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Polymers Jun 2024The roll coating method is of considerable significance in several industries, as it is applied practically in the production of paint, the manufacturing of PVC-coated...
The roll coating method is of considerable significance in several industries, as it is applied practically in the production of paint, the manufacturing of PVC-coated cloth, and the plastic industry. The current study theoretically and computationally analyses the Powell-Eyring fluids with variable viscosity during the non-isothermal roll-over web phenomenon. Based on the lubrication approximation theory (LAT), the problem was formulated. The system of partial differential equations (PDEs) obtained from the mathematical modeling was further simplified to a set of ordinary differential equations (ODEs) using suitable transformations. A regular perturbation method was implemented to obtain the solution in terms of velocity, pressure gradient, pressure, and flow rate per unit width. This study also captures important engineering characteristics such as coating thickness, Nusselt number, shear stress, roll/sheet separating force, and roll-transmitted power to the fluid. Along with a comparison between the present work and published work, both graphical and tabular representations wer made to study the effects of various factors. It was observed that the velocity profile is the decreasing function of non-Newtonian and Reynold viscosity parameters. In addition, the response surface methodology (RSM) was employed to investigate the sensitivity of the shear stress and the Nusselt number.
PubMed: 38932073
DOI: 10.3390/polym16121723 -
Polymers Jun 2024Carbon fiber-reinforced plastic (CFRP) is frequently utilized as a bolted joint material in aircraft applications because of its high specific strength and specific...
Carbon fiber-reinforced plastic (CFRP) is frequently utilized as a bolted joint material in aircraft applications because of its high specific strength and specific modulus. Therefore, the performance of CFRP under -50° is significant. Here, we discuss the specimens of two bolted connections (single-nailed and double-nailed) used for static load tensile and tensile fatigue tests. We obtained the failure curves and fatigue life relationships of the specimens with two different connection methods at different tightening torques (2 N/m, 4 N/m, and 6 N/m) and low room temperatures. Our analysis reveals the effect of the bolt tightening torque and temperature on the structural mechanical properties of a CFRP bolted joint. It provides a data reference for researchers to design a composite bolted joint structure in an airplane flight environment.
PubMed: 38932065
DOI: 10.3390/polym16121715 -
Polymers Jun 2024While extensive research has focused on understanding the degradation mechanisms of Poly(vinyl acetate) (PVAC) paint under different environmental conditions, limited...
While extensive research has focused on understanding the degradation mechanisms of Poly(vinyl acetate) (PVAC) paint under different environmental conditions, limited attention has been paid to the long-term stability of PVAC-based white glues, especially when used in artworks. This study investigates the accelerated degradation, under simulated photoaging, and isothermal treatment of a commercial PVAC-based white glue considered representative of this class of materials used in contemporary artworks to predict its durability and assess its behavior in art objects. Through accelerated aging experiments and comparison with natural aging observed in artworks, the study reveals the formation of chromophores and the release of plasticizers as key processes; in particular, the progressive darkening was considered an early indicator of degradation processes, before structural changes could be detected by FTIR or NMR spectroscopies. The plasticizer loss induces an increase in glass transition temperature, from 7 °C to temperatures higher than room temperature, affecting the adhesive's cohesive strength and contributing to the detachment of materials in artworks. The findings underscore the importance of preventive conservation measures to mitigate degradation issues in PVAC-based artworks.
PubMed: 38932062
DOI: 10.3390/polym16121712 -
Polymers Jun 2024Materials based on highly reactive α-tricalcium phosphate (α-TCP) powder were developed and evaluated. Furthermore, the impact of different polymeric additives, such...
Materials based on highly reactive α-tricalcium phosphate (α-TCP) powder were developed and evaluated. Furthermore, the impact of different polymeric additives, such as citrus pectin or polyacrylamide (PAAM) modified with sago starch, neem flower, or rambutan peel, on the physiochemical and biological properties of the developed materials was assessed. The addition of modified PAAM shortened the setting process of bone cements and decreased their compressive strength. On the other hand, the addition of citrus pectin significantly enhanced the mechanical strength of the material from 4.46 to 7.15 MPa. The improved mechanical properties of the bone cement containing citrus pectin were attributed to the better homogenization of cementitious pastes and pectin cross-linking by Ca ions. In vitro tests performed on L929 cells showed that 10% extracts from α-TCP cements modified with pectin are more cytocompatible than control cements without any additives. Cements containing PAAM with plant-derived modifiers show some degree of cytotoxicity for the highly concentrated 10% extracts, but for diluted extracts, cytotoxicity was reduced, as shown by a resazurin reduction test and live/dead staining. All the developed bone substitutes exhibited in vitro bioactivity, making them promising candidates for further biological studies. This research underscores the advantageous properties of the obtained biomaterials and paves the way for subsequent more advanced in vitro and in vivo investigations.
