The use of thermogravimetry to analyze a mixed plastic waste stream

The thermogravimetry of a mixed polymer waste stream has been studied and the weight-loss behaviour of this heterogeneous mixture has been compared with results obtained from the weight-loss curves of some individual polymers. The results suggest that the behaviour of the mixture cannot be predicted by the simple additive behaviour of the individual polymers since interactions can occur which influence the degradation weight-loss profiles. The heterogeneous polymeric waste studied was that generated from the shredding of old discarded automobiles. The results of the study indicate that while it is possible to determine what is present in a sample, the relevance of the data to a very heterogeneous waste stream is questionable.     

Studies of poly(vinyl chloride)/solution chlorinated polyethylene blends by inverse gas chromatography

The interactions between two polymers, poly(vinyl chloride) and solution chlorinated polyethylene, with a series of solvents have been studied using inverse gas chromatography. Values of the interaction parameters show the importance of specific interactions in these systems. From these values and studies of polymer mixtures, values of the polymer-polymer interaction parameter have been calculated. The values were small in agreement with values of the heat of demixing of the two polymers reported previously.Measurements using PTFE and kaolin as the substrate for these polymers show the importance of the substrate. Results suggest that the pore structure of PTFE leads to problems in obtaining reliable results.By making measurements for the mixed polymer system over a range of temperatures, it has been found possible to detect the temperature of phase separation. The phase diagram obtained agrees well with results reported previously.     

Etude de la compatibilite des systemes binaires constitues par le polychlorure de vinyle et polyacetate de vinyle—IV: L'influence de la masse moleculaire sur la compatibilite du systeme PVC/PV AC

Using kinetic thermogravimetry and phase-contrast microscopy, a study has been made on the influence of molecular weight upon compatibility in the solid state for the system PVC/PVAc. For the extreme mixtures 80 PVC/20 PVAc and 20 PVC/80 PVAc, completely different behaviour is shown; the thermal stability of the former is much greater and that of the latter much less than would be expected on the basis additivity. From the results for the various systems, an attempt is made to classify mixtures of solid polymers.     

Prediction of excess thermodynamic functions and activity coefficients of some polymeric liquid mixtures using a new equation of state

In this work, the excess thermodynamic properties, namely excess molar Gibbs energy, excess molar enthalpy, excess molar entropy, excess molar internal energy, and excess molar Helmholtz energy for four polymer mixtures and blends at different temperatures, pressures, and compositions have been calculated using the GMA equation of state. We have also calculated the activity coefficient for these polymeric mixtures using the GMA equation of state. The values of statistical parameters between experimental and calculated properties show the ability of this equation of state in reproducing and predicting the excess thermodynamic functions and activity coefficients for studied polymeric mixtures.     

Mixed polymer networks in the direct analysis of pharmaceuticals in urine by capillary electrophoresis

Two-component polymer mixtures of polyethylene oxide-polydextran have been investigated as unique separation media for capillary electrophoresis. The effects of concentration of the individual polymers and their mixtures on the electroosmotic velocity and electrophoretic mobility of small pharmaceutical compounds were investigated. The molecular masses of polymers, buffer concentrations and percentages of organic solvents and cyclodextrins were varied to explore their effects on the separation process.

The plate height against field strength curves were also generated for a better understanding of the kinetic processes involved. The two-component polymer mixtures were found as stable and selective media for the analysis of an anti-ulcer drug famotidine directly in untreated urine.     

Non-isothermal thermogravimetry, differential scanning calorimetry and chemiluminescence in degradation of polyethylene, polypropylene, polystyrene and poly(methyl methacrylate)

The degradation of pure polymers such as polyethylene, polypropylene, polystyrene and poly(methyl methacrylate) in nitrogen and oxygen was characterized by means of non-isothermal thermogravimetry, chemiluminescence and differential scanning calorimetry. The link between the results of the different methods based on Bolland Gee scheme of polymer oxidation is described. From the set of parameters determined from the thermogravimetry, the rate constants based upon the sum of several temperature dependent first-order processes were calculated and compared with those obtained by an iso-conversional method derived for several heating rates. Competition between propagation of oxidation and depolymerisation to monomer is proposed to explain the differences in kinetic behaviour of the examined polymers.     

