Journal of Polymers and the Environment最新文献

In the current study, a biocompatible zinc oxide (ZnO) nanoparticle embedded gellan gum (GG) (GG-ZnNP) sponge with excellent antibacterial activity, enhanced wound healing and hemostatic properties was presented. Firstly, ZnO nanoparticles were synthesized by co-precipitation methods and characterized through Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) analysis. The size distribution and morphology of the ZnO nanoparticles were investigated by applying dynamic light scattering (DLS) and transmission electron microscopy (TEM). Presence and distribution of the ZnO nanoparticles in GG sponges were examined with Energy-dispersive x-ray spectroscopy (EDX) Thermogravitational Analysis (TGA) conducted to evaluate the thermal stability of GG-ZnO sponges. Following that, ZnO nanoparticles were embedded into GG sponges to enhance their antimicrobial properties. The physicochemical properties of GG-ZnNP sponges were characterized by FTIR, Scanning Electron Microscopy (SEM), swelling and degradation tests. The agar disk diffusion test and colony-forming unit assay findings showed that all GG-ZnNP sponges had a strong antibacterial activity against Escherichia coli (E.coli) and Staphylococcus aureus (S. aureus) bacteria. Furthermore, in vitro blood absorption tests indicated that GG-ZnNP sponges could effectively shorten bleeding time and increase blood absorption capacity. Cell viability studies conducted by MTT and scratch assay with L929 fibroblast cells. MTT assay were performed to found applicable ZnO dose of the sponges to be use as a wound dressings. In vitro scratch assays showed that GG-ZnNP sponges promoted wound closure and re-epithelialization in L929 fibroblast cells at increasing incubation time. GG-ZnNP sponges have a significant and improvable potential for wound dressing applications with their antibacterial and superior hemostatic properties.

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Offshore platform decommissioning is a complex process that can cause marine damage. The circular economy can be used to implement sustainable initiatives in the decommissioning process. Mooring ropes, which commonly consist of poly(ethylene terephthalate) (PET) fiber, are one type of waste generated during offshore platform decommissioning. This study aims to demonstrate that the ring spinning process is a sustainable solution to recycling PET fibers from post-industrial mooring ropes (PMR-PET) by producing yarns containing 70–60% PMR-PET. One-way ANOVA and the Cochran test demonstrated that the yarns made with PMR-PET exhibit better tensile properties than those made with 100% commercial PET. Addition of PMR-PET produces a yarn with a higher crystallinity. The lower degradation temperatures of PMR-PET yarns are not enough to limit their use in textile products. This study demonstrates that recycling PMR-PET provides an opportunity to promote the circular economy and develop new yarns in the textile industry.

To significantly improve the crystallinity and crystallization rate of polylactide (PLA), plasticizer (polyethylene glycol, PEG) and nucleating agent (cellulose nanofibers, CNFs) were melt-blended with PLA to prepare PLA/PEG/CNF nanocomposites. The effects of PEG and/or CNFs and cooling rate on the crystallization kinetics of PLA were investigated by HS-POM, DSC, and WAXD. The non-isothermal crystallization kinetics of modified PLA samples were evaluated by the Jeziorny’s, Ozawa’s, and Mo’s models, while their non-isothermal crystallization activation energies were determined by Friedman’s method. The polarized optical micrographs showed that CNFs served as effective nucleating agents, increasing the nucleation density of PLA spherulites, but reducing their spherulite sizes; PEG improved the mobility of PLA chains and accelerated the growth rate of PLA spherulites, thus leading to larger spherulite sizes. The non-isothermal crystallization kinetics revealed that the crystallization temperature (T_c), crystallinity (X_C), and crystallization half-time (t_1/2) of all PLA-based samples decreased with increasing cooling rate. At the same cooling rate, the incorporation of 15 wt% PEG or 3 wt% CNFs increased T_c and X_C but decreased t_1/2 of PLA by enhancing spherulite growth rate and providing more crystal nuclei, respectively. Moreover, SEM micrographs showed that the addition of PEG improved the dispersion of CNFs within the PLA matrix, and the synergistic effect of PEG and CNFs more significantly increased T_c and X_C, but reduced t_1/2. The above results demonstrated that the combination of PEG and CNFs significantly enhanced the crystallization performance of PLA, providing insights for the design of high-performance PLA-based materials.

