Polycarbonate Phase Research Articles

Interfacial distribution of PMMA-grafted MWCNTs in immiscible blends for improved electrical conductivity

Engineering blend structure with interfacial distribution of nanoparticles is a cost-effective strategy for achieving materials with extraordinary performances. Herein, poly (methyl methacrylate) (PMMA) homopolymer was sparsely grafted onto the surface of hydroxylated multi-walled carbon nanotubes (MWCNTs-OH) by miniemulsion polymerization and such modified MWCNTs-g-PMMA were introduced into immiscible engineering blend of polycarbonate (PC) and polyvinylidene fluoride (PVDF) to prepare conductive polymer composites (CPCs). With the help of the miscibility of PMMA with PC and PVDF, MWCNTs-g-PMMA were selectively located at the interface of co-continuous PC/PVDF blend, while MWCNTs-OH were distributed in the PC phase. The interfacial distribution and aggregation of MWCNTs-g-PMMA endowed the ternary nanocomposite with long-term stable excellent electrical conductivity and ultralow percolation threshold of 0.002 vol%.

Effect of PC Percentages on Hardness and Notched Impact Strength of PBT/PC Blends

Polybutylene terephthalate (PBT) has been proven to be a potential material for modern car bumpers. However, the potential of PBT is limited by its low notched impact strength. The main aim of this study is the improvement in the notched impact strength of PBT by blending with polycarbonate (PC). PBT/PC blend at different ratios (95/5, 90/10, 85/15, 80/20) is investigated in notched Izod impact strength (ASTM D256) and hardness (ASTM D2240). Results are compared to those of neat PBT. It was found that notched Izod impact strength decreased with increasing PC rate in the blend, overall, from 4.35 kJ/m2 of neat PBT to 3.37 kJ/m2 of 80/20 blend. The microstructure of testing samples was observed through FESEM images taken at fracture surfaces to determine the cause of the decrease. The low interfacial adhesion between PBT and PC phases is believed to be the main reason. However, an increase in notched impact strength was shown, from 4.18 kJ/m2 of 95/5 blend to 4,71 kJ/m2 of 90/10 blend. This result is presumed to be due to the compatibilizing effect of PBT-PC copolymers formed during the melt blending process. Hardness testing result demonstrates neither significant improvement nor deterioration. It concluded that it is possible to improve the notched impact strength of PBT by blending with PC. The PBT/10% PC blend is a suitable choice for car bumper material since its notch impact strength is higher than neat PBT.

Fracture mechanism and scratch behaviour of MWNTs reinforced 70/30 (wt/wt) PC/ABS blends and their nanocomposites

In this work, multiwalled carbon nanotubes (MWNTs) are dispersed in 70/30 (wt/wt) polycarbonate (PC)/acrylonitrile butadiene styrene (ABS) (PC70ABS30) blends and their nanocomposites by the melt-processing method. The morphology observations suggest the development of matrix-droplet morphology. There exists an interaction between MWNTs and the PC phase, which is observed from Raman spectroscopic investigation. Dynamic mechanical analysis (DMA) studies show the increase in storage modulus values depicting the stiffening effect of MWNTs, tanδ value increase depicting the energy dissipation. The flexural and impact properties increase significantly. The mechanism of flexural fracture is craze formation in the skin layer with a shear band and facets formation in the bulk region as observed from the SEM investigation of a flexural fractured surface of MWNTs reinforced PC70ABS30 blends and their nanocomposites. In addition, the deformation at the edge, river-like pattern, striation associated shear bands, craze, cavitation, and facets formation are the impact fracture mechanism as observed from SEM investigation of impact fractured surface of MWNTs reinforced PC70ABS30 blends and its nanocomposites. Scratch studies reveal the improved dispersion of MNNTs at 0.5–1 wt% in PC70ABS30 blends and their nanocomposites with a slightly higher scratch coefficient of friction and scratching force.

Transparent PC/PMMA Blends with Enhanced Mechanical Properties via Reactive Compounding of Functionalized Polymers.

