Hasil untuk "Polymers and polymer manufacture"

Zak C. Eckel, Chaoyin Zhou, John H. Martin et al.

Conor S. Boland, U. Khan, Gavin Ryan et al.

G. D. Goh, Y. L. Yap, S. Agarwala et al.

Additive manufacturing (AM) has brought about a revolution in the way we can manufacture complex products with customized features. AM has paved its way in the application areas ranging from aerospace, automotive, consumer to biomedical. AM of composites has attracted special attention due to its promise in improving, modifying, and diversifying the properties of generic materials through introducing reinforcements. This review provides a detailed landscape of fiber‐reinforced composites processed via AM techniques. Different AM processes, various material formulations, and strengths and drawbacks of AM methods are discussed. Emphasis is paid to AM techniques focusing on continuous fibers, as they hold the promise of becoming the next‐generation composite fabrication methodology. The article also tries to identify the potential of AM technology for fiber‐reinforced composites and delves into challenges facing the area.

D. Tan

The uprising demands for electrical power and electrification requires advanced dielectric functionalities including high capacitance density, high energy density, high current handling capability, high voltage, high temperature, high thermal conductivity, light weight, and environmental reliability. Nanodielectric engineering emerges and attracts extensive efforts from many countries as a result. Unlike prior reviews focusing on lab scale nanocomposite study, this review focuses on recent innovations in polymer‐based nanodielectric design on a large scale and their film scale‐up efforts for advanced capacitors. The unconventional polymer‐nanofiller engineering and their process in the last two decades are discussed. The nanofunctionalized polymers on a molecular level for high dielectric constants and high dielectric strength are briefly described. The challenge associated with film scale‐up and retention of nanodielectric properties are then pointed out to be crucial toward a transfer of dielectric and capacitor technology. Several important attempts at scaling up dielectric films and capacitors recently supported by the US government and industry are reviewed. An alternative strategic approach to achieving high performance polymer films is introduced by leveraging 2D surface coating on commercially mature large‐scale polymer films. Future pathways for high quality scalable dielectric films exhibiting desirable dielectric properties and feasibility for capacitor manufacturing are suggested.

Nagaraj Nandihalli, Chia‐Jyi Liu, T. Mori

Abstract Organic thermoelectric (TE) materials capitalize on advantages such as low thermal conductivity, low-cost, eco-friendly, versatile processability, light-weight, mechanical flexibility, roll-to-roll production, which are advantageous for the development of portable and wearable self-powered electronics. On the negative side, the figure-of-merit of polymer TE materials is low, mainly owing to typical low electrical conductivity. Various efforts have been made to enhance the TE performance of organic TE materials, i.e. chemical or electrochemical doping, modification of molecular structure, and fabrication of polymer-based composites or blends, which is the simplest and most cost-effective method for modifying polymer properties. Solution-processed polymer/inorganic or organic hybrids pave the way for formulation of functional TE inks/paste which can be used to fabricate large scale cost-effective manufacturing of TE generators. In this review, we briefly summarize the TE properties of conjugated polymers, and focus on recent developments in polymer/carbon nanofillers (e.g. CNT, graphene, GO) composites and polymer/inorganic TE nanoparticles composites along with preparation methods and thermoelectric performance. Finally, we cover recent advances in the development of functional TE inks, processing techniques, and their usage in device fabrication using various printing techniques and review device output characteristics.

A. P. Golhin, Riccardo Tonello, J. Frisvad et al.

Surface roughness is gaining increasing recognition in the processing design methods of additive manufacturing (AM) due to its role in many critical applications. This impact extends not only to various AM product manufacturing but also to indirect applications, such as molding and casting. This review article discusses the role of processing on the surface roughness of AM-printed polymers with limited post-processing by summarizing recent advances. This review offers a benchmark for surface quality improvement of AM processes, considering the surface roughness of polymeric parts. For this purpose, it lists and analyzes the key processes and various printing parameters used to monitor and adjust surface roughness under given constraints. Four AM techniques for manufacturing polymeric parts are compared: fused filament fabrication (FFF), selective laser sintering (SLS), vat photopolymerization (VPP), and material jetting (MJT). A review and discussion of recent studies are presented, along with the most critical process parameters that affect surface roughness for the selected AM techniques. To assist in selecting the most appropriate method of 3D printing, comparable research summaries are presented. The outcome is a detailed survey of current techniques, process parameters, roughness ranges, and their applicability in achieving surface quality improvement in as-printed polymers.

