Glass Transition Temperature Of Polycarbonate Research Articles

High-precision local transfer of van der Waals materials on nanophotonic structures

Prototyping of van der Waals materials on dense nanophotonic devices requires high-precision monolayer discrimination to avoid bulk material contamination. We use the glass transition temperature of polycarbonate, used in the standard dry transfer process, to draw an in situ point for the precise pickup of two-dimensional materials. We transfer transition metal dichalcogenide monolayers onto a large-area silicon nitride spiral waveguide and silicon nitride ring resonators to demonstrate the high-precision contamination-free nature of the modified dry transfer method. Our improved local transfer technique is a necessary step for the deterministic integration of high-quality van der Waals materials onto nanocavities for the exploration of few-photon nonlinear optics on a high-throughput, nanofabrication-compatible platform.

Numerical simulation and experiment of wrinkle for multipoint thermoforming of resin sheet

The multi-point thermoforming (MPTF) process of resin sheet is introduced, the glass transition temperature of polycarbonate (PC) sheet is tested, and the material parameters of PC sheet are got. Numerical simulation of wrinkle for spherical part is carried out by ABAQUS, and the generated result of wrinkle with MPTF is elaborated. The effects of thickness, forming temperature and spherical radius on wrinkle are investigated by lots of numerical simulations, the outlines of spherical part with different thicknesses are extracted, and the maximum wrinkling value of spherical part with different forming temperatures and spherical radii are calculated. Then the multi-step multi-point thermoforming (MSMPTF) is chosen to depress wrinkle, and series of numerical simulations are put forward to get the forming step of non-wrinkle. Finally, MSMPTF experiment is done. Consequently, the spherical part has good outline shape, which illustrates that the MSMPTF technology is feasible to depress wrinkle.

Degradation of Polycarbonate Properties Under Thermal Aging

The aim of this paper is to characterize the thermal aging effect near the glass transition temperature of polycarbonate (PC) at different hold time. For this, the physicochemical characterization and mechanical behavior of PC after annealing at 120 °C for 72, 144 and 216 h were investigated. The microstructural analysis was conducted by scanning electron microscopy (SEM) and x-ray diffraction (XRD). Then, the aged samples were also analyzed using thermogravimetric analysis and mechanical tests. The microcracks were revealed by the SEM, and an increase in the volume of crystalline domains, for 72 and 144 h of the aging, was highlighted by XRD. Furthermore, a decrease in Young’s modulus and microhardness of PC was noted. It seems that the annealing of the PC at 120 °C, during the three durations, caused physical and chemical aging producing break in the bonds leading to a beginning of degradation which can cause a sudden failure of the material.

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

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.

Temperature Assisted in-Situ Small Angle X-ray Scattering Analysis of Ph-POSS/PC Polymer Nanocomposite.

Inorganic/organic nanofillers have been extensively exploited to impart thermal stability to polymer nanocomposite via various strategies that can endure structural changes when exposed a wide range of thermal environment during their application. In this abstraction, we have utilized temperature assisted in-situ small angle X-ray scattering (SAXS) to examine the structural orientation distribution of inorganic/organic nanofiller octa phenyl substituted polyhedral oligomeric silsesquioxane (Ph-POSS) in Polycarbonate (PC) matrix from ambient temperature to 180 °C. A constant interval of 30 °C with the heating rate of 3 °C/min was utilized to guise the temperature below and above the glass transition temperature of PC followed by thermal gravimetric, HRTEM, FESEM and hydrophobic analysis at ambient temperature. The HRTEM images of Ph-POSS nano unit demonstrated hyperrectangular structure, while FESEM image of the developed nano composite rendered separated phase containing flocculated and overlapped stacking of POSS units in the PC matrix. The phase separation in polymer nanocomposite was further substantiated by thermodynamic interaction parameter (χ) and mixing energy (Emix) gleaned via Accelrys Materials studio. The SAXS spectra has demonstrated duplex peak at higher scattering vector region, postulated as a primary and secondary segregated POSS domain and followed by abundance of secondary peak with temperature augmentation.

