Flexible and Bio‐Based Nonisocyanate Polyurethane (NIPU) Foams

Study on non-isocyanate polyurethane (NIPU) has been gaining attention as an environmentally friendly alternative to conventional polyurethane. However, current non-isocyanate polyurethane foams (NIPUFs) face limitations in practical applications due to its low mechanical strength and limited flame retardancy. In this study, tannic acid-based non-isocyanate polyurethane resins were synthesized using tannic acid with good chemical reactivity and flame retardancy as precursors. Tannic acid-based non-isocyanate rigid polyurethane foam (T-NIPUF) was then prepared using hexamethylenetetramine, citric acid, and glutaraldehyde as crosslinking agents. The structure of the synthesized T-NIPUF was analyzed using FT-IR and 1 H NMR, and the mechanical properties and flame retardancy according to the various crosslinking agent contents were evaluated by UTM, SEM, TGA, LOI, and ignition tests.

Catalytic carbon dioxide fixation by carbonation of glycerol, trimethylolpropane and pentaerythritol glycidyl ether, followed by curing with citric acid amino amides in the presence of cellulose carbonate, represents an attractive green chemistry route to non-isocyanate polyurethanes (NIPU) and bio-based NIPU composites. In comparison to traditional polyurethanes, neither fossil resources nor toxic isocyanates are required. The glycidyl ethers react with carbon dioxide in the presence of tetrabutylammonium bromide catalyst to produce the cyclic carbonates of glycerol (GGC), pentaerythritol (PEC), and trimethylolpropane (TMC). The carbon dioxide fixation is 22.4 wt% for GGC, 29.5 wt% for PEC and 28.3 wt% for TMC. The preferred bio-based curing agent comprises a blend (CAA) containing hexamethylene diamine (HMDA) and citric acid amino amides, prepared by polycondensation of triethyl citrate with excess HMDA. According to the in situ ATR-FTIR-monitoring of urethane formation, the addition of 1,4-diazabicyclo[2.2.2]octan (DABCO) as the catalyst enables room temperature curing, whereas in the absence of DABCO 70 °C is required. In comparison to the very soft GGC resins, the GGC–PEC and GGC–TMC blends, cured with HMDA and CAA, improve simultaneously the glass transition temperature from 20 to 58 °C and Young's modulus from 7 to 2500 MPa, unparalleled by the individual blend components. The phosgene-free conversion of cellulose with diphenyl carbonate affords cellulose carbonate as a coreactive bio-based filler for the preparation of cellulose–NIPU composites with in situ urethane-mediated interfacial coupling.

A method for obtaining non-isocyanate polyurethane (NIPU) foams from cyclic carbonate (CC) based on soybean oil was developed. For this purpose, cyclic carbonate was synthesized from epoxidized soybean oil and CO2 using various ionic liquids (ILs) as catalysts. Among the tested ILs, the highest selectivity (100%) and CC yield (98%) were achieved for 1-ethyl-3-methylimidazolium ([emim]Br). Without any purification, the resulting cyclic carbonate was reacted directly with diethylenetriamine as a model crosslinking agent to produce NIPU foams. It was found that the soybean oil-based CC synthesized with bromide imidazolium ionic liquids exhibited significantly shorter gelling times (8 min 50 s for [emim]Br and 9 min 35 s for [bmim]Br) compared to those obtained with the conventional TBAB catalyst (26 min 15 s). A shorter gelling time is a crucial parameter for the crosslinking process in foams. The obtained foams were subjected to mechanical tests and a morphology analysis.

The present study investigates the effect of the biodegradation time on the properties of condensation segmented nonisocyanate polyurethanes (NIPUs) using the aerobic strain of Gordonia alkanivorans. Polyurethane samples were prepared from phenolsulfonic acid, benzoic acid, polytetramethylene glycol (PTMG 1000) or oligooxypropylene triol (G 1000) and different amounts of formaldehyde. The emulsifying activity, protein concentration, pH, tensile strength and strain at break were evaluated as function of biodegradation time and formaldehyde content. The existence of a segmented structure was confirmed by the existence of two phase transitions in the glass transition temperatures of flexible segments and melting temperatures of hard segments. The tensile strength (TS) of NIPUs based on PTMG 1000 and 50% excess of formaldehyde decreased by about 20%, 60% and 95% after 10, 21 and 90 days of biodegradation. TS decrease was less pronounced for NIPUs prepared from G1000. The 21 days biodegradation caused the most significant changes in the pH, emulsifying activity and protein concentration. The highest degree of cross-linking induced by an excess of formaldehyde led to the highest resistance of NIPU to Gordonia alkanivorans. The DSC, FTIR, SEM and element concentration analyses demonstrated that biodegradation occurred mainly in hydrolysis sensitive hard segments and, to a lesser extent, in flexible oligomerol segments.