Reactive compounding of terminally phenolic OH-functionalized polycarbonate (PC) with epoxy-functionalized polymethylmethacrylate (PMMA) prepared by copolymerization with glycidyl methacrylate was investigated. It was spectroscopically demonstrated that a PC/PMMA copolymer was formed during the melt reaction of the functional groups. Zirconium acetylacetonate could catalytically accelerate this reaction. Correlations of the phenomenological (optical and mechanical) properties with the molecular level and mesoscopic (morphological) structure were discussed. By the investigated reactive compounding process, transparent PC/PMMA blends with two-phase morphologies were obtained in a continuous twin-screw extruder, which, for the first time, combined the high transmission of visible light with excellent mechanical performance (e.g., synergistically improved tensile and flexural strength and high scratch resistance). The transparency strongly depended on (a) the degree of functionalization in both PC and PMMA, (b) the presence of the catalyst, and (c) the residence time of the compounding process. The in-situ-formed PC/PMMA copolymer influenced the observed macroscopic properties by (a) a decrease in the interphase tension, leading to improved and stabilized phase dispersion, (b) the formation of a continuous gradient of the polymer composition and thus of the optical refractive indices in a diffuse mesoscopic interphase layer separating the PC and PMMA phases, and (c) an increase in the phase adhesion between PC and PMMA due to mechanical polymer chain entanglement in this interphase.

Polycarbonate/Poly(vinylidene fluoride)-Blend-Based Nanocomposites-Effect of Adding Different Carbon Nanofillers/Organoclay.

Carbon black (CB), carbon nanotubes (CNTs), and graphene nanoplatelets (GnPs) individually or doubly served as reinforcing fillers in polycarbonate (PC)/poly(vinylidene fluoride) (PVDF)-blend (designated CF)-based nanocomposites. Additionally, organo-montmorillonite (15A) was incorporated simultaneously with the individual carbon fillers to form hybrid filler nanocomposites. Microscopic images confirmed the selective localization of carbon fillers, mainly in the continuous PC phase, while 15A located in the PVDF domains. Differential scanning calorimetry results showed that blending PVDF with PC or forming single/double carbon filler composites resulted in lower PVDF crystallization temperature during cooling. However, PVDF crystallization was promoted by the inclusion of 15A, and the growth of β-form crystals was induced. The rigidity of the CF blend increased after the formation of nanocomposites. Among the three individually added carbon fillers, GnPs improved the CF moduli the most; the simultaneous loading of CNT/GnP resulted in the highest moduli by up to 33%/46% increases in tensile/flexural moduli, respectively, compared with those of the CF blend. Rheological viscosity results showed that adding CNTs increased the complex viscosity of the blend to a greater extent than did adding CB or GnPs, and the viscosity further increased after adding 15A. The electrical resistivity of the blend decreased with the inclusion of carbon fillers, particularly with CNT loading.

Nanomechanical study of polycarbonate/boehmite nanoparticles/epoxy ternary composite and their interphases

AbstractThermoplastic modified thermosets are of great interest especially due to their improved fracture toughness. Comparable enhancements have been achieved by adding different nanofillers including inorganic particles such as nanosized boehmite. Here, we present a nanomechanical study of two composite systems, the first comprising a polycarbonate (PC) layer in contact with epoxy resin (EP) and the second consisting of a PC layer containing boehmite nanoparticles (BNP) which is also in contact with an EP layer. The interaction between PC and EP monomer is tested by in situ Fourier transformed infrared (FT‐IR) analysis, from which a reaction induced phase separation of the PC phase is inferred. Both systems are explored by atomic force microscopy (AFM) force spectroscopy. AFM force‐distance curves (FDC) show no alteration of the mechanical properties of EP at the interface to PC. However, when a PC phase loaded with BNP is put in contact with an epoxy system during curing, a considerable mechanical improvement exceeding the rule of mixture was detected. The trend of BNP to agglomerate preferentially around EP dominated regions and the stiffening effect of BNP on EP shown by spatial resolved measurements of Young's modulus, suggest the effective presence of BNP within the EP phase.