Effect of the developed temperature field on the molecular interdiffusion at the interface in infrared welding of polycarbonate composites

Abstract In this study, the effects of the welding temperature field developed during the infrared assembly process on the joining properties of glass fiber reinforced polycarbonate/unreinforced polycarbonate with carbon black were investigated. The temperature field and the contact time govern together the quality of the adhesion at the welding interface. The effect of the semi-transparent glass fiber reinforced polycarbonate composite/unreinforced polycarbonate composite with carbon black interface was quantified in term of quadratic distance of diffusion or diffusion depth through the welding interface. First, an experimental setup for the temperature measurement was performed using infrared camera, during infrared welding of materials joints. Then, numerical simulations using commercial FEM software COMSOL Multiphysics ® allows simulating the temperature field by implementing a developed 3D heat source, in order to determine the generated heat source at the welding interface and the variation of the temperature field during the infrared welding process. The microstructural characterizations were investigated in order to inspect the welding zones quality and to observe their failure modes. The diffusion theory has then been applied to calculate the variation of the quadratic distance of diffusion versus time at different locations. The complete self-diffusion is supposed occurring only at temperature above the polycarbonate glass transition temperature (140 °C) and with a quadratic distance of diffusion superior to the mean square end-to-end distance. At the welding interface, the calculation of the quadratic distance of diffusion showed that a complete self-diffusion has not yet been reached. A perfect cohesion was not established.

Viscoelastic properties of polycarbonate-graphene nanoplatelets nanocomposite foams

The viscoelastic properties of polycarbonate (PC) nanocomposite foams containing graphene nanoplatelets (GnP), prepared by one and two-step supercritical CO2 dissolution, were characterized by dynamic-mechanical-thermal analysis. Three factors were detected to influence the mechanical performance of foams: relative density, the eventual presence of a PC crystalline phase and GnP's amount. Relative density was found to be the most important one, with the storage modulus following a power-law behavior with increasing relative density. Foams prepared in one-step presented higher storage moduli than two-step foams even having bigger cells, explained by their higher relative density. The eventual presence of PC crystals in one-step foams, induced by the combination of high CO2 dissolution temperatures and GnP's presence during foaming, was found to be the cause of their higher storage moduli when compared to two-step foams at similar relative density. A slight effect of GnP could only be observed in two-step foams with 5% GnP, as these foams displayed storage moduli as high as one-step foams having lower relative densities. Regarding the viscous contribution, PC's glass transition temperature resulted higher in one-step foams, related to a restriction in the molecular mobility of PC induced by the presence of a PC crystalline fraction and GnP.

Surface localization of poly(methyl methacrylate) in a miscible blend with polycarbonate

Poly(methyl methacrylate) (PMMA) in a miscible blend with polycarbonate (PC) is segregated on the high temperature side in the temperature gradient beyond the glass transition temperature of PC.

Bent polydimethylsiloxane–polycarbonate hybrid microdevice for on-chip flow-through polymerase chain reaction employing a single heater

We report on a bent microdevice made from elastomeric polydimethylsiloxane (PDMS) on a polycarbonate (PC) solid support. Its bent shape is well sustained, and this allows an on-chip flow-through polymerase chain reaction (PCR) to be performed employing a single heater. The PC support was bent to a predetermined angle by heating the substrate close to the glass transition temperature of PC, and the PDMS microdevice was physically adapted to the curvature of the bent PC. The relatively short plane of the bent PC substrate was then placed on top of a heater, leaving the relatively long plane floating in the air, on the entire surface of which a temperature gradient was established. The plane in contact with the heater represents the zone for denaturation, and the slanted plane floating in the air acts as the annealing/extension zone. Two targets with amplicon sizes of 230 and 282 bp were successfully amplified utilizing microdevices with 4° and 17° inclination angles, respectively, by employing a single heater in both cases and within 30 min. The system provides an effective alternative to conventional 3-temperature control flow-through PCR devices by minimizing the accessories and hence facilitating system miniaturization.

