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Polymer nanocomposites can be employed in diverse engineering applications where wear is a critical concern. Understanding the mechanical and wear properties as applied to polymer nanocomposites is crucial for comprehending the behaviour of workpieces. In this study, three types of nanographites were incorporated at a concentration of 2.5 wt% into a polyamide 6.6 matrix. The graphites differ owing its production process. Tests of wear, impact, and elastic deformation resistance, hardness, and morphology were conducted to evaluate the performance of the PA66/graphite nanocomposites. All nanocomposites exhibit a homogeneous morphology with good dispersion, distribution, and orientation of the nanographites in the matrix, suggesting the effectiveness of the processing methods employed. The incorporation of 2.5 wt% of nanographites A, B, and C improved the wear resistance of PA66 by 52%, 74%, and 44%, respectively. The PA66/graphite nanocomposites exhibited an increase in Shore D hardness up to 2.8%, and in elastic modulus between 8.3% and 13.0%. The impact resistance of the nanocomposites decreased by 15.4%–21.3%. The results revealed that the production process of the nanographites impacted the performance of the produced nanocomposites.

This study evaluated the ability of tea tree essential oil (TT) incorporated into polymer-clay bionanocomposites to in vitro eliminate resistant microorganisms towards applications in antibacterial wound healing. Antimicrobial bionanocomposites were prepared in two steps, namely sonication and melt intercalation, and montmorillonite clay and poly(acid lactic) (PLA) were chosen because they constitute a polymer-clay bionanocomposite to be applied in wound dressing. X-ray diffraction (XRD) results indicated good incorporation of the organic compounds, TT oil, and glycerol (G) (the latter used as a plasticizer) into the clay galleries. Dynamic-mechanical analysis (DMA) results showed a 2–30 % increase in storage modulus and up to 10 °C decrease in glass transition temperature, proving the influence of both TT oil and G on the stress transfer of the reinforcement clay phase. Thermogravitmetric analyses (TGA) revealed TT oil and G addition worsened the thermal stability of the bionanocomposites, which show a mass loss onset decrease up to 90 °C and a clay content between 1.5 and 3 wt%. In vitro antimicrobial activity tests revealed only the combinations of TT oil and G reduced Escherichia coli and Staphylococcus aureus satisfactorily and showed the antimicrobial activity of the bionanocomposites.

The inherent properties of cellulose nanofibers (CNFs) make them an interesting and sustainable choice for reinforcing polymeric matrices intended for the automotive, electronic, construction, and packaging sectors. Effective recycling and reuse of polyamide 6.6 significantly reduce the environmental impact of automotive components throughout its entire life cycle. Nanocomposites of recycled polyamide 6.6 and CNF and of virgin polyamide 6.6 and CNF were processed through dissolution in a formic acid/water mixture followed by melt extrusion and injection molding. The results show that pure recycled polyamide exhibited a thermal degradation onset temperature 10 °C lower and a 9 % lower crystallinity compared to pure virgin polyamide. The method used for processing the nanocomposites resulted in homogeneous dispersion and good anchoring of CNF in both polymer matrices. The processing method and the presence of CNF reduce the thermal stability by up to 15 °C for recycled polyamide nanocomposites and up to 26 °C for virgin polyamide nanocomposites. The processing method did not significantly impair the elastic modulus and tensile strength of both recycled and virgin polyamides, showing a 3 % and 1 % reduction in tensile strength for recycled and virgin polyamides, respectively. The incorporation of 1 wt% and 2 wt% of CNF in virgin polyamide showed an increase in the elastic modulus of 16 % and 5 %, respectively, and a reduction in ductility. In summary, this work offers an alternative processing pathway for nanocomposites of recycled or virgin polyamide 6.6 with CNF; however, some improvements are still necessary to achieve the reinforcing effect of CNF on the mechanical strength of the matrices.

Population growth and the way resources are being exploited are directly affecting the environment. The natural fiber market, for example, is worth billions of dollars and a huge amount of the fibers becomes waste. This considerable amount of waste motivates the study of the fibers as a reinforcement in polymeric matrix, which benefits both the environmental sustainability and technical-commercial development of new materials with good properties and reduced cost. In this study, jute fiber-reinforced composites previously manufactured from an industrial waste (W), polypropylene, compatibilizer, and nano-calcium carbonate (N), were exposed to natural and accelerated aging. The composites were tested by infrared spectroscopy, contact angle (CA) measurement, and tensile test. Infrared analysis showed greater oxidative degradation after accelerated aging. All CA values continued above 90° after natural aging. Among all compositions, the ones with the presence of N had the highest CA values, showing that N acted as a waterproofing agent. After accelerated aging, a significant decrease in all CA values was observed. The composites did not show significant variation in the elastic modulus after either aging. Deformation at break decreased significantly for compositions with no jute fiber in both aging programs. No remarkable reduction was observed in the compositions with jute fibers.

The volume of discarded solid wastes, especially plastic, which accumulates in large quantities in different environments, has substantially increased. Population growth and the consumption pattern of societies associated with unsustainable production routes have caused the pollution level to increase. Therefore, the development of materials that help mitigate the impacts of plastics is fundamental. However, bioplastics can result in a misunderstanding about their properties and environmental impacts, as well as incorrect management of their final disposition, from misidentifications and classifications. This chapter addresses the aspects and factors surrounding the biodegradation of bioplastics from natural (plant biomass (starch, lignin, cellulose, hemicellulose, and starch) and bacterial polyester polymers. Therefore, the biodegradation of bioplastics is a factor that must be studied, because due to the increase in the production of different bioplastics, they may present differences in the decomposition rates.

