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The effect of poly(lactic acid) (PLA) content on the curing of polyethylene glycol (PEG) based polyurethanes (PU) was investigated. Aiming to produce biobased PU foams, pentamethylene diisocyanate (PDI) was used. Fourier transform infrared spectroscopy (FTIR) found no curing evidence at 30 C and verified that the curing was completed at 300 C. This method tracks hydrogen bonding and NCO consumption.

Synthesis of bio‐polyurethane (Bio‐PU) using isosorbide (ISO) and poly(lactic acid) (PLA) diols, (propanediol based poly(lactic acid) (PLAP) and PLA esterified with Soybean oil (PLASO)) and pentamethylene (PDI) isocyanate were performed. Crosslinked Bio‐PUs were obtained, and the details of the curing kinetics were determined via Fourier transform infrared spectroscopy (FTIR) spectra and differential scanning calorimetry (DSC). Distinct curing behaviors between Bio‐PUs with different PLA diol formulations were observed. The addition of PLAP and PLASO increased the curing conversion at approximately 460% higher than Bio‐PU without PLA content, as verified by FTIR. The curing peak temperature (Tp) of Bio‐PUs with PLAP ranged from 94 to 163°C, while for PLASO Tp was 132–175°C. Bio‐PUs based on PLA diols displayed lower activation energy (Ea) during curing as demonstrated using Friedman model, and higher thermal stability as evidenced through thermogravimetric analyses. Reported data offer reliable tools to evaluate the best rote to synthesize biobased polyurethane and manipulate the degree of crosslinking based on composition and processing conditions, allowing product processing to the desired application.

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In this work eggshell membrane was added as biobased curing catalyst to epoxy (DGEBA), for comparison purposes the synthetic catalyst DEH 35 data was reported, the curing of compounds was followed through differential scanning calorimetry (DSC) under dynamic conditions and their kinetics were modeled using Kissinger, Friedman, Friedman model based and Málek approaches. From evaluated E A and ln A two steps of curing were verified, for the synthetic catalyst compound (S 5 ) E A abruptly increased for the degree of conversion 0.7 α > the opposite trend was observed for the eggshell membrane compound (M 10 ). It is supposed for S 5 E A increases due to the competitive reactions leading to viscosity increase until reach the solid phase with decrease of the reactive groups availability, hampering the crosslinking, whereas for M 10 E A decreases at 0.7 α > , hence invalidating the Kissinger model which assumes constant E A .

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This work investigated the curing and degradation behavior of compounds made with 1:1 of bisphenol A diglycidyl ether and epoxidized soybean oil, cured with itaconic acid (ITA) and succinic acid (SUC), coded as EP/ITA and EP/SUC. Complex peaks observed in differential scanning calorimetry are mostly due to the catalyzed curing and homopolymerization. Fourier transform infrared spectroscopy spectra suggest that the curing follows the SN 2 reaction mechanism for both compounds. Lower activation energies of curing were verified for EP/ITA compared to the EP/SUC, mainly due to their greater reactivity with the epoxy matrix at temperatures below the acids structures and melting points. Regarding thermal degradation, four steps were verified: acid degradation, degradation of the non-cross-linked material, degradation of cross-linked material, and carbon decomposition. EP/SUC with a molar ratio equal to 0.4 presented the lowest activation energy for degradation. The degradation's solid-state mechanisms analysis indicated that in EP/ITA and EP/SUC compounds the processes are controlled by nucleation and subsequent growth.

Polyurethane (PU) synthesis based on poly(ethylene glycol) (PEG) with isosorbide (ISO) and pentamethylene diisocyanate (PDI), named (ISOPUs) was carried out targeting PUs from renewable sources. The cross-linked ISOPUs were produced and the details of the curing kinetics were determined via Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). DSC scans displayed exotherms between 100 and 200 C, related to cross-linking. ISO addition accelerated the curing and the maximum curing rate (Cmax), with 91 C and 0.2964 min À1 for the compound with 70% ISO. FTIR spectra confirmed the interaction between OH (ISO/PEG) and NCO (PDI) groups, with total NCO consumption (band at 2267 cm À1 ).Through the thermogravimetric analyses (TGA), the PU/70% ISO presented weight loss at 146 C due to the degradation of ISO. ISOPUs displayed a decreased activation energy (Ea) during curing over a range of 100 to 42 kJ/mol for 0 < α < 5%, as demonstrated using the Friedman model, and higher thermal stability as evidenced through TG analyses. Curing and degradation kinetics were modeled using Friedman (FR), Kissinger-Akahira-Sunose (KAS), and Ozawa-Flynn-Wall (OFW). Overall, ISO accelerated the curing rate and increased the degradation Ea, suggesting high thermal stability for PUs with intermediate ISO contents, that is, 30%-50%. K E Y W O R D S biobased polyurethane, curing and degradation kinetics, Isosorbide, pentamethylene diisocyanate, poly(ethylene glycol) 1 | INTRODUCTION Polyurethanes (PU) based on renewable sources, such as bio-based polyols and diisocyanates are being synthesized with the objective to replace PUs from non-renewable sources, such as petroleum, and to reduce the use of toxic isocyanates. The synthesis of bio-based PUs from alternative resources, such as glucose has been growing considerably due to its potential to modify the mechanisms of curing and degradation, providing greater chemical, and physical stability. 1-4 In this context, Wang et al. 5 successfully cross-linked thermosetting PUs through the reaction of a bio-based diol with a monocyclic acetal structure and a trifunctional isocyanate reinforced with carbon fibers.The resulting material presented higher performance for application in the automotive, aerospace, and sports equipment industries.Polyurethanes synthesis takes place through urethane bonds by the polymerization of flexible segments (polyether or polyester), known as polyols, which have one or more OH groups, and rigid segments (diisocyanates) which have two or more NCO groups.