Arit Das, C. Chatham, Jacob J. Fallon et al.

Abstract The strengths of additive manufacturing (AM), especially the tool-less manufacturing paradigm and rapid production of low-volume products, are well-aligned with the needs of manufacturing of expensive, high-temperature resistant, engineering thermoplastic polymers. High temperature polymer parts made with AM for either tooling or end-use applications have been implemented in the aerospace, automotive, and biomedical fields. However, parts made from these polymers using traditional manufacturing processes are generally high-value parts in low-quantity production runs. Moreover, AM processing of these polymers present significant challenges due to limitations associated with large thermal gradients, residual stress buildup, and interlayer adhesion as well as the inability of the printers to consistently maintain required high processing temperatures. This review highlights the current state of the art for processing high-temperature (i.e., traditional processing temperatures exceeding 250°C) thermoplastic polymers by the melt-based, AM processes of material extrusion (MatEx) and laser powder bed fusion (PBF). The authors address common challenges to AM of high-temperature polymers and gaps in fundamental understanding of the process-structure-property relationships needed to identify the machine design, process parameter selection, and synthetic modifications to enable processing.

Zhangzhang Tang, Gao Deng, Yiyuan Sun et al.

Achieving 4D printing of shape memory polymers with both high strength and high transition temperature remains challenging due to the inherent incompatibility between the rigid molecular structure required for high strength and the molecular structure that moves on demand necessary for the shape memory effect, the limitations of high-performance polymer reaction kinetics, as well as internal stress during the printing process. Here, a direct ink writing (DIW) printed high-precision cyanate ester-urethane (CU) shape memory polymer with excellent performance was accomplished by incorporating two dynamic covalent bonds (carbamate and cyanuric acid) through copolymerizing cyanate ester with polyurethane acrylates. During curing, carbamate and cyanuric acid enable stress relaxation and polymer network rearrangement, facilitating the permanent reconfiguration of CU to form a novel triazine network structure. As a result, a high mechanical properties CU with excellent strength (83 MPa) and superior Young's modulus (2.37 GPa) were obtained, besides, the transition temperature (near 250 °C) is the highest in comparison to currently reported 4D-printed shape memory polymers. Furthermore, this reconfigurability was demonstrated by imprinting various surface patterns at microscopic level. Moreover, the reconfigurability of CU provides a novel strategy for smart molds in deformation and easy demolding. Overall, this study opens up a new avenue for the development of high-performance 4D printed shape memory polymers.

Julen Cortazar-Noguerol, Fernando Cortés, Iker Agirre-Olabide et al.

Elastomeric materials, such as silicone rubber, are widely used in engineering applications due to their high deformability and viscoelastic properties. Under quasistatic regime and small deformations their behavior can be considered purely elastic and can be characterized by the elastic modulus, shear modulus, and Poisson's ratio, which are interrelated in isotropic materials. Although standard methodologies exist for determining these properties, experimental measurements are known to be affected by the geometry of the tested samples. The influence of sample geometry on compressive modulus measurements is well understood, however, its effect on shear modulus measurements is less explored. This study investigates how the dimensions of cylindrical samples influence the experimental determination of both the compressive and shear moduli and, consequently, Poisson's ratio. Compression and torsion tests are performed on silicone rubber samples of varying diameters and lengths using a dynamic mechanical analyzer and a rheometer respectively. The results confirm that both the compressive and shear moduli are affected by sample geometry, leading to unrealistic values of Poisson's ratio. To account for these effects, a correction model is proposed for shear modulus measurements, complementing existing corrections for compressive tests. The model successfully describes experimental trends and provides a more reliable estimation of Poisson's ratio, aligning with theoretical expectations for nearly incompressible elastomers. These findings emphasize the importance of considering geometric effects in compressive and torsion tests and provide a framework for improving the accuracy of mechanical characterization in elastomeric materials.

Abhishek S. Chankapure, Rahul Karmakar, Srikanth Sastry et al.

