Polycarbonate Polymer Research Articles

Wear resistance of injection-molded thermoplastic denture base resins

Objective This study investigated the wear resistance of injection-molded thermoplastic denture base resins using nanoindentation instrument.Materials and methods Six injection-molded thermoplastic denture base resins (two polyamides, two polyesters, one polycarbonate, one polymethylmethacrylate [PMMA]) and a PMMA conventional heat-polymerized denture-based polymer control were tested. Elastic modulus, hardness, wear depth, and roughness were calculated using a nanoindentation instrument.Results Elastic modulus and hardness of the injection-molded thermoplastic denture base resins were significantly lower than those of the PMMA conventional heat-polymerized denture-based polymer. Wear depth of polycarbonate and PMMA conventional heat-polymerized denture-based polymer were significantly higher than that of other injection-molded thermoplastic denture base resins. The roughness of injection-molded thermoplastic denture base resins was significantly more than that of PMMA conventional heat-polymerized denture-based polymer after testing.Conclusions Wear resistance of injection-molded thermoplastic denture base was low compared to PMMA conventional heat-polymerized denture-based polymers.

Experimental observation on multiaxial ratchetting of polycarbonate polymer at room temperature

Multiaxial stress-controlled and mixed stress-strain-controlled cyclic tests were carried out to investigate the multiaxial ratchetting of polycarbonate (PC) polymer at room temperature. The effects of applied mean stress, stress amplitude, loading rate, loading path and loading history on the ratchetting are discussed. The results show that the multiaxial ratchetting mainly occurs in the direction of non-zero mean stress. In the multiaxial stress-controlled cases, the ratchetting strain increases with increasing mean stress and stress amplitude and decreasing stress rate. Different values of ratchetting strain were obtained in the multiaxial cyclic tests with seven different loading paths, and prior cyclic loading with higher stress level resulted in decreased ratchetting in the subsequent cyclic loading with lower stress level. In the multiaxial mixed stress-strain-controlled tests, the ratchetting increased with increasing axial (or equivalent shear) stress and torsional-angle (or axial-displacement) amplitude and decreasing applied deformation rate.

Viscoelastic–Viscoplastic Cyclic Deformation of Polycarbonate Polymer: Experiment and Constitutive Model

A series of uniaxial tests (including multilevel loading–unloading recovery, creep-recovery, and cyclic tension–compression/tension ones) were performed to investigate the monotonic and cyclic viscoelastic–viscoplastic deformations of polycarbonate (PC) polymer at room temperature. The results show that the PC exhibits strong nonlinearity and rate-dependence, and obvious ratchetting occurs during the stress-controlled cyclic tension–compression/tension tests with nonzero mean stress, which comes from both the viscoelasticity and viscoplasticity of the PC. Based on the experimental observation, a nonlinear viscoelastic–viscoplastic cyclic constitutive model is then constructed. The viscoelastic part of the proposed model is constructed by extending the Schapery's nonlinear viscoelastic model, and the viscoplastic one is established by adopting the Ohno–Abdel-Karim's nonlinear kinematic hardening rule to describe the accumulation of irrecoverable viscoplastic strain produced during cyclic loading. Furthermore, the dependence of elastic compliance of the PC on the accumulated viscoplastic strain is considered. Finally, the capability of the proposed model is verified by comparing the predicted results with the corresponding experimental ones of the PC. It is shown that the proposed model provides reasonable predictions to the various deformation characteristics of the PC presented in the multilevel loading–unloading recovery, creep-recovery, and cyclic tension–compression/tension tests.

Cancer cell aggregate hypoxia visualized in vitro via biocompatible fiber sensors

To fully understand biological behavior in vitro often dictates that oxygen be reported at either a local or a cellular level. Oxygen sensors based on the luminescent quenching of a specific form of electrospun fiber were developed for measurement of both gaseous and dissolved oxygen concentrations. Electrospinning was used to fabricate “core–shell” fiber configurations in which oxygen-sensitive transition-metal porphyrin complexes are embedded in an optically clear, gas permeable polycarbonate polymer ‘core’ while polycaprolactone provided a protective yet biocompatible ‘shell’. By taking advantage of the resulting high sensitivity and fast response of electrospun core–shell fiber sensors, we were able to locate and image hypoxic regions in contact with aggregates of glioblastoma cells. Nanoscale, biomimetic sensors containing oxygen-sensitive porphyrins are particularly well suited to biological applications. These ‘smart’ nanofiber based sensors do not consume oxygen, their mechanical and chemical characteristics can be finely tuned allowing tailoring of biocompatibility and microstructure. Core-shell nanofiber oxygen sensing fibers could provide real-time assessments of tumor cell response to pharmacological innovations designed to target hypoxic regions driving new knowledge and technological advancement.