PubMed: 38932061
DOI: 10.3390/polym16121711 -
Polymers Jun 2024Among the many benefits of implementing numerical analysis on real objects, economic and environmental considerations are likely the most important ones. Nonetheless, it...
Among the many benefits of implementing numerical analysis on real objects, economic and environmental considerations are likely the most important ones. Nonetheless, it is also crucial to constrain the duration and space necessary for conducting experimental investigations. Although these benefits are clear, the applicability of such models must be appropriately verified. This research subjected validation of numerical models depicting the behavior of unstrengthened and strengthened laminated veneer lumber (LVL) beams. As a reinforcement, a carbon fiber reinforced polymer (CFRP) sheet and laminates were used. Experiments were conducted on full-scale members within the framework of the so-called four-point bending testing method. Numerical simulations were performed using the Abaqus software. Two types of material models were examined for laminated veneer lumber: linearly elastic and linearly elastic-perfectly plastic with Hill's yield criterion. A distinction was made in the material properties of carbon composites based on their location on the height of the cross-section. The outlined numerical models accurately depict the behavior of real structural elements. The precision of predicting load-bearing capacity amounts to a few percent for strengthened beams and a maximum of eleven percent for unstrengthened beams. The relative deviation between numerical and experimental values of bending stiffness was at a maximum of seven percent. Applying the elastic-plastic model enables accurate representation of the load versus deflection relation and the distribution of stress and deformation of strengthened beams. Based on the findings, directives were provided for further optimization of the positioning of composite reinforcement along the span of the beam. Reinforcement design of existing laminated veneer lumber members can be made using presented methodology.
PubMed: 38932050
DOI: 10.3390/polym16121697 -
Polymers Jun 2024While the brittle polylactide (PLA) has a high durability among bioplastics, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) with certain ductility exhibits facile...
While the brittle polylactide (PLA) has a high durability among bioplastics, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) with certain ductility exhibits facile compostability. The addition of polybutylene adipate terephthalate (PBAT) may also be used to improve the ductility and toughness of brittle bioplastics. Binary and ternary blends of PLA/PBAT/PHBH based on either PLA or PHBH as the matrix have been manufactured using a twin-screw extruder. The melt rheological, mechanical, and morphological properties of the processed samples were examined. Binary blends of PLA/PHBH show superior strength, with the PLA75/PHBH25 blend exhibiting a tensile strength of 35.2 ± 3.0 MPa, which may be attributed to miscible-like morphology. In contrast, blends of PLA with PBAT demonstrate low strength, with the PLA50/PBAT50 blend exhibits a tensile strength of 9.5 ± 2.0 MPa due to the presence of large droplets in the matrix. PBAT-containing blends exhibit lower impact strengths compared to PHBH-containing blends. For instance, a PLA75/PBAT25 blend displays an impact strength of 1.76 ± 0.1 kJ/m, whereas the PHBH75/PBAT25 blend displays an impact strength of 2.61 ± 0.3 kJ/m, which may be attributed to uniformly dispersed PBAT droplets.
PubMed: 38932048
DOI: 10.3390/polym16121699 -
Polymers Jun 2024Ultra-high molecular weight polyethylenes (UHMWPEs) are significant engineering plastics for their unique properties, such as high impact resistance, abrasion... (Review)
Review
Ultra-high molecular weight polyethylenes (UHMWPEs) are significant engineering plastics for their unique properties, such as high impact resistance, abrasion resistance, weatherability, lubricity, and chemical resistance. Consequently, developing a suitable catalyst is vital in facilitating the preparation of UHMWPE. The late transition metal catalysts have emerged as effective catalysts in producing UHMWPE due to their availability, enhanced tolerance to heteroatom groups, active polymerization characteristics, and good copolymerization ability with polar monomers. In this review, we mainly focus on the late transition metal catalysts, summarizing advancements in their application over the past decade. Four key metals (Ni, Pd, Fe, Co) for generating linear or branched UHMWPE will be primarily explored in this manuscript.
