Advances in Polymer Technology最新文献

Aluminum alloys are commonly subjected to chromatization to improve adhesion and protect against corrosion. However, this process is harmful to health and the environment. In this context, hybrid organic–inorganic silane films obtained by the sol–gel process come out as alternatives, with the advantage of acting as coupling agents. In this study, a factorial design was used to optimize the sol–gel process of a tetraethoxysilane (TEOS)/3-glycidoxypropyltrimethoxysilane (GPTMS) system with the curing of an epoxy resin, seeking adhesive efficiency. The samples were characterized by a shear test, scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, goniometry, and viscosity. Both the resin curing and sol–gel transition processes began during the system preparation, before deposition. The most important factor for the adhesive efficiency of the coatings was the interaction between two factors: TEOS:GPTMS molar ratio and interval time to deposition. The coating with the highest amount of GPTMS showed the best adhesive efficiency for the shortest deposition interval, while the opposite occurred with the sample prepared with the lowest amount of GPTMS. The results were explained by the complex reactions involving the sol–gel system summed to the resin curing process overtime. The statistical study provided information for the processing optimization of this environmentally friendly adhesive.

The aim of the work was to use biologically active additives, such as amino acids, as an alternative to traditional vulcanization accelerators in acrylonitrile–butadiene rubber (NBR), as well as a discussion of their role and impact on crosslink density, mechanical properties, aging resistance, and thermal stability of the vulcanizates. The studies have shown that the use of amino acids, in comparison to traditionally used accelerators such as 2-mercaptobenzothiazole (MBT), 1,3-diphenylguanidine (DPG), and tetramethylthiuram disulfide (TMTD), did not shorten the vulcanization time of NBR composites. However, the applied compounds positively influenced other parameters of vulcanization. Amino acids facilitated the vulcanization process by stabilizing sulfur bonds, increasing the enthalpy of the crosslinking process, and maintaining the crosslink density of the vulcanizates at an appropriate level. Vulcanizates with amino acids such as cystine, creatine, cysteine, and histidine exhibited improved mechanical durability and resistance to aging under elevated temperatures. Additionally, the use of amino acids contributed to the achievement of better dynamic properties of the vulcanizates, making them an attractive alternative in the production of high-performance elastomeric materials.

This study investigated the preparation of sodium alginate (ALG)–gelatin (GEL) composite membranes containing natamycin (NA) for use as antifungal wound dressing. Membranes with different concentrations of NA (0, 100, 200, 500, and 1000 ppm) were fabricated through the solvent casting method and then cross-linked using calcium chloride. Analysis via Fourier transform infrared spectroscopy indicated potential interactions between NA and biopolymers, while scanning electron microscopy revealed an uneven distribution of NA crystals. The incorporation of NA increased the swelling capacity of the membranes without significantly affecting the mechanical properties, except at 1000 ppm, where the tensile strength and toughness decreased. Antifungal studies confirmed the efficacy of the NA-loaded membranes against Candida albicans, with the inhibition zones increasing in proportion to the NA concentration. In addition, the ALG–GEL-2 membrane exhibited resistance to microbial growth for at least 3 weeks at room temperature in the absence of Candida cell inoculation. Release kinetics studies demonstrated that about 50% of natamycin was released from the ALG–GEL-10 membrane within 24 h, following super case-II transport mechanisms. Cytotoxicity evaluation of the ALG–GEL-2 membrane indicated moderate toxicity against mouse fibroblasts at a 1:1 extract ratio.

This study develops and evaluates green biocomposites using agro-waste fibers, maize husk fiber composite (MFC), luffa fiber composite (LFC), and betelnut husk fiber composite (BFC) as core reinforcements in a central-layer unsaturated polyester resin (UPR) matrix, comparing their performance with a 5% glass fiber composite (5% GFC) and neat UPR. Fibers underwent alkali treatment to enhance interfacial adhesion beforehand lay-up fabrication. The composites were characterized via structural, mechanical, physical, thermal, and morphological analysis. Among the natural fiber systems, tensile (20.68 MPa) and compressive (87.6 MPa) strengths were highest for the BFC. LFC showed superior flexural strength (48.83 MPa) and microhardness (14.2 HV). MFC exhibited the highest impact strength (0.34 kJ m⁻²) and ductility (7.64% elongation). Natural fiber composites showed lower strength than glass fiber in all tests except hardness, and lower tensile and flexural strength than neat UPR. All agro-waste composites exhibited greater water uptake (up to 1.524%) and biodegradability (0.00072% mass loss) than neat UPR, but the central layer structure seemed protecting the natural reinforcements from the environmental effects. Thermal analysis revealed improved char yield in natural fiber systems, and confirmed that fiber addition (0.310–0.361 W m⁻¹ K⁻¹) had minimal effect on heat transfer, indicating matrix-dominated thermal behavior across all composites. Scanning electron microscopy (SEM) indicated weaker interfacial bonding compared to GFC. The work demonstrates the potential of central-layer agro-waste biocomposites as sustainable structural materials for automotive interiors, panels, and lightweight construction, with competitive functional properties and improved environmental performance. Future research should optimize fiber treatment, loading, and hybridization to enhance interfacial bonding and durability for broader engineering applications.

