Showing papers on "Polycarbonate published in 2021"

Pinwheel-Shaped Tetranuclear Organoboron Catalysts for Perfectly Alternating Copolymerization of CO2 and Epichlorohydrin.

Abstract: The copolymerization of carbon dioxide (CO2) and epoxides to produce aliphatic polycarbonates is a burgeoning technology for the large-scale utilization of CO2 and degradable polymeric materials. Even with the wealth of advancements achieved over the past 50 years on this green technology, many challenges remain, including the use of metal-containing catalysts for polymerization, the removal of the chromatic metal residue after polymerization, and the limited practicable epoxides, especially for those containing electron-withdrawing groups. Herein, we provide kinds of pinwheel-shaped tetranuclear organoboron catalysts for epichlorohydrin/CO2 copolymerization with >99% polymer selectivity and quantitative CO2 uptake (>99% carbonate linkages) under mild conditions (25-40 °C, 25 bar of CO2). The produced poly(chloropropylene carbonate) has the highest molecular weight of 36.5 kg/mol and glass transition temperature of 45.4 °C reported to date. The energy difference (ΔEa = 60.7 kJ/mol) between the cyclic carbonate and polycarbonate sheds light on the robust performance of our metal-free catalyst. Control experiments and density functional theory (DFT) calculations revealed a cyclically sequential copolymerization mechanism. The metal-free feature, high catalytic performance under mild conditions, and no trouble with chromaticity for the produced polymers imply that our catalysts are practical candidates to advance the CO2-based polycarbonates.

Effects of Functional Additives on Structure and Properties of Polycarbonate-Based Composites Filled with Hybrid Chopped Carbon Fiber/Graphene Nanoplatelet Fillers

Abstract: A rheology modifier (styrene-acrylonitrile copolymer, SAN) and a flame retardant (resorcinol bis(2, 6-dixylyl phosphate), RXP) were incorporated in polycarbonate (PC)/chopped carbon fiber (CCF)/graphene nanoplatelet (GNP) system to prepare PCbased composites (PC/SANx@(CCF+GNP), rPC/SANx@(CCF+GNP)i) by a twin-screw extruder. The rheological properties, thermal stability, flame retardancy and mechanical properties of composites were evaluated. Increasing shear rate and temperature induced obvious reduction of viscosity of all composites. By comparison, PC/SAN5@(CCF+GNP) possessed a greater viscous flow activation energy (Eη), showing higher temperature sensibility of viscosity. While PC/SAN0@(CCF+GNP) and rPC/SAN5@(CCF+GNP)1.5 had lower Eη values and exhibited different sensitivity of shearing force. Besides, SAN and RXP had obvious influences on the thermal stability of composites. Meanwhile, PC/SAN composites displayed improved flame retardancy from 31.9% of limiting oxygen index (LOI) and V-1 rating for PC/SAN composites to 37.9% of LOI and V-0 rating for composites containing 2.5% RXP. Additionally, mechanical strengths and moduli of PC/SAN composites were increased by SAN and RXP without impairing toughness. These results were attributed to matrix enhancement of SAN, the lubrication effect of lower molecular weight RXP and the enhancement of the interactions between matrix and fillers.

“Soft-rigid” synergistic reinforcement of PHBV composites with functionalized cellulose nanocrystals and amorphous recycled polycarbonate

Abstract: Herein, both rigid cellulose nanocrystal with photoactive groups (CNC-Cc) and amorphous polycarbonate (extracted from discarded CD) were functionalized as reinforcing agents to obtain poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/polycarbonate/CNC-Cc (PHBV/PC/CNC-Cc) composite films via a Pickering emulsion approach. With the addition of PC and CNC-Cc, an obvious “soft-rigid” synergistic effect on the performances of PHBV matrix was found. Compared to neat PHBV, the best mechanical strength/toughness of PHBV/PC/CNC-Cc-7 increased by 273.8%/821.9%. Meanwhile the PHBV/PC/CNC-Cc-7 nanocomposite showed excellent UV shielding, antioxidant, and antibacterial abilities, due to dynamic competition effect of amorphous PC and rigid CNC-Cc on the PHBV microstructure and interaction. Therefore, this work could solve the current problems of poor mechanical flexibility of biopolymers for potential applications in easy-oxidized food packaging.

