Hasil untuk "Polymers and polymer manufacture"

The cost effective synthesis and patterning of carbon nanomaterials is a challenge in electronic and energy storage devices. Here we report a one-step, scalable approach for producing and patterning porous graphene films with three-dimensional networks from commercial polymer films using a CO2 infrared laser. The sp3-carbon atoms are photothermally converted to sp2-carbon atoms by pulsed laser irradiation. The resulting laser-induced graphene (LIG) exhibits high electrical conductivity. The LIG can be readily patterned to interdigitated electrodes for in-plane microsupercapacitors with specific capacitances of >4 mF cm−2 and power densities of ~9 mW cm−2. Theoretical calculations partially suggest that enhanced capacitance may result from LIG’s unusual ultra-polycrystalline lattice of pentagon-heptagon structures. Combined with the advantage of one-step processing of LIG in air from commercial polymer sheets, which would allow the employment of a roll-to-roll manufacturing process, this technique provides a rapid route to polymer-written electronic and energy storage devices. The straightforward and scalable synthesis and patterning of graphene-based nanomaterials remains a technological challenge. Here, the authors use a CO2infrared laser, under ambient conditions, to directly produce and pattern porous graphene films with three-dimensional networks from commercial polymer films.

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

J. Banhart

Mehlika Karamanlioglu, R. Preziosi, G. Robson

Jie Xu, Hung‐Chin Wu, Chenxin Zhu et al.

Dan Zhao, A. Martinelli, Andreas Willfahrt et al.

Measuring temperature and heat flux is important for regulating any physical, chemical, and biological processes. Traditional thermopiles can provide accurate and stable temperature reading but they are based on brittle inorganic materials with low Seebeck coefficient, and are difficult to manufacture over large areas. Recently, polymer electrolytes have been proposed for thermoelectric applications because of their giant ionic Seebeck coefficient, high flexibility and ease of manufacturing. However, the materials reported to date have positive Seebeck coefficients, hampering the design of ultra-sensitive ionic thermopiles. Here we report an “ambipolar” ionic polymer gel with giant negative ionic Seebeck coefficient. The latter can be tuned from negative to positive by adjusting the gel composition. We show that the ion-polymer matrix interaction is crucial to control the sign and magnitude of the ionic Seebeck coefficient. The ambipolar gel can be easily screen printed, enabling large-area device manufacturing at low cost. Though polymer electrolytes with high ionic Seebeck coefficients are attractive for thermoelectric modules, demonstrating high performance n-type polymers required for modules remains elusive. Here, the authors report ambipolar ionic polymer gels with high ionic Seebeck coefficient.

Change Wu, Yu Ding, Min Xiao et al.

Poly(propylene carbonate-co-phthalate) (PPC–P), limited by inferior melt strength and heat resistance, exhibits poor foamability and thermal stability. This study enhances PPC-P through biodegradable PLA incorporation and HDI-induced dynamic vulcanization of terminal hydroxyl groups, improving the interfacial compatibility. The gel contents, rheological properties, crystallization behaviours, mechanical properties, compatibility and microstructures of the PPC-P/PLA blends are investigated in detail. By adjusting the compatibilizer-NCO dosage and PLA contents, the melt strength and viscoelasticity of the blends are effectively enhanced and regulated. Enhanced interfacial compatibility among PPC-P and PLA phases, improves the tensile strength and elongation at break of PPC-P/PLA composites, with values of 48.2 MPa and 12.9 %, respectively. By using the sub-critical CO2 as blowing agent, light weight and low-shrinkage PPC-P/PLA foams with well refined cell structures are successfully obtained, which can be attributed to the improved melt strength and the induced thermal stability. The relationship between the crosslinked-crystalline network and the foam quality are established, including CO2 solubility, cell microstructure, and dimensional stability. PPC-P/PLA foams show refined microstructures (cell size <50 μm, cell density >1.5 × 109 cells/cm3, VER >20), and low shrinkage (<25 %). Here, the crosslinks and crystals play multiple essential roles in increasing the melt strength and foamability of PPC-P, providing a widely applicable low-shrinkage strategy, which is crucial for the biodegradable foams.

