Band 40, Heft 1

Concerns about the effect on the environment and non-renewable nature of plastics have sparked a substantial field of study towards the creation of recyclable polymers. Vitrimers are a potential class of reusable polymers that have recently attracted a lot of interest. Like conventional thermosets in strength, durability, and chemical resistance, these materials offer the added benefit of being recyclable at the end of their useful life. Their chemical structure, which includes dynamic covalent crosslinks to provide stability while enabling reprocessing, is credited with this special characteristic. We lay out an overview of recent developments and their applications in epoxy based vitrimeric materials by using the different types of covalent adaptable networks (CANs) – single, dual and triple in this paper with a lot of attention on design tactics that make it easier to create circular materials of the future. Covalent Adaptable Networks (CAN), a novel polymer family that can bridge the gap between thermosets and thermoplastics, emerged in the recent years and uses dynamic covalent chemistry to crosslinked polymer networks. The field was enhanced in 2011 by Leibler and colleagues when they introduced the notion of vitrimers, which are crosslinked polymers that retain the integrity of their network even after heating and allow the covalent connections to be reallocated within them by associative exchange reactions. This review also demonstrates how the vitrimer community is paying attention to the need for sustainable material development by demonstrating the use of biobased building blocks in the synthesis of novel and high-performing vitrimers. Having outlined the primary characteristics of vitrimers, commercialization and development of vitrimers for different applications is emphasized to portray their benefits for self-healing, malleability, orthogonal processability, and various shape memories along with sustainable solutions to synthetic materials.

In the present work, agro-industrial waste has been blended with plastic waste to fabricate value added product and also reduce the environmental pollution. Tamarind seed powder (TSP) has been melt mixed with polypropylene (PP) waste in various proportions to prepare composite sheets. The composite specimens have been evaluated for their tensile strength, impact strength and hardness. In composites, highest tensile strength of 20.6 MPa and Young’s modulus of 953.3 MPa have been achieved with 30 wt% and 40 wt% of TSP, respectively. Composites have lower strength but better hardness than PP. Maximum hardness of 69.7 HRL has been obtained in composites with 40 wt% TSP. Poor interfacial bonding as observed in fractured specimens is responsible for lower strength in composites. However, the composite specimen has better thermal stability than PP. Weight loss has been observed in composite specimens with higher loading of TSP due to degradation of TSP upon subjecting the specimens to biodegradability tests. Based on the results obtained in the study, 40 wt% of TSP in the composites conveys suitable mechanical and thermal properties.

Materials development is essential for all industries to meet the current demands Limestone powder (LS), coconut shell fiber (CSF) and sugarcane bagasse fiber (SBF) were impregnated in a laminated glass fiber polymer matrix. The fiber to matrix ratio is 50 %, while SBF and CSF start replacing natural fibers at a rate of 5–15 %, and LS is always 5 %. The proposed fiber-reinforced composites were manufactured by compression molding (CMM) and the test samples were cut according to the ASTM for tensile, impact, moisture, scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermogravimetric (TGA) tests. The results showed that the strength of the materials is influenced by the impregnation of the fibers into the matrix phase. Impregnation of natural fibers in glass fiber composite structures at 10–15 % loading demonstrated a weight saving of 7–8 %, tensile strength ranging from 330 to 350 MPa, maximum moisture absorption of 3.4 g, and thermal stability around 300 °C. Addition of limestone powder resulted in improved bonding ability, better surface finish, and reduced porosity, as demonstrated by SEM analysis.

The duration of lesions is a matter of public health concern and requires the development and application of new materials to achieve satisfactory results in disease treatment. Polymeric films are promising options for controlled drug delivery, enabling improved drug delivery and treatment efficiency. The aim of this study is to develop natural polymeric films for the controlled release of mupirocin. Films based on combinations of κ -carrageenan and hyaluronic acid, crosslinked with Zn 2+ , were developed. Vibrational spectroscopy (Raman and infrared spectroscopies) was used to characterize the chemical structure and crosslinking process. Micro-Raman imaging and scanning electron microscopy were employed to observe the spatial distribution of the polymers and morphology of the samples, respectively. The uniformity of mass, thickness, and MUP concentration was, respectively, 0.0082 ± 0.0021 g, 0.2500 ± 0.0354 mm, and 3.751 ± 0.6242 % for film 1; 0.0045 ± 0.0009 g, 0.1000 ± 0.0224 mm, and 4.086 ± 0.3673 % for film 2; and 0.0030 ± 0.0010 g, 0.1000 ± 0.0606 mm, and 4.052 ± 0.3468 % for film 3. The percentages of antibiotics present in the films were lower than the total amount of antibiotics added (8.0 %), suggesting that losses occurred during film production. Swelling and release kinetics studies showed that the films had a good swelling capacity and controlled the drug release process. The antibacterial activities of the films against Staphylococcus aureus , Escherichia coli , Staphylococcus epidermidis, and Pseudomonas aeruginosa was determined using the inhibition zone method. The best activity was observed for the films containing 50 % hyaluronic acid and 50 % carrageenan. The results demonstrated that the carbohydrates used and crosslinking process can potentially be utilized for the controlled delivery of mupirocin.

