Agurtzane Mugica

Biodegradable polymer matrices, PCL and PBSA were used to fabricate magnetic composites with recycled NdFeB and rare earth-free lab-synthesized ferrite fillers (SrFe₁₂O₁₉ and SrFe₁₂O₁₉–CoFe₂O₄) across a wide filling range (1–90%).

A real-world laboratory accident highlights underestimated dermal risks posed by reactive isocyanates. First-aid actions and essential safety insights are shared to reinforce best laboratory safety practices.

Neodymium‐iron‐boron (NdFeB) magnets are essential because they show optimized magnetic properties for clean energy applications. They suffer nevertheless from their rare earth mine security of supply. The European Union considers them as key materials, encouraging their recycling to reduce the supply dependence on other countries. In this work, biodegradable poly(ε‐caprolactone) (PCL) is used to obtain PCL/NdFeB micro‐composites, with recycled NdFeB loadings of 0.25, 0.50, 0.75, 1.00, and 5.00 wt.%. Three different preparation techniques are employed: “melt mixing,” “solution‐mixing,” and “solution mixing and precipitation.” The crystallization behavior is studied by Differential Scanning Calorimetry (DSC) and morphology by Polarized Light Optical Microscopy (PLOM) and Phase Contrast Microscopy (PCM). Non‐isothermal and isothermal DSC experiments showed that the nucleation effect of NdFeB magnetic micro‐particles on PCL is more effective in the case of micro‐composites prepared by “solution and precipitation”. Non‐isothermal experiments evidenced the largest increase in the crystallization temperature, while the isothermal experiments showed the highest acceleration in the overall crystallization rate for the samples prepared by “solution and precipitation”. Besides, self‐nucleation tests confirmed these samples' most significant increase in nucleation efficiency. Finally, the nucleation effect of NdFeB micro‐particles on PCL is also proven by the reduction in spherulitic size observed after NdFeB particle incorporation.

In this work, we study for the first time, the isothermal crystallization behavior of isodimorphic random poly(butylene succinate)-ran-poly(ε-caprolactone) copolyesters, PBS-ran-PCL, previously synthesized by us. We perform nucleation and spherulitic growth kinetics by polarized light optical microscopy (PLOM) and overall isothermal crystallization kinetics by differential scanning calorimetry (DSC). Selected samples were also studied by real-time wide angle X-ray diffraction (WAXS). Under isothermal conditions, only the PBS-rich phase or the PCL-rich phase could crystallize as long as the composition was away from the pseudo-eutectic point. In comparison with the parent homopolymers, as comonomer content increased, both PBS-rich and PCL-rich phases nucleated much faster, but their spherulitic growth rates were much slower. Therefore, the overall crystallization kinetics was a strong function of composition and supercooling. The only copolymer with the eutectic composition exhibited a remarkable behavior. By tuning the crystallization temperature, this copolyester could form either a single crystalline phase or both phases, with remarkably different thermal properties.

Nanocomposites based on polycarbonate (PC) and different amounts of untreated graphene nanoplatelets (GnP) (from 1 to 7 wt %) were prepared by melt blending. The nanocomposites were thoroughly characterized employing the following techniques: broad band dielectric spectroscopy, thermally stimulated depolarization currents, differential scanning calorimetry, tensile testing, dynamic mechanical thermal analysis, and water vapor, carbon dioxide and oxygen permeability measurements. The presence of a MWS relaxation mode indicated the accumulation of electrical charges trapped at the interfaces of the polycarbonate with graphene 2D platelets. The addition of GnP produced nanocomposite materials with enhanced mechanical and barrier properties. The melt mixed PC/graphene nanocomposites prepared here exhibit well‐balanced properties, even though unmodified graphene nanoplatelets were used. In addition, the nanocomposites were obtained by a single extrusion process, which is easily scalable for industrial applications. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44654.

Employing the hydroxyl groups on the surface of Cloisite® 30B montmorillonite (Cl30B), the ring-opening polymerization of L-lactide was performed with a metal-free catalyst to yield a PLLA-g-Cl30B nanohybrid with low M_n grafted PLLA chains (i.e., 9 kg mol⁻¹). This nanohybrid was then melt mixed with PLA 4032D from NatureWorks, which is a slow-crystallizing PLA as it contains 2% D-isomers and has a high M_n value (i.e., 123 kg mol⁻¹). The samples were characterized by TEM, WAXS, SAXS, DSC and Polarized Light Optical Microscopy (PLOM) in order to study their crystallization kinetics in depth. The dispersion of the nanoclay was excellent and much better in the PLA/PLLA-g-Cl30B nanocomposites in comparison to PLA/Cl30B blends prepared as reference. In order to ascertain the role of the nanoclay, analogue PLA/PLLA blends without Cl30B were also prepared. The spherulitic crystallization kinetics from the melt was determined for all samples. The growth rate of neat PLA was accelerated approximately 3 times by incorporating the PLLA-g-Cl30B nanohybrid with an inorganic content of 5%. The overall crystallization kinetics from the glassy state of PLA was also accelerated in a similar way by the nanohybrid addition. Nevertheless, the PLA/PLLA blends crystallized even faster indicating that the dominant effect that causes the acceleration of the crystallization of PLA is the plasticization of PLA by the low M_n PLLA molecules. The changes in T_g of PLA also support this explanation. In the case of the PLA/PLLA-g-Cl30B nanocomposites, even though the plasticizing effect of the PLLA chains still dominates, their action is counterbalanced by their tethering on one end, as they are grafted to the surface of the exfoliated clay nanoplatelets.

The synthesis of symmetric cyclo poly(ε‐caprolactone)–block–poly(l(d)‐lactide) (c(PCL–b–PL(D)LA)) by combining ring‐opening polymerization of ε‐caprolactone and lactides and subsequent click chemistry reaction of the linear precursors containing antagonist functionalities is presented. The two blocks can sequentially crystallize and self‐assemble into double crystalline spherulitic superstructures. The cyclic chain topology significantly affects both the nucleation and the crystallization of each constituent, as gathered from a comparison of the behavior of linear precursors and cyclic block copolymers. The stereochemistry of the PLA block does not have a significant effect on the nonisothermal crystallization of both linear and cyclo PCL‐b‐PDLA and PCL‐b‐PLLA copolymers. image