Vitrimers are a class of crosslinked polymer that are capable of undergoing bond exchange reactions, allowing structural reorganization while maintaining overall network integrity. Two key features that are particularly relevant when this vitrimer concept is used to compatibilize immiscible polymer blends are how they affect the (i) bulk polymer density and (ii) interfacial activity of the crosslink groups. To probe these issues, we model both a bulk polymer melt and a thin film of a polymer melt both with explicit small molecular crosslinkers, in the associative limit, i.e., when the number of crosslinks are fixed. We show that the bulk density and the distribution of stickers within a polymer matrix is strongly influenced by their size and interactions with the base polymer. Specifically, when the crosslinkers are chemically compatible with the base polymer, then the overall packing fraction increases, regardless of crosslinker size, while it decreases when crosslinkers are incompatible with the polymers. Similarly, the crosslinkers segregate preferentially to the polymer-air interface when they are incompatible with the polymer chains, leading to a reduction interfacial tension. Thus, these incompatible crosslinkers should help in affecting both the miscibility of polymer blends, and also their compatibility by creating copolymer structures at the interface. These results demonstrate the key role of crosslinker-polymer interactions and crosslinker size on the structural and interfacial properties of vitrimer melts.

Gregory S. Sulley, G. Gregory, Thomas T D Chen et al.

Carbon dioxide/epoxide copolymerization is an efficient way to add value to waste CO2 and to reduce pollution in polymer manufacturing. Using this process to make low molar mass polycarbonate polyols is a commercially relevant route to new thermosets and polyurethanes. In contrast, high molar mass polycarbonates, produced from CO2, generally under-deliver in terms of properties, and one of the most widely investigated, poly(cyclohexene carbonate), is limited by its low elongation at break and high brittleness. Here, a new catalytic polymerization process is reported that selectively and efficiently yields degradable ABA-block polymers, incorporating 6–23 wt % CO2. The polymers are synthesized using a new, highly active organometallic heterodinuclear Zn(II)/Mg(II) catalyst applied in a one-pot procedure together with biobased ε-decalactone, cyclohexene oxide, and carbon dioxide to make a series of poly(cyclohexene carbonate-b-decalactone-b-cyclohexene carbonate) [PCHC-PDL-PCHC]. The process is highly selective (CO2 selectivity >99% of theoretical value), allows for high monomer conversions (>90%), and yields polymers with predictable compositions, molar mass (from 38–71 kg mol–1), and forms dihydroxyl telechelic chains. These new materials improve upon the properties of poly(cyclohexene carbonate) and, specifically, they show good thermal stability (Td,5 ∼ 280 °C), high toughness (112 MJ m–3), and very high elongation at break (>900%). Materials properties are improved by precisely controlling both the quantity and location of carbon dioxide in the polymer chain. Preliminary studies show that polymers are stable in aqueous environments at room temperature over months, but they are rapidly degraded upon gentle heating in an acidic environment (60 °C, toluene, p-toluene sulfonic acid). The process is likely generally applicable to many other lactones, lactides, anhydrides, epoxides, and heterocumulenes and sets the scene for a host of new applications for CO2-derived polymers.

Ching Hao Lee, F. N. M. Padzil, Seng Hua Lee et al.

In this review, the potential of natural fiber and kenaf fiber (KF) reinforced PLA composite filament for fused deposition modeling (FDM) 3D-printing technology is highlighted. Additive manufacturing is a material-processing method in which the addition of materials layer by layer creates a three-dimensional object. Unfortunately, it still cannot compete with conventional manufacturing processes, and instead serves as an economically effective tool for small-batch or high-variety product production. Being preformed of composite filaments makes it easiest to print using an FDM 3D printer without or with minimum alteration to the hardware parts. On the other hand, natural fiber-reinforced polymer composite filaments have gained great attention in the market. However, uneven printing, clogging, and the inhomogeneous distribution of the fiber-matrix remain the main challenges. At the same time, kenaf fibers are one of the most popular reinforcements in polymer composites. Although they have a good record on strength reinforcement, with low cost and light weight, kenaf fiber reinforcement PLA filament is still seldom seen in previous studies. Therefore, this review serves to promote kenaf fiber in PLA composite filaments for FDM 3D printing. To promote the use of natural fiber-reinforced polymer composite in AM, eight challenges must be solved and carried out. Moreover, some concerns arise to achieve long-term sustainability and market acceptability of KF/PLA composite filaments.

