Journal of Polymers and the Environment最新文献

Conductive hydrogel strain sensors have attracted great attention in various fields. However, most conductive hydrogels are rigid due to the polymerization of conductive polymers, which not only affects wearer comfort but also causes environmental concerns due to their non-biodegradable nature. To address these limitations, researchers have begun incorporating natural polymer compounds into hydrogels, including starch-based hydrogels. However, starch-based hydrogels hinder their applications due to their brittle fracture, poor freezing resistance, and insufficient electrical conductivity. Herein, a multi-functional, environmentally friendly, degradable starch-based conductive hydrogel was developed using a binary system of water and ethylene glycol (EG) as the solvents, starch and polyvinyl alcohol (PVA) as the skeletons, calcium chloride (CaCl₂) for conductivity, and gelatin and cellulose nanofibers to synergistically modify the physical cross-linked network. The hydrogel exhibited exceptional properties such as excellent stretchability (478.1%), high tensile strength (2.1 MPa), good toughness (3.7 MJ/m³), and good conductivity (0.22 S/m), as well as excellent anti-freezing and recyclability. Leveraging these properties, a wearable strain and temperature sensor with high sensitivity (GF = 0.74) and cycle stability over a wide strain range was developed, enabling convenient monitoring of human movement and body temperature physiological signals.

Blending polylactide (PLA) with poly(propylene carbonate) offers potential solution to mitigate the greenhouse effect due to PLA’s lower carbon dioxide (CO₂) emissions and its use of CO₂ as a monomer in PPC synthesis. In this investigation, a series of PLA and PPC blends were prepared using the solvent casting method to address their respective weaknesses. The blends exhibited partial compatibility, as evidenced by a noticeable shift in the glass transition temperatures toward each other. Tensile testing revealed that the incorporation of PPC improved the elongation properties of PLA. The degradation characteristics of the blend films were evaluated based on changes in the monolayer’s occupied area, the properties of the bulk film, and changes in surface morphology. Results indicated that PPC content accelerated hydrolytic degradation but slowed enzymatic degradation in the blends. Hydrolytic and enzymatic degradation significantly impacted the mechanical properties of PLA/PPC blends, prolonging the degradation process through chain scission.

Cellulose nanofibers (CNFs) have been widely studied for their reinforcing potential in high-performance composites. While there are numerous publications on CNF-reinforced composites in a variety of polymer matrices, few have considered the recyclability of such thermoplastic composites and whether the incorporation of CNFs deteriorates or improves their performance upon reprocessing. In this study, two thermoplastic resins, poly(lactic acid) (PLA), and glycol-modified polyethylene terephthalate (PETg), were prepared with CNF reinforcement and thermomechanically recycled to investigate the effect of CNF inclusion on the composite properties after reprocessing as well as their effect on the composites’ number of useful life cycles. Changes in mechanical, thermal, rheological, molecular, and microstructural properties of the composites and/or base resins were monitored as a function of cycle numbers. As is typical, the polymers’ molecular weight and mechanical performance deteriorated with continued processing. However, the addition of spray dried CNF was found to better maintain the mechanical performance of both polymers throughout multiple recycling steps as compared to neat samples. For example, the tensile strength of PETg with 20 wt% CNF after 6 processing cycles was found to exceed that of virgin neat PETg, and higher loadings of CNF were found to preserve a higher yield strength during multiple rounds of reprocessing compared to PETg composites with lower CNF loadings. Ultimately this study indicates that the addition of CNF to some thermoplastic materials can increase both their sustainability by offsetting the use of high-embodied energy resins and their circularity by enabling performance retention over more use cycles.

In this research, pure and composite separators based on poly (vinyl alcohol) (PVA) and silica nanoparticles were made by using non-solvent induced phase separation (NIPS) method. The research carried out includes examining Field emission scanning electron microscopy (FESEM) images, pores diameter distribution, porosity measurement, electrolyte uptake, electrolyte retention, contact angle with electrolyte, thermal shrinkage, X-ray Diffraction (XRD) analysis, Energy dispersive X-ray spectroscopy (EDX) analysis and charge and discharge analysis of the resulting lithium-ion batteries. The results obtained indicate improved performance, with increased polymer or silica concentrations leading to enhanced pore characteristics and lithium-ion battery discharge capacity density. According to the battery charge and discharge analysis, at rates of 0.1 C, 0.2 C, 0.5 C the discharge capacity density for a lithium-ion battery consisting of commercial PP separator (Celgard 2500) was 180, 172, 166 mA h g⁻¹ and for optimized composite separator was 200, 188, 174 mA h g⁻¹.