Relaxation and Miscibility of the Blends of a Poly (Ether Imide) (Ultem™) and a Phenol-A-Based Copolyester (Ardel™) by Inverse Gas Chromatography

Inverse gas chromatography (IGC) was used to analyze the secondary transition temperatures and the miscibility of binary mixtures of poly (ether imide) (Ultem™) and a copolyester of bisphenol-A with terephthalic and isophthalic acids (50/50) (Ardel™) in three compositions (25/50, 50/50 and 75/25). Retention diagrams of the mixtures of Ultem™ and Ardel™ for n-nonane, n-decane, n-butyl acetate and isoamyl acetate were obtained at temperatures between 60 and 285 °C. Second-order transition temperatures of the mixtures were determined according to the slope change in retention diagrams of the solvents. The glass transition temperatures of the mixtures suggested the miscibility of the polymers. Polymer–polymer interaction parameters of binary mixtures of the polymers were determined at temperatures between 260 and 285 °C by Flory–Huggins theory. The polymer–polymer interaction parameters were dependent on the solvent used. The small values of polymer–polymer interaction parameters close to zero suggest some weak interactions between the polymers in the mixture. It was concluded that it was possible to obtain more meaningful information related to the interactions of polymers in a mixture from IGC measurements, if binary polymer–solvent interaction parameters of the used solvent probes were around 0.5.

     

Synthesis of porous divinylbiphenyl copolymers and their sorptive properties towards phenol and its derivatives

Seven porous divinylbiphenyl polymers having the same nominal crosslinking degree (51.8 wt.%) have been synthesized using suspension polymerization method in the presence of the following inert diluents or their mixtures: toluene, heptane, dodecane, isooctane. The use of various inert diluents was aimed at changing the extent of polymeric network-diluent interactions. The obtained polymers have specific surface area in the range 50-300 m²/g depending on the type and amount of inert diluents used during polymerization. Their sorptive properties have been studied using dilute (0.5 mmol/l) aqueous solutions of phenol and its derivatives (2-chlorophenol, 2,4-dichlorophenol, 2,4,5-trichlorophenol, 2,6-dimethylphenol, 4-hydroxyphenol). It has been found that sorption, at low equilibrium concentration, follows the order: 2,4,5-trichlorophenol > 2,4-dichlorophenol > 2-chlorophenol > 2,6-dimethylphenol > phenol > 4-hydroxyphenol. Full characteristic of the porous structure of polymers has been obtained by nitrogen adsorption at 77K.     

Prediction of thermodynamic properties of some polymeric systems using an extended LJ potential-based equation of state up to high temperature–high pressure conditions

In this work, the extended Lennard-Jones potential-based equation of state (ELJ-based EoS) on which the effective near-neighbour pair interactions are LJ (12,6,3) type has been used to predict the specific volume and other thermodynamic properties of some semi-crystalline and liquid polymers and copolymers up to extremely high temperature–high pressure conditions. It seems that, at least in the dense regions, there are no upper- and lower-specific volume limitations in the applicability of the model for different polymeric systems. The parameters can be determined at any temperature for each compound using the temperature dependence of the parameters of ELJ-based EoS. The calculated parameters have been used to calculate the specific volume and other derived thermodynamic properties of different polymeric systems at any temperature and pressure. The ELJ-based EoS has been also compared with some previous studies.     

Thermochemical parameters of Ni(NO3)2 solutions in water + formamide + α-alanine mixtures at 298 K

The enthalpies of mixing of aqueous solutions of nickel(II) nitrate in water + formamide + α-alanine mixtures in the range of existing amide concentrations have been measured calorimetrically. From these data the standard enthalpies of electrolyte transfer from water into ternary mixtures have been calculated. The type and character of electrolyte transfer isotherms are discussed on the basis of the heats of transfer of individual ions that were studied earlier, as well as the contributions into these values that characterize structural changes in the solution and chemical ion-solvent interactions.     

