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A visible‐light‐induced, three‐component palladium‐catalyzed 1,4‐aminoarylation of butadienes with readily available aryl halides and aliphatic amines has been developed, affording allylamines with excellent E‐selectivity. The reaction exhibits exceptional control over chemo‐, regio‐, and stereoselectivity, a broad substrate scope, and high functional group compatibility, as demonstrated by the late‐stage functionalization of bioactive molecules. Mechanistic investigations are consistent with a photoinduced radical Pd(0)‐Pd(I)‐Pd(II)‐Pd(0) Heck‐Tsuji–Trost allylation cascade. [ABSTRACT FROM AUTHOR]

The present work proposes to investigate the effect of an ultrahigh molecular weight silicone rubber (UHMW-SR) and two ethylene methyl acrylate copolymers (EMA) with different methyl acrylate (MA) content on the mechanical and fire performance of a fireproof acrylonitrile butadiene styrene copolymer (ABS) composite, with an optimum amount of ammonium polyphosphate (APP) and aluminum diethyl phosphinate (AlPi). ABS formulations with a global flame retardant weight content of 20 wt.% (ABS P) were melt-compounded, with and without EMA and UHMW-SR, in a Brabender mixer. During this batch process, ABS P formulations with UHMW-SR and/or EMA registered lower torque values than those of ABS P. By means of scanning electron microscopy (SEM), it was possible to observe that all ABS composites exhibited a homogenous structure without phase separation or particle agglomeration. Slightly improved interfacial interaction between the well-dispersed flame-retardant particles in the presence of EMA and/or UHMW-SR was also noticed. Furthermore, synergies in mechanical properties by adding both EMA and UHMW-SR into ABS P were ascertained. An enhancement of molecular mobility that contributed to the softening of ABS P was observed under dynamic mechanical thermal analysis (DMTA). An improvement of its flexibility, ductility and toughness were also registered under three-point-bending trials, and even more remarkable synergies were noticed in Charpy notched impact strength. Particularly, a 212% increase was achieved when 5 wt.% of EMA with 29 wt.% of MA and 2 wt.% of UHMW-SR in ABS P (ABS E29 S P) were added. Thermogravimetric analysis (TGA) showed that the presence of EMA copolymers in ABS P formulations did not interfere with its thermal decomposition, whereas UHMW-SR presence decreased its thermal stability at the beginning of the decomposition. Although the addition of EMA or UHMW-SR, as well as the combination of both in ABS P increased the pHRR in cone calorimetry, UL 94 V-0 classification was maintained for all flame-retarded ABS composites. In addition, through SEM analysis of cone calorimetry sample residue, a more cohesive surface char layer, with Si-O-C network formation confirmed by Fourier transform infrared (FTIR), was shown in ABS P formulations with UHMW-SR. [ABSTRACT FROM AUTHOR]

Online near‐infrared spectroscopy technique is employed to investigate the kinetics of the anionic polymerization of butadiene with n‐butyllithium initiator in the presence of the microstructure modifier 1,2‐diethoxypropane (DEP) in cyclohexane solvent. A phenomenological kinetic model is developed to describe the anionic polymerization process in the presence of DEP, and its influence on the microstructure of polybutadiene under different conditions is determined. [ABSTRACT FROM AUTHOR]

Combining bamboo processing residues with lightweight magnesium oxychlorides can produce new composite building materials that increase the utilization rate of bamboo and also improve the performance of lightweight magnesium oxychlorides. However, the incompatible interface between the two materials leads to the poor performance of the resulting composites, which limits their application in construction engineering. In this paper, a synergistic effect between surfactants and styrene-butadiene latex was used to enhance the interfacial compatibility between bamboo scraps and lightweight magnesium oxychlorides. The structure formed between the two acted as a "bridge" that enhanced the cross-linking between bamboo scraps and lightweight magnesium oxychloride, thus forming a more stable bamboo fiber-lightweight magnesium oxychloride network. The lightweight composite material obtained in this paper showed a maximum compressive stress of 6.5 MPa and a softening coefficient of 0.75.It shows great development potential in the application of light weight, high strength and water resistance building decoration materials. [ABSTRACT FROM AUTHOR]

Four dimensional printing enables the advanced manufacturing of smart objects that can morph and adapt shape over time in response to stimuli such as heat. This study presents a single-material 4D printing workflow which explores the residual stress and anisotropy arising from the fused deposition modelling (FDM) printing process to create heat-triggered self-morphing objects. In particular, the study first investigates the effect of printing patterns on the residual stress of FDM-printed acrylonitrile butadiene styrene (ABS) products. Through finite element analysis, the raster angle of printing patterns was identified as the key parameter influencing the distribution of residual stresses. Experimental investigations further reveal that the non-uniform distribution of residual stress results in the anisotropic thermal deformation of printed materials. Thus, through the design of printing patterns, FDM-printed materials can be programmed with desired built-in residual stresses and anisotropic behaviours for initiating and controlling the transformation of 4D-printed objects. Using the proposed approach, any desktop FDM printers can be turned into 4D printers to create smart objects that can self-morph into target geometries. A series of 4D printing prototypes manufactured from conventional ABS 3D printing feedstock are tested to illustrate the use and reliability of this new workflow. Additionally, the custom-made wood–plastic composite (WPC) feedstocks are explored in this study to demonstrate the transposability of the 4D printing approach. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) is an innovative production process that allows for designing objects with self‐responsive properties exploiting the potentialities of nanotechnologies. In this context, acrylonitrile butadiene styrene (ABS) filled with multi‐walled carbon nanotubes (MWCNT) is printed via fusion deposition modeling (FDM) by setting two different printing directions, 0° and 90°. The investigation of the electrical properties of 3D printed parts demonstrates that the printing direction affects the pathway of electrical current flow and, consequently, the heating performance. A suitable setting of the raster angle allows the alignment of the carbon nanotubes along the printing direction. This alignment, verified through morphological investigations, strongly influences the heating properties due to the Joule effect. [ABSTRACT FROM AUTHOR]

Synthesis and polymerization performance of a kind of dilithium initiator soluble in non-polar solvent Abstract: A novel dilithium initiator soluble in non-polar solvent cyclopentane was prepared by the reaction of sec-butyl lithium and 2,6-dimethylpyridine in cyclopentane for 1 h, and compared with the traditional monolithium initiators, when the dilithium initiator was used for solution polymerization of styrene and butadiene, its dose was just half of that of the monolithium initiator; the measured number-average relative molecular weight (M(——)n) of styrene-butadiene rubber prepared by the dilithium initiator was in general agreement with the designed M(——)n and the gel permeation chromatography curve of the resulting product contained a relatively narrow and symmetrical single peak, which indicated that the dilithium initiator had high initiating activity.