Morphologies and properties of polycarbonate/polyethylene in situ microfibrillar composites prepared through multistage stretching extrusion

ABSTRACTThe sheets of polycarbonate (PC)/polyethylene (PE) in situ microfibrillar composites are successfully prepared directly through multistage stretching extrusion with an assembly of laminating‐multiplying elements (LMEs) instead of the secondary processing. The morphological development of the PC dispersed phase in PE matrix with increasing the number of LMEs during multistage stretching extrusion investigated by scanning electron microscope shows that core‐skin structure of the microfibrillar PC/PE composites during multistage stretching extrusion with 4 LMEs is weakened, and the diameter of the PC microfibrils is relatively more uniform, indicating that the shear field in LMEs greatly affects the morphology of PC dispersed phase in PE matrix. The tensile, crystalline, melting, orientation and rheological behavior of the PC/PE microfibrillar composites are also investigated. The results show that the PC microfibrils are helpful to increase complex viscosity and yield stress of the PE/PC composites. In addition, it is found that the glass transition temperature of PC in PE matrix reduced with increasing the number of LMEs during dynamic rheological testing. It is coincided with the results of DSC analysis of the PC/PE composites. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40108.

Charpy Impact of Sandwich Structural Composites (CFRP/PC/CFRP) of Polycarbonate (PC) Cores Covered with Carbon Fiber Cross Textile Reinforced Epoxy Polymer (CFRP) Thin Sheets as a Function of Temperature

The purpose of this study is to investigate a lighter, cheaper and possibly stronger alternative to CFRP, by obtaining the Charpy impact values (auc) of a sandwich structural composite (CFRP/PC/CFRP) constructed of a polycarbonate (PC) core between two thin plies of carbon cross textile fiber/epoxy (CFRP) within the temperature range of aircraft operation, from 200 to 403K below the glass transition temperature of PC (Tg = 422K). The auc of CFRP/PC/CFRP were compared with a 2.0mm thick 12-ply CFRP laminate. Results showed overall, the CFRP/ PC/CFRP had higher auc than the CFRP at each fracture probability (Pf) from 300 to 373K except at 200K with low Pf and 403K with high Pf. Specifically, although the volume fraction of carbon fiber (12%) of CFRP/PC/CFRP was much smaller than that (60%) of the CFRP, the auc at room temperature (300K) of CFRP/PC/CFRP was approximately 64% higher than that of CFRP at mid-fracture probability (Pf) of 0.50. Fracture modes of CFRP/PC/CFRP were explained by delamination between PC core and the CFRP thin sheet surfaces, bending plastic deformation, and CFRP fracture. The highest Weibull coefficient (n) was obtained at 323K. Based on the 3-parameter Weibull equation, the limiting impact value (as) also exhibited the highest value at 323K. In addition, the cost of CFRP/PC/CFRP was 40% lower than that of CFRP at the time of this study. Since the use of PC resin as the core enhanced the safety design at low cost, practical use of sandwich structural composites of CFRP/PC/CFRP is possible. [doi:10.2320/matertrans.M2011357]

Preparation and properties of polycarbonate/polyhedral oligomeric silsesquioxanes (POSS) hybrid composites

AbstractOctaphenylsilsesquioxane (PH‐POSS) and octa(γ‐methacryloxypropyl)silsesquioxane (MA‐POSS) were successfully synthesized by hydrolytic condensation of phenyltrichlorosilane and γ‐methacryloxypropyltrimethoxysilane, and characterized by Fourier transform infrared (FT‐IR), 1H and 29Si nuclear magnetic resonance (NMR), and matrix‐assisted laser desorption/ionization‐time of flight (MALDI‐TOF) mass spectrum. Morphology, degradation behavior, thermal, and mechanical properties of hybrid composites were studied by transmission electron microscopy (TEM), polarized optical microscopy (POM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), surface contact angle (SCA), tensile, and impact testing. Domains of PH‐POSS and MA‐POSS dispersed in the matrix with a wide size distribution in a range of 0.1–0.5 µm, while PH‐POSS exhibited a preferential dispersion. Because of the possible homopolymerization of MA‐POSS during the melt blending, the glass transition temperature of polycarbonate (PC)/MA‐POSS composites remained nearly unchanged with respect to PC/PH‐POSS composites that showed a depression of Tg due to the plasticization effect. It is interesting to note that the incorporation of POSS retarded the degradation rates of PC composites and thus significantly improved the thermal stabilities. SiO fractions left during POSS degradations were a key factor governing the formation of a gel network layer on the exterior surface. This layer possessed more compact structures, higher thermal stabilities, and some thermal insulation. In addition, percentage residues at 700°C (C700) significantly increased from 10.8% to 15.8–22.1% in air. Fracture stress of two composites showed a slight improvement, and the impact strength of them decreased monotonically with the increase of POSS loading. Copyright © 2011 John Wiley & Sons, Ltd.

