Coefficient Of Polymer Research Articles

Evaluation of polymer-preservative interactions for preservation efficacy: molecular dynamics simulation and QSAR approaches.

Preservatives are critical ingredients in various pharmaceutical and consumer products. In particular, a high efficacy preservative system is essential in enhancing the shelf-life and safety of these products. However, the development of such a preservative system heavily relies on experimental approaches. In this study, molecular dynamics (MD) simulation was complemented with quantitative structure-activity relationship (QSAR) modelling to comprehensively evaluate polymer-preservative interactions between three different polymers (polyethylene terephthalate, PET; polypropylene, PP; and cellulose) and a series of preservatives from the classes of aliphatic, aromatic, and organic acids. First, adsorption of preservatives onto polymer surfaces was simulated in an aqueous environment. The preservatives did not adhere to hydrophilic cellulose, but most preservatives were adsorbed by PET and PP in distinct configurations. Interaction energies (IEs) between the preservatives and the polymers generally increase from cellulose to PP and PET. The diffusion coefficients of preservatives are dependent on polymer nature, preservative structure, and their resulting molecular interactions. Linear and low molecular weight preservatives exhibit higher diffusion coefficients in polymers. For a particular preservative, diffusion coefficients increased in the order of cellulose < PET < PP. Finally, using MD properties and molecular descriptors of preservatives, QSAR models were developed to identify key descriptors of preservatives and predict their IEs and diffusion coefficients in polymers. This study demonstrates a computational approach for identifying critical materials properties, and predicting polymer-preservative molecular interactions in water. Such an approach streamlines the rational selection and design of high efficacy preservative systems for various pharmaceutical, food and cosmetic products. Furthermore, the integrated computational strategy also reduces trial-and-error experimental efforts, thereby accelerating the development of high efficacy preservative systems.

Influence of optical absorption of polysiloxane polymers on active fiber heating under lasing conditions

Optical properties of conventional polysiloxane polymers used in fiber optics were analyzed. Transmission spectra and absorption coefficients of polymers in the operating wavelength range of Yb and Er doped fiber lasers were measured. Heating of Yb-doped active fiber inside the industrial laser unit poured with a silicone polymer protective layer was investigated. A part of the pump power converted into heat during laser generation was evaluated using experimental data obtained by substituting the active fiber with an electrically heated copper wire. Mathematical model of fiber laser unit heating was developed.

Electrical Properties of the Carbon-Nanotube Composites Film Under Extreme Temperature Condition.

Carbon nanotube (CNT) composites have been widely investigated for electric heating applications (such as water heater, de-icing unit, and patternable micro heaters) owing to their rapid heating, flexibility and light-weight properties. For practical use of CNT composite as heating element applications, the change of resistance with varying temperature must be interpreted. In this study, electric heating behavior of CNT/Nylon 6 composite film (10 wt%) and CNT/Polydimethylsiloxane (PDMS) composite film (10 wt%) were evaluated by measuring the change in normalized resistance under extreme temperature from -50 °C to 100 °C. While CNT/PDMS composite film showed 25% normalized resistance change from -50 °C to 100 °C, in the case of CNT/Nylon 6 composite film, only 10% normalized resistance change was shown. The difference of resistance change is attributed to the difference of the polymer's coefficient of thermal expansion (CTE), which is a crucial factor to consider in the design of CNT composites as a heater or heating sensor. CNT/Nylon 6 composite film is appropriate for flexible heating unit and de-icing application, due to the lower degree of resistance change than that of CNT/PDMS composite film. In addition, a thermal cycling test was conducted to determine the thermal stability and repeatability of CNT composites.

Dynamic Analysis Model for the Diffusion Coefficient in High-Viscosity Polymer Solution

An accurate mass transfer model is required to calculate the diffusion coefficient in polymers to describe the mass transfer of volatiles in process intensification, especially in the devolatilization units. However, the diffusion coefficient actually is variate rather than a fixed value due to the changing concentration and viscosity of polymer in the process of devolatilization. In this work, removal rates of the volatiles in liquid film were obtained by the intelligent gravity analysis, and a discrete mathematical model was established to compute the instantaneous dynamic diffusion coefficients. On the basis of a large number of experimental data, a correlation of diffusion coefficients was developed by dimensionless regression analysis with temperature, concentration, viscosity, molar mass, molecular polarity, etc. It can well describe the diffusion process in polymers. Furthermore, a molecular simulation was conducted to explore the proper means of the bonding method and force field in the calculatio...