Morphology and Mechanical Properties of the Polyketone/Polycarbonate Blends Compatibilized with Polyamides

To enhance impact strength of polyketone (PK) without loss of stiffness, PK was blended with polycarbonate (PC) via melt mixing. Three types of polyamides (PAs) with varying structures, — polyamide 6 (PA6), polyamide 612 (PA612), polyamide 12 (PA12) — were employed as polymeric compatibilizers. To elucidate the effect of the structure of PAs on the compatibilization, morphology, mechanical properties, and fracture behavior of the blends were investigated. The addition of PA6 and PA612 reduced the size of dispersed particles by encapsulating the PC phase, while PA12 was found not to affect the morphology of the PK/PC blend. The change in particle size, glass transition temperature (Tg), and elongation at break exhibited that PA6 was the most effective compatibilizer for the PK/PC blends of this study. These results were interpreted with the change in interfacial tension between PK and PA due to the difference in polarity of the PAs. It was found that the impact strength was not highest in the blend with the smallest particle size. The observation of sub-surface damage zone also indicated that effective toughening by intensive crazing in polymer blends requires dispersed particles of optimum size.

Compatibility and toughening mechanism of poly(ethylene terephthalate)/polycarbonate blends

AbstractPoly(ethylene terephthalate) (PET)/polycarbonate (PC) blends with methyl methacrylate‐styrene‐butadiene copolymer as compatibilizer (CP) were prepared. Compared with pure PET, the notched impact strength of the blend was improved significantly, while high tensile strength and 50%–70% optical transparency could be maintained. In particular, for the PET/70 wt% PC sample the notched impact strength sharply increased by 955% with the addition of compatibilizer. The ΔTg of the two phases of the blends decreased on blending, exhibiting partial compatibility. Below 50 wt% PC, the dispersed PC phase presented uneven dispersion with large aggregates and a clear interface, while above 50 wt% PC a reverse phase transformation occurred and the PET phase was evenly dispersed in the PC matrix with small aggregates and obvious interface transition areas. The introduction of CP promoted spherical PC particles to uniformly disperse in the matrix, and the interface transition area of the two phases became very wide. Moreover, the CP itself ran through the matrix to form a ‘quasi‐network distribution’ and the compatibility was greatly improved, thus leading to an obvious enhancement of the impact toughness of the blend. © 2020 Society of Industrial Chemistry

Thermal Conductivity and Crystallography of Polypropylene/Polycarbonate/ Polypropylene-Graft-Maleic Anhydride Polymer Blend

The effect of blending polycarbonate (PC) into polypropylene (PP) matrix polymer on thermal conductivity and crystal structure was studied. The blends consisted of 5% to 35% of PC with 5% compatibilizer (polypropylene-graft-maleic anhydride or PP-g-MA), were compounded using twin-screw extruder and shaped into standard tests samples by compression molding. The thermal conductivity values for PP/PC/PP-g-MA blends were ranging from 0.22 – 0.24 W/m.K. When compared to Hanshin – Shtrikman model, the highest difference in the thermal conductivity values was 28.2% shown in 90/5/5 composition. The deviation was due to the exclusion of factors such as PC particulates’ geometry, size, and dispersion in PP matrix. X-ray Diffraction (XRD) test revealed the blends’ structures comprised of medium-range order domains, referring to imperfect crystals with nanoparticles. The locations of peaks in the XRD spectrum also suggest that the pure PP’s monoclinic alpha crystal appeared in all PP/PC/PP-g-MA blends and there was no other crystal obtained in the blends. From the result, the discovered traits of crystal structure displayed influence on the thermal conductivity of the blends. At the same time, reactive compatibilization was suspected to take place at the interface of PP and PC phases when PP-g-MA was introduced.

Thermally and electrically conducting polycarbonate/elastomer blends combined with multiwalled carbon nanotubes

In this article, we have studied thermal and dielectric conductivity and morphology of polycarbonate (PC)/ethylene–propylene copolymer (EPC)/multiwalled carbon nanotubes (MWCNTs) nanocomposites. Transmission electron microscopy has been used to investigate the localization and migration of MWCNTs within the matrix. The MWCNTs were located in the PC phase and at the interface of PC and EPC. The results showed that the thermal conductivity of the PC decreased with the increasing content of EPC elastomeric particles. However, at the same time, one could observe an increase of the thermal conductivity in the polymer blends along with an addition of MWCNT. The electrical conductivity of the PC/EPC blends containing 10 wt% of EPC increased with the incorporation of MWCNTs, and the conducting paths were formed at additive content less than 0.5 wt% of MWCNT.