A partially biobased self-blowing and self-hardening polyurethane foam from glucose-based non-isocyanate polyurethanes (g-NIPU) was prepared by reaction of glucose with dimethyl carbonate and hexamethylene diamine. However, these foam types generally require a high foaming temperature. In this paper, a self-blowing foam based on g-NIPU was prepared at room temperature by using maleic acid as an initiator and glutaraldehyde as a crosslinker. Water absorption, compression resistance, and fire resistance were tested. Scanning electron microscopy (SEM) was used to observe the foam cells structure. Middle infrared (ATR FT-MIR) and Matrix Assisted Laser Desorption Ionization Time-of-Flight (MALDI-TOF) mass spectrometry were used to help to analyze the reactions during the foaming process. The results obtained showed that self- blowing rigid foams have good compression, this being directly proportional to the foam density. Increasing the amount of glutaraldehyde or reducing maleic acid thickens the cell walls and increases the density of the foams. MALDI-TOF analysis showed that g-NIPU reacts with both maleic acid and glutaraldehyde. The foams presented poor fire resistance indicating that, as for isocyanate based polyurethane foams, addition of a fire retardant would be necessary.

Fabrication of ultraviolet resistant and anti-bacterial non-isocyanate polyurethanes using the oligomers from the reductive catalytic fractionated lignin oil

Nonisocyanate polyurethane (NIPU) thermoset networks were produced from a novel soybean-oil-derived poly(vinyl ether) (i.e., poly[(2-vinyoxy)ethyl soyate]) possessing cyclic carbonate functional groups in the fatty acid ester side chains of the polymer. Three different linear aliphatic diamines, namely, 1,6-hexamethylenediamine, 1,9-nonanediamine, and 1,13-tridecanediamine, were used to cross-link the cyclic carbonate-functional poly[(2-vinyoxy)ethyl soyate] [C-poly(2-VOES)]. All three of these diamines can be readily obtained from renewable resources. For comparison purposes, analogous NIPU networks were produced using cyclic carbonate-functional soybean oil (CSBO) in place of the C-poly(2-VOES). The chemical, thermal, viscoelastic, and mechanical properties of the six NIPU networks were characterized. With regard to the chemical nature of the soy-based, carbonate-functional component, it was found that the polymeric nature of C-poly(2-VOES) resulted in very different NIPU properties compared to analogou...

To improve the chemical resistance of non-isocyanate polyurethane (NIPU), two kinds of diglycidyl ether, bisphenol AF (E-AF) and perfluorooctyl glycidyl ether (PFGE), were selected to synthesize two different cyclic carbonates, bisphenol AF (EC-AF) and perfluorooctyl cyclic carbonate (PFGC), respectively. These cyclic carbonates were successfully used to prepare fluorine-containing non-isocyanate polyurethane coatings. The effects of PFGC amounts on the properties of NIPU were studied, and it was found that the contact angles of water, diiodomethane, and hexadecane were increased with the addition of PFGC and up to 106.7°, 80.2°, and 72.7°, respectively, whereas the pendulum hardness of NIPU coatings relatively decreased with the increase in PFGC contents. The NIPU coatings exhibited excellent flexibility, adhesion, and impact resistance. They also displayed good thermal stability with 5% weight loss temperature (T5%) ranging from 249 to 271°C. Moreover, these coatings possessed very low water uptake, excellent hydrophobic/oleophobic properties, and corrosion resistance properties.