Nowadays, the post-consumer polyethylene terephthalate (PET) waste from the packaging industry is one of the largest plastic waste streams worldwide. While clear PET waste is commonly recycled and is reused for textile and packaging applications (even with food contact), coloured PET waste`s degraded state limits its reusing potential. This highlights the urgent need to upgrade low-value PET waste. This study focuses on enhancing coloured recycled PET (rPET) quality by introducing an epoxide chain extender (CE) from 0 to 1 wt%, to improve rheological behaviour. Simultaneously, upcycling opportunities are explored by incorporating an eco-friendly phosphorous-based flame retardant (FR) from 0 to 10 wt%, to reduce flammability and thus enabling electrical and electronic applications, among others. The impact of each additive, as well as their combination, is evaluated on the chemical structure, thermal, rheological and burning behaviour of undervalued rPET. The optimal CE content is determined at 0.8 wt%, promoting branched and higher molecular weight polymer chains. Regarding FR, 6, 8 and 10 wt% highly enhance the fire resistance. Furthermore, the combination CE/FR enables a synergistic effect, notably improving burning behaviour. Additionally, the foaming potential of the resulting high-value rPET is assessed for the first time through one-step batch foaming using supercritical CO₂ as foaming agent, aiming to develop lightweight materials endowed with superior burning behaviour. The material containing 0.8 wt% CE reaches the lowest density (200 kg/m³) and a closed cellular structure with smaller cell diameters (8 ± 3 μm). Meanwhile, the combination of 0.8 wt% CE and 6 wt% FR gives rise to a foamed material with density of 659 kg/m³ and cell diameter of 7 μm. Thus, this batch procedure in one-step enables the formation of microcellular foams based on coloured rPET (cell size below 10 μm).

A biosensor for the determination of the phenol index in water bodies has been developed using enzymes immobilized on the redox-active polymer surface of a graphite paste electrode. Tyrosinase, laccase, and bacterial cell membrane fractions were used as biological materials. Redox polymers based on bovine serum albumin (BSA) and various electron transport mediators were synthesized for immobilization. It has been shown that a redox polymer based on ferrocene (FC) combined with single-walled carbon nanotubes (SWCNTs) is more promising for use in biosensors than a polymer based on safranin (SAF) based on electrochemical and analytical parameters. The best results were obtained with the “BSA-FC-SWCNT-tyrosinase” bioanalytical system, which has a lower limit of detectable concentrations of 1 × 10⁻³ mg/L, indicating the possibility of monitoring water environments with a phenol concentration corresponding to the maximum permissible concentration (MPC). The maximum analytical signal was generated at a temperature of 30 °С and a pH of 6.8. The biosensor was stable at concentrations of heavy metal ions up to 100 times the MPC, as well as at NaCl concentrations up to 5%. The system was tested on river water samples containing phenol. A statistical analysis of the results showed no significant difference between the biosensor results and those of standard analytical methods. The proposed approach will significantly reduce the analysis time, its labor intensity and cost.

In the realm of nanobiotechnology the bio-inspired and bioengineered nanoparticles have immense impetus in view of their unique and diverse implications. This research describes an eco-friendly method for the in situ synthesis of an Ag NP fabricated over gellan gum functionalized Fe₃O₄ NPs (Fe₃O₄@gellan gum-Ag) and its subsequent catalytic and biological uses. The morphological and physicochemical properties of this material were evaluated applying a variety of instrumental methods, including FT-IR, FE-SEM, TEM, EDS, elemental mapping, XRD, and ICP. The as synthesized Fe₃O₄@gellan gum-Ag NPs was used as a nanocatalyst in the catalytic application to reduce nitrobenzene derivatives. A UV–Vis spectrophotometer was used to track the reduction process. Through eight additional cycles, we assessed the sustainability of this catalyst based on its recyclable qualities. Furthermore, the nanocomposite’s bioapplication for in vitro anticancer research against the breast cell lines MCF-7 and SKBR3 was expanded through the use of the MTT assay. The material caused a dose-dependent reduction in the malignant breast cell line’s cell survival. Regarding the MCF-7 (Michigan Cancer Foundation-7) and SKBR3 (Sloan–Kettering breast cancer) cell lines, the nanocomposite was found to have IC50 values of 41.2 and 39 µg/mL. In the near future, cancer management may appear extremely promising, considering the amazing results the developed nanocomposite demonstrated.

The semi-crystalline poly-(R)-3-hydroxybutyrate (PHB) is a biobased and biodegradable polymer. This makes it a promising alternative to polypropylene (PP), especially for packaging applications. PHB has excellent barrier properties to O₂, CO₂, and H₂O, but is susceptible to degradation from heat and hydrolysis. The epoxy chain extender Joncryl^® was added to PHB in a simulated recycling process to reverse the degradation due to processing. The effects of the chain extender and the degradation due to processing were investigated with thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), small strain oscillatory plate-plate rheometry, tensile tests, and notched Charpy impact tests. With the addition of the chain extender, a decrease in peak crystallization temperature and tensile modulus, and an increase in zero-shear viscosity and elongation at break were observed. For each additional processing step the zero-shear viscosity, the elongation at break, and the notched impact strength decreased, while the tensile modulus increased. The effect of the thermal load during processing on the material properties is significantly higher compared to the effect of the addition of the chain extender. Therefore, the practical application of the investigated chain extender alone in a multi-stage recycling process seems limited. This is due to the low processing temperature of PHB, which seems to limit the full potential of Joncryl^® due to the slow reaction speed at this temperature.