An easy-to-use microfluidic interconnection system to create quick and reversibly interfaced simple microfluidic devices

The presented microfluidic interconnection system provides an alternative for the individual interfacing of simple microfluidic devices fabricated in polymers such as polymethylmethacrylate, polycarbonate and cyclic olefin polymer. A modification of the device inlet enables the direct attachment of tubing (such as polytetrafluoroethylene tubing) secured and sealed by using a small plug, without the need for additional assembly, glue or o-rings. This provides a very clean connection that does not require additional, potentially incompatible, materials. The tightly sealed connection can withstand pressures above 250 psi and therefore supports applications with high flow rates or highly viscous fluids. The ease of incorporation, configuration, fabrication and use make this interconnection system ideal for the rapid prototyping of simple microfluidic devices or other integrated systems that require microfluidic interfaces. It provides a valuable addition to the toolbox of individual and small arrays of connectors suitable for micromachined or template-based injection molded devices since it does not require protruding, threaded or glued modifications on the inlet and avoids bulky and expensive fittings.

Effect of part thickness, glass fiber and crystallinity on light scattering during laser transmission welding of thermoplastics

Abstract It is important to understand how laser energy scatters within the transparent component in order to predict and optimize the laser transmission welding process. This paper examines the influence of part thickness, glass fiber and crystallinity levels on the distribution of laser light after transmission through amorphous polycarbonate (PC) and semi-crystalline polymers such as polyamide 6 (PA6), polypropylene (PP), and polyethylene (PE). An experimental technique based on laser-scanned lines of progressively increasing power was used to assess the transmitted energy distribution. This distribution was characterized using a two-parameter model that captures scattered and un-scattered components of the laser beam. The results clearly show how the scattering is increased by increasing the numbers of interactions between laser light and phase boundaries either by increasing the particle concentration (i.e., glass fiber level and crystallinity) or increasing part thickness.

Irradiation influence on Mylar and Makrofol induced by argon ions in a plasma immersion ion implantation system

Mylar and Makrofol polycarbonate polymers were irradiated by Ar ions in a plasma immersion ion implantation (PIII) system. The surface wettability of both polymers was investigated by employing the contact angle method. The measured contact angles were found to depend on the surface layer properties. Good wetting surfaces were found to depend not only on surface roughness but also on its chemistry that analyzed by Fourier transform infrared (FTIR) spectroscopy. Surfaces topography and roughness was investigated and correlated to their surface energy which studied with the aid of acid-base model for evaluating the improvement of surface wettability after irradiation. PIII improves polymers surface properties efficiently in a controllable way.

Mechanical, Electromagnetic, and X-ray Shielding Characterization of a 3D Printable Tungsten–Polycarbonate Polymer Matrix Composite for Space-Based Applications

Material-extrusion three-dimensional (3D) printing has recently attracted much interest because of its process flexibility, rapid response to design alterations, and ability to create structures ‘‘on-the-go’’. For this reason, 3D printing has possible applications in rapid creation of space-based devices, for example cube satellites (CubeSat). This work focused on fabrication and characterization of tungsten-doped polycarbonate polymer matrix composites specifically designed for x-ray radiation-shielding applications. The polycarbonate–tungsten polymer composite obtained intentionally utilizes low loading levels to provide x-ray shielding while limiting effects on other properties of the material, for example weight, electromagnetic functionality, and mechanical strength. The fabrication process, from tungsten functionalization to filament extrusion and material characterization, is described, including printability, determination of x-ray attenuation, tensile strength, impact resistance, and gigahertz permittivity, and failure analysis. The proposed materials are uniquely advantageous when implemented in 3D printed structures, because even a small volume fraction of tungsten has been shown to substantially alter the properties of the resulting composite.