Supercritical CO 2-assisted embossing for studying cell behaviour on microtextured surfaces

Recently, cell responses to micro- and nanoscale structures have attracted much attention. Although interesting phenomena have been observed, we have encountered some difficulties in elucidating purely topographical effects on cell behaviour. These problems are partially attributable to the introduction of functional groups and the persistence of chemicals during surface processing. In this study, we introduced supercritical CO 2-assisted embossing, which plasticizes a polycarbonate plate by dissolving supercritical CO 2 and thus can emboss wide-scale patterns onto the plate at a lower temperature than the polycarbonate glass transition temperature. Uniform micro- and nanopatterned surfaces were observed across the whole area of the polycarbonate plate surfaces. Nickel, fluorine, and nitrogen were not detected on the fabricated surfaces, and the surface carbon-to-oxygen ratios were equivalent to the theoretical ratio (C:O = 84.2:15.8) calculated from the polycarbonate molecular structure. Human mesenchymal stem cells were cultured on the fabricated microlens and nanogroove substrata. Cell-adhered areas became smaller on the microlens than on non-treated polycarbonate. Meanwhile, cells aligned along the ridges of nanogrooves with valleys deeper than 90 nm. This supercritical CO 2-assisted embossing can produce fine substrates for studying the effects of surface topography of synthetic materials on cell behaviours.

Studies on Polycarbonate and Polydimethylsiloxane Rubber Blends

Polycarbonate (PC) and polydimethylsiloxane (PDMS) rubber blend were made by melt blending using a twin-screw extruder. The blends were characterized by mechanical testing, thermal studies, electrical properties and morphological studies. The notched lzod impact strength increased greatly when the rubber content was 20%. The morphology of PC/PDMS blends showed dispersed rubber particle in the PC matrix. The impact strength, which increased with PDMS rubber concentration, has been analyzed on the basis of the interphase adhesion and crazing mechanisms. Tensile and flexural modulus as well as strength decreased with increase in PDMS rubber content. Predictive models have been used to explain the tensile modulus and strength properties. Incorporation of PDMS decreases the glass transition temperature of PC and facilitates its processing. Scanning electron microscopy has been employed to study the phase structure.

Correlation of processing parameters and in situ temperatures for electron beam irradiated polycarbonate

Temperature measurements were performed for polycarbonate samples under electron beam irradiation for a total dose of 200 kGy at different dose fractionations. The samples were irradiated with a commercial electron beam accelerator and total dose was applied at different number of passes under the beam. Peak temperatures by beam heating obtained during irradiation varied significantly with different amounts of energy deposited per pass. For one-pass irradiation (200 kGy), the peak temperature recorded exceeded the polycarbonate's glass transition temperature.

Chemical Modification of Bisphenol A Polycarbonate by Reactive Blending with Cyclic Anhydrides

Reactive blending with cyclic anhydrides in the melt is a promising process to modify the chemical structure of bisphenol A polycarbonate (PC) by insertion of ester moieties leading to consistent changes in the chemical and physical properties of PC. In particular, by the reaction with succinic anhydride it is possible to insert aliphatic moieties in the polymer backbone, decreasing the melt viscosity and the glass transition temperature of PC (and thus increase its processability). The reaction, that is catalysed by Lewis acids (e. g. titanium butoxide), proceeds through the formation of carbonyl carbonate groups that undergo decarboxylation leading to ester moieties. No side reactions have been detected by NMR analysis. The addition of phosphorous acid as catalyst quencher at the end of the process gives rise to polymers with good colour and thermal stability.

