Search Results (387)

The development of sustainable coatings that combine reprocessability with active functionalities remains a central challenge for the composites sector. In this work, a healable, electrically conductive coating was formulated using epoxidized castor oil (ECO) as a bio-based matrix, dibutyl phosphate (DBP) as a transesterification catalyst, and short recycled carbon fibres (RCFs, 2 mm in length) as a conductive filler at loadings of 10 and 20 phr. Formulations were UV-cured via cationic photopolymerization and characterized across the full liquid-to-solid processing chain. FT-IR and photo-DSC showed that increasing RCF content progressively reduced curing rate and conversion, an effect attributed to light scattering/absorption by the fibres and restricted chain mobility, although gel content remained above 98% in all cases. DMTA showed that RCF did significantly affect the glass transition temperature but markedly increased the rubbery storage modulus and apparent crosslink density, consistent with a physical reinforcement mechanism. Stress relaxation tests confirmed the dynamic bond exchange behaviour in all formulations, with the apparent activation energy decreasing from 112 kJ/mol for the neat resin to 33–34 kJ/mol upon RCF incorporation. This significant reduction suggests that the presence of RCF facilitates the bond-exchange process, potentially through interfacial interactions between the polymer network and the fibre surface. However, the specific molecular mechanism responsible for this effect cannot be established from the present data. Electrical conductivity peaked at 10 phr RCF (3.6 × 10⁻³ S/m), enabling measurable Joule heating, while the 20 phr formulation showed reduced conductivity linked to voids and lower conversion. Thermally triggered healing at 120 °C for 6 h restored mechanical integrity, which is higher than reference values, demonstrating the coating’s capacity for repeated repair through its dynamic covalent network. Full article

Polysaccharide-based organic-inorganic hybrid carriers combine renewable polymer matrices with inorganic phases that can modify mechanical integrity, swelling, barrier performance, payload retention, and release behavior. This review critically evaluates alginate as a reference matrix together with chitosan, cellulose/nanocellulose, starch/maltodextrin, pectin, carrageenan, and related polysaccharides, focusing on how matrix chemistry, inorganic-phase properties, interfacial interactions, and fabrication route govern encapsulation efficiency, loading, structural stability, swelling, mechanical and barrier properties, storage retention, and release kinetics. Silica and mesoporous silica, clays and halloysite, layered double hydroxides (LDHs), metal oxides, hydroxyapatite, magnetic particles, and metal-organic frameworks are compared according to their reservoir, reinforcing, diffusion-controlling, responsive, and safety-related functions. Representative quantitative findings illustrate the importance of hybrid architecture; for example, incorporation of LDHs into an alginate matrix reduced erythropoietin release after 108 h from 86% to 24% while increasing mechanical performance by approximately 5–30-fold. In this review, particular attention is given to volatile and bioactive compounds, for which storage retention, oxidation stability, headspace behavior, and application-relevant release are as important as initial encapsulation efficiency. Key challenges, such as long-term stability, standardization of release studies, scalability, safety assessment, and performance in real formulations, are also discussed, together with future directions for sustainable, application-specific hybrid carrier systems. Overall, the review provides a structure-property-application framework for selecting matrix-filler-processing combinations for controlled-release systems. Full article

In recent decades, due to the rapid development and application of wireless communication, flexible electronics, and smart devices, electromagnetic interference (EMI) and radiation pollution have been intensified, creating an urgent demand for efficient EMI shielding materials. Carbon nanostructures such as graphene and carbon nanotubes are considered promising candidates due to their excellent properties, such as high electrical conductivity, low density, large specific surface area, and flexibility. This work reports our recent results in the design and testing of polymer nanocomposites with irradiated hybrid carbon nanostructure (graphene/multi-walled carbon nanotubes) used as EMI shielding materials. Five representative composites with varying filler loadings (AH of 15% and AM1 of 20 wt%), thicknesses (0.208–0.48 mm), and e-beam irradiation doses (from 50 to 400 kGy) were systematically characterized using SEM, FTIR, TGA/DSC, and vector network analyzer (VNA) measurements in the S-band (2.65–3.90 GHz). The effects of different e-beam irradiation doses and hybrid carbon contents on conductive network construction, interface engineering, and porous or layered structures on EMI shielding performance are discussed. Experimental results show that all studied composites exhibited strong absorption-dominant behavior (SE_A), while the multiple reflection component (SE_M) was found to be negligible. Both filler loading and sample thickness significantly enhanced shielding performance, with a pronounced synergistic interaction observed between these parameters. A quadratic Response Surface Methodology (RSM) model was developed to correlate the total shielding effectiveness (SE_T) with thickness and filler content, yielding high predictive accuracy (R² > 0.96). The model enables efficient optimization of composite design for targeted shielding levels. Full article