Kingkini Roychoudhury, Shreerang Pande, Indrakanty S. Shashank et al.

It has been shown that under high cylindrical confinement, two ring polymers with excluded volume interactions between monomers, segregate to two halves of the cylinder to maximize their entropy. In contrast, two ring polymers remain mixed within a sphere, as there is no symmetry breaking direction [Nat Rev Microbiol, 8, 600-607 (2010)]. Therefore, in order to observe emergent organization of ring polymers in a sphere, we can introduce an asymmetric topological modification to the polymer architecture by creating a small loop and a big loop within the ring polymer. We consider the bead-spring model of polymers where there are only repulsive excluded volume interactions between the monomers ensuring that the organization we observe is purely entropy-driven. We find that for a single topologically modified polymer within a sphere, the monomers of the bigger loop are statistically more probable to be found closer to the periphery. However, the situation is reversed when we have multiple such topologically modified polymers in a sphere. The monomers of the small loops are found closer to the walls of the sphere. We can increase this localization and radial organization of polymer segments by increasing the number of small loops in each ring polymer. We study how these loops interact with each other within a polymer, as well as with loops of other polymers in spherical confinement. We compare contact maps of multiple such topologically modified polymers in a sphere. Finally, we discuss the plausible relevance of our studies to eukaryotic chromosomes that are confined within a spherical nucleus.

سمانه قنبرلو, داود کاه فروشان, حسین عبداللهی

گازهای گلخانه­ای به‌ویژه کربن دی­اکسید، در اثر استفاده از سوخت­های فسیلی افزایش یافته است. رویکردهایی برای کاهش تغییرات آب و هوایی جهانی وجود دارند که از جملة آن­ها می­توان به برجذب و ذخیرة کربن دی­اکسید اشاره کرد. در میان انواع برجاذب­های کربن دی­اکسید، مواد پلیمری متخلخل به‌دلیل مساحت سطح زیاد و تنظیم‌پذیر، خواص گرمایی-مکانیکی مناسب، چگالی کم، پایداری فیزیکی‌شیمیایی زیاد، سینتیک سریع، استحکام و ظرفیت برجذب زیاد از گزینه­های بسیار مناسب برای برجذب کربن دی­اکسید هستند. پلیمرهای متخلخل مانند پلیمرهای ابرشبکه‌ای (HCP)، چارچوب­های آلی کووالانسی (COFs)، پلیمرهای متخلخل آلی (POPs)، پلیمرهای ریزمتخلخل مزدوج (CMPs) و چارچوب‌های تری‌آزینی کووالانسی (CTFs) محدودة برجذب CO2 را در حدود mmol.g-1 3 تا mmol.g-1  6 در دمای K 273 و فشار bar 1 نشان می‌دهند. هر یک از  پلیمرها در فرایند برجذب CO2، خواص و چالش­های منحصربه‌فردی دارند. برای مثال، HCPها و CMPها سطح ویژة بیشتری دارند، درحالی­که زیست‌پلیمرها به‌دلیل انعطاف­پذیری در زیست‌­تخریب‌پذیری و ارزانی، نسبت به سایر پلیمرها برتری دارند. CMPها به‌دلیل مواد اولیة کم‌وزن، بیشتر در زمینه­های الکتریکی کاربرد دارند. درحالی­که پژوهشگران به HCPها به‌خاطر طرز تهیة راحت و سریع نسبت به سایر POPها، بیشتر توجه کرده‌اند. هرچند افزایش ظرفیت برجذب این پلیمرها نیازمند تغییراتی در سطح آن‌هاست. نتایج این بررسی نشان می‌دهد، پلیمرها می‌توانند به‌عنوان ابزارهای کارآمد و پایدار برای برجذب کربن دی­اکسید و کاهش آثار گلخانه‌ای استفاده شوند.

Yun-Cheng Zhao, Xing-Yu Wang, Ke Shang et al.

