Abstract The present work involved the surface modification of waste coffee grounds (WCG) via cold plasma using Ar as the precursor gas. The untreated and plasma-treated WCG particles were mixed with high-density polyethylene (HDPE) at a 20/80 wt% ratio of filler to polymer by using a two-roll mill followed by a hydraulic press. The effect of plasma surface treatment on the performance of composites was investigated using various analytical techniques, including tensile and izod impact strength tests, thermogravimetric analysis (TGA), contact profilometry analysis, density measurements, and scanning electron microscopy (SEM). The incorporation of WCG resulted in a reduction in both the impact strength and tensile strength of the composite material. Nevertheless, plasma surface treatment resulted in significant improvements in both impact strength and tensile strength compared to WCG composites that had not been subjected to cold plasma. The TGA results demonstrated that cold plasma treatment increased the thermal stability of WCG/HDPE composites, as the onset temperature of decomposition of plasma-treated WCG composites was higher than that of untreated WCG composites. The SEM images revealed modifications at the fiber-matrix interface, corroborating the improved mechanical properties after treatment with cold plasma. The contact profilometry analysis showed an enhancement in surface roughness, affirming the effect of plasma treatment on the WCG surface. These findings suggest that cold plasma can be utilized as an effective method for the modification of agro-waste materials and the production of high-performance, eco-friendly composite materials.
Abstract Core-shell emulsion electrospinning combined with sacrificial templating shows great promise for constructing multifunctional tissue engineering scaffolds, yet systematic quantitative research on processing-structure-performance relationships remains insufficient. This work presents an integrated fabrication strategy coupling sol-emulsion electrospinning and sacrificial fiber templating to engineer dual-functional porous fibrous scaffolds that achieve synchronized sustained bioactive delivery and efficient cell infiltration. Nerve growth factor (NGF)-loaded core-shell nanofibers were optimized via a water-in-oil emulsion system, and interconnected macroporous networks were introduced by co-electrospinning with polyvinylpyrrolidone (PVP) sacrificial fibers followed by selective water leaching, with pore characteristics flexibly tuned by PVP concentration and flow rate. A triadic correlation model of “wettability-pore structure-mechanical properties” was established to quantify the intrinsic interrelations among processing conditions, scaffold microstructure and overall functional performance. The proposed “Emulsion Dynamic Balance Point” is identified as the critical determinant for fiber morphology, mechanical integrity and controlled release behavior. Under optimal formulation, the core-shell fibers deliver an NGF encapsulation efficiency of 90.0 ± 0.4 %, an ultralow 24-h burst release of 7.1 % and 89.3 % cumulative release over 30 days through a dual-diffusion-barrier mechanism. The scaffold pore size and porosity are tunable in the ranges of 2.88–16.88 μm and 72.3–85.7 %, respectively. The triadic model reveals pore structure as the central governing hub: enlarged porosity enhances capillary-driven topological hydrophilicity but inevitably reduces tensile strength, and a Pareto-optimal formulation balancing cell infiltration capacity and mechanical compatibility is determined. Notably, the macroporous structure does not compromise sustained NGF release kinetics, enabling independent and synergistic tuning of biochemical cues and three-dimensional topological microenvironment.This work provides a low-cost, scalable pathway for controllable manufacturing of multifunctional fibrous biomaterials, and the proposed theoretical framework offers generalizable design principles for advanced regenerative medicine applications.
Abstract The study explores the influence of layer thickness, infill pattern, and nozzle temperature on tensile strength, hardness, and relative density of FDM printed specimens of polylactic acid (PLA). Eighteen different sets of parameters were explored during the study, including two layers of thickness (0.1 and 0.2 mm), three different infill patterns (concentric, rectilinear, and octogram spiral), and three nozzle temperatures (210, 220, and 230 °C). The tensile test was done following ISO 527-2, the hardness test according to ASTM D2240, and the measurement of relative density was done using the Archimedes principle. From the results, it can be observed that the effect of layer thickness is significant where samples of 0.1 mm exhibited tensile strengths of 35–49 MPa compared to samples of 0.2 mm with tensile strengths of 34–48 MPa. The highest tensile strength was exhibited by concentric infill pattern due to its continuous load-bearing capacity, followed by rectilinear while the lowest was recorded by octogram spiral infill pattern. There was a significant correlation between the tensile strength and relative density ( r = 0.89, p < 0.001), and it reached its maximum at a value of 99 %. Analysis of the failure showed that rectilinear pattern had ductile failure, while octogram spiral pattern failed by delamination.
Abstract Fiber orientation, fiber length distribution, and spatial morphology gradients govern the mechanical performance of injection-molded fiber-reinforced thermoplastic composites. Predicting these features accurately requires modeling frameworks that span flow kinematics, fiber interaction mechanics, and process–structure linkage. This paper reviews the principal modeling approaches used for morphology prediction in short-fiber (SFRT) and long-fiber reinforced thermoplastics (LFRT), from foundational Jeffery-based orientation theory through Folgar–Tucker formulations, reduced-strain and anisotropic diffusion closures, coupled orientation–length frameworks, and physics-informed hybrid approaches. Classical models offer computational efficiency and are well integrated into commercial solvers but assume constant fiber length, limiting their applicability in LFRT systems where breakage, evolving aspect ratio, and orientation–length coupling dominate morphology. Coupled frameworks improve fidelity but remain research-level tools. Illustrative worked examples, calibrated against published experimental data are used to convey the practical magnitude of model disagreement for both SFRT and LFRT geometries. Industrial deployment barriers including mesh sensitivity, closure instability, and parameter non-transferability are examined. The review also addresses the comparatively under-explored linkage between predicted morphology and mechanical property estimation, and identifies weld-line morphology and interfacial sizing effects as open research gaps.
This study presents a comprehensive investigation into the development of sustainable, high-performance elastomeric composites based on ethylene propylene diene monomer (EPDM) reinforced with recycled nano-tungsten oxide (WO3). The work focuses on the effect of using recycled WO(3 )on enhancing the thermal stability, flame retardancy, and chemical durability of the composites. The recycled nano-filler was incorporated into the EPDM matrix at various loadings (0-20 phr). Flame retardancy was evaluated using horizontal burning tests and limiting oxygen index (LOI) measurements, in which the WO(3 )content significantly reduced the burning rate from 15 mm/min to 4 mm/min and increased the LOI to 21.7 %. Thermal gravimetric analysis (TGA), conducted from room temperature to 600 degrees C, demonstrated a marked improvement in thermal stability, with the onset decomposition temperature shifting from 221 degrees C to 228 degrees C and a 22 % increase in char residue at 600 degrees C. Furthermore, chemical resistance was evaluated by immersion in xylene, nitric acid (HNO3), and sodium hydroxide (NaOH). Swelling measurements in xylene indicated a robust filler-polymer interaction, reducing the solvent uptake by 3.65 %. A comparative study of Shore A hardness before and after chemical immersion revealed that WO3-filled EPDM maintained its structural integrity better than neat EPDM, with a minimal hardness loss (less than 10 %) after acidic and basic treatment. Optical microscopy confirmed these results, showing significantly lower surface degradation and pitting in the reinforced composites compared to the neat rubber. These findings position the recycled WO3/EPDM composite as a robust, eco-friendly material for industrial applications requiring high thermal and chemical resilience.