Lithium Ion Conducting Block Copolymers: Conductivity and Battery Performance

Polymeric solid electrolytes are an enabling technology for an all solid-state lithium battery using an intercalation or metal anode. In this study, random and block copolymers with polar functional groups were characterized for use in lithium batteries. The focus of this talk is on the lithium ion conductivity and structure-property relationship of the solid polymer electrolyte. The block copolymer is synthesized by sequential raft polymerization of different monomers. The first block is poly(acrylate) or poly(styrene), which is imparts sufficient mechanical properties to the polymer. The second block is poly(carbonate) (PC) or polyethylene glycol (PEG) to solvate the lithium ions. Nano-phase separation occurs when the polymer is cast due to differences in polarity between the two blocks. Lithium salts and plasticizer are included in the polymer mixture. The interconnected polycarbonate phase provides ion conducting channels for lithium ion conduction. The mechanical properties of the solid polymer electrolyte are also improved by creating a crosslinking network. Experimentally, a series of block co-polymers with different molecular weight and block ratio have been synthesized. The chemical structure of the block co-polymers was characterized by NMR and gel permeation chromatography. The nano-phase separation is confirmed by small angle scattering spectroscopy. Li ion conductivity was measured by electrochemical impedance spectroscopy (EIS). The battery performance was tested with Li metal anode and LiFePO4 cathode. The relationship between polymer structure, nano-phase separation and membrane performance will be discussed in this talk.

Influence of Polycarbonate on the Crystallization Behavior of Poly(Trimethylene Terephthalate)/Polycarbonate Blends

To determine the factors influencing the retardation of the crystallization of poly(trimethylene terephthalate) (PTT) when PTT is blended with polycarbonate (PC), different PTT/PC blends were prepared via the melt mixing method. The relationships between the crystallization behavior and blend composition, as well as the phase morphology, were investigated. The results showed that the predominant reason for the retardation in crystallization is due to the PC content and phase morphology. The PC influences the crystallization of PTT via two methods. First, it retards PTT crystallization. Secondly, the PC exhibits a nucleation effect on the PTT crystallization which is, however, much weaker compared to the negative effect PC exerts with regards to PTT crystallization. When the processing temperature and shear rate remains unchanged, the two effects of PC determine the crystallization behavior of the blend. The phase morphology, which is strongly dependent on the mixing temperature and the shear rate, and which is also related to mixing time, had an appreciable impact on PTT crystallization. In the case of similar adhesion with the interface, a finer PC phase domain would show a slightly stronger nucleation effect on PTT crystallization.

Effect of Compatibility on the Foaming Behavior of Injection Molded Polypropylene and Polycarbonate Blend Parts.

To improve the foaming behavior of a common linear polypropylene (PP) resin, polycarbonate (PC) was blended with PP, and three different grafted polymers were used as the compatibilizers. The solid and foamed samples of the PP/PC 3:1 blend with different compatibilizers were first fabricated by melt extrusion followed by injection molding (IM) with and without a blowing agent. The mechanical properties, thermal features, morphological structure, and relative rheological characterizations of these samples were studied using a tensile test, dynamic mechanical analyzer (DMA), scanning electron microscope (SEM), and torque rheometer. It can be found from the experimental results that the influence of the compatibility between the PP and PC phases on the foaming behavior of PP/PC blends is substantial. The results suggest that PC coupling with an appropriate compatibilizer is a potential method to improve the foamability of PP resin. The comprehensive effect of PC and a suitable compatibilizer on the foamability of PP can be attributed to two possible mechanisms, i.e., the partial compatibility between phases that facilitates cell nucleation and the improved gas-melt viscosity that helps to form a fine foaming structure.