Starve-fed polymer extrusion has become an important strategy for improving process control, energy efficiency, and product quality, but it also introduces partially filled flow regimes that are not captured by classical flood-fed concepts. This review provides a critical assessment of starve-fed operation in single-screw and corotating twin-screw extruders, structured by extruder type and process region. Key experimental techniques, including screw pull-out/quench analysis, window-based and optical visualization, residence time distribution (RTD) measurements, mixing assessments, ultrasonic sensing, pressure profiling, and specific mechanical energy (SME) monitoring, are reviewed with emphasis on how starve feeding modifies melting mechanisms, fill level, RTD, and energy consumption. The experimental evidence base is particularly strong for starve-fed single-screw extrusion, where pull-out and RTD studies clearly demonstrate a transition from contiguous solid-bed melting to mixed conductive/dispersed melting; corresponding data for starve-fed twin-screw extruders remain comparatively scarce and are often limited to local visualization and RTD in selected elements. Modeling approaches are then summarized, from early analytical and empirical models to modern global feed-to-die descriptions utilized to partially filled operation. Their capabilities and limitations are discussed separately for single- and twin-screw machines, highlighting where starve-fed conditions can be treated by adapted flood-fed models and where new formulations are required. Finally, advanced numerical techniques, computational fluid dynamics (CFD), discrete element method (DEM), and smoothed particle hydrodynamics (SPH), are reviewed with respect to extruder type and phase: DEM for granular solids conveying in the feed region, CFD for free-surface melt flow in partially filled single screws and selected twin-screw sections, and SPH for resolving starved and intermeshing flows with explicit free surfaces. The achievements and current limitations of these methods are identified, along with future research needs in improved modeling of partially filled regions, tighter coupling between DEM and CFD/SPH, real-time process monitoring, and scale-up strategies for industrial starve-fed extrusion.

This work reports on the synthesis and characterization of nanostructured composites based on proton-exchanged montmorillonite (MMT-H⁺) and conducting polymers, namely, polyaniline (PANI), polypyrrole (PPy), and poly(aniline-co-pyrrole) (P(ANI-co-Py)), prepared via in situ oxidative polymerization using ammonium persulfate (APS) as the oxidant. Structural investigations by X-ray diffraction (XRD), X-ray fluorescence (XRF) spectrometry, Fourier-transform infrared (FT-IR) spectroscopy, and scanning electron microscopy (SEM) confirmed the successful intercalation of the polymers within the MMT-H⁺ interlayers. The copolymer P(ANI-co-Py) exhibited an intermediate basal spacing (d (001) = 24.86 Å), larger than that of PANI (22.87 Å) and PPy (22.46 Å). SEM analysis revealed pronounced morphological differences: PANI generated porous and granular structures, PPy formed dense globular aggregates, whereas the copolymer displayed heterogeneous porosity, leading to increased surface area and enhanced interfacial interactions. Optoelectronic and electrochemical analyses (UV–Vis and cyclic voltammetry [CV]) highlighted clear synergistic effects in the P(ANI-co-Py)/MMT-H⁺ nanocomposite. The electrochemical tunability originates from the combined redox activity of aniline (ANI) and pyrrole (Py) units, resulting in merged and broadened redox responses intermediate between those of the corresponding homopolymers, while UV–Vis spectra exhibit broadened absorption bands indicative of extended conjugation. Thermal characterization using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) demonstrated superior thermal stability of the copolymer nanocomposite, marked by an extended degradation range (200–600°C), a 40% increase in residual mass at 800°C, and a delayed degradation onset compared to the homopolymer systems. These improvements were attributed to nanoconfinement and cross-linking effects. These results identify P(ANI-co-Py)/MMT-H⁺ as a thermally stable and electrochemically tunable nanocomposite with optimized morphology, suitable for high-temperature electronic applications and advanced functional coatings.