Introducing a novel low energy gamma ray shield utilizing Polycarbonate Bismuth Oxide composite.

Abstract: The fabrication of different weight percentages of Polycarbonate-Bismuth Oxide composite (PC-Bi2O3), namely 0, 5, 10, 20, 30, 40, and 50 wt%, was done via the mixed-solution method. The dispersion state of the inclusions into the polymeric matrix was studied through XRD and SEM analyses. Also, TGA and DTA analyses were carried out to investigate the thermal properties of the samples. Results showed that increasing the amount of Bi2O3 into the polymer matrix shifted the glass transition temperature of the composites towards the lower temperatures. Then, the amount of mass attenuation coefficients of the samples were measured using a CsI(Tl) detector for different gamma rays of 241Am, 57Co, 99mTc, and 133Ba radioactive sources. It was obtained that increasing the concentration of the Bi2O3 fillers in the polycarbonate matrix resulted in increasing the attenuation coefficients of the composites significantly. The attenuation coefficient was enhanced twenty-three times for 50 wt% composite in 59 keV energy, comparing to the pure polycarbonate.

Randomly Distributed Sulfur Atoms in the Main Chains of CO2 -Based Polycarbonates: Enhanced Optical Properties.

Abstract: Polymeric materials possessing both high refractive indices and high Abbe numbers are much in demand for the development of advanced optical devices. However, the synthesis of such functional materials is a challenge because of the trade-off between these two properties. Herein, a synthetic strategy is presented for enhancing the optical properties of CO2 -based polycarbonates by modifying the polymer's topological structure. Terpolymers with thiocarbonate and carbonate units randomly distributed in the polymers' main chain were synthesized via the terpolymerization of cyclohexene oxide with a mixture of CO2 and COS in the presence of metal catalysts, most notably a dinuclear aluminum complex. DFT calculations were employed to explain why different structural sequence were obtained with distinct bimetallic catalysts. Varying the CO2 pressure made it possible to obtain terpolymers with tunable carbonate linkages in the polymer chain. More importantly, optical property studies revealed that terpolymers with comparable thiocarbonate and carbonate units exhibited a refractive index of 1.501 with an enhanced Abbe number as high as 48.6, much higher than the corresponding polycarbonates or polythiocarbonates. Additionally, all terpolymers containing varying thiocarbonate content displayed good thermal properties with Tg >109 °C and Td >260 °C, suggesting little loss in the thermal stability compared to the polycarbonate. Hence, modification of the topological structure of the polycarbonate is an efficient method of obtaining polymeric materials with enhanced optical properties without compromising thermal performance.

Mechanical Performance of Fused Filament Fabricated and 3D-Printed Polycarbonate Polymer and Polycarbonate/Cellulose Nanofiber Nanocomposites

Abstract: In this study, nanocomposites were fabricated with polycarbonate (PC) as the matrix material. Cellulose Nanofiber (CNF) at low filler loadings (0.5 wt.% and 1.0 wt.%) was used as the filler. Samples were produced using melt mixing extrusion with the Fused Filament Fabrication (FFF) process. The optimum 3D-printing parameters were experimentally determined and the required specimens for each tested material were manufactured using FFF 3D printing. Tests conducted for mechanical performance were tensile, flexural, impact, and Dynamic Mechanical Analysis (DMA) tests, while images of the side and the fracture area of the specimens were acquired using Scanning Electron Microscopy (SEM), aiming to determine the morphology of the specimens and the fracture mechanism. It was concluded that the filler’s ratio addition of 0.5 wt.% created the optimum performance when compared to pure PC and PC CNF 1.0 wt.% nanocomposite material.

Rapid Melt Crystallization of Bisphenol-A Polycarbonate Jointly Induced by Pressure and Flow

Abstract: Bisphenol-A polycarbonate (PC) is an intrinsically crystallizable polymer. Its industrial parts, however, invariably remain in an amorphous state due to its extremely slow crystallization kinetics....