Development of Composite Material Based on Polyphenylene Sulfone for 3D Printing

The effect of talc and various polymer additives on the basic mechanical properties of polyphenylene sulfone was studied. It was found that with an increase in the concentration of the filler, there is an increase in the elastic strength and a decrease in the plastic properties of polyphenylene sulfone. The physicomechanical properties of various polymer-polymer composites based on polyphenylene sulfone are considered. High efficiency of polycarbonate as a modifier of toughness is revealed. An efficient method has been developed for producing a composite with high values of impact strength and modulus of elasticity, based on the characteristics of the distribution of the filler in the polyphenylene sulfone polycarbonate binary system. It is shown that the concentration of the filler in the polycarbonate phase reduces the impact strength, whereas its concentration in the polyphenylene sulfone phase followed by the introduction of polycarbonate results in an impact-resistant and high modulus composite. Samples obtained by the 3D printing method exhibit high mechanical characteristics.

Double percolated MWCNTs loaded PC/SAN nanocomposites as an absorbing electromagnetic shield

This research reports on the preparation and characterization of absorbing electromagnetic (EM) nanocomposite shields based on polycarbonate (PC)/ polystyrene-co-acrylonitrile (SAN) 60/40 blend containing low contents of multi-walled carbon nanotubes (MWCNTs). The nanocomposites were prepared using a melt-compounding process at a temperature of 260 °C. The melt linear viscoelastic results together with scanning electron microscopy (SEM) micrographs implied a co-continuous type morphology, which remained unchanged by the addition of nanoparticles (NPs). The results of dynamic mechanical thermal analysis (DMTA) suggested a preferential localization of MWCNTs in the PC phase, evidenced by the transmission electron microscopy (TEM) micrograph. The direct current (DC) electrical conductivity results showed a low electrical double percolation threshold around 0.32 wt% of MWCNTs. A maximum DC electrical conductivity of 0.0834 S/cm was obtained for 1 wt% MWCNTs-filled nanocomposite. Applying EM theory based on the measured dielectric permittivity and magnetic permeability [over the X-band frequency (8.2–12.4 GHz)] suggested a maximum shielding efficiency of 25–29 dB for the 1 wt% MWCNTs-filled nanocomposite with a thickness of 10 mm. In addition, the contribution of the absorption mechanism below and above the electrical percolation threshold was studied. It was revealed that the shielding performance of the nanocomposites is mainly due to noticeable absorption of EM waves above the percolation threshold, which was attributed to the induced conductance loss as a result of the formation of conductive paths.

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

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 electron microscopy (SEM). Two glass transition temperatures on the tan δ curves were detected. This confirms the immiscibility of PC and EPC phases. Different content of multi-walled carbon nanotubes (MWCNTs) were added to the PC/EPC blends and the interfacial adhesion between MWCNTs and PC/EPC blend were shown using transmission electron microscopy (TEM). The MWCNTs were located in the PC phase and at the interfaces of PC and EPC phases. Moreover, the storage modulus (E′) of polymer blends was changed by the increasing content of EPC elastomer and MWCNTs. The value of E′ of PC decreased with an incorporation of EPC. While, along with an addition of MWCNTs in the PC/EPC blends an increase of E′ was visible. The strong interfacial interactions between the matrix and MWCNTs played the main role in increasing the values of the E′ of the nanocomposites.

Effect of mixing temperature on the carbon nanofiller distribution in immiscible blends of polycarbonate and polyolefin

We studied the selective localization of carbon nanofillers, such as multi-walled carbon nanotube (MWCNT) and graphene nanoplatelet (GNP), in immiscible polymer blends composed of polycarbonate (PC) and polyethylene (PE) or ethylene-propylene copolymer (EPR). It was found that the distribution state of the carbon nanofillers in the composites is greatly affected by the mixing temperature and the species of nanofillers. MWCNTs resided in the PE or EPR phase in the composites, which cannot be explained by the difference in the interfacial tension. A similar morphology was detected in the PC/GNP/PE composite prepared at 300°C. In contrast, the PC/GNP/PE composite prepared at the low temperature (250°C) and the PC/GNP/EPR composites have the carbon nanofillers mostly in the PC phase. The selective localization in the PE or EPR phase is attributed to the surface adsorption of PE or EPR chains on the carbon nanofillers, which is more obvious for PE and at the high mixing temperature. These results demonstrate that both the species of carbon nanofillers and the mixing temperature affect the carbon nanofiller distribution in the immiscible blends.