Attapulgite (ATP; palygorskite) is a fibrous magnesium aluminum silicate that can reinforce hydrated polymer networks, provide a surface for molecular interactions, and participate in formulation-dependent ion or drug delivery. Although ATP has been studied most extensively in bone-oriented composites, its more distinctive role in cartilage repair may be as a spatially controlled regulator of the scaffold microenvironment rather than as a uniformly distributed bioactive filler. This review therefore examines ATP from a cartilage-first perspective. Direct ATP evidence, effects of modified ATP, performance of complete drug-loaded formulations, and cross-material extrapolations are considered separately. Current cartilage data support injectability, shear-thinning, photocrosslinking, mechanical reinforcement, and sustained intra-articular delivery but do not yet establish durable hyaline cartilage regeneration. In osteochondral constructs, ATP is more plausibly restricted to the calcified-cartilage interface or subchondral region, where reinforcement and mineral-associated functions may be beneficial, while high or uniform cartilage-side loading could increase stiffness, hypertrophy, or ectopic mineralization. This interpretation leads to testable design rules: define the ATP material fingerprint, map dose and spatial distribution, distinguish the true carrier phase, and assess cartilage matrix quality, lubrication, anti-hypertrophic stability, interface mechanics, persistence, and synovial safety. ATP should thus be developed as a dose-controlled and spatially restricted component whose value depends on material–tissue matching and direct mechanistic validation. Full article

The limited utilization of raw clays in the rubber industry is primarily attributed to an inadequate understanding of the complex interactions between clay minerals, their accessory minerals, and the polymer matrix. This study compares two local raw clays (SIT and KLE) with a reference industrial clay (REF) to demonstrate how differences in mineralogical composition affect the mechanical properties of natural rubber (NR)-based composites. Mineralogical characterization techniques (XRD, TGA-DSC, and IR) reveal distinct profiles: REF exhibits well-crystallized kaolinite as its dominant phase, whereas SIT contains a high proportion of quartz with less crystalline kaolinite, and KLE shows a complex mineral assemblage including swelling minerals (montmorillonite and chlorite). Microstructural analysis of NR/clay composites reveals a physical dispersion of clay particles within the polymer matrix without evidence of intercalation, with greater homogeneity observed for REF and SIT. Rheological properties indicate that curing times increase with increasing filler content, a trend that is particularly pronounced for KLE due to its interactions with the curing system. NR/REF composites outperform NR/SIT and NR/KLE in all evaluated mechanical properties, including the modulus at 300% elongation (6.1 MPa vs. 3.3 and 2.7 MPa), tensile strength, hardness, and tear resistance. This study establishes that reinforcement efficiency is directly linked to high kaolinite crystallinity, the absence of swelling minerals, and low concentrations of accessory minerals. Based on these findings, untreated local clay soils are not suitable for the manufacture of NR inner tubes and require appropriate pre-treatment prior to use. Full article

Graphene, with excellent mechanical and self-lubricating properties for polymer modification, can be single- or multi-layered (3–10 layers). In this study, molecular dynamics simulations have been employed to qualitatively explore the relative trends and internal modification mechanism of polyimide (PI) modification by single-layer graphene and three-layer graphene with different sizes. Small-sized single-layer graphene (SSLG), small-sized multi-layer graphene (SMLG), large-sized single-layer graphene (LSLG), and large-sized multi-layer graphene (LMLG) were introduced into the PI matrix at an identical mass fraction with initially uniform dispersion during model construction. The tensile mechanical and frictional behaviors of graphene-modified PI were systematically examined. The results indicate that graphene addition effectively improves both the mechanical and tribological properties of PI. At a fixed filler mass fraction, SSLG exhibits the strongest interaction with PI, with a binding energy of 396.8 kJ/mol. The fractional free volume of SSLG-reinforced PI reaches 15.3%, which is considerably lower than the value calculated for pure PI (20.3%). The average elastic modulus of the SSLG-modified PI is 70.4% higher than that of pure PI, an increase which exceeds that of the SMLG-modified PI (45.2%), LSLG-modified PI (26.5%), and LMLG-modified PI (14.0%). In terms of tribological properties, the SMLG-modified PI exhibits optimal friction with an average friction coefficient of 0.105, which is 48.3% lower than that of pure PI and lower than the values for the SSLG (0.138), LSLG (0.156), and LMLG (0.182) systems. This work mainly draws qualitative structure-property rules and provides key theoretical fundamentals and design principles for tailoring the mechanical and tribological performance of high-performance graphene-reinforced polyimide composites. Full article