Polyurea (PUA) is widely recognized for its excellent waterproofing and impact resistance, making it a popular choice for protective coatings. However, its inherent flammability and rapid reaction kinetics pose significant challenges for both fire safety and processing. In this study, a Schiff base latent curing agent (D2000-MIBK) and a phosphate-containing polyol (OP550) were employed to develop a solvent-free, intrinsically flame-retardant, slow-curing PUA. The incorporation of D2000-MIBK effectively moderated the curing process, addressing the rapid reaction typical of conventional PUA systems, while OP550 significantly improved flame retardancy and mechanical performance. At just 2.22 wt%, OP550 enabled PUA-2 to achieve a UL-94 V-0 rating, demonstrating self-extinguishing behavior and reduced flaming drips. Thermogravimetric analysis confirmed that OP550 promoted char formation without altering the thermal decomposition profile of PUA, while dynamic mechanical analysis showed increased stiffness with negligible impact on the glass transition temperature. PUA-2 exhibited exceptional mechanical properties, including a tensile strength of 15.4 MPa, elongation at break of 1287.5 %, and tearing strength of 65.4 N mm−1, as well as excellent resistance to acidic, alkaline, and saline environments. Atomic force microscopy revealed optimized microphase-separated morphology, enhancing interfacial interactions and contributing to improved toughness and flexibility. This study introduces a novel strategy for developing high-performance PUA materials with superior flame retardancy, mechanical robustness, and controllable curing, offering significant potential for applications in protective coatings and structural components under demanding conditions.

Timo Hofmann, Kevin Klier, Ralf- Urs Giesen et al.

In this publication, the effects of finely ground silicone elastomer recyclate powder (>50 μm) as a filler in a solid silicone rubber were investigated. The results indicated that when peroxide-curing high consistency silicone rubber is used, the recycled material has no influence on the crosslinking. In the rheological tests, however, it was observed that the viscosity increases with increasing filler content. The present study analyzed the tensile test and compression set to reveal an influence on the elastic properties of the material. The compression set increases by approx. 22 % compared to the reference value up to 60 phr recyclate content. In terms of tensile strength, the recyclate leads to a decrease in maximum stress of up to 45 % and elongation of up to 25 %. In contrast to the elastic properties, however, no significant change in hardness can be seen as a result of using the recycled powder.

Hui Chen, Jianfeng Ou, Hu Li et al.

Hyperelastic materials, noted for their exceptional elastic recovery and durability, are widely utilized across diverse engineering applications. Accurate evaluation of their mechanical properties under operational conditions is essential for quality control and structural integrity assessment. This study proposes a non-destructive indentation methodology for rubber-like materials based on the energy equivalence principle, focusing on materials governed by the Mooney–Rivlin and Arruda–Boyce constitutive models. A composite dual-conical indentation model (CDIM) is developed by integrating the energy equivalence principle with the two constitutive frameworks. Model parameters were systematically calibrated through comprehensive finite element simulations and subsequently validated through large-scale parametric finite element analyses involving both forward predictions and reverse parameter identifications. Experimental validation was conducted via composite dual-conical indentation tests on four rubber-like materials. The uniaxial mechanical properties derived from indentation data exhibited strong agreement with conventional tensile test results. The proposed method enables accurate, reliable, and non-destructive evaluation of hyperelastic material properties, providing a practical framework for in-situ mechanical characterization and supporting enhanced quality assurance in industrial applications.

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.

J. Praveenkumara, Pallepattu Madhu, T. G. Gowda et al.

Abstract In the recent days, the target for researchers and scientists is to develop a material which fulfills the parameters such as lightweightness, manufacturability, durability and low-cost materials. The different polymers were coined for the fabrication of composites due to recyclability, cheaper cost and easy of manufacturing. In order to increase the performance and efficiency, the hybridization was invoked in the composites. Hybridization is a process which enhances the properties of polymer matrix composites by incorporating two or more similar or dissimilar fibers in the same composite material. To overcome the drawbacks in polymer composites, the material is filled with synthetic fillers, which elevates the properties of composites and strengthened the fiber matrix interface. Hence this review aims to outline the effect of different synthetic fillers on polymer composites by means of mechanical, thermal and morphological studies.

Debasish Mohanty, V Shreyas, Akshaya Palai et al.