The Bethe–Salpeter equation (BSE) that results from the GW approximation to the self-energy is a frequency-dependent (nonlinear) eigenvalue problem due to the dynamically screened Coulomb interaction between electrons and holes. The computational time required for a numerically exact treatment of this frequency dependence is O(N6), where N is the system size. To avoid the common static screening approximation, we show that the full-frequency dynamical BSE can be exactly reformulated as a frequency-independent eigenvalue problem in an expanded space of single and double excitations. When combined with an iterative eigensolver and the density fitting approximation to the electron repulsion integrals, this reformulation yields a dynamical BSE algorithm whose computational time is O(N5), which we verify numerically. Furthermore, the reformulation provides direct access to excited states with dominant double excitation character, which are completely absent in the spectrum of the statically screened BSE. We study the 21Ag state of butadiene, hexatriene, and octatetraene and find that GW/BSE overestimates the excitation energy by about 1.5–2 eV and significantly underestimates the double excitation character. [ABSTRACT FROM AUTHOR]

In this research, a novel 3D printed core and natural fiber polyester composite skin based thick sandwich panel was developed as structural material for domestic and commercial infrastructure applications. The main objective of this research was to analyze how the carbon quantum dots (C-dots) from agriculture waste strengthen the softer thermoplastic acrylonitrile butadiene styrene (ABS) core and overall sandwich panel's load bearing properties. The core of sandwich was prepared using additive manufacturing method whereas the skin was developed by hand layup method. According to the results the C-dots of 20 phr into the ABS improved the compression properties of core in both flatwise and edgewise directions. A highest tensile and flexural strength of skin was observed to be 114 and 146 MPa respectively. The addition of C-dots improved the load bearing effect and also restricts the deformation against load. This performance improved novel 3D printed core and bamboo fiber skin sandwich could be used as an alternative construction and building material where the commercial plywood and other forms of powder wood face damages via weather and termite issues. Highlights • Higher filler volume of up to 20 phr of carbon quantum dots in acrylonitrile butadiene styrene (ABS) were developed • Novel 3D printed thin walled core of 1 mm diameter was developed using carbon quantum dots and ABS. • Bamboo fiber-polyester skin with highest tensile strength of 114 MPa was developed. • Improved flatwise compression and tensile strength were achieved for ABS core with 20 phr of Carbon quantum dots • Flexural strength and edgewise compression properties were improved with 20 phr of Carbon quantum dots in ABS. [ABSTRACT FROM AUTHOR]

The paper develops a design feasibility study of a multi-tubular polytropic fixed bed reactor for the one-stage ethanol to 1,3-butadiene (ETB) process employing a modified MgO-SiO 2 catalyst. The analysis quantifies the effect of the internal diffusion on scaling up the catalyst activity and selectivity by considering a complex chemistry of seven parallel/series reactions described by detailed kinetic modelling. The efficient numerical solution takes advantage from the MATLAB™ function bvp5c. The simulation model allows scanning the catalytic process by profiles of species' concentrations, reaction rates and effectiveness factors, inside the catalyst particle and over the reactor. The butadiene yield is controlled by the accumulation in particle of ethanol and key intermediates, as acetaldehyde and crotonaldehyde, related to internal chemical reaction with diffusion and external mass and heat transport rates. The catalyst performance depends significantly on the pellet size that becomes optimization variable for catalyst selection and reactor design. Catalyst particles in the range 2 to 3 mm with tubes of to 25 to 40 mm diameters are the most efficient for achieving 80% butadiene carbon selectivity suitable for an industrial process. The modelling approach is generic for calculating the catalyst effectiveness and designing catalytic chemical reactors involving complex reactions. [Display omitted] • Design of multi-tubular reactor for one-stage bioethanol to 1,3-butadiene process, MgO/SiO 2 catalyst, particle modelling. • Generic method for computing porous catalyst effectiveness involving complex reactions by using MATLABTM bvp5c routine • Catalyst particles of 2 to 3 mm achieve 84 % carbon selectivity with 25 to 40 mm tube diameter at 1.5 bar and 390 °C. [ABSTRACT FROM AUTHOR]

Thermoplastic polymers are widely used in industry to generate parts with reasonable production costs, lightweight, chemical stability, sustainability, and recyclability compared to other materials such as metals, metalloids, or even thermoset polymers. The innovative additive manufacturing (AM) techniques, e.g., fused deposition modelling (FDM), can be used to fabricate thermoplastic products with complex geometries and specific properties. However, the mechanical integrity of those FDM-printed plastic parts can be greatly impacted by a phenomenon named material anisotropy. In this study, an experimental study on a popular 3D printing polymer material—acrylonitrile butadiene styrene (ABS)—is performed to determine how FDM process parameters affect the mechanical properties of the printed ABS parts. This study uniquely concentrates on investigating mechanical anisotropy in FDM-printed ABS, delving into a combination of key printing parameters for a comprehensive exploration. Meanwhile, a finite-element-based numerical analysis is also utilised to numerically evaluate the influences of infill percentage and build orientations on the mechanical properties of the 3D-printed ABS materials for comparison. It generates a better understanding of material anisotropy and helps to find the optimal FDM process parameters to print high-quality ABS parts and may attract industrial interests in transitioning from traditional ABS part production methods such as injection moulding or hot pressing to additive manufacturing. [ABSTRACT FROM AUTHOR]

