Mirna Alejandra Mosiewicki

This work investigates the effect of a bio-based plasticizer derived from used sunflower oil on the crystallization behavior of poly (lactic acid) (PLA), comparing it with that of the conventional plasticizer tributyrin. This study aims to explore biodegradable alternatives to petroleum-based materials and to evaluate their potential in modulating PLA crystallization kinetics without altering the crystalline structure of the resulting sustainable material solutions with tailored performance. PLA-based films containing 5%, 10%, and 15% plasticizer were prepared and characterized by differential scanning calorimetry (DSC), polarized optical microscopy (POM), and X-Ray diffraction (XRD). DSC analysis showed a decrease in the glass transition temperatures upon plasticization, with tributyrin producing a more pronounced effect than the recycled sunflower oil plasticizer. XRD patterns confirmed that the crystalline form of PLA remained unchanged regardless of plasticizer type or content. POM revealed that both plasticizers influenced crystallization kinetics, with the bio-plasticizer promoting larger and more sparsely distributed spherulites than tributyrin, indicating differences in nucleation efficiency and crystal growth. Crystallization kinetics were further analyzed using the Avrami model, the Lauritzen-Hoffman theory, and the isoconversional method. Avrami analysis indicated that nucleation mechanisms were largely unaffected, although the overall crystallization rate increased upon plasticization. Lauritzen-Hoffman analysis confirmed crystallization in Regime III, controlled by nucleation, while isoconversional analysis showed reduced activation energy in plasticized PLA. These findings highlight the ability of bio-derived plasticizers to modulate PLA crystallization, promoting the valorization of a food industry residue as a sustainable plasticizer. This study hopes to contribute relevant knowledge to emerging areas of polymer processing, such as 3D printing, to develop sustainable and high-performance PLA-based materials.

The natural aging of polymers obtained by polymerization of chemically modified oleic or lauric acids with a precursor based on soybean oil was evaluated by comparing infrared spectra, color parameters, contact angles, thermal degradation temperatures, dynamic mechanical properties, and the characteristic nanoscale parameters of positron annihilation lifetime spectra, obtained for samples recently prepared and aged at room temperature for 24 months. The results denoted that physicochemical changes occurred in the materials due to aging, which were evidenced as variations in some structural and physical properties in all the studied polymers. These changes were explained in terms of the network characteristics (i.e., crosslinking density, pendant dangling chains, steric impediment, presence of labile double bonds) and the competitive degradative processes (i.e., crosslinking, chain scission, formation of small volatile molecules) that take place during aging. Results from positron annihilation lifetime spectroscopy indicated that although the average free volume of the tested samples remained almost constant after aging, the number of nanoholes decreased because smaller voids disappeared, thus changing free volume hole size distribution. This study is the result of a careful and systematic experimental design, lasting more than 2 years, therefore representing a considerable investment of time, effort, and resources to produce findings that are not only scarce but also crucial for advancing the development of new materials, especially those based on biomass. Practical Applications : The physicochemical and mechanical characteristics of these polymers, with high green carbon content and environmental benefits, can be tailored for use in different applications by selecting the type and proportion of the precursor in the formulation. In turn, the effects of natural aging are of fundamental importance when defining the type and duration of use. Their characteristics, both before and after natural aging, make them good candidates for structural, decorative, and surface protection applications, especially in indoor environments.

A highly functionalized biobased derivative of ricinoleic acid (MMRA) was synthesized through a two‐step procedure: maleinization of the hydroxyl group naturally present in this fatty acid followed by methacrylation of the carboxylic acid groups. The chemical structure of MMRA was confirmed by ¹H NMR, infrared spectroscopy, gel permeation chromatography and analytical determinations. Thermoset polymers were further obtained by the free radical polymerization of MMRA with different amounts of styrene. The dependence of the color/transparency and tensile properties on sample composition was evaluated. Moreover, thermogravimetric and dynamic mechanical analyses were carried out to further characterize the obtained materials. All polymers were highly translucent with lightness values in the range 87.4–90.8 and opacity values below 13%. Their glass transition temperatures (T_g) ranged from 61.5 °C for the homopolymer MMRA to 104 °C for the copolymer containing 30 wt% MMRA. The rubbery storage modulus increased with MMRA content confirming the high functionality of the green precursor that led to polymers with high crosslinking density. Notably, pronounced damping capacity was also found in all copolymers made from MMRA / styrene. © 2021 Society of Chemical Industry

Fatty acid based precursors were synthesized by a one‐step reaction from oleic or lauric acids and glycidyl methacrylate to be used later in polymer formulations. Different times of reaction, amounts of catalyst and initial ratios of reactants were evaluated, obtaining conversions higher than 0.9 for the best conditions. The monomers obtained are interesting alternatives to synthetics since they combine low cost with environmental advantages (i.e. higher bio‐carbon content). These polymeric precursors were reacted separately in cationic and free radical polymerizations with styrene (50 wt%) to evaluate their potential as greener monomers. The lauric acid precursor and free radical polymerization were the alternatives that produced elastomeric materials with higher glass transition temperatures and storage moduli. These results were related to the lesser plasticizing effect of the shorter fatty acid chain, in comparison with that of the oleic acid based monomer, and to a lower free volume in the formed structure during curing. Moreover, all the obtained polymers exhibited shape memory properties that can be activated by temperature changes. © 2018 Society of Chemical Industry

The activation of unconstrained shape recovery in bio‐based polymeric nanocomposites is successfully achieved using magnetic nanoparticle heating. The materials investigated in this work present several distinct physical and chemical characteristics worth pointing out: they can be deformed and the original shape can be recovered by remotely heating the samples above their switching temperature, which is determined by their glass transition temperatures. Also, their chemical composition is largely based on biomass (the polymeric matrix contains more than 50 wt.% of raw tung oil). Magnetic heating performance is strongly affected by both the physical properties and the concentration of the nanoparticles loaded into the matrix. The concentration of nanoparticles is associated with the formation of agglomerates or clusters, which determines the dipolar interactions among the nanoparticles. The particles used in this work are able to absorb enough energy from an alternating magnetic field to heat the matrix and initiate the shape recovery. Although the sample with the highest content of magnetic solute (10 wt.%) presents the highest degree of agglomeration, it is also the sample with the best remote activation of shape recovery, according to the temperature reached under magnetothermal measurements and the time of actuation.

A series of flexible polyurethane foams with different polyol compositions were synthesized through the replacement of a portion of the petroleum‐based polyether polyol with biobased polyols, namely, glycerol (GLY) and hydroxylated methyl esters (HMETO). HMETO was synthesized by the alkaline transesterification of tung oil (TO; obtaining GLY as a byproduct) and the subsequent hydroxylation of the obtained methyl esters with performic acid generated in situ. FTIR spectroscopy, ¹H‐NMR, and different analytical procedures indicated that the hydroxyl content increased significantly and the molecular weight decreased with respect to those of the TO after the two reaction steps. The characterization of the obtained foams, achieved through the measurement of the characteristic reaction times, thermal and dynamic mechanical analysis, scanning electronic microscopy, and density measurements, is reported and discussed. The most important changes in the modified foams were found with the addition of GLY to the formulation; this led to an increased foam density and storage rubbery modulus, which were associated with a higher crosslinking density because of the decrease in the chain length between crosslinking points. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43831.