PubMed: 38932038
DOI: 10.3390/polym16121688 -
Polymers Jun 2024Unprecedented plastic production has resulted in over six billion tons of harmful waste. Certain insect taxa emerge as potential agents of plastic biodegradation.... (Review)
Review
Unprecedented plastic production has resulted in over six billion tons of harmful waste. Certain insect taxa emerge as potential agents of plastic biodegradation. Through a comprehensive manual and bibliometric literature analysis, this review analyses and consolidates the growing literature related to insect-mediated plastic breakdown. Over 23 insect species, representing Coleoptera, Lepidoptera, and 4 other orders, have been identified for their capacity to consume plastic polymers. Natural and synthetic polymers exhibit high-level similarities in molecular structure and properties. Thus, in conjunction with comparative genomics studies, we link plastic-degrading enzymatic capabilities observed in certain insects to the exaptation of endogenous enzymes originally evolved for digesting lignin, cellulose, beeswax, keratin and chitin from their native dietary substrates. Further clarification is necessary to distinguish mineralisation from physicochemical fragmentation and to differentiate microbiome-mediated degradation from direct enzymatic reactions by insects. A bibliometric analysis of the exponentially growing body of literature showed that leading research is emerging from China and the USA. Analogies between natural and synthetic polymer's degradation pathways will inform engineering robust enzymes for practical plastic bioremediation applications. By aggregating, analysing, and interpreting published insights, this review consolidates our mechanistic understanding of insects as a potential natural solution to the escalating plastic waste crisis.
PubMed: 38932021
DOI: 10.3390/polym16121671 -
Polymers Jun 2024Conversion of chemical feedstocks derived from fossil fuels to virgin polymer, manufacturing of plastics in coal-dependent economies, and increasing consumption of... (Review)
Review
Conversion of chemical feedstocks derived from fossil fuels to virgin polymer, manufacturing of plastics in coal-dependent economies, and increasing consumption of virgin polymers for plastics packaging contribute significantly to environmental issues and the challenges we face. Nowadays, promoting sustainable development has become the consensus of more and more countries. Among them, the recycling of multilayer packaging is a huge challenge. Due to the complexity of its structure and materials, as well as the limitations of existing recycling frameworks, currently, multilayer packaging cannot be commercially recycled thus resulting in a series of circular economy challenges. It is undeniable that multilayer packaging offers many positive effects on products and consumers, so banning the use of such packaging would be unwise and unrealistic. Developing the appropriate processes to recycle multilayer packaging is the most feasible strategy. In recent years, there have been some studies devoted to the recycling process of multilayer packaging. Many of the processes being developed involve the use of solvents. Based on the recycled products, we categorised these recycling processes as solvent-based recycling, including physical dissolution and chemical depolymerisation. In physical dissolution, there are mainly two approaches named delamination and selective dissolution-precipitation. Focusing on these processes, this paper reviews the solvents developed and used in the last 20 years for the recycling of polymers from multilayer packaging waste and gives a summary of their advantages and disadvantages in terms of cost, product quality, ease of processing, and environmental impact. Based on existing research, one could conclude that solvent-based recycling methods have the potential to be commercialised and become part of a standard recycling process for polymer-based multilayer packaging. The combined use of multiple solvent-based recycling processes could be a breakthrough in achieving unified recycling of multilayer packaging with different components.
PubMed: 38932020
DOI: 10.3390/polym16121670 -
Polymers Jun 2024This study examines the applicability of an unknown composition waste plastic bag sample as bitumen modifier. The waste components were initially characterized to...
This study examines the applicability of an unknown composition waste plastic bag sample as bitumen modifier. The waste components were initially characterized to identify the type of plastics and the level of impurity. Asphalt binder performance was examined for rutting, thermal, and age resistance. The results revealed that the waste plastic bags, predominantly consisted of Low-Density Polyethylene (LDPE) and Linear Low-Density Polyethylene (LLDPE) and contained 6.1% impurities. The binder tests indicated that the waste plastic bags enhanced the rutting resistance of bitumen by one grade, with its modification more similar to LLDPE, rather than LDPE. The thermal degradation and aging properties of the modified binders demonstrated that the bitumen modified by the waste plastic bags exhibited slightly lower resistance to temperature and aging compared to virgin LDPE and LLDPE. This was attributed to the impurities contained in the waste plastic. In conclusion, the analyzed waste plastic bags proved to be suitable for use in binder modification, presenting a viable alternative to virgin LLDPE.
PubMed: 38932018
DOI: 10.3390/polym16121669