Mass customization is designing and manufacturing customized products with mass production efficiency and speed. Additive manufacturing (AM), one of the mass customization methods, is still expensive compared to mass production but continues to develop and become widespread daily. In addition, additive manufacturing has numerous limitations, such as slow print speed, less accuracy and repeatability, and limited material selection for a particular application. Therefore, this article determined the optimum parameters to improve dimensional accuracy in the AM method. The most common materials used in the additive manufacturing method are acrylonitrile butadiene styrene (ABS) and polylactic acid. Dimensional accuracy is one of the most critical parameters to meet quality standards in additive manufacturing, as in all production methods. Dimensional accuracy is the most critical parameter for smooth joining, especially for interlocking parts. The production parameters of an AM affect dimensional accuracy and the product's mechanical properties and surface quality. Optimal parameters vary to ensure dimensional accuracy in different ways. This study determined optimum parameters for dimensional accuracy, minimum filament consumption, and the production time of some basic shapes produced using ABS material by the FDM method. Cubic infill pattern, two shells, 50% infill pattern, and 0.2 mm wall thickness can be considered optimal for all shapes, although the optimal parameters for different shapes are different. Artificial neural networks (ANN) were used for the estimation of the experimental results. The estimations (R2) made by ANN in this study are over 90%. [ABSTRACT FROM AUTHOR]

Three layers film shaped by thermocompression of acrylonitrile butadiene styrene copolymer and polycarbonate have been analyzed in dynamic mechanical thermal analysis in tensile mode. They present two peaks as the film is loaded perpendicularly to the layers and three peaks as the film is loaded in parallel to the layers. Numerical computations confirm that the origin of this peak is not related to a mechanical issue such as the transmission of the imposed deformation from one layer to the other. Using this method, it is demonstrated that this third peak can only be obtained assuming a material transition with its own behavior between layers. Tan δ measurements provide a simple and useful experimental tool to understand more about the interfacial zone in polymer blends. [ABSTRACT FROM AUTHOR]

Renewable 1,3-butadiene (1,3-BD, C4H6) was synthesized from the tandem decyclization and dehydration of biomass-derived tetrahydrofuran (THF) on weak Brønsted acid zeolite catalysts. 1,3-BD is a highly solicited monomer for the synthesis of rubbers and elastomers. Selective conversion of THF to 1,3-BD was recently measured on phosphorus-modified siliceous zeolites (P-zeosils) at both high and low space velocities, albeit with low per-site catalytic activity. In this work, we combined kinetic analyses and QM/MM calculations to evaluate the interaction of THF with the various Brønsted acid sites (BAS) of Boric (B), Phosphoric (P), and Sulfuric (S) acid modified silicalite-1 catalysts toward a dehydra-decyclization pathway to form 1,3-BD. Detailed kinetic measurements revealed that all three catalysts exhibited high selectivity to 1,3-BD ca. 64–96% in the order of S-MFI > P-MFI > B-MFI at a given temperature (360 °C). Notably, the S-MFI maintained a selectivity >90% for all evaluated process conditions. The computational results suggested that the nature of the Brønsted acid sites and the adsorption energetics (relative THF-acid site interaction energies) are distinct in each catalyst. Additionally, the protonation of THF can be improved with the addition of a water molecule acting as a proton shuttle, particularly in S-MFI. Overall, S-containing zeosils exhibited the ability to control reaction pathways and product distribution in dehydra-decyclization chemistry optimization within microporous zeolites, providing another alternative weak-acid catalytic material. [ABSTRACT FROM AUTHOR]

In pursuit of materials that contribute to the reduction of power consumption and carbon emissions, the tribological properties of composites in automotive, aerospace, and power generation applications have become increasingly critical. This research examines the tribology of a novel Acrylonitrile Butadiene Styrene (ABS) composite, synthesized through an innovative solvent-assisted fluidization process. This technique involved swelling polymer pellets in acetone, followed by reinforcement with dual additives, Titanium Dioxide and Tungsten (TiO2W), in varying weight percentages (2.5%, 5%, 7.5%, and 10%). Experimental analysis revealed that the incorporation of these additives enhanced the material's Shore D hardness, with a peak value of 78 achieved at a 5% reinforcement level. Tribological assessments conducted with a tribometer under a constant sliding velocity of 0.5 m/s and a normal load of 10 Newtons over a 500-meter distance indicated that the addition of 2.5% TiO2W to the ABS matrix resulted in the lowest mass wear rate (2x10-7 g/Nm) and a coefficient of friction (COF) of 0.191. These findings suggest that the strategic inclusion of TiO2W additives into ABS composites can significantly improve their wear resistance and hardness, which are essential for their performance in demanding environments. The research offers a foundation for the development of ABS-based materials with superior tribological properties for critical applications, potentially leading to enhanced energy efficiency and reduced environmental impact. [ABSTRACT FROM AUTHOR]

The stereoselective polymerization of conjugated dienes promoted by using transition metal complexes has attracted much interest in both industrial and academic environments for the relevance of polydienes as synthetic rubbers and for the challenging reaction mechanisms. Among the different transition metal complexes, those based on group IV have been demonstrated to be versatile and efficient catalysts. Titanium complexes are generally more active than zirconium complexes. A rare exception to this trend is represented by a series of Zr(IV) complexes supported by (anilidomethyl)pyridine ligands that, after activation by using Al(iBu2H)/MAO, were found to be highly active affording exclusively cis-1,4-polybutadiene. To rationalize this unexpected trend and to obtain more insights into the parameters that control the reactivity of group IV complexes, a theoretical investigation of the entire polymerization mechanism, employing density functional methods, was undertaken. In the framework of the widely accepted polymerization scheme, the different intermediates featuring h4 (both cis and trans) coordination of the monomer and h1 or h3 (syn or anti)allyl coordination of the growing chain were scrutinized. Subsequently, the effects of the metal center on the free-energy profiles of the elementary steps involved in the reaction were examined. The results presented herein aim to achieve a better knowledge of the influence of the metal on the polymerization rates and on the stereoselectivity of the reaction. [ABSTRACT FROM AUTHOR]