Comparative study of pyrolytic decomposition of polymers alone or in EVA/PS,EVA/PVC and EVA/cellulose mixtures

The behavior of mixtures of EVA–PS, EVA–PVC and EVA–cellulose in various proportions were investigated under pyrolysis. A kinetic model with an independent pathway is proposed for the weight loss and compared with the experimental and theoretical results obtained in a previous study with individual polymers. The kinetic parameters were determined and online IR spectrometric analysis used to follow the evolution of the gaseous pyrolysis products versus the temperature. The result shows good agreement for the EVA–PS mixture and confirms the hypothesis of an independent pathway. However, in the case of EVA–PVC and EVA–cellulose mixtures, the polymers affect one other in the pyrolysis reaction.     

Dissociation constants of phenols in methanol--water mixtures

A preferential solvation model that relates solute properties with solvent composition in binary mixtures has been applied to the dissociation pKa values of a set of 28 substituted phenols in methanol-water mixtures. The parameters of the model allow estimation of the pKa value of each phenol for any methanol-water composition. Moreover, it is demonstrated that the pKa values of the whole set of phenols at any methanol-water composition are linearly related to the pKa values of the phenols in water. Equations that relate the correlations' slope and intercept values with the solvent composition have been derived and tested with the set of phenols. The general parameters obtained for these equations allow an accurate calculation of the pKa value of any phenol, even of those not included in the original set, at any methanol-water composition solely from the pKa value of the phenol in water. These calculated pKa values can be used for quantitative structure-HPLC retention relationships. The method is tested by comparison of the calculated pKa values with the HPLC determined pKa values of 26 phenols in a polymeric column with a 50% methanol as mobile phase.     

Acoustic,excess thermodynamical,molecular interaction and anti-microbial activity studies on binary liquid mixtures of geranyl acetate and benzyl benzoate in the temperature range of 303.15K–318.15K

The binary organic liquid mixture of geranyl acetate + benzyl benzoate was taken at different mole fractions and various temperatures 303.15K, 308.15K, 313.15K and 318.15K and measured their density, ultrasonic sound velocity and viscosity. Data from experiments were used to calculate variations in binary systems at different temperatures regarding excess acoustic parameters. Variations in ultrasonic velocity, intermolecular free length, and adiabatic compressibility were among these. To estimate the coefficients and standard errors for the excess/deviation functions, multi-parametric non-linear regression analysis was used to fit a Redlich-Kister polynomial with the calculated excess/deviation functions. Changes in these properties with temperature and composition have been investigated in the molecular interactions between the molecules of the binary mixtures. FTIR spectra also support the results. Furthermore, liquid mixtures and individual compounds were studied for their antibacterial activity.     

含酯基多孔聚合物小球色谱固定相

合成了PM和PA两个系列甲基丙烯酸甲酯或丙烯酸甲酯与二乙烯苯的多孔聚合物,测定了它们的物理、化学性能和气相色谱性能,并评价其极性。通过实例说明它们对各种混合物的分离情况;保留时间较短,柱温较低,选择性较高,性能优于PorapakT或其它极性相近的商品聚合物固定相。     

Thermal decomposition kinetics and compatibility studies of primaquine under isothermal and non-isothermal conditions

Primaquine (PQ) is the drug of choice for the radical cure of Plasmodium vivax malaria, and currently being administered in solid dosage form. In this study, the compatibility studies were carried out using differential scanning calorimetry (DSC), thermogravimetry (TG), and fourier transformed infrared (FT-IR). Non-isothermal and isothermal methods were employed to investigate kinetic parameters under nitrogen and air atmospheres using TG. The DSC investigations obtained by physical mixtures showed slight alterations in the melting temperatures of PQ with some excipients. The FT-IR confirmed the possible interactions obtained by DSC for the physical mixtures with PQ and lactose, magnesium stearate and mannitol. The results showed that the thermal decomposition followed a zero order kinetic in both atmospheres in non-isothermal method. The activation energy in both methods using nitrogen atmosphere was similar, and in air atmosphere the activation energy decreased.     