The increasing generation of agricultural and industrial waste has created a growing need for sustainable materials that can reduce environmental burdens while maintaining desirable performance. This study explores the development of hybrid composites using pinecone waste and cottonseed waste generated during spinning operations as reinforcement materials in epoxy and PCL (polycaprolactone) matrices. Four composite formulations were produced and evaluated in terms of their physical, mechanical, thermal, morphological, and crystallographic characteristics. Density, water absorption, tensile, compressive, flexural, and thermal conductivity properties were measured using standard testing procedures. Surface morphology and fiber–matrix interactions were examined through scanning electron microscopy (SEM), while X-ray diffraction (XRD) was used to investigate the crystalline structure of the composites. The epoxy-based formulations exhibited superior tensile and flexural performance, reduced moisture uptake, and lower thermal conductivity, indicating their suitability for interior and semi-structural applications. In comparison, the PCL-based composites demonstrated higher compressive load resistance and greater deformation capability, suggesting potential use in biodegradable packaging and cushioning materials. SEM analysis revealed noticeable differences in filler distribution and interfacial characteristics among the formulations, whereas XRD confirmed the crystalline features associated with both the polymer matrices and lignocellulosic reinforcements. Overall, the results demonstrate a practical route for converting forestry residues and spinning-industry waste into functional composite materials, supporting waste valorization and resource-efficient material development. Full article

Polymethylmethacrylate (PMMA) is still the most widely used prosthetic polymer, although its biological inertness and vulnerability to mechanical stress and microbiological colonization are gradually restricting its therapeutic lifespan. This narrative review develops a conceptual framework, three ceramic modifiers corresponding to three distinct biofunctional strategies, to logically guide the design of the next generation of PMMA-based prosthetic dentures. We critically analyze the transformation of hydroxyapatite (HA), silica (SiO₂), and titanium dioxide (TiO₂) from passive fillers to active functional phases, offering unique, complementary therapeutic advantages. Therefore, HA confers osteoconductive and bone affinity, SiO₂ provides surface reactivity, tunable bioactivity, and drug release capacity, while TiO₂ provides mechanical reinforcement, chemical stability, and photocatalytic antibacterial activity. These ceramics used in PMMA matrices result in hybrid materials that outperform standard resins in terms of structural, mechanical, and biological performance. Recent research on binary and ternary systems (e.g., HA–TiO₂, SiO₂–HA, and HA–SiO₂–TiO₂ in PMMA) has indicated synergistic effects, such as increased osteoblast proliferation, reduced biofilm development, improved fracture toughness, and favorable corrosion resistance in simulated oral environments. A decision matrix is also provided to assist the clinician in selecting the best ceramic for a given clinical function of a prosthetic base or provisional repair. Although polymer–ceramic hybrid systems show remarkable translational potential, there are still obstacles to be addressed in terms of long-term interfacial stability, standardized synthesis processes, and regulatory mechanisms. This review proposes a framework of PMMA as a multimodal biofunctional engineering platform rather than a basic structural polymer and provides a roadmap for the development of intelligent, interactive, and clinically durable prosthetic materials. Full article

This study presents, for the first time, an assessment of the dual role of waste enamels from heating device production in asphalt mixtures, as additives to modify euro bitumen (50/70) and as fillers, with a detailed analysis of their influence on properties of asphalt mixtures. Three types of enamels were investigated—premix (WEP), classic (WETM), and acid-resistant (WEART). Different characterization methods confirmed that these materials possess a borosilicate matrix enriched with various elements, including heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn). Although classified as hazardous by-products, enamels replaced 100% of conventional stone dust filler, with confirmed leaching test. Their role in bitumen modification was interpreted through a structure–property approach: bitumen (4–6 wt.%) acts as a viscoelastic polymer-like matrix, while enamel particles serve as micro-scale reinforcements that govern binder–filler interactions. The results demonstrate that, despite their hazardous nature, waste enamels are compatible with asphalt technology containing 5 wt.% bitumen, achieving satisfactory stability, acceptable deformation response, and favorable volumetric characteristics. By valorizing industrial waste in this novel way, this study opens a sustainable pathway for transforming hazardous materials into functional components for the asphalt industry. Full article

