperature (Tg) NIPU values.
Figure 10
Figure 10
Tensile strength results (ASTM 412-D). (a) Stress at break, (b) elongation at break, (c) Young’s modulus.
Scheme 3
Scheme 3
Hybrid NIPU synthesis (f′CC tunning). Cyclic carbonate groups and derivatives are in red. Amine groups in green. Epoxide groups and derivatives in blue.
Figure 11
Figure 11
Swelling index comparative results of NIPU–HNIPUs.
Figure 12
Figure 12
HNIPUs TGA analysis. (a) HNIPUs (H2O), (b) HNIPUs (EtOH).
Figure 13
Figure 13
Glass transition temperature (Tg) comparative values for NIPU-HNIPUs.
Figure 14
Figure 14
Tensile strength results for H-NIPUs (ASTM 412-D). (a) Stress at break, (b) elongation at break, (c) Young’s modulus.
Figure 15
Figure 15
SEM photographs of the internal structure of the NIPUs. (a) Inner part, (b) full section.
See this image and copyright information in PMC

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