Sabyasachi Behera, P. Mahanwar

ABSTRACT Superabsorbent polymers are a class of polymeric materials that have the ability to absorb and retain a large amount of water and aqueous solutions. They are composed of three-dimensional polymeric networks that do not dissolve in water but swell considerably in aqueous medium. The synthetic superabsorbent polymers are replacing the natural ones because of their high absorption capacity, availability of wide varieties of raw materials and longer durability. Due to their hydrophilic, non-toxic, biodegradable, and biocompatible properties, they are the most desirable products for various applications such as drug delivery, agriculture, bioremediation, fire fighting, biosensors, food industries, thermal energy storage, and tissue engineering. This article reviews the literature concerned with the classification of superabsorbent polymers, their manufacturing processes, their properties, and the factors affecting them and their applications. Agriculture is one of the growing sectors due to the requirement of food to meet the growing demands of the expanding global population. The technology of controlled or sustained release of agrochemicals and superabsorbents is a boon to the agricultural sector. The review elaborates the literature related to the drug delivery and agricultural application of the hydrogels in detail.

Prashant Paraye, R. M. Sarviya

ABSTRACT This review presents a comprehensive exploration of the advancements in polymer composites, focusing on their performance, manufacturing processes, recycling techniques, and sustainable practices. With the increasing demand for high-performance materials in various industries, including aerospace, automotive, and construction, polymer composites have emerged as a pivotal solution, offering unparalleled strength, durability, and lightweight properties. This review explores the essential characteristics of polymer composite materials and blends, highlighting the synergy between various matrices and reinforcements that lead to improved material properties. Significant emphasis is given to high-performance composites, where the integration of innovative materials and additives has led to revolutionary applications. By examining the material properties and performance, this review highlights the capabilities of polymer composites to meet rigorous requirements in special cases and extreme conditions. Furthermore, it explores the environmental impact of these materials, promoting sustainable practices throughout their lifecycle. The critical role of recycling in the manufacturing process is dissected to unveil strategies that not only mitigate environmental harm but also promote the circular economy in the composite industry. It addresses both the challenges and opportunities presented by these materials, offering insights into future directions for research and application. GRAPHICAL ABSTRACT

S. Korzeniowski, Robert C. Buck, Robin M. Newkold et al.

Fluoropolymers are a distinct class of per‐ and polyfluoroalkyl substances (PFAS), high molecular weight (MW) polymers with fluorine attached to their carbon‐only backbone. Fluoropolymers possess a unique combination of properties and unmatched functional performance critical to the products and manufacturing processes they enable and are irreplaceable in many uses. Fluoropolymers have documented safety profiles; are thermally, biologically, and chemically stable, negligibly soluble in water, nonmobile, nonbioavailable, nonbioaccumulative, and nontoxic. Although fluoropolymers fit the PFAS structural definition, they have very different physical, chemical, environmental, and toxicological properties when compared with other PFAS. This study describes the composition, uses, performance properties, and functionalities of 14 fluoropolymers, including fluoroplastics and fluoroelastomers, and presents data to demonstrate that they satisfy the widely accepted polymer hazard assessment criteria to be considered polymers of low concern (PLC). The PLC criteria include physicochemical properties, such as molecular weight, which determine bioavailability and warn of potential hazard. Fluoropolymers are insoluble (e.g., water, octanol) solids too large to migrate into the cell membrane making them nonbioavailable, and therefore, of low concern from a human and environmental health standpoint. Further, the study results demonstrate that fluoropolymers are a distinct and different group of PFAS and should not be grouped with other PFAS for hazard assessment or regulatory purposes. When combined with an earlier publication by Henry et al., this study demonstrates that commercial fluoropolymers are available from the seven participating companies that meet the criteria to be considered PLC, which represent approximately 96% of the global commercial fluoropolymer market. Integr Environ Assess Manag 2023;19:326–354. © 2022 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Julia Jockusch, M. Özcan

Additive manufacturing (AM) processes are increasingly used in dentistry. The underlying process is the joining of material layer by layer based on 3D data models. Four additive processes (laser stereolithography, polymer jetting, digital light processing, fused deposition modeling) are mainly used for processing dental polymers. The number of polymer materials that can be used for AM in dentistry is small compared to other areas. Applications in dentistry using AM are limited (e.g. study models, maxillo-facial prostheses, orthodontic appliances etc.). New and further developments of materials are currently taking place due to the increasing demand for safer and other applications. Biocompatibility and the possibility of using materials not only as temporarily but as definitive reconstructions under oral conditions, mechanically more stable materials where less or no post-processing is needed are current targets in AM technologies. Printing parameters are also open for further development where optical aspects are also important.