The development of sustainable polymer composites reinforced with renewable resources and advanced nanomaterials has attracted considerable attention for multifunctional engineering applications. In this study, an environmentally friendly epoxy-based biocomposite (EBC) reinforced with coconut shell powder (CSP) and graphene nanopowder (GNP) was successfully produced through a casting process. CSP was employed as a bio-based filler, while GNP was incorporated at concentrations ranging from 0 to 0.75 wt.% to improve the overall performance of the composites. The effects of GNP loading on bulk density, tensile strength, elongation at break, Shore D hardness, thermal conductivity, dielectric properties, thermal stability, mechanical and microstructural characteristics were systematically investigated. The results demonstrated that the incorporation of GNP significantly enhanced the multifunctional properties of the improved EBCs. Bulk density increased from 1137.5 to 1143.1 kg m⁻³ with increasing GNP content. The optimum tensile strength of 28.6 MPa and Shore D hardness of 77.4 were achieved at 0.45 wt.% GNP, indicating effective stress transfer and strong interfacial interactions between the epoxy matrix, CSP, and GNP. Thermal conductivity increased from 0.110 to 0.149 W m⁻¹ K⁻¹, while the dielectric constant increased from 3.06 to 4.25 with increasing GNP concentration. Thermogravimetric analysis revealed improved thermal stability and enhanced char formation in graphene-containing composites. FTIR analysis confirmed that graphene acted primarily as a physical reinforcement without altering the fundamental chemical structure of the epoxy network. SEM and EDX investigations demonstrated improved structural compactness, homogeneous filler dispersion, and successful graphene incorporation. The findings indicate that GNP and CSP reinforced EBCs possess significant potential for lightweight structural materials, thermal management systems, dielectric components, and sustainable multifunctional engineering applications. Full article

The food packaging sector widely relies on polymeric materials, and as sustainability concerns grow, commodity polymers need to be replaced with innovative and more sustainable materials. Thermoplastic polyurethane (TPU) is a versatile elastomeric polymer characterized by flexibility, strength, chemical and abrasion resistance, and biocompatibility. However, it presents some limitations, notably in terms of functional properties (i.e., barrier properties). The use of nano-sized renewable fillers, such as cellulose nanocrystals (CNCs), may improve these properties, extending the applicability range of TPU. In this work, bio-based TPU nanocomposites were obtained by adding commercial silane-modified cellulose nanocrystals (Si−O−CNC) at different contents (1–5 wt.%). The nanocomposites were produced via melt mixing followed by compression molding and were characterized in terms of chemical (FTIR), morphological, thermal, mechanical, rheological, wettability, and barrier properties (i.e., water vapor permeability, WVP and oxygen transmission rate, OTR). The presence of Si−O−CNC promoted hydrogen bonding interactions with the TPU matrix, affecting the microphase separation and organization of the hard segments. These microstructural changes improved thermal stability, reduced WVP and OTR, and increased tensile properties at lower nanofiller contents (1–3 wt.%). At higher contents, partial nanofiller aggregation was observed, leading to a reduction in mechanical performance. Overall, these results suggest that TPU/Si−O−CNC nanocomposites have promising potential as sustainable food packaging materials. Full article

The contributions of BaTiO₃ as the filler and 3-glycidoxypropyltrimethoxysilane as the binder in the matrices of styrene–ethylene–butylene–styrene are evaluated for extended applications in medicine and dentistry. The determinations of stability are achieved by chemiluminescence (CL) under isothermal and nonisothermal modes, measuring the values of oxidation induction time (OIT) and onset oxidation temperature (OOT), respectively, which characterize the progress of material oxidation. The calculation of activation energies for the progress of oxidation from isothermal CL measurements based on OIT values provides proof of the modification of interaction activity on the polymer/barium titanate interface. The increases in the activation energy values from 80 kJ mol⁻¹ for neat polymer to 83 kJ mol⁻¹ for SEBS/BaTiO₃ 1 wt% and 109 kJ mol⁻¹ for SEBS/BaTiO₃ 1 wt%/GPTMS 1 wt% is evidence of the contribution of silane to the structuration of the polymer surface. The influence of the two compounds, filler and additive, makes possible the extension of oxidation induction temperatures measured at 170 °C from 36 min, displayed by pristine polymer, to 245 min and 278 min for the titanate composites free of silane and in the presence of GPTMS 1 wt%, respectively. Full article

