Novel Epoxidized Brazil Nut Oil as a Promising Plasticizing Agent for PLA.

This work evaluates for the first time the potential of an environmentally friendly plasticizer derived from epoxidized Brazil nut oil (EBNO) for biopolymers, such as poly(lactic acid) (PLA). EBNO was used due to its high epoxy content, reaching an oxirane oxygen content of 4.22% after 8 h of epoxidation for a peroxide/oil ratio of 2:1. Melt extrusion was used to plasticize PLA formulations with different EBNO contents in the range of 0-10 phr. The effects of different amounts of EBNO in the PLA matrix were studied by performing mechanical, thermal, thermomechanical, and morphological characterizations. The tensile test demonstrated the feasibility of EBNO as a plasticizer for PLA by increasing the elongation at break by 70.9% for the plasticized PLA with 7.5 phr of EBNO content in comparison to the unplasticized PLA. The field-emission scanning electron microscopy (FESEM) of the fractured surfaces from the impact tests showed an increase in porosity and roughness in the areas with EBNO addition, which was characteristic of ductile failure. In addition, a disintegration test was performed, and no influence on the PLA biodegradation process was observed. The overall results demonstrate the ability of EBNO to compete with other commercial plasticizers in improving the ductile properties of PLA.

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.

Physicochemical Characterization of Novel Epoxidized Vegetable Oil from Chia Seed Oil.

In this study, a novel epoxidized vegetable oil (EVO) from chia seed oil (CSO) has been obtained, with the aim to be employed in a great variety of green products related to the polymeric industry, as plasticizers and compatibilizers. Previous to the epoxidation process characterization, the fatty acid (FA) composition of CSO was analyzed using gas chromatography (GC). Epoxidation of CSO has been performed using peracetic acid formed in situ with hydrogen peroxide and acetic acid, applying sulfuric acid as catalyst. The effects of key parameters as temperature (60, 70, and 75 °C), the molar ratio of hydrogen peroxide:double bond (H2O2:DB) (0.75:1.0 and 1.50:1.0), and reaction time (0-8 h) were evaluated to obtain the highest relative oxirane oxygen yield (Yoo). The evaluation of the epoxidation process was carried out through iodine value (IV), oxirane oxygen content (Oo), epoxy equivalent weight (EEW), and selectivity (S). The main functional groups were identified by means of FTIR and 1H NMR spectroscopy. Physical properties were compared in the different assays. The study of different parameters showed that the best epoxidation conditions were carried out at 75 °C and H2O2:DB (1.50:1), obtaining an Oo value of 8.26% and an EEW of 193 (g·eq-1). These high values, even higher than those obtained for commercial epoxidized oils such as soybean or linseed oil, show the potential of the chemical modification of chia seed oil to be used in the development of biopolymers.

Comparative Study of the Properties of Plasticized Polylactic Acid with Maleinized Hemp Seed Oil and a Novel Maleinized Brazil Nut Seed Oil.

In this study, for the first time, Brazil nut seed oil was chemically modified with maleic anhydride to obtain maleinized Brazil nut seed oil (MBNO). The same process was developed to obtain maleinized hemp seed oil (MHO). The use of MBNO and MHO was studied as bio-based plasticizers by incorporating them with different contents ranging from 0 to 10 phr in a polylactic acid (PLA) matrix. By means of mechanical, thermal and thermomechanical characterization techniques, the properties of the different formulations were studied to evaluate the plasticizing effect of the MBNO and MHO. With the addition of both plasticizers, a significant increase in ductile properties was observed, reaching an increase in elongation at break of 643% with 7.5 phr MBNO and 771% with 10 phr MHO compared to neat PLA. In addition, it has been observed that the mechanical resistant properties do not decrease, since the oils enhance the crystallization of PLA by increasing the free volume between its chains and counteracting the effect. Finally, a disintegration test was carried out under thermophilic conditions at 58 °C for 27 days, demonstrating that the incorporation of MHO and MBNO does not significantly affect the biodegradability of neat PLA.

Contribution to a Circular Economy Model: From Lignocellulosic Wastes from the Extraction of Vegetable Oils to the Development of a New Composite.

The present works focuses on the development of a novel fully bio-based composite using a bio-based high-density polyethylene (Bio-HDPE) obtained from sugar cane as matrix and a by-product of extraction of chia seed oil (CO) as filler, with the objective of achieving a circular economy model. The research aims to revalorize an ever-increasing waste stream produced by the growing interest in vegetable oils. From the technical point of view, the chia seed flour (CSF) was chemically modified using a silane treatment. This treatment provides a better interfacial adhesion as was evidenced by the mechanical and thermal properties as well as field emission scanning electron microscopy (FESEM). The effect of silane treatment on water uptake and disintegration rate was also studied. On the other hand, in a second stage, an optimization of the percentage of treated CSF used as filler was carried out by a complete series of mechanical, thermal, morphological, colour, water absorption and disintegration tests with the aim to evaluate the new composite developed using chia by-products. It is noteworthy as the disintegration rate increased with the addition of CSF filler, which leads to obtain a partially biodegradable wood plastic composite (WPC) and therefore, becoming more environmentally friendly.

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 (Ea, f(α) and A) at different heating rates. The apparent activation energy, Ea, 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 Ea (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 αM is between 0 and αp and αM < αp∞. Using as reference the model proposed by Sesták-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.

Development of Polylactic Acid Thermoplastic Starch Formulations Using Maleinized Hemp Oil as Biobased Plasticizer.

In this study, hemp seed oil was reacted with maleic anhydride in an ene reaction to obtain maleinized hemp seed oil (MHO). The use of MHO as a plasticizer and compatibilizer has been studied for polylactic acid (PLA) and thermoplastic starch (TPS) blends (80/20, respectively). By mechanical, thermal and morphological characterizations, the addition of MHO provides a dual effect, acting as plasticizer and compatibilizer between these two partially miscible biopolymers. The addition of MHO up to 7.5 phr (parts by weight of MHO per hundred parts of PLA and TPS) revealed a noticeable increase in the ductile properties, reaching an elongation at break 155% higher than the PLA/TPS blend. Furthermore, contrary to what has been observed with maleinized oils such as linseed oil, the thermal properties do not decrease significantly as a result of the plasticizing effect, due to the compatibilizing behavior of the MHO and the natural antioxidants present in the oil. Finally, a disintegration test was carried out in aerobic conditions at 58 °C, for 24 days, to demonstrate that the incorporation of the MHO, although causing a slight delay, does not impair the biodegradability of the blend, obtaining total degradation in 24 days.