Showing papers on "Polycarbonate published in 2018"

Reprocessable Acid-Degradable Polycarbonate Vitrimers

Abstract: Vitrimers are cross-linked polymer networks containing linkages that undergo thermally activated, associative exchange reactions, such that the cross-link density and overall network connectivity are preserved. Polycarbonates are industrially relevant polymers that, to our knowledge, have not yet been explored as vitrimers. We developed hydroxyl-functionalized polycarbonate networks that undergo transcarbonation exchange reactions at elevated temperatures in the presence of catalytic Ti(IV) alkoxides. The rate of transcarbonation within the networks, estimated through stress relaxation experiments, was tuned by adjusting the catalyst loading or hydroxyl group concentration in the networks. The polymer networks exhibit recovery of their tensile strength and plateau storage modulus (71–133%) after reprocessing. In addition to being reprocessable, the networks were hydrolyzed and decarboxylated in aqueous acid to recover 80 wt % of the precursor to the bifunctional cyclic carbonate monomer. These observation...

Hot-pressing induced orientation of boron nitride in polycarbonate composites with enhanced thermal conductivity

Abstract: Thermally conductive polymer composites are commonly used in thermal management field because of their wide range of utilization, ease of processing and low cost. However, conventional polymer composites usually suffer from an undesired enhancement of thermal conductivity. Herein, we report on boron nitride (BN) plates/polycarbonate composites in which BN plates are aligned via hot-pressing. Since the orderly arrangement of BN plates can provide pathways for phonon transport, the obtained composites possess a maximum thermal conductivity of 3.09 W m−1 K−1 along the aligned direction as the BN loading reaching 18.5 vol%. The thermal infrared characterization also indicates that BN/polycarbonate composites perform higher heating or cooling rate due to the good heat conduction capacity. This strategy can potentially pave the way for the design and preparation of highly thermally conductive and mechanically strong materials for thermal-management applications.

Excellent Electromagnetic Interference Shielding and High Electrical Conductivity of Compatibilized Polycarbonate/Polypropylene Carbon Nanotube Blend Nanocomposites

Abstract: Herein, we have fabricated a series of immiscible blend nanocomposites based on polycarbonate/polypropylene (PC/PP) by uniformly dispersing multiwall carbon nanotubes (MWCNTs) via a melt mixing technique. The effect of polypropylene-grafted maleic anhydride (PP-g-MA) as a compatibilizer has played a pivotal role in reducing the interfacial tension and thereby enhancing the attenuation performance of PC/PP blends. The substantial effect of compatibilization on the dispersion of MWCNTs has resulted in higher conductivity values of 0.33 S cm–1, which is a major requirement for designing EM shields. Nevertheless, both the uncompatibilized and compatibilized blend nanocomposites have shown viscoelastic phase separation processes. The percolation networks of MWCNTs in compatibilized PC/PP blends were clearly observed using a high resolution transmission electron microscope. There was also a remarkable 5-fold decrease in the percolation threshold and 2.5 fold increase in total shielding effectiveness (54.78 dB) ...

A review of filled and pristine polycarbonate blends and their applications

Abstract: Polycarbonate is an important thermoplastic polymer. Due to its high performance, polycarbonate has a range of engineering applications in construction, automotive, aircraft, data storage, electrical, and telecommunication hardware. However, polycarbonate’s use is limited in advanced applications due to limitations, such as strong hydrophobicity, relatively limited chemical functionality, high melt viscosity, notch sensitivity of mechanical properties, and relative softness. Blending with other thermoplastic polymers improves its physical characteristics. The present review outlines up-to-date developments concerning the design and application of polycarbonate blends. A particular emphasis has been given to establish polycarbonate blends such as:• polycarbonate/polyethylene• polycarbonate/poly(methyl methacrylate)• polycarbonate/poly(vinylchloride)• polycarbonate/ polystyrene• polycarbonate/polyurethane• polycarbonate/polyester• polycarbonate/poly(ɛ-caprolactone).To improve the polycarbonate blend propert...

Solution blending preparation of polycarbonate/graphene composite: boosting the mechanical and electrical properties

Abstract: We report on the preparation of polycarbonate-based graphene (PC/G) composites, by using a simple and scalable solution blending method to disperse single (SLG) and few layer (FLG) graphene flakes, prepared by liquid phase exfoliation (LPE), in the polymer matrix. A solvent-exchange process is carried out to re-disperse the exfoliated SLG/FLG flakes in an environmentally friendly solvent, i.e. 1,3dioxolane, which is also used to dissolve the polycarbonate pellets, thus facilitating the mixing of the polymer dispersion with the SLG/FLG flakes. The loading of SLG/FLG flakes improves the mechanical and thermal properties, as well as the electrical conductivity of the polymer, reaching a +26% improvement of the elastic modulus at 1 wt% loading, and an electrical conductivity 10^-3 S m^-1 at 10 wt% with a percolation threshold achieved at 0.55 vol%. The as-prepared PC/G composite with the aforementioned reinforced properties can be a promising material for 3D printing-based applications.

A ReaxFF-Based Molecular Dynamics Simulation of the Pyrolysis Mechanism for Polycarbonate

Abstract: Polycarbonate (PC) is considered a promising substitute for insulating materials due to its excellent insulation and mechanical properties. The main cause for PC insulation aging is the breakage of chemical bonds at high temperatures. The reactive force field (ReaxFF) method is first employed in a molecular dynamics (MD) simulation of polycarbonate pyrolysis to elucidate the mechanism for thermal aging at the atomic level. The results show that the main reaction pathway for breakage of the polycarbonate main chain is C–O bond breakage of the terminal group or between PC monomers. CO2, CO, CH4, and H2 are the major products generated following polycarbonate pyrolysis. The formation mechanisms of these dominant products are detailed for the first time based on the simulation trajectories. The activation energy and pre-exponential factor extracted from the ReaxFF simulations show good agreement with experimental results. The fracturing of the main chain and the production of small molecule gases both decreas...