Cellulose-based nanomaterials, particularly cellulose nanofibers (CNF) and cellulose nanocrystals (CNC), have been widely explored as reinforcing agents in polymer composites owing to their high aspect ratio, crystallinity, and abundant surface hydroxyl groups. However, their application in bio-based leather-like polymeric materials, which require a unique balance of mechanical robustness, durability, and moisture tolerance, remains insufficiently systematized. This review critically examines the translatability of CNF and CNC reinforcement strategies to sustainable leather substitutes derived from bacterial cellulose (BC), plant fibers, and other bio-resources, with a focus on addressing key performance limitations such as low mechanical strength, dimensional instability, and poor durability. Particular emphasis is placed on structure–property relationships governed by dispersion behavior, polymer–filler interfacial interactions, and surface modification strategies in moisture-sensitive and multiphase systems. Unlike existing reviews that primarily address nanocellulose reinforcement in general polymer composites, this work adopts an application-driven perspective tailored to leather-like materials. In addition to discussing reinforcement mechanisms, the review considers scalability, multifunctionality, and economic feasibility, while explicitly acknowledging current limitations, including the scarcity of direct studies on leather-like systems and long-term durability data. By defining both opportunities and constraints, this review proposes a practical material design framework for the development of next-generation, high-performance, and environmentally responsible leather alternatives.

In this study, polylactic acid (PLA) nanocomposites reinforced with halloysite nanotubes (HNTs) were fabricated via melt extrusion followed by compression molding. Surface modification of HNTs was conducted using polyethyleneimine (PEI) and PN40 to improve interfacial interaction and dispersion of HNTs within the PLA matrix. The effects of HNT surface modification on the structural, thermal, and mechanical properties of the PLA matrix was systematically evaluated. Zeta potential and Fourier-transform infrared (FTIR) analyses confirmed the successful functionalization of HNTs, with PEI treatment exhibiting a more pronounced surface charge modification compared to virgin and PN40-modified HNTs. SEM and atomic force microscopy (AFM) images demonstrated that the dispersion and interfacial adhesion of HNTs in the PLA matrix were significantly enhanced in the nanocomposites containing PEI–modified HNTs. Thermal analyses revealed that the incorporation of HNTs led to a slight increase in the glass transition and melting temperatures, as well as enhanced thermal degradation resistance. Moreover, nanocomposites containing 3 wt% PEI–modified HNTs exhibited the highest thermal stability, with the temperature at 5 and 10 wt% weight loss, and the temperature of maximum degradation rate observed in the derivative thermogravimetric (DTG) curve measured at 349.9, 359.5, and 396.9°C, respectively. These values represent increases of 9.8, 10.5, and 14.4°C compared to pure PLA. Tensile testing demonstrated that the nanocomposites containing 1–3 wt% PEI–modified HNTs achieved the highest tensile strength, showing an increase of over 7% relative to pure PLA. Overall, the results demonstrate that surface modification of HNTs, particularly with PEI, effectively improves dispersion, matrix–filler adhesion, and the thermomechanical performance of nanocomposites.

Linear low-density polyethylene (LLDPE), a semicrystalline polymer featuring short-chain branched architectures, displays crystallization behavior that is highly sensitive to molecular topology and processing conditions. In this study, the nonisothermal crystallization kinetics of LLDPE composites filled with diatomite (DE), graphene (G), and their hybrid (DE/G) were investigated via differential scanning calorimetry (DSC). The Mo method and Vyazovkin’s isoconversional approach were employed to determine the crystallization kinetic parameters. The results indicate that G exerts the most significant nucleation effect on LLDPE crystallization, reducing the crystallization activation energy by 30 kJ/mol, and t_1/2 decreases from 0.78 to 0.48 min, and the crystallization rate increases by approximately a factor of 1.63 at a cooling rate of 15 K/min. These variations are primarily attributed to the influence of G on the crystallization rate and melting point of LLDPE.

Lignin is one of the available biopolymers on earth, so it can play a vital role in moving toward a bio-based society. In this paper, lignin derived from non-wood sources like bagasse and kash was characterized in order to facilitate its valorization. Lignin obtained from the soda liquor was considered as technical lignin, and it was compared with the acidic dioxane-extracted lignin from the corresponding non-wood. The isolated lignins were characterized using elemental analysis, methoxyl content determination, molecular weight distribution, FT-IR spectroscopy, and advanced NMR techniques (quantitative ³¹P and 2D HSQC). The methoxyl groups per C₉ unit in dioxane lignin from bagasse were 1.20, which was slightly higher than that of kash dioxane lignin (1.16/C₉). Technical lignins showed comparable or slightly lower methoxyl content per C₉ unit. The weight-average molecular weight (Mw) of technical lignin was lower than that of corresponding dioxane lignin. The phenolic hydroxyl groups in technical lignin were higher than those of corresponding dioxane lignin, as observed from ³¹P NMR analysis. Furthermore, 2D HSQC NMR analysis showed that both lignins were primarily composed of syringyl (S) and guaiacyl (G) units, with the S-unit type being dominant. These findings provide valuable information on the structural and chemical properties of non-wood lignins, supporting their potential utilization in bio-based applications.