Access to Biorenewable and CO2-Based Polycarbonates from Exovinylene Cyclic Carbonates

Abstract: We investigate the scope of the organocatalyzed step-growth copolymerization of CO2-sourced exovinylene bicyclic carbonates with bio-based diols into polycarbonates. A series of regioregular poly(oxo-carbonate)s were prepared from sugar- (1,4-butanediol and isosorbide) or lignin-derived (1,4-benzenedimethanol and 1,4-cyclohexanediol) diols at 25 degrees C with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as a catalyst, and their defect-free structure was confirmed by nuclear magnetic resonance spectroscopy studies. Their characterization by differential scanning calorimetry and wide-angle X-ray scattering showed that most of them were able to crystallize. When the polymerizations were carried out at 80 degrees C, some structural defects were introduced within the polycarbonate chains, which limited the polymer molar mass. Model reactions were carried out to understand the influence of the structure of alcohols, the temperature (25 or 80 degrees C), and the use of DBU on the rate of alcoholysis of the carbonate and on the product/linkage selectivity. A full mechanistic understanding was given by means of static- and dynamic-based density functional theory (DFT) calculations showing the determining role of DBU in the stability of intermediates, and its important role in the rate-determining steps is revealed. Furthermore, the origin of side reactions observed at 80 degrees C was discussed and rationalized by DFT modeling. As impressive diversified bio-based diols are accessible on a large scale and at low cost, this process of valorization of carbon dioxide gives new perspectives on the sustainable production of bioplastics under mild conditions.

Controlled attachment of polycarbonate nanoparticles on carbon fibers for increased resin impregnation and interfacial adhesion in carbon fiber composites

Abstract: The favorable interfacial properties of carbon fibers (CFs) and matrix are the key to the design and fabrication of a CF reinforced composite with superior micromechanical properties for various modern technological applications. However, high viscosity of a thermoplastic polymer makes resin infusion difficult, resulting in poor impregnation into CFs, ultimately leading to insufficient interfacial adhesion during composites fabrication process. Here the polycarbonate nanoparticles (PC-NPs) were pre-coated on the CFs from PC-NP aqueous solution and formed compact microstructure, which significantly improved the resin impregnation around CFs and interfacial adhesion between CFs and PC matrix. This PC-NP assisted CF/PC composite exhibits an increased interfacial shear strength up to 37.03 MPa, which is ~67.25% higher than that of un-coated CF/PC composite. Moreover, the tensile strength and flexural strength are enhanced remarkably by ~41.06% and ~22.16% increase, respectively. These results therefore demonstrate that the attachment of thermoplastic PC-NPs is a facile, environmental-friendly and viable approach in design and modification of the interfacial properties of CFs and PC matrix, which can be expanded for other multifunctional CF-reinforced composites with unique micromechanical properties for various practical applications.

FFF 3D Printing in Electronic Applications: Dielectric and Thermal Properties of Selected Polymers

Abstract: The present study is a focused and comprehensive analysis of the dielectric and thermal properties of twenty-four 3D printed polymers suitable for fused filament fabrication (FFF) in electronic applications. The selected polymers include various thermoplastic elastomers, such as thermoplastics based on polycarbonate (PC), polyethylene terephthalate glycol (PETG), and acrylonitrile butadiene styrene (ABS-T). Their overall thermal behavior, including oxidation stability, glass transition, and melting temperature, was explored using simultaneous thermal analysis (STA) and differential scanning calorimetry (DSC). Considering their intended usage in electronic applications, the dielectric strength (Ep) and surface/volume resistivity (ρs/ρv) were comprehensively tested according to IEC 60243-1 and IEC 62631-3, respectively. The values of the dielectric constant (e’) and loss factor (e”) were also determined by broadband dielectric spectroscopy (BDS). While, on the one hand, exceptional dielectric properties were observed for some thermoplastic elastomers, the materials based on PCs, on the other hand, stood out from the others due to their high oxidation stability and above average dielectric properties. The low-cost materials based on PETG or ABS-T did not achieve thermal properties similar to those of the other tested polymers; nevertheless, considering the very reasonable price of these polymers, the obtained dielectric properties are promising for undemanding electronic applications.