Synthesis and characterization of 1 K waterborne non-isocyanate polyurethane epoxy hybrid coating

Non-isocyanate polyurethanes (NIPUs) represent a sustainable alternative to conventional isocyanate-based systems, eliminating toxic reagents while maintaining good performance. In this study, bio-based NIPU coatings were synthesized from carbonated soybean oil (CSBO) via the carbonation of epoxidized soybean oil (ESBO) using carbon dioxide (CO2), followed by polymerization with ethylenediamine (EDA) and varying concentrations of 3-aminopropyltriethoxysilane (APTES) (0–20 wt%). The amine groups of EDA and APTES participate in the ring-opening of cyclic carbonates to form β-hydroxyurethane linkages, while the triethoxysilane moieties of APTES may undergo hydrolysis–condensation to produce Si–O–Si domains, resulting in a β-hydroxyurethane–siloxane hybrid network. The optimized formulation CEA-5 exhibited the best, including a tensile strength of 3.3 MPa, elongation at break of ~150%, glass transition temperature (Tg) of ~7 °C, and thermal stability up to ~350 °C, where major thermal degradation happens. The synthesized coating material also shows adhesion (3.6 MPa on oak for CEA-10), hydrophobic behavior (water contact angle (WCA) ~102° for CEA-5), good chemical and ultraviolet (UV) resistance, and shape memory. The synergistic effect of urethane hydrogen bonding and siloxane crosslinking imparted enhanced toughness, flexibility, and durability. These findings express a scalable, eco-friendly strategy for producing silane-modified NIPU coatings with good mechanical, thermal, and coating performance suitable for sustainable industrial coating and adhesive applications.

Diamine derivatives of dimerized fatty acids and bio-based polyether polyol as sustainable platforms for the synthesis of non-isocyanate polyurethanes

Chapter 7 - Nonisocyanate Polyurethanes

Experiments were performed to characterize the mechanical response of a 15 pcf flexible polyurethane foam to large deformation at different strain rates and temperatures. Results from these experiments indicated that at room temperature, flexible polyurethane foams exhibit significant nonlinear elastic deformation and nearly return to their original undeformed shape when unloaded. However, when these foams are cooled to temperatures below their glass transition temperature of approximately -35 o C, they behave like rigid polyurethane foams and exhibit significant permanent deformation when compressed. Thus, a new model which captures this dramatic change in behavior with temperature was developed and implemented into SIERRA with the name Flex_Foam to describe the mechanical response of both flexible and rigid foams to large deformation at a variety of temperatures and strain rates. This report includes a description of recent experiments. Next, development of the Flex Foam model for flexible polyurethane and other flexible foams is described. Selection of material parameters are discussed and finite element simulations with the new Flex Foam model are compared with experimental results to show behavior that can be captured with this new model.

In this work, three different cyclic carbonates are obtained from renewable diols and transformed into carbamates by reacting them with renewable 11‐amino undecanoic acid methyl ester to synthesize non‐isocyanate poly(ester urethane)s in a sustainable manner. A procedure using 2,3‐butanediol (2,3‐BDO) as a renewable starting material to synthesize a cyclic carbonate with dimethyl carbonate (DMC) is introduced, catalyzed by 1,5,7‐triazabicylco[4.4.0]dec‐5‐ene (TBD). Three purification strategies, i.e., column chromatography, extraction, and distillation, are compared regarding their E‐Factors. Propylene glycol (PG) and ethylene glycol (EG) are used as alternative starting materials to broaden the substrate scope and compare material properties, their cyclic carbonates likewise react to carbamates with 11‐amino undecanoic acid methyl ester. All carbamates are then polymerized in a bulk polycondensation reaction, yielding non‐isocyanate polyurethanes (NIPUs), specifically poly (ester urethane)s, with molecular weights (Mn) up to 10 kDa. Complete characterization is reported using differential scanning calorimetric (DSC), size exclusion chromatographic measurements (SEC), 1H‐NMR as well as IR spectroscopy. The rheological properties of the poly(ester urethane)s are investigated in the framework of small amplitude oscillatory shear (SAOS) and uniaxial elongation.

Bio- and CO2-sourced non-isocyanate polyurethane (NIPU) microcellular foams were prepared using supercritical carbon dioxide (scCO2) foaming technology.