Conventional methods for synthesising polyurethane hydrogels encompass toxic isocyanates and organic solvents, limiting their eco-friendliness and ease of synthesis. In response, this study introduces an innovative approach to synthesising fructose-based non-isocyanate polyurethane (NIPU) hydrogel (FNHG), eliminating the need for isocyanates. Initially, fructose-based NIPU (FNPU) was synthesised using dimethyl carbonate and hexamethylene diamine under mild reaction conditions, paving the way for a greener polyurethane variant. Subsequently, a free radical polymerization technique was employed in an aqueous medium. This process allowed for the integration of poly(sodium acrylate), and N, N-methylene bisacrylamide, leading to to the development of FNHG. Remarkably short gelation time of just 30 min at 60 ℃ was achieved, signifying a significant advancement in the synthesis process. The synthesized NIPU-based hydrogels exhibited outstanding efficiency in the removal of crystal violet (CV) and malachite green (MG) dyes from aqueous media. With an impressive removal efficiency of 96.87% for CV and an astounding 99.8% for MG, these hydrogels demonstrated high effectiveness in remediation efforts. The study’s novelty lies in both the synthesis methodology, utilising FNPU, and the exceptional efficiency exhibited by these hydrogels in eliminating diverse dyes from contaminated water. Furthermore, the structure of FNPU was confirmed using FTIR and ¹H NMR spectroscopy, adding robustness to our findings. This research not only presents a solution to the limitations of traditional polyurethane synthesis but also demonstrates the potential of fructose-based NIPU hydrogels (FNHG) as eco-friendly and efficient agents for water purification.

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Polylactic acid (PLA) is the main candidate among the synthetic polymers for food packaging application. However, its poor processing and mechanical performance have limited its practical application. Here, we prepared a supertough thermoplastic vulcanizate (TPV) using PLA and ethylene vinyl acetate (EVA) copolymer with optimized EVA composition. The dynamic curing agent, dicumyl peroxide (DCP), was used as EVA-DCP masterbatch to improve its curing efficiency. Cellulose nanocrystals (CNCs) were further used as the biocompatible and renewable nanofiller, used in the form of PLA-CNC masterbatch, leading to improved mechanical strength and shape memory performance (SMP). Dynamically curing the thermoplastic elastomer (TPE) precursors diminished the temperature-dependency of elastic modulus ((E^{prime})) prior to PLA’s glass transition. Thus, improving the shape fixity (FR) of the TPVs compared to their TPEs as the TPVs showed (FR>98%) while the TPV60 (60% PLA) showed the highest FR of 100%. The TPVs showed higher recovery ratio (RR) with (RR>87.25%) with the TPV60 containing 1.5% CNC, which showed the highest RR of 94.1%. The mechanical performance analyses showed that the optimized TPV: CNC possesses a supertough nature, achieved by tuning the rheological behavior and morphology of the final TPVs. The results were quite promising for smart food packaging applications.

Cellulose nanofibrils are distinguished bionanomaterials known for their unique morphology, thermal stability, and ability to form networks, yet they encounter challenges in compatibility with hydrophobic matrices, limiting their application in various applications. This study introduces an innovative surface modification method to address the high hydrophilicity of CNFs. The novelty lies in the use of lipase as a biocatalyst in combination with renewable grafting agents, specifically butanoic and oleic acids. The lipase successfully esterified both acids onto the CNFs, with butanoic acid exhibiting a higher surface concentration, resulting in a more substantial reduction in hydrophilicity. Contact angle measurements demonstrated a notable shift, from 10.84° for untreated CNF to 68.4° and 55.1° for CNFs grafted with butanoic and oleic acid residues, respectively. While there were only slight alterations in crystallinity, thermal stability, and brittleness, lipase proved to be an effective catalyst for modifying the CNF surface with fatty acids. This approach offers a method to mitigate the high hydrophilicity of CNFs without compromising their key properties. Furthermore, it can be proposed as a means to tailor CNF for water-resistant applications in fields such as electronics, packaging, and Pickering emulsions.

Graphical Abstract

The structure of the lipase protein was sourced from the Protein Data Bank (PDB), first referenced by Xie et al. [38]

This study focuses on the synthesis and characterization of new magnetic nanoparticles complexed with copper, designated as Fe₃O₄@gly@cyclohexylidene-spiro[indoline-[1,3]dithiine]@Cu (FMNP). The structural confirmation of these nanoparticles was achieved through several techniques, including SEM imaging, VSM curves, XRD patterns, TGA and DTG curves, ICP-OES spectroscopy, and FT-IR spectrum analysis. Quantum mechanical studies were also conducted to precisely determine the complex’s position. These nanoparticles demonstrated antimicrobial properties against fungal, Gram-negative, and Gram-positive bacterial strains. The minimum fungicidal concentration (MFC) values ranged from 64 to 128 μg/mL, and the minimum bactericidal concentration (MBC) values varied between 8 and 256 μg/mL, indicating superior inhibitory effects on some microbial species compared to existing antibiotics. Furthermore, the FMNP nanoparticles were utilized in fabricating a crosslinked Oxidized Pectin-Fish Collagen Peptides hydrogel (FHGEL) aimed at adsorbing Congo red from aqueous solutions. The study of FHGEL’s adsorption capacity revealed that incorporating 0.03% FMNP significantly enhanced its ability to adsorb Congo red, showing a 3- to 4-fold increase compared to the hydrogel alone. The adsorption mechanism was attributed to dispersion mechanisms and the relaxation of macromolecules within a three-dimensional polymer network. This was supported by the FHGEL’s adsorption data fitting the R–P model, with the heterogeneity factor (n) value from the Sips isotherm model approaching 1.5, and a maximum adsorption capacity of 750.4 mg/g as predicted by the R–P model. The research findings indicate that all hydrogels adhere to the pseudo-second-order kinetics model, suggesting that FMNP could hold promising applications in the field of nanotechnology and environmental remediation.