The growing volume of industrial waste and the need for sustainable material solutions drive the search for cost-effective fillers and energy-efficient processing methods for polymer composites. This study investigates the valorization of brick dust (BD), a fine ceramic waste, as a reinforcing filler for unsaturated polyester resin (UPR), combined with microwave (MW) treatment applied at different stages of composite fabrication. The brick dust was comprehensively characterized using laser diffraction, SEM, EDX, XRD, and FTIR, revealing an environmentally safe aluminosilicate powder with a mean particle size of 3–6 µm, plate-like morphology, and surface hydroxyl groups favorable for matrix interaction. The optimal filler content was found to be 50 phr, which increased flexural strength by 6.5%, flexural modulus by 134%, tensile strength by 11%, and impact strength by 40% compared to neat UPR. Among the MW strategies evaluated, post-curing of the fully polymerized composite for 120 s proved most effective, yielding further improvements in flexural strength (110 MPa, +34.1%), flexural modulus (8250 MPa, +49.7%), impact strength (13.8 kJ/m², +119%), and Shore D hardness (88). MW post-curing also increased the gel fraction from 95.0% to 97.8%, raised the thermal stability index (THRI) from 150.6 to 165.8, and reduced equilibrium water absorption from 0.62% to 0.47% with a reversibility index of 87.5%. Fracture surface analysis confirmed a transition from interfacial debonding to cohesive matrix failure, with ultra-thin polymeric veils replicating the scaly filler structure. These results demonstrate that microwave post-curing synergistically enhances the mechanical, thermal, and moisture-resistant properties of brick dust-filled polyester composites. Full article

The increasing accumulation of glass-fiber-reinforced polymer (GFRP) waste poses significant environmental challenges, calling for effective and scalable recycling strategies. In this work, a solvent-assisted cold mixing process was employed to incorporate very high amounts of GFRP (up to 75 wt%) into recycled expanded polystyrene (ePS). The composites were deeply characterized, with particular attention to the role of particle size distribution and filler content. The results demonstrated that GFRP granulometry played a key role in determining composite performance. Intermediate particle sizes (0.25 mm) provided the best balance between dispersion, interfacial interaction, and mechanical properties, whereas excessively fine fractions introduced defects and reduced impact resistance (from 0.7 to 2.0 kJ/m² going from dust to 0.25 mm at 75 wt%). Notably, the solvent-assisted approach has been widely recognized as an effective strategy to ensure homogeneous dispersion even at high filler contents, allowing subsequent melt processing without re-agglomeration. Recycled composites retained most of their chemical and mechanical properties after reprocessing, with only moderate performance losses mainly related to fiber fragmentation. Overall, this study demonstrates an effective and sustainable route for the simultaneous valorization of ePS and GFRP waste, enabling the production of highly loaded composites with preserved functionality and improved resource efficiency. Full article

Bio-based and biodegradable polymer composites based on polylactic acid (PLA) and polybutylene succinate-co-adipate (PBSA) were developed for rigid food packaging applications. Agro-industrial residues consisting of ground leaves and branches derived from tangerine tree cultivation (pruning) were used as fillers at high loading (30 wt%) before (PRE) or after (POST) extraction of bioactive compounds. The influence of blend composition (PLA/PBSA 60/40 and 30/70), filler extraction, and the addition of antioxidants (0.5 wt%) on material properties was systematically investigated. Composites were processed via extrusion and injection molding and characterized through FTIR, SEM, tensile testing and thermal analysis. The results show that polymer blend morphology affects mechanical behavior, with co-continuous structures (60/40) exhibiting improved ductility compared to dispersed systems (30/70). The incorporation of lignocellulosic residues increased stiffness but reduced elongation at break. Extraction treatment significantly modified filler morphology and interfacial interactions, slightly improving dispersion and processability. The effect of the extracted bioactive compounds on the thermal stabilization of biocomposites was also investigated. Overall, the findings demonstrate the potential of combining biodegradable polymer blends with treated agricultural residues to produce sustainable rigid packaging materials while supporting a bio-circular approach. In fact, preliminary extraction of valuable compounds from tangerine pruning waste appears to be a convenient strategy for its efficient cascade valorization. Full article