The present study assesses, using a theoretical approach, the performances of two widely used fixed-bed reactors for the ethanol-to-butadiene (ETB) one-stage (Lebedev) process: multibed adiabatic reactors (MBAR) with inter-bed heating and a multitubular reactor (MTR). The mathematical model consists of mass and heat conservation equations at catalyst particle and particle bed scales, coupled with a published kinetic model specific for a modified MgO–SiO2 catalyst. The process simulations at the level of catalyst particle have shown that the inter-phase concentration and temperature gradients are negligible, the only physical step with a limiting influence on process kinetics being the internal diffusion. A simplified version of the reactor model was also formulated, including empirical expressions developed in the study for the calculation of internal effectiveness factors. The reactor simulations highlighted that the MBAR with inter-bed heating by injection of hot reactants provides worse butadiene (BD) yields as a consequence of reduced reaction times (due to reactant by-pass of catalyst beds). The MBAR with inter-bed heating using heat exchangers provides better performances but inferior to those of MTR if the number of catalyst beds is less than six. A preliminary optimization study for the MBAR and MTR is also presented. The results showed that the maximization of BD yield has the drawback of a low BD production rate, whereas the maximization of BD production rate corresponds to a relatively low BD yield and high ethanol and inert recycles. A trade-off between the two extreme cases can be attained by maximizing the income generated by reactor operation. [ABSTRACT FROM AUTHOR]

1,3-Butadiene (BD) is classified as a human carcinogen, and occupational exposure should be minimized. This study examined the effectiveness of personal protective equipment (PPE) during the clean-up and repair of a storage tank containing sludge contaminated with BD. A total of 66 workers participated, providing repeat urine samples before and after the shift. Overall, 1286 samples were analyzed for 1,2-dihydroxy-4-(N-acetylcysteinyl)butane (DHBMA) and the isomers 2-hydroxy-1-(N-acetylcysteinyl)-3-butene and 1-hydroxy-2-(N-acetylcysteinyl)-3-butene (MHBMA). Both DHBMA and MHBMA are urinary metabolites of BD and serve as biomarkers for recent BD exposure. Established correlations between the urinary concentrations of these biomarkers and airborne BD levels allowed for exposure assessment. However, conclusions regarding the exceedances of occupational exposure limits can vary depending on whether DHBMA or MHBMA levels are considered. This study investigated this discrepancy by estimating the apparent urinary half-lives of DHBMA and MHBMA using sequential individual post- and pre-shift samples. The results indicated that the longer urinary half-life of MHBMA (19.7 ± 3.1 h) led to its accumulation during the work week, in contrast to DHBMA, which has a shorter half-life (10.3 ± 1.9 h) and showed limited accumulation. When the kinetic information was used to adjust for the MHBMA build-up over the week, the discrepancy with DHBMA resolved, confirming that exposure limit values were not exceeded and validating the effectiveness of the PPE used. In the context of biomonitoring, this study provides valuable insights into biomarker selection based on specific objectives. MHBMA is recommended for scenarios with uncertain exposure timing and activities, whereas DHBMA is the preferred biomarker for evaluating the effectiveness of protective measures in known exposure settings.

A low vinyl polybutadiene (PB)-polyvinylpyridine （PVP） diblock copolymers (lvPB-b-PVP) with the same segment length of PB but different segment length of PVP and controllable molecular weight and its distribution was designed and synthesized using anionic polymerization method. The molecular structure of the polymer was analyzed by gel permeation chromatography and nuclear magnetic resonance spectroscopy. The results showed that the polydispersity index of the molecular weight was 1.09-1.21, where the mole fraction of vinyl was 10.4%-11.5%, number-average molecular weight of low vinyl PB was 5.0 kg/mol, number-average molecular weight of PVP was about 5-30 kg/mol, and number-average molecular weight of the block copolymer was 10-35 kg/mol. This polymer was expected to has certain potential application value in self-assembly. Because the hydrogen bonding ability of P 2 VP and P 4 VP in the polymer was significantly different, the retention time of gel permeation chromatography of lvPB-b-P 2 VP shortened with the increase of its molecular weight, while the retention time of lvPB-b-P 4 VP was constant and the same as that of PB precursor.

Adhesion properties of metal-composite bonds are crucial in defining composite capability with other metallic components, and failures could lead to severe accidents. Hence, the study is aimed at the development and characterization of metal-composite bonds using different rigid adherends and adhesive materials (thermoset and thermoplastics). Among natural fibers, jute was used, while aramid, carbon, and glass woven reinforcements were employed from synthetic fibers. A simultaneous comparison of both thermoset and thermoplastic matrices was done using epoxy, polypropylene (PP), and polyvinyl butadiene (PVB) as adhesive materials. Floating roller delamination characterization proved variation in adhesion qualities governing different failure modes by varying adhesive even in a single rigid adherend. The highest fracture toughness was observed for aluminum-jute bonds made with PP and PVB that was due to toughness of matrix and intralaminar failure. Carbon being brittle in nature showed the most fluctuated performance with a 90% difference between the highest value of carbon-PVB and the lowest value of carbon-epoxy. Thermoplastic matrices owing to plasticity offered overall more fracture toughness than brittle thermoset resin. Furthermore, intralaminar was the dominant failure mechanism in the jute-based bond made with thermoplastic matrix. [ABSTRACT FROM AUTHOR]