Density and Viscosity of Alkyl Acetates + Aromatic Hydrocarbons at (303.15 and 313.15) K

Densities and viscosities have been determined for binary mixtures of isopropyl acetate or isobutyl acetate with o-xylene, m-xylene, p-xylene and ethyl benzene at (303.15 and 313.15) K for the entire composition range. The excess molar volumes and deviations in viscosity have been calculated from the experimental values. The variations of these parameters, with composition of the mixtures and temperature, have been discussed in terms of molecular interactions occurring in these mixtures. Further, the viscosities of these binary mixtures were calculated theoretically from their corresponding pure component data by using empirical relations, and the results were compared with the experimental findings.     

Quantifying interactions between cell receptors and adhesion ligand-modified polymers in solution

Specific interactions between cells and cell-interactive polymers in solution were investigated by the fluorescence resonance energy transfer (FRET) technique and rheological measurements. The green fluorescence emission was dramatically reduced when rhodamine-stained cells were mixed with a fluorescein-labeled RGD-alginate solution, compared with those mixed with no RGD-containing alginate solution, which indicated an occurrence of FRET and existence of specific interactions between the cells and the polymers in solution. Rheological measurements also confirmed the formation of ordered structures of cell/polymer mixtures, caused by specific cell-polymer interactions. The FRET method was able to provide a useful means of investigating cell-polymer interactions, both in a qualitative and quantitative manner, and this approach to monitoring and controlling specific interactions between cells and polymers could be useful in the design and tailoring of polymeric carriers for cells, as well as for biological drugs, especially for tissue engineering applications.     

The influence of polymer structure and component ratios on blend miscibility

The mean field, rigid lattice treatment as applied to polymer mixtures has been used to estimate segment-segment interaction parameters for a wide range of polymers. These parameters incorporate, without distinction, contributions from non-combinatorial entropy effects, dispersion forces and any specific interactions that operate in the polymer blend. Thus while these parameters can be used to predict successfully the nature of the phases in untested polymer blends, structural effects may also play a role in determining miscibility, and these may have to be assessed individually. Examples of structural effects are described using chlorine-containing polymers and blends of copolymers with an anhydride ring attached in two different ways to the polymer chain. The extension of binary interaction parameters to the prediction of phase behaviour in complex ternary copolymer blends and the effect on the phase behaviour of changing the component ratios in the blends, is also illustrated.     

Prevention of protein adsorption by flexible and rigid chain molecules

The ability of tethered polymer layers to reduce the non-specific adsorption of proteins is studied using a molecular theory. The protein adsorption isotherms are calculated for flexible and rigid molecules as well as for mixtures. It is found, in agreement with earlier predictions, that flexible polymers are more effective in preventing protein adsorption. The interactions of the polymer with the surface are shown to be very important in determining the ability of the polymer layer to reduce the adsorption of proteins. Further, it is found that one can tune the adsorption of a certain protein conformation by changing the interactions between the surface and the polymer segments or the composition in the case of mixtures. It is found that the optimal layers to obtain large reduction of protein adsorption and availability of functional groups for binding are obtained by using mixtures of flexible and rod-like molecules. The role of the polymer-surface interactions is shown to be different for the kinetic control of protein adsorption as compared to thermodynamic control. The application of the findings as guidelines for the molecular design of biocompatible materials is discussed.     

Impact of Low-Dosage Inhibitors on Clathrate Hydrate Stability

Summary: Development of more capable low-dosage hydrate inhibitors (LDHI) is of crucial importance to oil and gas industry. Those efforts have been severely hindered so far by lack of clear understanding of molecular-level mechanisms, both thermodynamic and kinetic, which make certain chemical compounds into efficient inhibitors. An accurate representation of intermolecular potentials between polymeric low dosage inhibitors and hydrate-water-gas surfaces is essential for modelling systems containing these components. A two-stage computational study was undertaken of two proven LDHIs, polyvinylpyrrolidone (PVP) and polyvinylcaprolactam (PVCap), in aqueous solutions under various conditions. We have first carried out ab initio density functional theory (DFT) calculations for PVP and PVCap polymers with molecular weight spanning from monomers to polymeric chains. Molecular dynamics were then employed to investigate thermodynamic and kinetic processes that affect hydrate nucleation and growth. Comparison with experiments has also shown that calculated potential is able to mimic the characteristic behaviour of methane hydrate and PVP complexes.