Scaffolds of poly(ε-caprolactone) (PCL) and their biocomposites with 0, 1, 3, and 5 wt.% Biosilicate® were fabricated by the generative manufacturing process coupled with a vertical miniscrew extrusion head to application for restoration of bone tissue. Their morphological characterization indicated the designed 0°/90° architecture range of pore sizes and their interconnectivity is feasible for tissue engineering applications. Mechanical compression tests revealed an up to 57% increase in the stiffness of the scaffold structures with the addition of 1 to 5 wt.% Biosilicate® to the biocomposite. No toxicity was detected in the scaffolds tested by in vitro cell viability with MC3T3-E1 preosteoblast cell line. The results highlighted the potential application of scaffolds fabricated with poly(ε-caprolactone)/Biosilicate® to tissue engineering.

Nanocomposites of an organic-modified montmorillonite (MMT) and polyamide 6 (PA6) with a residual monomer were produced by melt mixing in a torque rheometer. By wide angle X-rays diffraction (WAXD), intercalated/exfoliated structures were observed in the PA6/MMT nanocomposites with 3 and 5 wt. (%) of MMT; on the other hand, when 7 wt. (%) of MMT was added, a nanocomposite with exfoliated structures was obtained due to the predominant linking reactions between the residual monomer and the "nanoclays" organic surfactant. Solutions of these PA6/MMT nanocomposites at 15, 17 and 20 wt. (%) in formic acid were prepared. The 3 and 5 wt. (%) nanocomposites were successfully electrospun; however, electrospinning of the 7 wt. (%) nanocomposite was not possible. WAXD, scanning and transmission electron microscopy results showed that the 3 and 5 wt. (%) nanofibers with average diameter between 80-250 nm had exfoliated structures. These results indicate that the high elongational forces developed during the electrospinning process changed the initial intercalated/exfoliated structure of the nanocomposites to an exfoliated one.

Polyamide 66 (PA66) nanofibers of different molecular weights were obtained by electrospinning of formic acid solutions. An ionic salt, NaCl, was also added to the solutions to increase the conductivity. PA66 concentrations between 15-17 wt.(%)/v and electrical fields between 2.0 and 2.5 kV/cm were the best conditions to produce the smallest nanofibers; however, the addition of NaCl increased the fibers average diameters.The characterization of the fibers was done by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), wide angle X rays diffraction (WAXD) and Fourier Transformed Infrared (FTIR). As the molecular weight decreased, the nanofibers average diameters also decreased; however, critical number average and weight average molecular weights were necessary for electrospinning. As the amounts of carboxyl terminal groups (CTG) increased, the nanofibers average diameters decreased; however, above CTG's critical values of 8.7 x 10-5 mol.g-1 no electrospinning was possible. The addition of ionic salt increased the electrical conductivity of the solutions and increased the nanofibers' average diameters. By DSC, residual solvent in all the electrospun mats was found; two melting endotherms, one between 248 and 258 °C and the other one between 258 and 267 °C, depending on the sample were also observed. These endotherms were attributed to the melting, re-crystallization and re-melting of the PA66 α-phase. The nanofibers had low % of crystallinity compared to a textile fiber. By WAXS and FTIR, confirmation of the presence of α-phase crystals, of small dimensions and highly imperfect and of a very small amount of β and γ-phases crystals in the nanofibers structure was obtained.

The development of α and β-phases and the molecular orientation of injection molded disks of two isotactic polypropylene (i-PP) resins were studied by wide angle X-ray diffraction (WAXD) and pole figures. A nucleated (NPP) and non-nucleated (HPP) polymers were analyzed. The main proposal of this article was the comprehensive study of the interrelations between the processing conditions, phase contents and PP α-phase molecular orientation of injection molded PP resins. In both resins, it was observed that the α-phase was present in all regions along the thickness while the β-phase was present mainly in the external layers, decreasing from the surface to the core; however this last phase was present in a very small amount in the NPP resin. For both polymers, the orientation of the macromolecules c-axis was higher along the flow direction (RD) than along the transverse direction (TD). The b-axis of the PP α-phase molecules was oriented to the thickness direction (ND). The orientation of the c-axis along RD and b-axis along ND of the NPP samples was considerably higher than of the HPP samples, due to the NPP faster crystallization kinetics. For both polymers, the most influential processing parameters on the molecular orientation were the mold temperature and flow rate. The results indicate that, as the mold temperature increased, the characteristic molecular orientation of PP α-phase, with c-axis along RD and b-axis along ND, decreased. With increase in the flow rate an increase of the c-axis molecular orientation of the samples along RD was observed.

Oriented β‐phase films were obtained by utilizing two different techniques: conventional uniaxial drawing at 80 °C of predominantly α‐phase films, and by drawing almost exclusively β‐phase films obtained by crystallization at 60 °C from dimethylformamide (DMF) solution with subsequent pressing. Wide angle X‐ray diffraction (WAXD) and pole figure plots showed that with the conventional drawing technique films oriented at a ratio (R) of 5 still contained about 20% of phase α, a crystallinity degree of 40% and β‐phase crystallographic c‐axis orientation factor of 0.655. Drawing at 90 °C and with R = 4 of originally β‐phase films results in exclusively β‐phase films with crystallinity degree of 45% and orientation factor of 0.885. Crystalline phase, crystallinity degree, and crystallographic c‐axis orientation factor of both phases were also determined for α‐phase oriented films obtained by drawing α‐phase films at 140 °C. For films drawn at 140 °C the α to β phase transition drops to about 22%. Reduction in crystallinity degree with increasing R is more pronounced at draw temperature of 140 °C compared with 80 °C. Moreover, for both phases the c‐axis orientation parallel to the draw direction is higher at draw temperature of 140 °C than at 80 °C. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2793–2801, 2007 [ABSTRACT FROM AUTHOR]