Antimicrobial/Antifouling Polycarbonate Coatings: Role of Block Copolymer Architecture

The high prevalence of catheter-associated infections accounts for more than 3 billion dollars annually in hospitals, and antimicrobial polymer coatings on catheter surface may serve as an attractive weapon to mitigate infections. Triblock polycarbonate polymers consisting of three critical components including antifouling poly(ethylene glycol) (PEG), antimicrobial cationic polycarbonate, and a tethering or adhesive functional block were synthesized. In this study, the block topology or placement of the distinctive blocks was varied and their efficacy as antimicrobial and antifouling agents investigated on coated surfaces. The individual blocks were designed to have comparable lengths that were subsequently grafted onto a prefunctionalized catheter surface through covalent bonding under mild conditions. The anchoring/adhesive functional moiety based on a maleimide functional carbonate was positioned at either the center or end of the polymer block and subsequently tethered to the surface via Michael addition chemistry. The placement of the adhesive block was investigated in terms of its effect on antimicrobial and antifouling properties. The surface coated with the polymer containing the center-positioned tethering block (2.4k-V) was unable to prevent bacteria fouling, even though demonstrated higher bacteria killing efficacy in solution as compared to the surface coated with the polymer containing the end-positioned tethering block (2.4k-S). In contrast, the 2.4k-S coating resisted fouling of both Gram-positive S. aureus and Gram-negative E. coli effectively under conditions that simulate the device lifetime (1 week). Moreover, the coating prevented protein fouling and platelet adhesion without inducing significant hemolysis. Consequently, this antibacterial and antifouling polymer coating is an interesting candidate to prevent catheter-associated bloodstream infections.

Low-cost replication of self-organized sub-micron structures into polymer films

In this paper, the results of exploiting self-organized sub-micron polystyrene (PS) wrinkle patterns possessing random orientation, in preparation of a nickel stamp for hot embossing purposes, are presented. Self-organized patterns were prepared employing a method in which a stiff cross-linked capping layer on the topmost part of the soft polystyrene layer was created by using reactive ion etching (RIE) device with mild conditions and argon as a process gas, and the wrin- kle formation was initiated thermally. Different surface patternings were obtained using silicon and stainless steel (SST) wafers as substrates. Prepared Ni-stamps were employed in hot embossing of polycarbonate (PC) and cyclo-olefin polymer (COP) films, using a nano-imprinting process. The replication quality of the self-organized wrinkle structures in PC and COP films was monitored by comparing the shape and dimensions of the original and final surface structures. The hot embossed sub-micron scale features, originally formed on stainless steel substrate, were found to have influence on the optical properties of the PC and COP films by lowering their reflectances.

Fabrication of transparent conductive aluminum zinc oxide nanostructured thin film on polycarbonate substrate for heat mirror applications

In this work an aluminum zinc oxide nanostructure thin film was deposited on polycarbonate polymer substrates using a magnetron sputtering technique. X-ray diffraction, field emission scanning electron microscopy and X-ray photoelectron spectroscopy methods were used to investigate the structure, morphology and surface composition of the thin film. The transmittance and reflectance of the aluminum zinc oxide thin film was investigated by a UV-VIS-NIR spectrophotometer. The sheet resistance of the aluminum zinc oxide thin film was measured by the four point probe method. The average reflectance in the near infrared region and the sheet resistance of the aluminum zinc oxide thin film were 30% and 105 Ω/sq, which encourages the heat mirror of the aluminum zinc oxide thin film.

<i>γ</i>-Ray Modifications of Optical/Chemical Properties of Polycarbonate Polymer

This work was aimed to investigate the changes brought about in the polymer polycarbonate irradiated to different doses of γ-radiation. Yellowing of the samples with the increase of γ-absorbed dose was observed. The changes in the optical properties were studied by recording UV-Visible absorbance spectra of the pristine and irradiated polycarbonate films. A simultaneous coexistence of direct and indirect band gaps was observed. The indirect band gap values were found lower in comparison to the corresponding values of direct band gap in the pristine and γ-irradiated poly-carbonate. Both types of the optical band gap energies had decreasing tendency with the increasing γ-radiation dose. Urbach energy was also determined from the tail of absorption edge which was found to have increasing tendency with progressive γ-radiation dose. Increase in carbon cluster size with the increasing γ absorbed dose was also shown. This increase in the number of carbon atoms (N) in a cluster can be correlated to the optical energy band gap (Eg). Moreover, the FTIR spectra of pristine and irradiated PC samples suggest chain scissoring with apparently the elimination of carbon di/monoxide.