The packaging industry faces a shortage of high-strength bio-derived polyesters that can rival polyethylene derivatives, resulting in the overexploitation of fossil resources. By condensing lignin-derived 2-methoxyhydroquinone with methyl 4-chloromethyl benzoate, the diester dimethyl 4,4’-(((2-methoxy-1,4-phenylene)bis(oxy))bis(methylene))dibenzoate (M) was synthesized. Using monomer M and hydroquinone hydroxyethyl ether, aliphatic-aromatic copolyesters P₁-P₄ were prepared via melt polycondensation reaction employing various aliphatic diacids (1,4-butanedioic acid, 1,6-hexanedioic acid, 1,8-octanedioic acid, and 1,12-dodecanedioic acid). The chemical structures of the copolyesters were elucidated using FTIR and ¹H NMR, while their properties were characterized through gel permeation chromatography, differential scanning calorimetry, thermogravimetric analysis, tensile testing, and dynamic mechanical analysis. GPC analysis revealed that the average molecular weight (M_w) of copolyesters P₁–P₄ ranged from 4.22 to 5.03 × 10⁴ g/mol, while thermal property analysis indicated that the copolyesters thermal stability decreased with increasing aliphatic diacid spacer length unit. Also, the glass transition temperature (T_g) and melting point (T_m) decreased from 90 to 68 °C and 182–158 °C, respectively. Mechanical analysis showed a decrease in tensile modulus from 1740 to 1010 MPa, as well as yield strength from 76 to 54 MPa, but indicated an increase in elongation at break from 236 to 295%, owed to the growth of carbon chains which increases the proportion of flexible units in the polymer chain. The degradability study indicated a modest degradation rate from 3.9 to 5.1% after 30 weeks from P₁–P₄, with low ecotoxicity in all cases. P₄, consisting of 1,12-dodecanedioic acid, exhibited the highest degradation rate, due to its low proportion of benzene units. These findings provide insights into the structure-property relationships of aliphatic-aromatic copolyesters while contributing to the advancement of high M_w polyesters with performance comparable to conventional petroleum-derived polyesters, aligning with the strategy of green low-carbon, energy-saving, reduction, and sustainable development of polymeric materials.

A series of epoxidized isobutyl esters (EIE) derived from soybean oil deodorizing distillate (SODD) were synthesized via esterification with isobutanol followed by epoxidation. Epoxidized isobutyl soyate (EIS), epoxidized isobutyl soyate distillate (EISD), as well as the epoxidized esters of the main fatty acids contained in SODD, namely, epoxidized isobutyl linoleate (EIL), and epoxidized isobutyl oleate (EIO) were also synthesized and assessed as environmentally friendly plasticizers for polylactide (PLA). A comparison of the plasticizing efficiency of 10 wt.% of these EIE on PLA properties is addressed in this work. The effects of the different EIE on mechanical properties (tensile and impact tests) at 21 ºC, thermal transitions and thermal degradation, dynamic-mechanical thermal properties and dimensional change with temperature, and morphology are evaluated and compared with commercial epoxidized soybean oil (ESBO), and acetyl tributyl citrate (ATBC). Tensile tests indicate that EIE provide increased elongation at break from 8.8% (neat PLA), up to 10–32%, depending on the EIE. EIE seem to be more compatible with PLA as observed by field emission scanning electron microscopy (FESEM) since they do not give evidence of phase separation, or plasticizer saturation, which is clearly observed with ESBO. Regarding thermal properties, all EIE provide a noticeable decrease in the glass transition temperature (T_g) from 61.6 ºC (neat PLA), down to values ranging from 42 to 48 ºC, remarkably lower than the decrease provided by ESBO with a T_g value of 56.6 ºC. These findings reveal that EIE are promising plasticizers for PLA with balanced properties and contribute to improve its intrinsic brittleness by increasing the impact toughness.

Herein, we prepared functional chitosan films reinforced with chitin nanocrystals by supercritical solvent impregnation with a variety of essential oils, i.e. mentha, clove, and cinnamon. Two different chitosan film structures were evaluated, smooth and compact films obtained by casting; and highly porous films prepared by lyophilization process. The effect of the film morphology, essential oil impregnation and the presence of chitin nanowhiskers on the properties of the films were extensively investigated by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and tensile testing; while the bioactive functions were evaluated by measuring the antioxidant and antimicrobial activities. It was found that the impregnation of essential oils is much higher in porous films, confering notable antioxidant and antimicrobial activity. The incorporation of chitin nanocrystal does not influence on the impregnation process, and only improves slightly the antioxidant performance, which is clearly appreciable in the case of films obtained by casting with an increase of ca. 35% from chitosan without to samples with 5 wt% of chitin nanowhiskers. Nevertheless, an important enhancement of the mechanical properties, particularly in elastic modulus, is clearly appreciated with the incorporation of chitin nanowhisker into the films, with values of 50% higher in comparison with chitosan without nanowishers. However, the elongation at break and tensile strength values suffer a slight decrease.

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