Predicting the Effects of Composition, Molecular Size and Shape, Plasticization, and Swelling on the Diffusion of Aromatic Additives in Block Copolymers

The rate of diffusion of small molecules within polymer matrices is important in an enormous scope of practical scenarios. However, it is challenging to perform direct measurements of each system of interest under realistic conditions. Free volume theories have proven capable of predicting diffusion coefficients in polymers but often require large amounts of physical constants as input. Therefore, we adapted a version of the Vrentas–Duda free volume theory of diffusion such that the necessary parameters may be obtained from a limited set of diffusion data collected at the temperature of interest using commercially available and automated sorption equipment. This approach correlates the size and shape of molecules to their trace diffusion coefficient, D, such that D of very large, solid diffusants can be predicted based on properties measured for condensable vapor diffusants. Our analysis was based on the volume-averaged transport properties of polyaromatic color additives within segmentally arranged poly(...

Electrospun Polymer Fiber Lasers for Applications in Vapor Sensing

A sensing approach based on laser emissionfrom polymer fiber networks is presented. Poly(methyl methacrylate) (PMMA) fibers doped with a laser dye are fabricated by electrospinning. They form random loop resonators, which show laser emission upon optical pumping. The shift of the spectral position of the narrow lasing modes upon uptake of alcohol vapors (model vapors are methanol and ethanol) serves as sensor signal. Thus, the high sensitivity related to the spectral line shifts of cavity‐based transducers can be combined with the fiber's large surface to volume ratio. The resulting optical sensors feature excellent sensing performance due to the large overlap (more than 80%) of light field and transducer. The shift of the laser modes results from the swelling of the polymer when exposed to solvent vapors. Due to distinctly different diffusion coefficients in polymers, the uptake dynamics reflected in the transient shift of the lasing peaks can be used to discriminate ethanol and methanol vapor in mixtures of them. The sensing mechanism is expected to be applicable to other solvent vapors that cause polymer swelling.

Off-Lattice Flory–Huggins Approximations for the Tailored Calculation of Activity Coefficients of Organic Solutes in Random and Block Copolymers

Predicting activity coefficients in polymers for arbitrary solute and polymers is of general interest for packaging, environmental, and membrane applications. We examined the extensions of the proposed off-lattice approach [Gillet et al. Ind. Eng. Chem.Res. 2009, 2010] for random and block copolymers. Based on a comparison with an explicit representation of random copolymers, the principles of a mean-field approximation using only the properties of homopolymers have been established. The approach was successfully validated against the Flory–Huggins coefficients collected by Fornasiero et al. [AIChE J. 2002] for 19 aromatic solutes in ethylene-vinyl acetate with acetylation rates varying from 33% to 100%. The role of substituents and isomerism is elucidated. Previously collected data and this study suggest that the real chemical affinity of substituted aromatic compounds for water could be strongly underestimated by previous oversimplified rules and that tailored methods, such as this one, would be preferable.

Study on the method measuring the drag coefficient of polymers in flows by using a scanning probe microscope

Study on the method measuring the drag coefficient of polymers in flows by using a scanning probe microscope

THE EFFECT OF THE IONIZING RADIATION ON THE TRIBOLOGICAL PROPERTIES OF THERMOPLASTIC POLYMERS RUBBING AGAINST STEEL

The paper describes the effects of gamma radiation doses on the tribological and mechanical properties of selected thermoplastic polymers: PEEK, PEI, PET, and PA6. Samples of those polymers were irradiated with gamma rays of energy 1, 1.2, 3, 4, 5 MeV and with the intensity of the radiation beam 4, 7, 10, 30, 40 μA. With an increasing dose of radiation, properties such as microhardness, the friction coefficient of polymers, and the wear rate are changed. The chemical structure of the irradiated polymer may be changed by crosslinking but also by chain scission. The modified polymers may be used in medical science, electronics, and space technology. In this article, we report the results of steel C45 – thermoplastics (PEEK, PEI, PET, and PA6) friction couple during the slip motion. The analysis is focused on the friction coefficient, wear rate, and microhardness. Kinematic parameters of the experiment in slide movement were constant and defined by the following values: contact pressure p = 1MPa and sliding velocity v = 1m/s. The authors observed that, as gamma radiation dose increased, the microhardness and friction coefficient increased and their wear intensity decreased. Polymers change their microstructure and molecular structure when they are subjected to gamma ray irradiation, which results in modification on many important physical and chemical properties.

The Power of Heterogeneity: Parameter Relationships from Distributions.

Complex scientific data is becoming the norm, many disciplines are growing immensely data-rich, and higher-dimensional measurements are performed to resolve complex relationships between parameters. Inherently multi-dimensional measurements can directly provide information on both the distributions of individual parameters and the relationships between them, such as in nuclear magnetic resonance and optical spectroscopy. However, when data originates from different measurements and comes in different forms, resolving parameter relationships is a matter of data analysis rather than experiment. We present a method for resolving relationships between parameters that are distributed individually and also correlated. In two case studies, we model the relationships between diameter and luminescence properties of quantum dots and the relationship between molecular weight and diffusion coefficient for polymers. Although it is expected that resolving complicated correlated relationships require inherently multi-dimensional measurements, our method constitutes a useful contribution to the modelling of quantitative relationships between correlated parameters and measurements. We emphasise the general applicability of the method in fields where heterogeneity and complex distributions of parameters are obstacles to scientific insight.