Melt mixing of polycarbonate/multi-wall carbon nanotube composites

—Composites of polycarbonate (PC) with multi-wall carbon nanotubes (MWNT) of different concentrations are prepared by diluting a PC based masterbatch containing 15 wt% MWNT using melt mixing in a DACA-Micro Compounder (4 g scale). Electrical resistivity measurements indicate that the percolation of MWNT is reached between 1 and 1.5 wt%. In addition, melt rheology was applied as another sensitive method to detect the percolation of the nanotubes. Atomic Force Microscopy and visual observations of the composite dispersions in a PC-solvent were used to characterise the state of MWNT dispersion. Differential Scanning Calorimetry and Dynamic Mechanical Analysis were applied to detect changes in the glass transition temperature of PC as a result of processing and of MWNT interactions with the PC matrix including the state of dispersion. In addition, DMA confirmed the reinforcement effect of the nanotubes. The results show that the nanotube incorporation also influences the processing behaviour. Due to the enhancement in melt viscosity by adding nanotubes and the enhanced shear forces, the molecular weight of the PC in the composites is reduced as compared to PC extruded under the same conditions. This effect leads to changes in the glass transition temperature and modulus which counteracts the effects originating from the nanotube-polymer interaction.

Positron Annihilation Lifetime Spectroscopy for Measuring Free Volume during Physical Aging of Polycarbonate

Free volume relaxation of polycarbonate (PC) as a function of aging time was investigated by means of positron annihilation lifetime spectroscopy at three different temperatures below the PC glass transition temperature. A clear decrease of the intensity of orthopositronium (o-Ps) was observed, while the o-Ps lifetime remained substantially unchanged. This was attributed to a decrease in the number of cavities in the system. The process was successfully modeled according to the Struik model, which describes a relaxation time dependent on both the temperature and the distance from equilibrium.

Studies of an epoxy-compatibilized poly(phenylene sulfide)/polycarbonate blend

Tensile properties, morphology and thermal behaviour of a poly(phenylene sulfide) (PPS)/polycarbonate (PC) binary system and an PPS/PC/epoxy ternary system were investigated. It was observed that the viscosityaverage molecular weight ( M ν ) of the PC fraction was decreased during the melt blending of PC with PPS. This phenomenon was more pronounced as PPS concentration increased. By melt blending PPS and PC with epoxy as a compatibilizer, a shift of glass transition temperature of PC to a lower temperature could be somewhat prevented. It is suggested that epoxy coupled the degraded PC chains generated by blending with PPS. In contrast to PPS/PC binary system, phase separation in the PPS/PC/epoxy ternary system could hardly be observed in the scale of scanning electron micrographs. The tensile strength and tensile modulus of PPS/PC/ epoxy system were remarkably improved (more than 100%) compared to those of the epoxy-free system. It was found that the improvement in tensile properties is mainly due to the homogeneous morphology by blending a small amount of epoxy with PPS and PC.

Modification of polycarbonate with miscible polyurethane elastomers

Polyurethane elastomers (PUEs) based on 4,4′-diphenylmethane diisocyanate and aliphatic polycarbonate diols and/or polytetramethylene glycols have been found to be miscible with polycarbonate (PC). Incorporation of 0–10% of PUEs in melt mixing decreases the glass transition temperature of PC (by 0–30°C), facilitates its processing, and improves its resistance to hydrothermal ageing. No phase separation in blends was detected by means of the absorption of the visible light and differential scanning calorimetry measurements. Dynamic mechanical and static bending measurements concurrently show a slight increase in the glassy state modulus, which can be viewed as an ‘antiplasticizing’ effect of PUEs in PC. This effect and the miscibility of PC with PUEs can be ascribed to their strong interaction, probably due to the formation of hydrogen bonds between urethane and carbonate groups.