Protein-like dynamics of polycarbonate polymers in water.

The dynamics of amphiphilic peptide-mimicking polycarbonate polymers are investigated, considering variations in polymer length, monomer sequence, and monomer modification. The polymers are simulated in aqueous solution with atomistic molecular dynamics simulations and an empirical force field. Various structural polymer properties, interaction strengths, and solvation free energies are derived. It is found that water is a less favorable solvent for these polymers than for peptides. Moreover, polymers readily adopt irreversibly a compact state that consists of a variety of distinct compact conformations that are adopted through frequent transitions. Furthermore, the polymers exhibit a strong propensity to form large aggregates. The driving forces for these processes appear to be a hydrophobic effect and more favorable polymer-solvent interactions of aggregates that overcome the otherwise strong mutual repulsion between the positively charged polymers. Replacing hydrophobic residues with polar side chains destabilizes the compact conformations of the polymers. Our results also indicate that the monomer sequence has little effect on the overall solvation properties of the polymer molecule. However, the sequence influences flexibility and compactness of the monomer in solution. Overall, the results of this work confirm the protein-like characteristics of these polymers and elucidate the role of single residues in influencing the structure and aggregation in aqueous solution.

An experimental study on uniaxial ratcheting of polycarbonate polymers with different molecular weights

The uniaxial ratcheting was experimentally observed on the polycarbonate (PC) polymers with different molecular weights (i.e., PC-7030PJ and PC-7020PJ) at room temperature. The effects of mean stress, stress amplitude, stress rate and peak hold-time on the ratcheting were observed. The results show that obvious ratcheting deformation occurs in the two prescribed polycarbonate polymers subjected to the stress-controlled cyclic loading; and the ratcheting strain accumulates cyclically in the direction of non-zero mean stress. The ratcheting greatly depends on the mean stress and stress amplitude, and the ratcheting strain increases more rapidly as the mean stress and stress amplitude increase. The ratcheting of two prescribed polycarbonate polymers is also significantly time-dependent, the ratcheting strains observed in the load cases with longer peak hold-time and at lower stress rate are larger than that with shorter peak hold-time and at higher stress rate. More importantly, a comparison of the ratcheting of two prescribed polycarbonate polymers shows that, at room temperature, the ratcheting of the polycarbonate polymer with a larger molecular weight (i.e., PC-7030PJ) is more remarkable than that with a smaller one (i.e., PC-7020PJ).

Optical and electrical properties of aluminum zinc oxide (AZO) nanostructured thin film deposited on polycarbonate substrate

Transparent polymer materials, due to their unique properties, such as light weight, optical transparency, and electrical and mechanical properties, have become very attractive as a replacement for inorganic glass substrates in a wide range of optoelectronic applications. In this research, aluminum zinc oxide nanostructured thin film was deposited on polycarbonate polymer substrates using a magnetron sputtering technique. The structure, morphology, and surface composition of the thin film were investigated by X-ray diffraction and field emission scanning electron microscopy. The optical and electrical properties of the thin film were investigated by UV–VIS-NIR spectrophotometer, ellipsometer, and four point probe method. The X-ray diffraction pattern showed that the aluminum zinc oxide thin film had a polycrystalline structure. The optical and electrical results indicated that the refractive index, band gap, and sheet resistance of the aluminum zinc oxide thin film were 1.8, 3.2eV, and 265Ω/sq, respectively.

Controlled nanodot fabrication by rippling polycarbonate surface using an AFM diamond tip.