In the present study, stress sensitivity of modified binders in the multiple stress creep and recovery (MSCR) test and its relationship with rutting resistance of the asphalt mixtures are investigated. For this purpose, different groups of styrene butadiene styrene (SBS), polyphosphoric acid (PPA) and SBS + PPA modified binders were produced; in each of which, the binders have the same continuous high temperature performance gradings (PGs) and linear viscoelastic (LVE) properties. The MSCR tests were performed at 40°C, 55°C, and at the PG temperatures of the modified binders to consider a wide range of high pavement temperatures. To depict the stress sensitivity, stress levels of 12.8, 25.6, and 40 kPa were added to the MSCR standard procedure and the non-recoverable compliance (Jnr) and percent recovery (R) parameters were obtained at all the stress levels applied. To study the rutting resistance of asphalt mixtures prepared with the same asphalt binders, the flow number (FN) and |E*| parameters were determined at 40°C and 55°C, through the dynamic creep and dynamic modulus performance tests, respectively. Results of the MSCR test show that at the temperature range considered, the standard stresses are not sufficient to enter the modified binders into nonlinear region, thus higher stress levels should be applied to assess the nonlinearity and address the true rutting potential. Results of the mixtures performance tests show great correlations with the results of the MSCR of the modified binders at the nonlinear stress levels, especially with the Jnr parameter, regardless of the test temperatures. [ABSTRACT FROM AUTHOR]

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The article presents a method for obtaining new composites using the well-known mineral expanded perlite (EP), and the industrial polymer butadiene rubber (BR). For the design of composites, a joint oxidative chlorophosphorylation reaction of BR and EP (as well as BR and modified EP) was carried out, and the modifications resulting from these reactions were further hydrolyzed. The structure and morphology of the obtained samples were characterized in detail using Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, X-ray powder diffraction, as well as scanning electron microscopy, and energy-dispersive X-ray analysis. EP and BR were separately modified with a similar reaction and characterized for data interpretation. [ABSTRACT FROM AUTHOR]

Germylyne complex Cp*(OC)2Cr≡Ge{C(SiMe3)3} (1) reacted with methyl vinyl ketone to give an η3‐allyl complex 2 with an oxagermacyclopentenyl ring. An analogous η3‐allyl complex 3 with a germacyclopentenyl ring was obtained by the reaction with butadiene, a non‐polar conjugated molecule, under photoirradiation. These reactions are accompanied by cleavage of the Cr≡Ge triple bond. On the other hand, the reactions of complex 1 with alkynes under photoirradiation resulted in clean substitution of a CO ligand of 1 to afford (η2‐alkyne)germylyne complexes, where the Cr≡Ge triple bond is intact. [ABSTRACT FROM AUTHOR]

To address the problems of brittleness and poor elastic deformation ability of oil‐well cement stone, styrene‐butadiene latex powder was prepared using emulsion polymerization with styrene, liquid polybutadiene, 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid, and fumaric acid as raw materials. The dispersion properties of styrene‐butadiene latex powder in water were investigated, as well as the elastic enhancement effect of the powder in cement. The test results showed that styrene‐butadiene latex powder has good dispersion performance in water and is not easy to agglomerate, which can improve the fluidity of cement slurry. The elastic modulus of cement stone mixed with styrene butadiene latex powder is 43.1% and 27.8% lower than that of blank cement stone without styrene‐butadiene latex powder and the cement stone mixed with commercially available latex powder, respectively. The results of the mechanism analysis showed that the styrene‐butadiene latex powder can be filled in the cement stone, improved the compactness of the cement stone, buffered the external stress impact, and improve the elasticity of the cement stone. [ABSTRACT FROM AUTHOR]

Tungsten carbide (WC), a superhard and thermally stable ceramic, is widely used in several industries. Its exceptional features portray WC as a promising reinforcement and stabilizing agent for popular polymeric matrices deployed in material extrusion (MEX) 3D-Printing, such as Acrylonitrile Butadiene Styrene (ABS). This potential was investigated in depth and is presented herein. ABS/WC nanocomposite filaments were prepared by melt extrusion and tested. A filler loading of 0 wt % up to 10 wt % WC, in 2 wt % steps were fabricated. The impact of the WC nanopowder content on the structural, rheological, thermal, mechanical, and morphological characteristics of nanocomposite filaments and 3D printed samples was investigated with the aid of fifteen (15) different tests. The experiments revealed excellent thermal stability of the developed nanocomposites, as well as non-Newtonian shear thinning behavior of their melts, which is encouraging for their processability. WC nanoparticles impressively upgraded the mechanical capacity of the optimized nanocomposites in comparison to that of pure ABS. ABS with 4.0 wt % WC grade exhibited a noticeable increase in most of the mechanical characteristics; Compressive, flexural, and tensile strength all rose by 25.9%, 29.4%, and 20.9% respectively, while the microhardness increased by 100.3%, showing potential for use in applications requiring high wear resistance. The findings of the current research indicate that novel cost-effective ABS/WC composites have high potential and industrial merit for a variety of demanding applications with ABS-based composites. [Display omitted] • Acrylonitrile butadiene styrene/Tungsten Carbide nanocomposites in Additive Manufacturing. • Mechanical, thermal, spectroscopic, rheological, and morphological characterization. • Nanocomposites with an enhanced mechanical response. • Advanced Additive Manufacturing materials for demanding applications, especially requiring high-wear resistance. [ABSTRACT FROM AUTHOR]

Natural flammability properties of acrylonitrile butadiene styrene (ABS) seriously limit the use of ABS polymers in industries. Improving the flammability performance of ABS by using halogenated additives has been a very common method in the past. However, with increasing environmental awareness, the use of halogen‐containing additives has been severely limited over time. Therefore, we aimed to use halogen‐free flame‐retardant additives in our study to improve the flame‐retardant properties of ABS. ABS‐based composites containing 20, 25, 30 % aluminum diethyl‐phosphinate (AlPi) and ammonium polyphosphate (APP) halogen‐free flame‐retardant additives by weight, were prepared using a twin‐screw extruder. V0 rating according to UL 94 standard for the thickness of 1.5 mm, limiting oxygen index (LOI) value higher than 28 %, and glow wire flammability index of 960 °C were aimed in this study. To improve the LOI values of flame‐retardant ABS composites, pentaerythritol (PER), zinc borate (ZB), and magnesium hydroxide were used. The highest LOI value was obtained to be 28.1 % by using 12.5 wt.% AlPi, 12.5 wt.% APP, 5 wt.% PER and 3 wt.% ZB. The effect of flame retardants on mechanical properties (flexural and tensile properties), impact properties (Izod and Charpy‐notched impact strength), thermal properties, melt flow index, and morphology (scanning electron microscopy) of ABS were also examined. [ABSTRACT FROM AUTHOR]