HF Transport Coefficients in Polymers Used for Microelectronic Applications

In order to better understand the sorption and outgassing mechanism of gases in relation to wafers containers (FOUP), we have measured HF gas transport coefficients for different FOUP polymers. Gas sorption is governed by surface adsorption, followed by diffusion and solubility. Cross contamination between FOUP and wafer occurs when polymers outgas contaminants into the surrounding environment. Diffusion is the key parameter to understanding cross contamination within the FOUP environment. In this work, we present the transport coefficients obtained for gaseous HF at cleanroom conditions (Patm, 21 ± 2°C &amp; 40% RH) using the sorption kinetic method, based on Fick’s law, for thin films (&lt;80μm) of polycarbonate (PC), polyetherimide (PEI) and a low absorbing polymer named Entegris Barrier Material (EBM) that constitute FOUPs. The resulting kinetic curves show Fick’s behavior, where obtained HF diffusion coefficients are between 3.7 X10-10 and 42 x10-12 cm2/s and are significantly lower than diffusion coefficients obtained for H2O using a gas permeation method. Nevertheless, the similar order of magnitude between the HF and the H2O permeability coefficients obtained by the two methods validates the sorption kinetic method. Finally, the obtained coefficients were used in numerical simulation in order to forecast polymer behavior.

Correlation between Frequency and Sound Absorption Coefficient of Polymer Reinforced Natural Fibre

Aspect ratio which is the ratio between the length and diameter of the fiber affects the sound absorption performance of the polymer reinforced natural fiber (ramie or bamboo fiber). The aim of this study is to choose the specific frequency –which is important for industrial application- to obtain an optimal sound absorption coefficient (α) by designing a certain aspect ratio.The acoustic was measured using impedance tube of The ASTM E- 1050=98 standard. Fiber length was 10 mm, while the diameter of the fiber was measured by using a digital optical microscope measurement with an average diameter of 110.4 microns. The morphology of the material was observed by using scanning electron microscope (SEM). Fourier Transform Infrared (FTIR) spectroscopy was used to identify the presence of certain functional groups in a molecule. The results indicated that the average of the sound absorption coefficient of the polymer reinforced ramie fiber reached 0,836 at low frequency of 125 Hz and 0,537 at medium frequency of 1000 Hz, and aspect ratio of 90, while the sound absorption coefficient of the polyester material reinforced bamboo fiber reached 0.973 at medium frequency of 1000 Hz.

Prediction of Solubilities and Partition Coefficients in Polymers Using COSMO-RS

Recent results concerning the prediction of thermodynamic properties of solutes in polymers are presented. In particular, the computation of vapor–liquid and gas–liquid equilibria (i.e., liquid and gas solubilities) in different polymers and partition coefficients between the polymer and a solvent phase are addressed. Calculations have been carried out using COSMO-RS theory which combines quantum-chemical calculations with efficient statistical thermodynamics for intermolecular interactions. Predictions for vapor–liquid equilibria and for partition coefficients have been improved by incorporation of polymer-specific entropic contributions due to free volume effects. It is demonstrated that a high predictive accuracy is obtained if the polymer is sufficiently characterized by its composition, density, and crystallinity. The approach is currently limited to gaseous and liquid solutes and to linear, i.e. non-cross-linked polymers without any significant swelling.

A synergistic approach to the polydispersity of polymers

A scheme for calculating polydispersity coefficients of polymers during chain propagation in living polymerization is proposed on the basis of the synergistic approach (the master equation) with allowance for fluctuations in the number of free radicals at the stage of initiation. The molecular-mass-distribution function of living chains is calculated. The form of this function is shown to be dependent on the ratio between the constants of the elementary stages of chain initiation and propagation.

Thermo-Optic and Dispersion Properties of Host–Guest Doping Polymer

A diazobenzene chromophore molecule was synthesized using the diazo-coupling reaction. The host–guest doping polymer was prepared based on host polyacrylate and guest diazobenzene chromophore. The UV-induced trans/cis photoisomerization and the reflex-isomerization behavior of the polymer were investigated. The results indicated that the polymer could undergo photochromism after a given UV wavelength photoinduction. The measurements of refractive index (n) and thermo-optic coefficient (dn/dT) were demonstrated at different wavelengths and temperatures by ATR technique. The refractive index dispersion curves and Sellmeyer coefficients of polymer were obtained by Sellmeyer equation. The experimental results indicated that the obtained host–guest doping polymer material would be useful for the design of high performance thermo-optic switch and optical storage device.