The single scratching test of polymer polycarbonate (PC) sample surface using an atomic force microscope (AFM) diamond tip for fabricating ripple patterns has been studied with the focus on the evaluation of the effect of the tip scratching angle on the pattern formation. The experimental results indicated that the different oriented ripples can be easily machined by controlling the scratching angles of the AFM. And, the effects of the normal load and the feed on the ripples formation and their periods were also studied. Based on the ripple pattern formation, we firstly proposed a two-step scratching method to fabricate controllable and oriented complex three-dimensional (3D) nanodot arrays. These typical ripple formations can be described via a stick-slip and crack formation process.

Thermal and strain rate sensitive compressive behavior of polycarbonate polymer - experimental and constitutive analysis

The mechanical behavior of polycarbonate (PC) polymer was investigated under the effect of various temperatures and strain rates. Characterization of polymer was carried out through uniaxial compression tests and split Hopkinson pressure bar (SHPB) dynamic tests for low and high strain rates respectively. The experiments were performed for strain rates varying from 10 −3 to 103 and temperature range of 213 to 393 K. By conducting these experiments, the true stress–strain (SS) curves were obtained at different temperatures and strain rates. The results from experiments reveal that the stress–strain behavior of polycarbonates is different at lower and higher strain rates. At higher strain rate, the polymer yields at higher yield stress compared to that at low strain rate. At lower strain rate, the yield stress of the polymer increases with the increase in strain rate while it decreases significantly with the increase of temperature. Likewise, initial elastic modulus, yield and flow stress increase with the increase in strain rate while decreases with the increase in temperature. The yield stress increases significantly for low temperature and higher strain rates. On the basis of experimental findings, a phenomenological constitutive model was employed to capture the mechanical behavior of polymer under temperature and loading rate variations. The model predicted the yield stress of polymer at varying strain rate and temperature also it successfully predicted the compressive behavior of polymer under entire range of deformation.

Bisphenol A Migration Study in Baby Feeding Bottles of Selected Brands Available in the Indian Market

The wide applications of polycarbonate (PC) and other polymers in the kitchen ware and food storage containers increase the risk of human exposure to bisphenol A (BPA), mainly through food and water. BPA results in endocrine disorders in humans; health impacts caused by the chemical vary with body weight and exposure dosage. The present study aims to test the safety of using PC bottles, for feeding infants with respect to BPA and the migration rate of BPA from the containers, while storing hot water at 70°C, for 1 h. Three different popular brands of PC baby feeding bottles were subjected to the tests. BPA residues were extracted with ethyl acetate and quantified using HPLC with PDA detector. The test reveals that BPA migrates from PC baby feeding bottles at 19 ng ml -1 of hot water (70°C), stored for 1 h.

Hard coating for polymer substrates through lamination and peeling of porous anodized zirconia.

Transparent and hard zirconia (ZrO2) films with thicknesses in the range of 1.5 to 1.8 microm were successfully formed on various polymer surfaces, i.e., polycarbonate (PC), polystyrene (PS), polyethylene terephthalate (PET) and polymethylmethacrylate (PMMA) with excellent adhesion and without cracking, while preserving their bulk properties. Our process is based on a lamination of porous anodized ZrO2 membranes (PAZMs) to the polymer surfaces through capillary action, followed by simple peeling with tweezers to remove the unanodized metal Zr foil. The resulting PAZM-laminated surfaces exhibited excellent surface chemical and physical durability. Our technique also allowed the reuse of a single Zr foil piece multiple times for several anodization and lamination cycles.

Non destructive evaluation of selected polymers by multiple scattering of 662 keV gamma rays

In this paper, multiple scattering of 662 keV gamma photons from targets of Carbon, Aluminium, Iron, Copper and polymers (Polypropylene, Polycarbonate, Polymethyl methacrylate, Polytetraflouroethylene and Polyvinyl chloride) is studied experimentally. Backscattered photons are detected by a NaI(Tl) detector placed at an angle of 90° to the incident beam. The single scattered events are reconstructed analytically to extract multiple scattered photons from the measured spectra. We observe that the number of backscattered photons increases with an increase in target thickness, and saturates at a particular value of the target thickness. This saturation thickness decreases with increasing atomic number of the target. The saturation thickness of the multiple scattering is used to assign effective atomic number of polymers. The experimental results are compared with the results obtained by Monte Carlo N-particle simulation code.