Influence of functionalized calcium carbonate nanofillers on the properties of melt-extruded polycarbonate composites

Abstract: In an effort toward developing better tribological properties of polycarbonate (PC), a reinforcement with calcium carbonate (CaCO3) nanoparticles (3% by weight), in the size range of 30–60 nm, func...

Effect of Catalyst on the Molecular Structure and Thermal Properties of Isosorbide Polycarbonates

Abstract: The effects of catalyst on the molecular weight, chemical structure, and yellowness of isosorbide-based polycarbonate (ISB-PC) in the melt-transesterification and polycondensation stages were investigated. Results showed that the high steric hindrance and intramolecular hydrogen bonding of the endohydroxyl group (endo–OH) of ISB enabled its reactivity to be lower than that of the exohydroxyl group (exo–OH). We also found that the reactivity of endo–OH with diphenyl carbonate can be preferentially activated by strong electrophilic catalysts, and that the configuration of the ISB-PC chain strongly depended on the reactivity balance between endo–OH and exo–OH. Various catalysts with different coordinate capacities, acidity coefficients, and radius of metal ion were further tested. Catalysts with a calcium or zinc ion showed a higher reactivity of endo–OH than exo–OH, resulting in a high glass-transition temperature of ISB-PCs. Results suggested as well that the thermal stability of ISB-PC may be correlated t...

Improved thermal properties by controlling selective distribution of AlN and MWCNT in immiscible polycarbonate (PC)/Polyamide 66 (PA66) composites

Abstract: A stable co-continuous morphology was achieved in immiscible polycarbonate (PC)/polyamide 66 (PA66) blend by controlling the selective distribution of multi-walled carbon nanotubes (MWCNT) and aluminum nitride (AlN) nanoparticles. SEM and TEM tests proved that hybrid fillers were both located in PA66 phase. Selective etching process was applied to confirm the gradual variation of morphologies. It indicated that the compatibilities between PC and PA66 were gradually enhanced since the phase size reduced significantly and the interface of two phases blurred after the fillers were incorporated. DMA confirmed that the glass transition temperature of PC and PA66 appeared a trend to merge, besides, the tensile properties were enhanced. TGA indicated that the in-situ generated PC-b-PA66 copolymer played an important role in the compatibilization effect. Besides, the raised interconnectivities were proved by theoretical models and the maximum thermal conductivity of 1.3 W/mK at hybrid fillers loading of 24.78 vol% was obtained.

Spherical Polybutylene Terephthalate (PBT)-Polycarbonate (PC) Blend Particles by Mechanical Alloying and Thermal Rounding.

Abstract: In this study, the feasibility of co-grinding and the subsequent thermal rounding to produce spherical polymer blend particles for selective laser sintering (SLS) is demonstrated for polybutylene terephthalate (PBT) and polycarbonate (PC). The polymers are jointly comminuted in a planetary ball mill, and the obtained product particles are rounded in a heated downer reactor. The size distribution of PBT–PC composite particles is characterized with laser diffraction particle sizing, while the shape and morphology are investigated via scanning electron microscopy (SEM). A thorough investigation and characterization of the polymer intermixing in single particles is achieved via staining techniques and Raman microscopy. Furthermore, polarized light microscopy on thin film cuts enables the visualization of polymer mixing inside the particles. Trans-esterification between PBT and PC during the process steps is investigated via vibrational spectroscopy and differential scanning calorimetry (DSC). In this way, a new process route for the production of novel polymer blend particle systems for SLS is developed and carefully analyzed.

Effect of SEBS-g-MAH addition on the mechanical, rheological, and morphological properties of polycarbonate/acrylonitrile–butadiene–styrene blends:

Abstract: In this research, the effect of maleic anhydride–grafted styrene–ethylene/butylene–styrene (SEBS-g-MAH) compatibilizer on different properties of polycarbonate and poly(acrylonitrile–butadiene–styr...

Simple and Efficient Approach toward Photosensitive Biobased Aliphatic Polycarbonate Materials

Abstract: Fatty acids were used as precursors for the synthesis of photosensitive polycarbonate materials In order to avoid multistep reactions, a simple and straightforward methodology toward the synthesis of photosensitive monomers has been developed Hence, a fatty acid–based cyclic carbonate bearing an unsaturation was synthesized and subsequently polymerized in a controlled manner (Đ = 107) by organo-catalyzed ring-opening polymerization (ROP) A thio-cinnamate derivative was then readily synthesized via a one-pot reaction and grafted onto the polycarbonate backbone by thiol–ene reaction The content of photoresponsive cinnamoyl moiety grafted on the polycarbonate was tunable with the reaction time Such functionalized polycarbonates could be crosslinked (by UV irradiation at 365 nm) and partially decrosslinked (irradiated at 254 nm) and exhibit versatile properties ranging from rather tough materials to elastomeric networks with respect to the content of the photosensitive cinnamoyl moiety grafted on the po

Nanocomposites based on polymer blends: enhanced interfacial interactions in polycarbonate/ethylene-propylene copolymer blends with multi-walled carbon nanotubes

Abstract: In this article, the phase separation in the melt blended polycarbonate (PC) and ethylene propylene copolymer (EPC) has been studied with dynamic mechanical thermal analysis (DMTA) and scanning ele...

Novel approach to fabricate a stable superhydrophobic polycarbonate

Abstract: A novel approach to fabricating a stable superhydrophobic PC using a phase separation method and selecting a solvent/non-solvent without requiring any surface chemical modification and high chemica...