Novel biocomposites from biobased PC/PLA blend matrix system for durable applications

Polycarbonate (PC) and poly(lactic acid) (PLA) were used to create a blend which was used to as a matrix for high performance glass fiber composites. A novel high temperature blending allowed creating the blend having both high impact strength and high heat resistance. According to Atomic Force Microscopy studies, an impact modifier phase was concentrated almost exclusively in brittle phase allowing the blend to achieve high impact strength with low impact modifier content. Using this high performance PC/PLA blend as a matrix, glass fiber composites were successfully created and characterized. It is found that the small amount of glass fiber loading of bellow 7.5 phr allowed the new PC/PLA blend based composites to maintain excellent elongational properties and good impact strength not observed in most commercial composites. It is found that PLA and PC phases form co-continuous morphology in blend allowing these novel composites reaching high heat resistance of over 133 °C which further increased to over 145 °C in glass fiber composites. Two matrices based on linear and branched PC were prepared and tested. It is found that glass fiber composites based on branched PC/PLA matrix demonstrate superior mechanical and heat resistance properties over linear PC/PLA matrix composites. A competitive weight-to-strength ratio, excellent heat resistance (as compared to commercial PC/ABS composites) as well as relatively low density makes novel biocomposites suitable for wide range of structural and durable applications such as in automotive and electronic industries.

Microstructure, thermal stability, and mechanical properties of modified polycarbonate with polyolefin and silica nanoparticles

In this manuscript, the supramolecular structure and dynamic mechanical thermal behavior of the polycarbonate (PC)/ethylene propylene copolymer (EPC)/silica (SiO2) nanocomposites (NCs) have been studied. The morphological analysis of the fractured Izod impact surfaces revealed the mechanism of energy absorption for the elastomeric particle in front of the crack growth. The cracks growth and deformation of voids around the EPC phase are the main factors for energy absorption during the notched‐Izod impact test. The presence of the SiO2 nanoparticles (NPs) in the PC phase causes the increase in the values of the impact strength for the NCs specimens. No new peaks and bonds were observed in the Fourier transform infrared (FTIR) spectra, and consequently, the phase behavior of the PC/EPC blends did not change significantly upon SiO2 addition. The dynamic mechanical thermal analysis result confirms the existence of two glass transitions temperatures and independence of all components in the system. Examination of the interfacial studies revealed that the SiO2 NPs do not exist at the interface of PC and EPC. In addition, applying SiO2 NPs into the blends improved the storage modulus (E′) and thermal stability of the PC/EPC/SiO2 NCs. Copyright © 2017 John Wiley & Sons, Ltd.

A thermomechanical study on selective dispersion and different loading of graphene oxide in polypropylene/polycarbonate blends

ABSTRACTCarbon nanofiller reinforced polymeric materials offer the opportunity to obtain materials with desired properties. In the present study, effects of different loading of graphene oxide (GO) on the compatibility, thermomechanical, and morphological properties of incompatible polypropylene (PP)/polycarbonate (PC) polymer blends were investigated. The neat blend and blend nanocomposites were prepared by using a twin‐screw extruder under controlled shear pressure to explore the role of GO on thermomechanical properties of blends. Fourier transform infrared analysis showed the presence of GO in PC phase which was further confirmed by differential scanning calorimetry and morphological analysis. It was observed that up to loading of 0.5%, GO preferable dispersed in only PC phase and then dispersed in both PP and PC phase with further increase in GO loading due to increase in viscosity of PC phase. Field emission scanning electron microscopy investigation of PNCs showed the coalescence of PC phase with increase of GO loading. Tensile analysis confirmed that 1% of GO loading produced highest reinforcement in thermomechanical properties and further increase of GO loading deteriorate the mechanical properties. Dynamic mechanical analysis also showed high storage modulus for 1% loading. Thermal stability of 1% GO loaded nanocomposite was found to be higher than other blend nanocomposites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45062.