Cobalt complexes carrying 2‐acetyl‐6‐iminopyridine ligand are synthesized and characterized. Single‐crystal X‐ray diffraction reveals the cobalt ion is chelated with two nitrogen atoms and an acetyl oxygen atom additionally. A significant prolonged Co–O distance (2.3960(57) Å) is found, indicative of a labile character. Activated by diethylchloroaluminum, all complexes show high conversion rates for isoprene and myrcene polymerizations, affording cis‐1,4/3,4 regulated 1,3‐diene polymers. The polymerization of butadiene, interestingly, gives predominant cis‐1,4 selectivity (>99.2%) with moderate activity. The substituent at ortho‐position of arylimine plays a minor role in controlling activity and selectivity as well as the molecular weight of the resultant polymers. The properties of resultant poly(1,3‐diene)s are stable even in a wide range of operational conditions, such as [Al]/[Co] varied from 20 to 600, temperature spanning from 0°C to 60°C, and monomer–catalyst ratio from 1000 to 4000. These additional benefits of minimum fluctuation in catalytic performances may be suitable for industrial polymerization process. [ABSTRACT FROM AUTHOR]

A new cationic palladium complex [Pd(η5-C5H5)(PPh2Cy)2]BF4 (I) is prepared by the reaction of [Pd(acac)(PCyPh2)2]BF4 with cyclopentadiene in the presence of BF3·OEt2. The structure of complex I is determined by XRD. Results of the DFT studies at the BP86-D3/def2-TZVP level of theory along with QTAIM and NOCV methods suggest that the hapticity of the cyclopentadienyl ligand in I adopts an intermediate type of coordination between η3 and η5. Compound I demonstrates a catalytic activity in the reaction of 1,3-butadiene telomerization with methanol with a catalyst turnover number up to 43100 (mol·BD)/(mol·Pd) for 6 h and a 76% selectivity to telomeres. [ABSTRACT FROM AUTHOR]

Although the discovery of the GaI complex salt [Ga(PhF)2‐3][Al(ORF)4] (RF=C(CF3)3, PhF=C6H5F) invoked the preparation of a diverse library of cationic Ga(I) coordination complexes and clusters, studies on small molecule activation with low‐valent GaI cations are scarce. Herein, a first experimental study on the reactivity of a monomeric Ga(I) cation activated with a pyridine–diimine pincer ligand (in [Ga(PDIdipp)][Al(ORF)4]) towards small‐molecules is reported. First controlled oxidative additions of the GaI cation into C−Cl, H−P and P−P bonds are presented. Moreover, the [4+1]cycloaddition to butadienes was achieved. Intriguingly, the isolated, blue insertion product into the P−P bond of P4 allows for the quantitative release of the P4 molecule upon reaction with AlEt3 and butadienes. Reversible P4 insertion of main‐group metals has previously been reported for Ge and Sn, respectively. The experimental study is supported by high‐level computational analysis of the in‐part reversible oxidative additions at the DLPNO‐CCSD(T)/def2‐TZVPP//PBEh‐3c/def2‐mSVP level of theory with COSMO‐RS solvation in 1,2‐difluorobenzene. [ABSTRACT FROM AUTHOR]

Although the discovery of the GaI complex salt [Ga(PhF)2‐3][Al(ORF)4] (RF=C(CF3)3, PhF=C6H5F) invoked the preparation of a diverse library of cationic Ga(I) coordination complexes and clusters, studies on small molecule activation with low‐valent GaI cations are scarce. Herein, a first experimental study on the reactivity of a monomeric Ga(I) cation activated with a pyridine–diimine pincer ligand (in [Ga(PDIdipp)][Al(ORF)4]) towards small‐molecules is reported. First controlled oxidative additions of the GaI cation into C−Cl, H−P and P−P bonds are presented. Moreover, the [4+1]cycloaddition to butadienes was achieved. Intriguingly, the isolated, blue insertion product into the P−P bond of P4 allows for the quantitative release of the P4 molecule upon reaction with AlEt3 and butadienes. Reversible P4 insertion of main‐group metals has previously been reported for Ge and Sn, respectively. The experimental study is supported by high‐level computational analysis of the in‐part reversible oxidative additions at the DLPNO‐CCSD(T)/def2‐TZVPP//PBEh‐3c/def2‐mSVP level of theory with COSMO‐RS solvation in 1,2‐difluorobenzene. [ABSTRACT FROM AUTHOR]

Polymers are widely employed in many areas, e.g. transport, packaging, electronic devices, etcetera. Among them, acrylonitrile–butadiene–styrene (ABS) is one of the most employed polymers due to its mechanical properties, its ease to mechanize and recyclability. Nevertheless, according to the fire properties, ABS behaviour is usually worse than other polymers, therefore, they have to be upgraded with flame retardant additives. To characterize the fire behaviour of a certain material is necessary to address several typology of tests, providing relevant properties such as thermal conductivity, flammability and heat released. However, researchers may not always be able to run all tests due to the lack of apparatus or samples. Therefore, it is necessary to seek bibliographic sources. As one might expect, for a given material, the property values should be similar, regardless of who performs the test. However, sometimes slightly different results are obtained, which may be due to different causes, such as differences in test set-up and in material composition/manufacture. These differences in properties may lead researcher to doubt which data to use. This paper presents the results of different types of tests using neat ABS polymer. Additionally, these results are compared with the data from literature, discussing the similarities/differences and offering a more comprehensive characterization of ABS. The laboratory techniques included in this work are: thermogravimetric analysis, differential scanning calorimetry, laser flash analysis, smoke density, cone calorimeter, fire propagation and flammability. [ABSTRACT FROM AUTHOR]