Probabilistic material flow analysis and emissions modeling for five commodity plastics (PUR, ABS, PA, PC, and PMMA) as macroplastics and microplastics✰

Abstract: Detailed knowledge about polymer flows through the anthroposphere and into the environment is information essential to the better management of plastics. Currently, only limited knowledge about specific polymer flows is available. This work aimed to model those flows for five polymers: polyurethane (PUR), acrylonitrile butadiene styrene (ABS), polyamide (PA), polycarbonate (PC) and polymethyl methacrylate (PMMA). Probabilistic material flow analysis (PMFA) was used to quantify flows from production in 45 product categories to their end-of-life in Europe and Switzerland. We then considered 40 release pathways for macro- and microplastic flows to assess polymer release into Switzerland's environment. PMFA results showed considerable variations between the polymers considered because their flows through the anthroposphere are determined by their different uses. Total macro- and microplastic emissions into Switzerland's environment in 2018 were estimated at masses of 208±76 t for PA, 179±98 t for PUR, 79±26 t for PC, 36±23 t for PMMA and 25±6 t for ABS. Relative to Switzerland's total production and imports, this amounted to total releases of 0.23% of PA, 0.07% of PUR, 0.16% of PC, 0.32% of PMMA and 0.14% of ABS. Contributions as released microplastics ranged from 18% of PMMA to 75% of ABS. These results showed that the amounts of the polymers considered released into the environment were much smaller than previously assumed in simpler release estimates, and they may be more realistic for countries with well-functioning waste treatment systems.

TiO2 Coatings Via Atmospheric-Pressure Plasma-Enhanced Chemical Vapor Deposition for Enhancing the UV-Resistant Properties of Transparent Plastics.

Abstract: Herein, TiO2 coatings were deposited on photodegradable polymers for protection from UV irradiation using the atmospheric-pressure plasma-enhanced chemical vapor deposition (AP-PECVD) technique. Polymethylmethacrylate (PMMA) and polycarbonate (PC) substrates were coated with titanium tetraisopropoxide as the precursor in an open-air atmospheric-pressure nonequilibrium argon plasma jet. The AP-PECVD-derived TiO2 coatings exhibited good adhesion to PMMA and PC. The TiO2 coatings could shield more than 99% of UV light in the wavelength range of 200-300 nm, without affecting the transmittance of visible light. UV irradiation tests on polymer films demonstrated that the degradation rates of PMMA and PC were significantly reduced by one-tenth after they were coated with TiO2 films.

Methoxy-Functionalized Glycerol-Based Aliphatic Polycarbonate: Organocatalytic Synthesis, Blood Compatibility, and Hydrolytic Property.

Abstract: Polymers that are biocompatible and degradable are desired for tissue engineering approaches in the treatment of vascular diseases, especially for those involving small-diameter blood vessels. Herein, we report the compatibility of a newly developed glycerol-based aliphatic polycarbonate possessing simple methoxy side groups, named poly(5-methoxy-1,3-dioxan-2-one) (PMDO), with blood cells and plasma proteins as well as its susceptibility to hydrolysis. As a consequence of the organocatalytic ring-opening polymerization (ROP) of a methoxy-functionalized cyclic carbonate derived from glycerol, PMDO with a sufficiently high molecular weight (Mn 14 kg/mol) and a narrow distribution (DM 1.12) was obtained for evaluation as a bulk biomaterial. This study demonstrates for the first time the organocatalytic ROP of a glycerol-based cyclic carbonate in a controlled manner. Compared with the clinically applied aliphatic polycarbonate poly(trimethylene carbonate) (PTMC), PMDO inhibits platelet adhesion by 33% and denaturation of fibrinogen by 23%. Although the wettability of PMDO based on water contact angle was almost comparable to those of PTMC and poly(ethylene terephthalate), the reason for the inhibited platelet adhesion and protein denaturation appeared to be related to the presence of specific hydrated water formed in the hydrated polymer. The improved hydration of PMDO also enhanced the susceptibility to hydrolysis, with PMDO demonstrating a slightly higher hydrolytic property than PTMC. This simple glycerol-based aliphatic polycarbonate has the following benefits: bio-based characteristics of glycerol and improved blood compatibility and hydrolytic biodegradability stemming from moderate hydration of the methoxy side groups.

