Polymerization kinetic pathways of epoxidized linseed oil with aliphatic bio‐based dicarboxylic acids

Recent advancement in synthesizing bio-epoxy nanocomposites using lignin, plant oils, saccharides, polyphenols, and natural rubbers: A review

Due to environmental issues, production costs, and the low recycling capability of conventional epoxy polymers and their composites, many science groups have tried to develop a new type of epoxy polymers, which are compatible with the environment. Considering the precursors, these polymers can be produced from plant oils, saccharides, lignin, polyphenol, and natural resins. The appearance of these bio-polymers caused to introduce a new type of composites, namely bio-epoxy nanocomposites, which can be classified according to the synthesized bio-epoxy, the used nanomaterials, or both. Hence, in this work, various bio-epoxy resins, which have the proper potential for application as a matrix, are completely introduced with the synthesis viewpoint, and their characterized chemical structures are drawn. In the next steps, the bio-epoxy nanocomposites are classified based on the used nanomaterials, which are carbon nanoparticles (carbon nanotubes, graphene nanoplatelets, graphene oxide, reduced graphene oxide, etc.), nano-silica (mesoporous and spherical), cellulose (nanofibers and whiskers), nanoclay and so on. Also, the features of these bio-nanocomposites and their applications are introduced. This review study can be a proper guide for developing a new type of green nanocomposites in the near future.

Epoxidized and Maleinized Hemp Oil to Develop Fully Bio-Based Epoxy Resin Based on Anhydride Hardeners

The present work aims to develop thermosetting resins using epoxidized hemp oil (EHO) as a bio-based epoxy matrix and a mixture of methyl nadic anhydride (MNA) and maleinized hemp oil (MHO) in different ratios as hardeners. The results show that the mixture with only MNA as a hardener is characterized by high stiffness and brittleness. In addition, this material is characterized by a high curing time of around 170 min. On the other hand, as the MHO content in the resin increases, the mechanical strength properties decrease and the ductile properties increase. Therefore, it can be stated that the presence of MHO confers flexible properties to the mixtures. In this case, it was determined that the thermosetting resin with balanced properties and high bio-based content contains 25% MHO and 75% MNA. Specifically, this mixture obtained a 180% higher impact energy absorption and a 195% lower Young’s modulus than the sample with 100% MNA. Also, it has been observed that this mixture has significantly shorter times than the mixture containing 100% MNA (around 78 min), which is of great concern at an industrial level. Therefore, thermosetting resins with different mechanical and thermal properties can be obtained by varying the MHO and MNA content.

Self-healing waterborne polyurethane coatings with high transparence and haze via cellulose nanocrystal stabilized linseed oil Pickering emulsion

Protection coatings with self-healing ability can significantly enhance their anti-corrosion properties and service life. In this study, self-healing waterborne polyurethane (WPU) coatings with high transparence and haze were facile fabricated via cellulose nanocrystal (CNC) stabilized linseed oil (LO) Pickering emulsion. Sustainable CNCs displayed outstanding emulsifying ability and stability to stabilize LO Pickering emulsion. The size of LO Pickering emulsion droplets decreases with the CNC concentration, while the emulsion fraction and surface coverage by CNCs increase with CNC concentration, leading to a more stable Pickering emulsion. The self-healing rates of WPU coatings at varied time, temperature, CNC and catalyst concentration were investigated. Higher temperature, larger emulsion droplets, and with driers employed as catalysts generally lead to faster self-healing rate. The WPU self-healing coatings displayed much better abrasion resistance and mechanical properties than pristine WPU due to the incorporation of CNCs. Moreover, the WPU self-healing coatings show a high transparence and haze due to light scattering, and their applications as coatings of lamp covers and glass to achieve uniform light distribution and privacy protection with high light transmission were further demonstrated.

Kinetic Analysis of the Curing Process of Biobased Epoxy Resin from Epoxidized Linseed Oil by Dynamic Differential Scanning Calorimetry

The curing process of epoxy resin based on epoxidized linseed oil (ELO) is studied using dynamic differential scanning calorimetry (DSC) in order to determine the kinetic triplet (E_a, f(α) and A) at different heating rates. The apparent activation energy, E_a, has been calculated by several differential and integral isoconversional methods, namely Kissinger, Friedman, Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS) and Starink. All methods provide similar values of E_a (between 66 and 69 kJ/mol), and this shows independence versus the heating rate used. The epoxy resins crosslinking is characterized by a multi-step process. However, for the sake of the simplicity and to facilitate the understanding of the influence of the oxirane location on the curing kinetic, this can be assimilated to a single-step process. The reaction model has a high proportion of autocatalytic process, fulfilling that α_M is between 0 and α_p and α_M < αp∞. Using as reference the model proposed by Šesták–Berggren, by obtaining two parameters (n and m) it is possible to obtain, on the one hand, the kinetic parameters and, on the other hand, a graphical comparison of the degree of conversion, α, versus temperature (T) at different heating rates with the average n and m values of this model. The good accuracy of the proposed model with regard to the actual values obtained by DSC gives consistency to the obtained parameters, thus suggesting the crosslinking of the ELO-based epoxy has apparent activation energies similar to other petroleum-derived epoxy resins.

Interpretation and Physical Meaning of Kinetic Parameters Obtained from Isoconversional Kinetic Analysis of Polymers

Several successful examples—where physically sounded kinetic information was obtained from thermoanalytical data in different application fields, such as polymerization of thermosetting resins, biobased polymers and nanocomposites, crystallization and glass transition of semi-crystalline polymers and their nanocomposites—are here presented and discussed. It is explained how the kinetic parameters obtained from advanced isoconversional methods can be interpreted in terms of reaction mechanisms or changes in the rate-limiting step of the overall process, in the case of complex chemical reactions or complex physical transitions, and how these parameters can be used to extract model-fitting parameters.