Block copolymers based on polyethylene (PE) and ethylene butadiene rubber (EBR) were obtained by successive controlled coordinative chain transfer polymerization (CCTP) of a mixture of ethylene and butadiene (80/20) and pure ethylene. EBR‐b‐PE diblock copolymers were synthesized using the {Me2Si(C13H8)2Nd(BH4)2Li(THF)}2 complex in combination with n‐butyl,n‐octyl magnesium (BOMAG) used as both the alkylating and chain transfer agent (CTA). Triblock and multiblock copolymers featuring highly semi‐crystalline PE hard segments and soft EBR segments were further obtained by the development of a bimetallic CTA, the pentanediyl‐1,5‐di(magnesium bromide) (PDMB). These new block copolymers undergo crystallization‐driven organization into lamellar structures and exhibit a variety of mechanical properties, including excellent extensibility and elastic recovery in the case of triblock and multiblock copolymers. [ABSTRACT FROM AUTHOR]

A series of amine–imine cobalt complexes (Co1–Co7) has been prepared and characterized. The complexes Co3, Co4, and Co6 have a distorted tetrahedral geometry, as determined by single crystal X-ray diffraction. In the presence of ethylaluminum sesquichloride (EASC), Co3 exhibited ultra-high activity toward butadiene (Bd) polymerization (up to 7813 kgpolymer mol−1 h−1). The activity is higher than any yet recorded for which yield high cis-1,4 polybutadiene by the well-defined late-transition metal catalytic system. The catalyst also exhibited excellent tolerance towards the ratio of Co/Bd and broad temperature stability. At a ratio of Bd/Co3 = 50 000, the complexes Co1–3 can afford polybutadiene with yields higher than 96% within 2 hours. At −20 °C to 100 °C, the complex Co3 afforded relatively high polymer yields at low catalyst concentrations (Bd/Co3 = 25 000). In addition, all polymers showed a relatively high molecular weight (up to 1.06 × 106 g mol−1). [ABSTRACT FROM AUTHOR]

The paper presents theoretical calculations and experimental data on the permittivity of conductive porous acrylonitrile butadiene styrene. It is found that spectrum regions with differential absorption are caused by the volume resonance of electromagnetic waves inside pores and in the matrix material between them. Resonant frequencies with increased differential absorption can be controlled by changing the pore space, dimension, and matrix permittivity. [ABSTRACT FROM AUTHOR]

The purpose of this work was to investigate the structural, thermal, micromechanical and tribological properties of novel polymer/metal composite materials for bearing applications. Copper (Cu)-filled Acrylonitrile Butadiene Styrene (ABS) composites were mixed in a laboratory scale by an internal mixer with two blade impellers, and then injection-molded. Neat ABS, ABS+5wt% Cu, ABS+10wt% Cu, and ABS+15wt% Cu were the four materials that were tested. The dispersion of Cu particles in the ABS matrix was investigated using Scanning Electron Microscopy (SEM) and a micro-tomography scan. The filler particles have a uniform distribution in the matrix, according to the observations. The incorporation of Cu filler also refined an increase in the glass transition temperature from Differential Scanning Calorimetry (DSC) and less intensity in the amorphous phase by X-ray diffraction (XRD). Nanoindentation tests were carried out to characterize the micro-mechanical behavior of the composites. Friction and wear analysis were also examined using a pin-on-disk tribometer. Compared with neat ABS, all the micro-composites showed much higher indentation hardness, Vickers hardness, and indentation elastic modulus. It was also concluded that the incorporation of Cu filler into ABS simultaneously improved the friction and wear properties of the composites, which contributed to the suitability of the micro-filled composites with hard metallic particles for a wider range of mechanical components for bearing applications. [ABSTRACT FROM AUTHOR]

The multicomponent injection molding of liquid silicone rubbers (LSR) with thermoplastics, such as polybutylene terephthalate (PBT) or polyamide (PA), is a state-of-the-art technique and is used in the manufacturing process for many components in the automotive industry and in the field of sanitary engineering. Standard thermoplastics, such as acrylonitrile butadiene styrene (ABS), cannot be bonded with silicone rubbers in injection molding because of their low heat deflection temperature. In this study, we investigated ABS grades approved for medical applications to show how dynamic mold heating and various pretreatment methods for thermoplastic surfaces can be used to produce ABS-LSR test specimens. In addition, such components' sterilization effect on the adhesive bond will be shown. [ABSTRACT FROM AUTHOR]

The efficient separation of butadiene (1,3‐C4H6) from C4 hydrocarbons is a critical step in petrochemical processes. However, the traditional cryogenic distillation suffers from energy‐intensity and serious environmental stress, necessitating the development of alternative technologies for efficient 1,3‐C4H6 separation. Herein, a 1,3‐C4H6 recognition mixed matrix membrane is reported via incorporating metal copper encapsulated a metal‐organic framework (CuBTC@Cu) into elastic poly(dimethylsiloxane) (PDMS). The resulting CuBTC@Cu/PDMS membrane can efficient separate 1,3‐C4H6 from various C4 hydrocarbons including 1,3‐C4H6/n‐C4H8, 1,3‐C4H6/iso‐C4H8, 1,3‐C4H6/n‐C4H10 and 1,3‐C4H6/iso‐C4H10, yielding superior selectivity of 5.11, 6.35, 4.78, and 10.30, respectively, with 1,3‐C4H6 permeability of 53240 Barrer. Notably, the appropriate π‐complexation interaction between butadiene molecules and CuBTC@Cu as well as suitable transmission channel size enable the membrane only permeable to 1,3‐C4H6 and block the permeation of other C4 hydrocarbons, showing a unique 1,3‐C4H6 recognition behavior in membrane separation. The concept of affinity‐relying separation combining molecular sieving would open a new direction for designing gas membranes for efficient light hydrocarbon separations. [ABSTRACT FROM AUTHOR]