Textile-Grade Carbon Fiber-Reinforced Polycarbonate Composites: Effect of Epoxy Sizing

Abstract: Epoxy-sized textile-grade polyacrylonitrile (PAN) carbon fiber (TCF) with 450 K filaments (CFTF, ORNL) was reinforced in the polycarbonate (PC) matrix using a compression molding technique. The epo...

Polymer Composites Based on Polycarbonate (PC) Applied to Additive Manufacturing Using Melted and Extruded Manufacturing (MEM) Technology.

Abstract: As part of the present work, polymer composites used in 3D printing technology, especially in Melted and Extruded Manufacturing (MEM) technology, were obtained. The influence of modified fillers such as alumina modified silica, quaternary ammonium bentonite, lignin/silicon dioxide hybrid filler and unmodified multiwalled carbon nanotubes on the properties of polycarbonate (PC) composites was investigated. In the first part of the work, the polymer and its composites containing 0.5–3 wt.% filler were used to obtain a filament using the proprietary technological line. The moldings for testing functional properties were obtained with the use of 3D printing and injection molding techniques. In the next part of the work, the rheological properties—mass flow rate (MFR) and mechanical properties—Rockwell hardness, Charpy impact strength and static tensile strength with Young’s modulus were examined. The structure of the obtained composites was also described and determined using scanning electron microscopy (SEM). The porosity, roughness and dimensional stability of samples obtained by 3D printing were also determined. On the other hand, the physicochemical properties were presented on the basis of the research results using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), wide angle X-ray scattering analysis (WAXS) and Fourier Transform infrared spectroscopy (FT-IR). Additionally, the electrical conductivity of the obtained composites was investigated. On the basis of the obtained results, it was found that both the amount and the type of filler significantly affected the functional properties of the composites tested in the study.

Thermal/Electrical Properties and Texture of Carbon Black PC Polymer Composites near the Electrical Percolation Threshold

Abstract: Polycarbonate (PC), a thermoplastic polymer with excellent properties, is used in many advanced technological applications. When PC is blended with other polymers or additives, new properties, such as electrical properties, can be available. In this study, carbon black (CB) was melt-compounded with PC to produce polymer compounds with compositions (10–16 wt.% of CB), which are close to or above the electrical percolation threshold (13.5–14 wt.% of CB). Effects due to nanofiller dispersion/aggregation in the polymer matrix, together with phase composition, glass transition temperature, morphology and textural properties, were studied by using thermal analysis methods (thermogravimetry and differential scanning calorimetry) and scanning electron microscopy. The DC electrical properties of these materials were also investigated by means of electrical conductivity measurements and correlated with the “structure” of the CB, to better explain the behaviour of the composites close to the percolation threshold.

Additive Manufacturing-Based In Situ Consolidation of Continuous Carbon Fibre-Reinforced Polycarbonate

Abstract: Continuous carbon fibre-reinforced thermoplastic composites have convincing anisotropic properties, which can be used to strengthen structural components in a local, variable and efficient way. In this study, an additive manufacturing (AM) process is introduced to fabricate in situ consolidated continuous fibre-reinforced polycarbonate. Specimens with three different nozzle temperatures were in situ consolidated and tested in a three-point bending test. Computed tomography (CT) is used for a detailed analysis of the local material structure and resulting material porosity, thus the results can be put into context with process parameters. In addition, a highly curved test structure was fabricated that demonstrates the limits of the process and dependent fibre strand folding behaviours. These experimental investigations present the potential and the challenges of additive manufacturing-based in situ consolidated continuous fibre-reinforced polycarbonate.