Abstract The accurate prediction of throughput and the melting process in single-screw extruders are crucial for the design and optimization of plasticizing units, as the melting process is often the rate-limiting factor and markedly influences final product quality. While the design of these units has long relied on empirical values and simplified analytical models, Computational Fluid Dynamics (CFD) now offers a powerful alternative for process analysis. However, its predictive accuracy strongly depends on the precision of the underlying physical models. This work aims to improve and validate a numerical two-phase simulation model for plasticizing extruders. To this end, extensive experimental investigations were conducted using screw pull-out tests, following the method of Maddock, on an extruder with a 30 mm diameter. Utilizing High-Density Polyethylene (HDPE) and two different three-zone screws, a broad dataset was generated through a statistical design of experiments by systematically varying screw speed and barrel temperature. Based on this experimental data, targeted adjustments were made to a CFD model that builds upon the continuum approach by Karrenberg and further advanced by Dörner and Schall. The key improvements include the implementation of models for the bulk density and thermal conductivity, which account for the porosity of the bulk material in the screw channel as a function of pressure and temperature. The validation of the improved model shows good agreement between simulation and experiment. Throughput is predicted with high precision, and the simulated melting profiles reproduce the expected melting mechanism, although the melting lengths appear to be underestimated when compared with the cross-sections from the screw pull-out experiments, the accuracy of which is subject to discussion. Analyses at the process limits, where unmelted material was observed exiting the extruder, likewise revealed that the model overestimates the melting performance, although the extent of overestimation is smaller. This study demonstrates that by adapting the physical sub-models, particularly by considering porosity, the predictive accuracy of CFD simulations can be markedly increased, especially with respect to throughput, thus providing an alternative tool for extruder design.

Abstract This study investigates the mechanical performance of sandwich composites comprising basalt (B) and aramid (A) fiber-reinforced skins with a PVC foam core, focusing on the effects of fiber hybridization and stacking sequence. Tensile, flexural, and 25 J impact tests were conducted to evaluate monolithic and hybrid configurations. Monolithic Basalt (B 5 /PVC/B 5 ) exhibited lower tensile strength (average ∼109.5 MPa) with higher flexural modulus (average ∼36.7 GPa) compared to Aramid (A 5 /PVC/A 5 ) skins. Conversely, Aramid skins (A 5 /PVC/A 5 ) demonstrated higher flexural strain (average ∼1.35 %), indicating greater ductility. Hybrid configurations balanced these properties; the BA-PVC (B 3 A 2 /PVC/A 2 B 3 ) arrangement achieved optimal energy absorption (average ∼25 J) under impact, outperforming AB-PVC (A 2 B 3 /PVC/B 3 A 2 ) (average ∼20 J). Tensile testing revealed A 5 /PVC/A 5 had the highest strength (average ∼136.7 MPa), while B 5 /PVC/B 5 showed the highest strain (average ∼9.56 %). Flexural testing confirmed B 5 /PVC/B 5 possessed the highest strength (43.7 MPa) and modulus (36.7 GPa). Stacking sequence critically governed failure modes, with basalt-dominated exteriors prioritizing stiffness but suffering abrupt core shear failure, while Aramid exteriors enhanced damage tolerance through progressive matrix cracking and fiber bridging. The PVC core’s low shear modulus amplified delamination in stiff hybrids, underscoring interfacial adhesion as a key limitation. Findings reveal that the BA-PVC architecture (Aramid outer/Basalt inner) optimally balances strength, ductility, and impact resistance.

Abstract Technical polymer profiles are often extruded while dragging them into a water bath. However, complex profiles may require additional forming tools. For example, geometrically complex profiles, such as PVC-window frames, require the use of a series of calibrators for satisfying severe geometric requirements. Calibrators are also required for rapid and homogeneous cooling as well, they must however be designed in such a way to minimize the temperature gradient along the profile thickness and hence to minimize the residual stresses of thermal origin. Within the context of numerical simulation of extrusion flows, a calibrator brings an additional downstream constraint to the kinematic equation which governs the extrudate surface shape. In the present paper, we propose a simple engineering approach for modelling calibrators used in profile extrusion, and we apply it to the non-isothermal simulation of the extrusion process for a 3D non-symmetric profile.

Abstract As a biodegradable material, polylactic acid (PLA) is widely used in healthcare industries, however, its bacterial properties cannot meet the requirements. Chitin, a natural antibacterial agent, is difficult to directly melt blend with PLA due to agglomeration. In order to enhance the compatibility between chitin and PLA, in this study, firstly, chitin was decomposed by cellulase to prepare enzymolysis chitin (EC). The viscosity and particle size of EC were measured and the optimal enzymolysis conditions were chosen. Then, the modified chitin antibacterial agent (MCAA) was prepared by mixing EC with glyceryl triacetate (GTA) and polyethyleneglycol (PEG), and the biodegradable PLA/MCAA composite was prepared by melt blending. Finally, the tensile, thermal, antibacterial properties, and the micromorphology of the PLA/MCAA composite were investigated. The results show that at a pH of 6.4 and a temperature of 55 °C, EC exhibited low viscosity and particle size after an enzymatic hydrolysis time of 4.5 h. Compared with PLA, PLA/MCAA composite exhibited better antibacterial effects against Escherichia coli and Staphylococcus aureus. Furthermore, in comparison to the PLA/chitin composite, there was less agglomeration in the PLA/MCAA composite, and the particle distribution of MCAA was more uniform.