K. Formela, M. Kurańska, M. Barczewski

Limited petroleum sources, suitable law regulations, and higher awareness within society has caused sustainable development of manufacturing and recycling of polymer blends and composites to be gaining increasing attention. This work aims to report recent advances in the manufacturing of environmentally friendly and low-cost polymer materials based on post-production and post-consumer wastes. Sustainable development of three groups of materials: wood polymer composites, polyurethane foams, and rubber recycling products were comprehensively described. Special attention was focused on examples of industrially applicable technologies developed in Poland over the last five years. Moreover, current trends and limitations in the future “green” development of waste-based polymer materials were also discussed.

Ruslan Melentiev, N. Yu, G. Lubineau

Polymer metallization via cold spray additive manufacturing is an emerging thermal spray approach for deposition of thick metallic coatings on polymers and fiber-reinforced composites that promises high productivity, ecofriendliness, and scalability of the coating process. In polymer metallization via cold spray, solid metallic powder is accelerated by a supersonic stream of preheated gas and propelled toward a polymer substrate, where it is built layer-by-layer via impact-induced heating and particle deformation. Since the pioneering study at Cambridge in 2006, nearly 50 experimental reports on polymer metallization via cold spray have been published, half of which have appeared within the past three years. This review distinguishes cold spray from other thermal spray methods, analyzes the peculiarities of cold spraying on polymers and fiber-reinforced composites, outlines the historical establishment of the field, and summarizes the available literature on polymer metallization via cold spray. The major focus here is on the influence of the cold spray process parameters on the deposition efficiency, adhesion strength, electrical conductivity and other properties of metallic coatings formed on polymers and fiber-reinforced composites. The promising applications of cold spray additive manufacturing in lightning strike protection, electroplating, osseointegration, antifouling, antivirus, e.g. anti-Covid-19 surfaces, and other surface functionalizations have been reviewed. Finally, recommendations were given on how to enhance the data reuse in future studies on polymer metallization via cold spray.

T. Ramakrishnan, M. D. Mohan Gift, S. Chitradevi et al.

There are a slew of elements at work in the composites sector, from people and markets to technology and innovation, that are continually reshaping the industry's structure. For now, composite materials' winning combination of high strength-to-weight ratio continues to propel them into new areas, but other attributes are just as crucial. These properties, which may be customized for unique purposes, result in a completed product requiring fewer raw materials and fewer joints and fasteners, as well as reduced assembly times, thanks to composite materials. To lower product lifespan costs, composites also have demonstrated resilience in industrial applications to temperature extremes as well as corrosion and wear. Polymers, ceramics, and metals can all be used as matrices. Thermoplastic (TP) resin is the second most prevalent matrix type, and it is becoming increasingly popular among composite makers. By melting or softening and then chilling the material, thermoplastic linear polymer chains are generated and may be reformed into shaped solids. It is common for thermoplastics to be offered in sheet or panel form, which may be treated using in situ consolidation processes, such as pressing, to manufacture durable, near-net-shape components without the need for an autoclave or vacuum bag cure. Correcting abnormalities or fixing harm done in service is possible with reformability.

Kerong Yang, Weijiang Chen, Yushun Zhao et al.

Epoxy polymer-based dielectric materials play a crucial role in advanced electronic devices and power equipment. However, high voltage-stress applications impose stringent requirements, such as a high dielectric strength, on epoxy polymers. Previously reported studies have shown promising material architectures in the form of epoxy polymer-nanoparticle dielectrics, which can restrict the movement of high-energy electrons by the interface charge traps associated with the various interfacial regions. However, these high-energy electrons inevitably traverse the epoxy polymer matrix and destroy the molecular structure, thereby creating a weak link for dielectric breakdown. In this study, a general strategy is developed to improve the dielectric strength by constructing interface charge traps in the molecular structure of the epoxy polymer matrix, using the -CF3 group in partial replacement of the -CH3 group. The proposed strategy increases the dielectric strength (39.5 kV mm-1) and surface breakdown voltage (26.9 kV) of the epoxy polymer matrix by 22.08% and 13.3%, respectively, because the interface charge trap hinders the movement of high-energy electrons. At the same time, the strategy does not degrade the mechanical and thermal properties. The results hold potential for wide application in the manufacturing of advanced future electrical and electronic equipment requiring resilience to high-voltage stress.