Rh(C2H4)2 species grafted on the HY zeolite framework significantly enhance the activation of H2 that reacts with C2H4 ligands to form C2H6. While in this case, the simultaneous activation of C2H4 and H2 and the reaction between these species on zeolite-loaded Rh cations is a legitimate hydrogenation pathway yielding C2H6, the results obtained for Rh(CO)(C2H4)/HY materials exposed to H2 convincingly show that the support-assisted C2H4 hydrogenation pathway also exists. This additional and previously unrecognized hydrogenation pathway couples with the conversion of C2H4 ligands on Rh sites and contributes significantly to the overall hydrogenation activity. This pathway does not require simultaneous activation of reactants on the same metal center and, therefore, is mechanistically different from hydrogenation chemistry exhibited by molecular organometallic complexes. We also demonstrate that the conversion of zeolite-supported Rh(CO)2 complexes into Rh(CO)(C2H4) species under ambient conditions is not a simple CO/C2H4 ligand exchange reaction on Rh sites, as this process also involves the conversion of C2H4 into C4 hydrocarbons, among which 1,3-butadiene is the main product formed with the initial selectivity exceeding 98% and the turnover frequency of 8.9 × 10−3 s−1. Thus, the primary role of zeolite-supported Rh species is not limited to the activation of H2, as these species significantly accelerate the formation of the C4 hydrocarbons from C2H4 even without the presence of H2 in the feed. Using periodic density functional theory calculations, we examined several catalytic pathways that can lead to the conversion of C2H4 into 1,3-butadiene over these materials and identified the reaction route via intermediate formation of rhodacyclopentane. [ABSTRACT FROM AUTHOR]

Abstract Nitrile rubber (NBR) is commonly used as a stator rubber for screw pumps because of its excellent mechanical properties. However, under hightemperature conditions, using NBR for long-term operations is [...]

To compute the electronic excitation energies, a state-specific multireference Møller–Plesset perturbation theory (SSMRPT) with a complete active space configuration interaction reference function constructed using the orbitals obtained by the density functional theory (DFT) is presented as an accurate, as well as computationally affordable, and efficient protocol at the level of second order. The global hybrid B3LYP (Becke, 3-parameter, Lee–Yang–Parr) functional has been used to generate orbitals. The present method, called DFT-SSMRPT, uses perturbers that are individual Slater determinants and accounts for the coupling between the nondynamical and dynamical correlation effects. We have applied the new method to compute excitation energies in conjugated systems of π-electrons such as trans-1,3-butadiene, trans,trans-1,3,5-hexatriene, and all-trans-1,3,5,7-octatetraene. The ordering of the excited states is correctly reproduced by the DFT-SSMRPT calculations. The relative ordering of low-lying excited 1Bu and 1Ag states alters when the length of the polyene changes. The results match reasonably well with the literature including experimental and best theoretical findings. The accuracy of the method is sufficient to discern the energy gap between the close low-lying singlet and triplet states. The DFT-SSMRPT appears as an affordable computational ab initio avenue for a qualitatively correct description of excitation energies. [ABSTRACT FROM AUTHOR]

The photochemical dynamics of double-bond-containing hydrocarbons is exemplified by the smallest alkenes, ethylene and butadiene. Chemical substituents can alter both decay timescales and photoproducts through a combination of inertial effects due to substituent mass, steric effects due to substituent size, and electronic (or potential) effects due to perturbative changes to the electronic potential energy surface. Here, we demonstrate the interplay of different substituent effects on 1,3-butadiene and its methylated derivatives using a combination of ab initio simulation of nonadiabatic dynamics and time-resolved photoelectron spectroscopy. The purely inertial effects of methyl substitution are simulated through the use of mass 15 "heavy-hydrogen" atoms. As expected from both inertial and electronic influences, the excited-state dynamics is dominated by pyramidalization at the unsubstituted carbon sites. Although the electronic effects of methyl group substitution are weak, they alter both decay timescales and branching ratios by influencing the initial path taken by the excited wavepacket following photoexcitation. [ABSTRACT FROM AUTHOR]

Abstract The efficient separation of butadiene (1,3‐C4H6) from C4 hydrocarbons is a critical step in petrochemical processes. However, the traditional cryogenic distillation suffers from energy‐intensity and serious environmental stress, necessitating the development of alternative technologies for efficient 1,3‐C4H6 separation. Herein, a 1,3‐C4H6 recognition mixed matrix membrane is reported via incorporating metal copper encapsulated a metal‐organic framework (CuBTC@Cu) into elastic poly(dimethylsiloxane) (PDMS). The resulting CuBTC@Cu/PDMS membrane can efficient separate 1,3‐C4H6 from various C4 hydrocarbons including 1,3‐C4H6/n‐C4H8, 1,3‐C4H6/iso‐C4H8, 1,3‐C4H6/n‐C4H10 and 1,3‐C4H6/iso‐C4H10, yielding superior selectivity of 5.11, 6.35, 4.78, and 10.30, respectively, with 1,3‐C4H6 permeability of 53240 Barrer. Notably, the appropriate π‐complexation interaction between butadiene molecules and CuBTC@Cu as well as suitable transmission channel size enable the membrane only permeable to 1,3‐C4H6 and block the permeation of other C4 hydrocarbons, showing a unique 1,3‐C4H6 recognition behavior in membrane separation. The concept of affinity‐relying separation combining molecular sieving would open a new direction for designing gas membranes for efficient light hydrocarbon separations.

A series of styrene-butadiene di-block copolymers with high cis-1,4 unit content (greater than 92%) polybutadiene (PB) and isotactic-rich polystyrene (PS) (mmmm > 65%) was synthesized using α-diimine nickel catalysts (Ni-diimine). Four different Ni-diimine catalysts were synthesized via a complexing reaction between nickel (II) naphthenate and laboratory-made α-diimine ligands L1, L2, L3 and L4, which have different steric volume structures. The results indicate that the Ni-diimine catalyst prepared using the L4 ligand with a higher steric volume can effectively initiate the block polymerization of butadiene and styrene, and the resulting polymer has distinguished cis-1,4 structure unit PB and high isotactic-selective PS block. Differential scanning calorimetry and electrochemical performance tests show that these block copolymers with cis-1,4-regulated and isotactic-selective polymerization have advantages in terms of high-temperature and low-temperature resistance as well as corrosion resistance. Therefore, these copolymers are expected to be widely used in some harsh industrial environments.