Polymers play a crucial role in the development of engineering materials, with applications ranging from mechanical to biomedical fields. However, the limited polymerization processes constrain the variety of organic building blocks that can be experimentally tested. We propose an open-source computational generative pipeline that integrates neural-network-based discriminators, generators, and query-based filtration mechanisms to overcome this limitation and generate hypothetical polymers. The pipeline targets properties, such as ionization potential (IP), by aligning various representational formats to generate hypothetical polymer candidates. The discriminators demonstrate improvements over state-of-the-art models due to optimized architecture, while the generators produce novel polymers tailored to the desired property range. We conducted extensive evaluations to assess the generative performance of the pipeline components, focusing on the polymers' ionization potential (IP). The developed pipeline is integrated into the DeepChem framework, enhancing its accessibility and compatibility for various polymer generation studies.

Kim Jeong-Ki, Bandi Rajkumar, Dadigala Ramakrishna et al.

Cellulose nanofibrils (CNFs) are versatile materials, but their sensitivity to humidity affects performance. Esterification with fatty acids enhances the hydrophobicity of CNF films. This study compared gas- and liquid-phase esterification using three fatty acid chlorides at different dosages. Gas-phase esterification minimally affected cellulose crystallinity, maintaining a crystallinity index exceeding 55.8%, whereas liquid-phase esterification significantly reduced crystallinity. Gas-phase esterification achieved hydrophobicity (water contact angle >100°) with less fatty acid chlorides (0.50 eq/OH) compared to liquid-phase esterification (1.00 eq/OH). Tensile strength significantly dropped in the liquid phase (68.4–6 MPa) and up to an 8-fold decrease in the elastic modulus. Conversely, gas-phase esterification maintained tensile strength over 40 MPa, and elastic modulus increased by a minimum of 2.5 times. However, gas-phase esterification resulted in a 5-fold reduction in elongation at break (%). Thermogravimetric analysis indicated a high T max of 362°C for liquid-phase esterified samples and a substantial 24.9% residual weight for gas-phase esterified samples.

Guk-Yun Noh, Ki Jung Kim, Eun Ji An et al.

This study explores the structure-property relationships in colorless polyimides (CPIs) synthesized from stereoisomeric (exo- and endo-form) alicyclic dianhydrides, combined with various diamines. The structural configurations of 5,5’-(1,4-phenylene)bis[hexahydro-(3aR,4R,5R,7S,7aS)-rel-4,7-Methanoisobenzofuran-1,3-dione] (BzDA-exo) and 5,5-(1,4-phenylene)bis(hexahydro-4,7-methanoisobenzofuran-1,3-dione) (BzDA-endo) were confirmed as exo- and endo-forms, respectively, through 1H NMR and 2D NOESY NMR analyses. Wide-angle X-ray scattering (WAXS) data revealed that stereoisomeric structures influence polymer chain packing in synthesized CPIs. The investigation extended to the chemical and physical structure-dependent properties such as physical, thermal and optical properties of the PIs. Notably, structure-dependent physical and thermal properties were evident, with a particularly strong structure-property relationship manifesting in the coloration and yellow index (Y.I.) of PIs. These systematic characterizations offer profound insights into the design and optimization of chemical and physical structures in CPIs, highlighting the versatility of stereoisomeric monomers for various applications.

Soyeon Park, K. Fu

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.

Xifan Wang, Franziska Schmidt, D. Hanaor et al.

Here we introduce a versatile stereolithographic route to produce three different kinds of Si-containing thermosets that yield high performance ceramics upon thermal treatment. Our approach is based on a fast and inexpensive thiol-ene free radical addition that can be applied for different classes of preceramic polymers with carbon-carbon double bonds. Due to the rapidity and efficiency of the thiol-ene click reactions, this additive manufacturing process can be effectively carried out using conventional light sources on benchtop printers. Through light initiated cross-linking, the liquid preceramic polymers transform into stable infusible thermosets that preserve their shape during the polymer-to-ceramic transformation. Through pyrolysis the thermosets transform into glassy ceramics with uniform shrinkage and high density. The obtained ceramic structures are nearly fully dense, have smooth surfaces, and are free from macroscopic voids and defects. A fabricated SiOC honeycomb was shown to exhibit a significantly higher compressive strength to weight ratio in comparison to other porous ceramics.