The influence of carbon multi-walled nanotubes (MWCNTs) and halloysite nanotubes (HNTs) on the physical, thermal, mechanical, and electrical properties of EVA (ethylene vinyl acetate) copolymer was investigated. EVA-based nanocomposites containing MWCNTs or HNTs, as well as hybrid nanocomposites containing both nanofillers were prepared by melt blending. Scanning electron microcopy (SEM) images revealed the presence of good dispersion of both kinds of nanotubes throughout the EVA matrix. The incorporation of nanotubes into the EVA copolymer matrix did not significantly affect the crystallization behavior of the polymer. The tensile strength of EVA-based nanocomposites increased along with the increasing CNTs (carbon nanotubes) content (increased up to approximately 40% at the loading of 8 wt.%). In turn, HNTs increased to a great extent the strain at break. Mechanical cyclic tensile tests demonstrated that nanocomposites with hybrid reinforcement exhibit interesting strengthening behavior. The synergistic effect of hybrid nanofillers on the modulus at 100% and 200% elongation was visible. Moreover, along with the increase of MWCNTs content in EVA/CNTs nanocomposites, an enhancement in electrical conductivity was observed.

A series of poly(hexamethylene 2,5-furanodicarboxylate)-block-poly(tetrahydrofuran) (PHF-b-F-pTHF) copolymers were synthesized using a two-stage procedure, employing transesterification and polycondensation. The content of pTHF flexible segments varied from 25 to 75 wt.%. ¹H nuclear magnetic resonance (NMR) and Fourier transformed infrared spectroscopy (FTIR) analyses were applied to confirm the molecular structure of the materials. Differential scanning calorimetry (DSC), dynamic mechanical measurements (DMTA), and X-ray diffraction (XRD) allowed characterizing the supramolecular structure of the synthesized copolymers. SEM analysis was applied to show the differences in the block copolymers’ morphologies concerning their chemical structure. The influence of the number of flexible segments in the copolymers on the phase transition temperatures, thermal properties, as well as the thermo-oxidative and thermal stability was analyzed. TGA analysis, along with tensile tests (static and cyclic), confirmed the utilitarian performance of the synthesized bio-based materials. It was found that an increase in the amount of pTHF caused the increase of both number-average and weight-average molecular weights and intrinsic viscosities, and at the same time causing the shift of the values of phase transition temperatures toward lower ones. Besides, PHF-b-F-pTHF containing 75 wt.% of F-pTHF units was proved to be a promising thermoplastic shape memory polymer (SMP) with a switching temperature of 20 °C.

In this work, hybrid filler systems consisting of multi-walled carbon nanotubes (MWCNTs) and nano carbon black (nCB) were incorporated by melt mixing in low-density polyethylene (LDPE). To hybrid systems a mixture of MWCNTs and nCB a mass ratio of 1:1 and 3:1 were used. The purpose was to study if the synergistic effects can be achieved on tensile strength and electrical and thermal conductivity. The dispersion state of carbon nanofillers in the LDPE matrix has been evaluated with scanning electron microscopy. The melting and crystallization behavior of all nanocomposites was not significantly influenced by the nanofillers. It was found that the embedding of both types of carbon nanofillers into the LDPE matrix caused an increase in the value of Young’s modulus. The results of electrical and thermal conductivity were compared to LDPE nanocomposites containing only nCB or only MWCNTs presented in earlier work LDPE/MWCNTs. It was no synergistic effects of nCB in multi-walled CNTs and nCB hybrid nanocomposites regarding mechanical properties, electrical and thermal conductivity, and MWCNTs dispersion. Since LDPE/MWCNTs nanocomposites exhibit higher electrical conductivity than LDPE/MWCNTs + nCB or LDPE/nCB nanocomposites at the same nanofiller loading (wt.%), it confirms our earlier study that MWCNTs are a more efficient conductive nanofiller. The presence of MWCNTs and their concentration in hybrid nanocomposites was mainly responsible for the improvement of their thermal conductivity.

In this work, new bio-based copoly(ester amide)s were synthesized by a two-step melt polycondensation process, using 2,5-furanedicarboxylic acid dimethyl ester (DMFDC), 1,3-propanediol (PDO), and 1,3-diaminopropane (DAP), with different DAP content. The chemical structure of the obtained poly(trimethylene 2,5-furandicarboxylate)-co-poly(propylene furanamide) (PTF-co-PPAF) copolymers was confirmed by nuclear magnetic resonance (¹H NMR) and Fourier-transform infrared (FTIR) spectroscopy. Gas chromatography/mass spectrometry was used to provide more details of the polycondensation process. Thermal properties of the obtained materials were characterized by means of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic–mechanical thermal analysis (DMTA). The copolymers were amorphous and their glass transition temperature increased with the increase in the poly(propylene furanamide) (PPAF) content. The synthesized PTF-co-PPAF copolymers exhibited improved thermal and thermo-oxidative stability up to 300 °C. In addition, from the performed mechanical tests, it was found that along with the increase in PPAF content, Young's modulus increased, while at the same time, the value of elongation at break decreased. Graphical Abstract