Abstract Optimization is generally referred to as making the best and most effective use of materials. Optimization plays the most significant role when it comes to the field of research and development. Developing new products needs the best results with optimal time, cost, and resources. Especially in the case of industrial experiments, optimizing materials can save time, money, and manual power. So, it is necessary to have a comprehensive knowledge of various optimizing techniques currently adopted in industry. Hence this review covers the multiple types of polymer matrix composites manufacturing techniques currently adopted in industry, focusing on the manufacturing problems from the optimization perspective. Also, this review addresses some of the optimization approaches that current researchers attempt at every step of their research journey. Generally, optimization has to be coupled with the advancement of the manufacturing process that provides an ideal solution for cost reduction, energy consumption minimization, and improved competitiveness while assuring the end products’ quality. Stochastic algorithms such as Genetic Algorithms and Particle Swarm Optimization are examples of advanced statistical optimization techniques adopted by researchers in solving process parameters. Furthermore, experimental approaches such as the Taguchi Method and Response Surface Methodology for polymer matrix composite manufacturing optimization are also discussed in this review. Last but not least, a brief overview of how 3D printing can benefit the fabrication of polymer matrix composites is mentioned.

Abstract Ultra-high molecular weight polyethylene (UHMW-PE) fibers and bacterial nanocellulose (BNC) display exceptional mechanical properties alongside the outstanding tribological properties of UHMW-PE while showing unrestricted biocompatibility. For combining the intrinsic advantages of both materials, the present work demonstrates an approach that integrates the slurry-based laser fusion of PE-polyvinylpyrrolidone (PE-PVP) composites and the subsequent bacterial biosynthesis of nanocellulose. PE-PVP composites exhibiting a fraction of 10 % of UHMW-PE fibers were additively manufactured through the locally selective laser-based layer-wise evaporation and subsequent sintering of aqueous suspensions, yielding fiber composites with a water-soluble matrix. The in situ synthesis of bacterial nanocellulose exploits the gelling and dissolving of high-molecular PVP in aqueous media. By allowing for the infiltration of printed PE-PVP composites with nanocellulose-producing Komagataeibacter xylinus, a multiscale composite of polyethylene fibers and bacterial nanocellulose was obtained, corroborating the infiltration of micrometer-scale PE fibers with nanoscale cellulose fibers. Release experiments using methylene blue confirmed the potentials of PE-BNC composites for drug delivery applications, showing first order sigmoidal release kinetics.

Abstract Additive manufacturing techniques have made it possible to create lighter and stronger lattice structures with intricate repeating geometric patterns which can be utilized for various industrial applications. Although several studies have reported on the effects of lattices with varying geometry on mechanical properties, fewer studies have investigated the effects of post-processing parameters on mechanical properties of these lattices. As such, this study investigates the effects of solid fraction of octet truss-based lattices and the effect of heat treatment on the mechanical properties of 3D printed octet truss lattices. Experimental findings revealed that Young’s Modulus and strength of lattices were enhanced upon heat treatment where tensile strength and stiffness of lattices with 40 % solid fraction improved by 20.55 % and 29.11 % respectively. Besides, it was found that the lattices without and with heat treatment obeyed the Ashby’s classic scaling law reasonably well for both modulus-density and strength-density relationship.

Abstract Zinc alginate (ZnAlg) was prepared and subsequently employed to modify ammonium ligninsulfonate-based polyurethane foams (PUFs). A range of analytical techniques, including thermogravimetry, integral programmed decomposition temperature, activation energy, smoke density, cone calorimetry and scanning electron microscopy, were employed to characterise the modified PUFs. The results demonstrated that PUFA15Z5 (15 % ammonium lignin sulfonate and 5 g ZnAlg) with the lowest mass loss exhibited the second-highest sample decomposition temperature (T50 %), second-highest peak temperature (TMAX2), IPDT and activation energy. Furthermore, the PUFA15Z5 sample exhibited the smallest smoke density (23.11) and the highest light transmittance (67.11 %). The peak heat release rate, total heat release, smoke production rate, total smoke release and four fire risk assessment indicators of PUFA15Z5 were the lowest, while its carbon residue was the densest. The results demonstrated that PUFA15Z5 exhibited the most favourable thermal stability, flame retardant properties and the lowest smoke toxicity. These findings provide a valuable reference for subsequent biomass-based flame retardant modified polyurethane foams (PUFs).

Abstract There is currently considerable interest in high-density polyethylene (HDPE)/ultra-high-molecular-weight polyethylene (UHMWPE) blends as recyclable all-polyolefin materials with favorable mechanical properties that can be processed by continuous melt-mixing. Optimal mixing is required to improve the mechanical properties of polymer blends by ensuring their dispersibility and low degradation. In the present study, we investigated the effects of mixing temperature on the dispersion and degradation behaviors of HDPE/UHMWPE blends. Neat HDPE and a HDPE blend comprising 5 % UHMWPE were obtained by melt-mixing while changing the input energy in an internal batch mixer under a nitrogen atmosphere. The temperature of the mixer was set at 200 °C for neat HDPE, and at 180, 200, and 220 °C for the HDPE/UHMWPE blends. Optical microscopy and thermal analysis revealed that the dispersion of UHMWPE in HDPE was accelerated at higher mixing temperatures. However, in the high input energy range, mixing at 200 °C resulted in the most favorable dispersion. Gel permeation chromatography and rheological measurements suggested that chain scission and branching/crosslinking due to degradation were accelerated at higher mixing temperatures, even when mixing in a nitrogen atmosphere. Chemiluminescence measurements suggested that chain scission and branching/crosslinking were caused by an initial oxidation reaction. Furthermore, for the same input energy, the maximum shear stress increased as the mixing temperature decreased, but the mixing time and thermal history increased as the mixing temperature increased. The results suggest that in a blend comprising HDPE and UHMWPE, mixing at the molecular level due to high temperature and fine dispersion of UHMWPE due to shear stress proceed simultaneously. On the other hand, the results also confirmed that degradation was more influenced by the promotion of oxidation due to high temperatures and prolonged mixing than by shear stress.