Composite materials are extensively utilized in the aerospace industry. Nevertheless, fire hazards persist as a significant safety challenge. Exposure to fire environments causes pyrolysis in composite materials, resulting in diminished structural integrity and the emission of heat, gases, and smoke, thereby posing significant risks to passenger safety and flight operations. To examine the thermal response of composite panels under unilateral heating, we selected a representative carbon fiber epoxy composite panel commonly found in aircraft structures. A thermal response test platform was established to perform high-temperature experiments on the composite panels. Utilizing principles of energy conservation, the Arrhenius thermal decomposition rate, and mass conservation equations, a nonlinear mathematical model was formulated to predict the time-temperature profiles of both exposed and unexposed surfaces of the composite panel under thermal radiation. The results demonstrate that the developed model effectively predicts the time-temperature profiles of both surfaces, showing good agreement with experimental data. Steady-state temperature errors were calculated at 2.5 % and 5.7 %, respectively, both falling below the 10 % threshold, thus confirming the validity of the numerical computation.

The crystallization of organic-based materials occurs under conditions far from equilibrium, leading to patterns that grow as propagating waves into the surrounding unstable fluid medium. This problem was reformulated considering the concept of thermal forces of preexisting 2D patterns. A new finite difference numerical scheme was tested. Dendritic islands were distributed in the liquid-viscous fluid. It induced a heterogeneous thermal distribution nearby the dendritic islands. The evolution of the isoline of the temperature versus time reveals fractal patterns within the inter-dendritic liquid. The physical origin of the fluctuations is guided by the proximity of the dendrites, i.e. lack of space. Moreover, the gradient of temperature is depicted by isocline pictures. Fractal patterns may be considered advantageous and be taken as a key point to the next step, i.e. the crystal growth in an environment subjected to rapid variations of temperature.

Polyoxymethylene (POM) and ultra-high molecular weight polyethylene (UHMWPE) are widely used in aerospace, petrochemical, marine engineering, medical equipment and other fields, because of their high elasticity, low density, high strength and high toughness. This paper studied the solid–liquid contact phenomenon by measuring the contact angle between these two polymers and water droplets. The orthogonal test data of surface contact angle between UHMWPE/water and POM/water were processed by using the range analysis method. The effects of surface texture, shape and size on the wettability of UHMWPE and POM were studied. The results show that there is a significant correlation between the roughness of UHMWPE and POM and the contact angle, and the trend is basically the same. Through the relationship between roughness of different texture surfaces and contact angle range R , it can be concluded that the greater the roughness, the lower the influence of surface texture size parameters. The influence of four texture shapes on the surface wettability of UHMWPE and POM was analyzed. The results show that the surface wettability of UHMWPE and POM is affected by four texture shapes in the order of square > circle > hexagon > groove shape, and that different surface texture parameters have different effects on the contact angle of water droplets on different texture shapes. The surface wettability of UHMWPE is more easily affected by the structure width W . The surface wettability of POM is more easily affected by the spacing width B , and it shows stronger hydrophobicity. This discovery may provide a certain reference value for the preparation of hydrophobic and superhydrophobic surfaces. It is great significance to optimize the surface texture and improve the wettability of the material.

Machine learning methods were applied to investigate changes in material properties during degradation, focusing on bio-based PLA and a PLA/native potato starch compound (50 wt%). Sixteen aging conditions involving various temperatures and humidity levels, and aging durations were examined. Characterization of aged samples involved tensile tests, FTIR analysis, weight or density measurements, and injection molding data. These data served as inputs to develop and compare predictive models of mechanical properties like Young’s modulus and elongation at break. Linear and polynomial regression, as well as multilayer perceptron (MLP) models were employed to evaluate their prediction accuracy. The best model accuracy (RMSE = 0.33) was achieved by segregating the dataset by material type and employing linear regression. Notably, employing two independent variables such as temperature and humidity led to high model quality (RMSE = 0.35). Effect diagrams revealed strong alignment between actual and modeled data, highlighting the comparative strengths of each modeling approach.

Three-dimensional viscoelastic flow numerical models for the polymer coextrusion process were established on the basis of two different wall conditions and solved via finite element methods. The influence of polymer melt viscosity on the coextrusion process was investigated by analyzing die swell, melt interlayer interface stability and flow field distribution under two different wall slip conditions, namely, sticky adhesive condition and fully slip non adhesive condition. The results indicate that in the traditional coextrusion process with sticky adhesive condition, the die swell, interface stability and flow field distribution change with the melt viscosity, but the effects of the shell melt viscosity differ from those of the core melt viscosity. The die swell, interface offset degree and radial flow strength (orthogonal to the flow direction) increase with increasing shell melt viscosity and decrease with increasing core melt viscosity. The die pressure drop, shear rate and first normal stress difference increase with increasing shell or core melt viscosity, but the influence of the shell melt viscosity is much greater than that of the core melt viscosity. In the gas-assisted coextrusion process with fully slip non adhesive condition, the die swell, interface stability and flow field distribution are not affected by the viscosity of both polymer melts which means that the flow behavior in the coextrusion channels is independent of the polymer viscosity. There is no die swell or interface deviation phenomenon, nor any melt radial flow. The die pressure drop, shear rate and first normal stress difference are close to zero, except in the close vicinity of the die inlet. This approach not only ensures product quality but also solves the problem of material selection for polymer coextruded products. In addition, the goal of energy conservation and consumption reduction has been achieved, and the energy savings and consumption reduction effects are particularly significant for high-viscosity melts.