Erosion of polyimide modified by amorphous silica sol in the stream of oxygen plasma

Polymeric coatings derived from Kapton H polyimide, thermoplastic polyimide (PI), and a composite with amorphous silica sol (PI-SS) were irradiated in a magnetoplasma dynamic accelerator of oxygen plasma simulating the action of atomic oxygen (AO). The volumetric erosion coefficients of polymers were calculated, and the comparative analysis of the stability of coatings was performed. The changes in morphology of polymer surfaces before and after irradiation were studied by means of scanning electron microscopy. It was shown that the PI-SS composite has increased resistance to atomic oxygen. The composition of the PI-SS composite was found at which the particles of silica sol are uniformly dispersed over the polymer volume that explains a better resistance of PI-SS polymeric-inorganic compositions to the action of atomic oxygen. The lowest stability was registered for the coating based on Kapton H polyimide. The surfaces of all coatings after irradiation were found to possess a carpetlike morphology. Each polymer featured a number of distinctive peculiarities of the surface structure caused by the differences in the chemical structure of the polymides under investigation.

Prediction of Solvent Diffusivities in Amorphous Polymers by Free-Volume Theory: Group Contribution and PALS Methods

A group contribution-based model was proposed to predict solvent diffusion coefficients in amorphous polymers with the free-volume conceptual framework. Based on the van der Waals volume of polymer structural units, this model provides a novel way to estimate the hole free volume of polymer in its rubbery state, which is the effective space for solvent jump. All the parameters with respect to polymer can be determined by group contribution method using the knowledge of polymer structure, and no adjustable parameters are required. Calculated solvent diffusion coefficients in polymers were in good agreement with published experimental results. A linear dependence was found between logarithm of infinite dilution diffusion coefficient of various organic solvents and hole free volume in four common polymers. In addition, the hole size distribution from positron annihilation lifetime spectroscopy (PALS) measurements was investigated to reaffirm the reliability of this model, on the basis that the ratio of polymer hole free volume to total free volume from microscopic viewpoint should be equivalent to that from macroscopic viewpoint.

Reflective-type configuration for monitoring the photobleaching procedure based on surface plasmon resonance

A new scheme to monitor the photoinduced bleaching procedure with ultraviolet light based on surface plasmon resonance (SPR) using attenuated total reflection configuration is presented. The configuration, which is very sensitive to the changes of refractive index and nonlinear optical (NLO) coefficient of polymer, can prevent the effect of the fundamental wave and can be used to determine the nonlinear coefficient d33. With the formulation in this paper, the nonlinear coefficient d33 can be measured by comparing the second harmonic generation intensity generated by SPR from the metal–nonlinear optical (NLO) polymer interface and that from the metal–quartz interface. The remaining second-order NLO coefficients are 78% and 47% for the cross-linked and side-chain polymer, respectively.

Prediction of infinite dilution solvent activity coefficient in rubbery polymer solutions using Engaged Species Induced Clustering (ENSIC) model

AbstractIt is extremely important to predict infinite dilution solvent activity coefficients in rubbery polymers in design and operation of polymer‐related processes. Many models have been developed to predict the activity coefficients. However, the accuracies of these models are not satisfactory. This article advances a method for predicting the infinite solvent dilution activity coefficients in the rubbery polymers, using the Engaged Species Induced Clustering (ENSIC) model. It elucidates the physiochemical significance and mathematical meaning of the parameters in the ENSIC model. In this article, the ENSIC approach has been proven to agree extremely well with the experimental data in both correlating the finite dilution solvent activity coefficient and predicting the infinite dilution solvent activity coefficient for rubbery polymer/solvent systems. In other words, both the ENSIC equation and its derivative at extremely low solvent concentration are in good agreement with the experimental data. In addition, the article indicates that the ENSIC model is much more accurate than another kind of empirical models‐ the F–H and related models in predicting the infinite dilution solvent activity coefficients in polymer solutions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1668–1675, 2006

Infinite Dilute Activity and Diffusion Coefficients in Polymers by Inverse Gas Chromatography

The infinite dilute activity and diffusion coefficients of solvents in poly(vinyl alcohol) and cross-linked poly(vinyl alcohol) are determined by using inverse gas chromatography technique with a packed column. Experimental results for water, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1-pentanol, and 3-methyl-1-butanol in poly(vinyl alcohol); for water, methanol, and ethanol in cross-linked poly(vinyl alcohol) at different temperatures are presented. The van Deemter equation is used to obtain diffusion coefficients of solvents from the variation of chromatographic peak under the different flow rates of carrier gas. The interdependence on the infinite dilute diffusion coefficient and temperature follows Arrhenius equation well. Diffusion constant and activation energy are obtained from the Arrhenius equation.