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Shear-induced formation of crystal nuclei in polyamide 11 (PA 11) was studied using a conventional parallel-plate rheometer. Crystallization of PA 11 after shearing the melt at different rates for 60 s was followed by the evolution of the complex viscosity. The sheared samples showed in an optical microscope a gradient structure along the radius, due to the increasing shear rate from the center to the edge. The critical shear rate for shear-induced formation of nuclei was identified at the position where a distinct change of the semicrystalline superstructure is observed, being at around 1 to 2 s−1. Below this threshold, a space-filled spherulitic superstructure developed as in quiescent-melt crystallization. Above this value, after shearing at rates between 1 and 5 s−1, an increased number of point-like nuclei was detected, connected with formation of randomly oriented crystals. Shearing the melt at even higher rates led to a further increase of the nuclei number and growth of crystals oriented such that the chain axis is in parallel to the direction of flow. In addition, optical microscopy confirmed formation of long fibrillar structures after shearing at such condition. The critical specific work of flow of PA 11 was calculated to allow a comparison with that of polyamide 66 (PA 66). This comparison showed that in the case of PA 11 more work for shear-induced formation of nuclei is needed than in the case of PA 66, discussed in terms of the chemical structure of the repeat unit in the chains. Graphical abstract

Bio-based composites made of poly(L-lactic acid) (PLLA) and β-cyclodextrin/d-limonene inclusion complex (CD-Lim) were prepared by melt extrusion. Encapsulation of volatile d-limonene molecules within β-cyclodextrin cages was proven to be a successful strategy to prevent evaporation during high-temperature processing. However, small amounts of limonene were released upon processing, resulting in the plasticization of the polymeric matrix. Morphological analysis revealed good dispersion of the filler, which acted as a nucleating agent, favoring the growth of PLLA crystals. The composites′ lowered glass transition temperature upon the addition of CD-Lim was also proved by thermomechanical analysis (DMA). Moreover, DMA revealed constant stiffness of modified materials at room temperature, which is crucial in PLLA-based formulations.

Cynara Cardunculus plant was used as source of seed oil. The epoxidized oil (ECO) and presscake waste fibers (CP) recovered from post-oil extraction, were recombined for developing PLA functional biocomposites, according to “zero waste” circular economy approach. Different compositions of PLA/CP and PLA/CP/ECO were prepared in form of platelets and investigated by thermal, morphological, structural and mechanical analyses. The poor interfacial adhesion between the hydrophobic PLA matrix and short, hydrophilic and randomly dispersed presscake fibers, well evidenced by morphological analysis, was responsible of PLA thermal degradation hastening, Tg decreasing and tensile properties dropping down, since no mechanical stress transfer occurred from the polymer to the dispersed phase. The inclusion of ECO slightly improved the above properties due to its mild compatibilizing action inducing a fairly tightening of the macromolecular structure. The recycling of CP waste fibers was effective in hastening the polymer biodegradation in common soil under environmental conditions. Indeed, biocomposites recovered after 90 days of soil burial tests evidenced morphological features typical of late stage PLA biodegradation, a drastic dropping down of molecular weights and a decreasing of PLA thermal stability. These experimental evidences, not detected in soil buried neat PLA, assessed that the inclusion of CP waste fibers inside PLA matrix, represented a valid route to promote a fast and easy PLA biodegradation if compared to the composting method commonly used, for which severe atmosphere conditions and specific microbial population are necessary.

The performances of a commercial Mg/Al hydrotalcite (Pural© MG76) in biodiesel production have been tested in an autoclave and in a continuous packed bed reactor. The obtained results have shown that calcined Mg/Al hydrotalcite (Pural© MG76) is a promising heterogeneous catalyst for biodiesel production because is sufficiently active, deactivates slowly and can easily be regenerated.

In this work, biodegradable films based on poly (lactic acid) (PLA) and corn thermoplastic starch (TPS), additivated with epoxidized cardoon oil plasticizer (ECO) at 3% by weight with respect to PLA mass fraction, were prepared by melt extrusion process and compression molding. The effect of ECO on structural, thermal, mechanical, barrier, and spectral optical properties of the films was investigated. Spectroscopic analysis evidenced the development of physical interaction between oil and polymers, mainly PLA. In addition, no oil migration occurrence was detected after six months of film preparation, as evidenced by oil mass evaluation by precipitation as well as by 1H-NMR methods, thus highlighting the good inclusion of oil inside the polymeric network. The plasticizing action of the oil induced a lean improvement of the interfacial adhesion between hydrophobic PLA and hydrophilic TPS, particularly accentuated in PLA80_ECO composition, as evidenced by morphological analysis of blend fracture surfaces. TGA data underlined that, differently from TPS-based films, PLA-based systems followed one degradative thermal profile suggesting a slight compatibilization effect of epoxidized oil in these films. The shifting of Tg values, by differential scanning calorimetry (DSC) analysis, indicated a weak miscibility at molecular level. Generally, in the investigated blends, the phase separation between PLA and TPS polymers was responsible for the mechanical properties failing, in particular, the tensile strength evidenced a negative deviation from the rule of mixtures, particularly marked in TPS-based blends, where no physical entanglements occurred between the polymers since their immiscibility even in presence of ECO. The epoxidized oil strongly improved the barrier properties (water vapor permeability (WVP) and oxygen permeability (O2P)) of all the films, likely developing a physical barrier to water and oxygen diffusion and solubilization. With respect to neat PLA, PL80 and PL80_ECO films evidenced the improvement of surface wettability, due to the presence of polar groups both in TPS (hydroxyl residues) and in epoxidized oil (oxirane rings). Finally, following to the conditioning in climatic chamber at T = 25 &deg, C and RH = 50%, PLA80 film became opaque due to TPS water absorption, causing a light transmittance decreasing, as evidenced by spectral optical analysis.