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The corresponding states correlation with the surface tension (γ) of polymers after Patterson et al. has been modified by considering the molecular weight (M) dependence of the equation-of-state parameters, which may be estimated by either the Flory-Orwoll-Vrij (FOV) theory or the cell model (CEM). It has been found that the corresponding states principle-cum-FOV predicts the γs of polystyrene melts over a wide range of M satisfactorily. However, its CEM counterpart is rather irrelevant to the present system of interest. Indeed, the three classical linear equations proposed for the variations of γ with M are intimately correlated with the foregoing models, and hence, facilitating the predictions of the γs of polymer end groups. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 697–703, 1998

The swelling behavior of the networks of natural rubber, an epoxidized natural rubber, low-density polyethylene, polystyrene, and poly(methyl methacrylate) are studied in six classes of solvents at 60°C. The data of the swelling coefficient are successfully treated by a modified version of the empirical equation proposed by Gee, as to determine the solubility parameter of a polymer, δ2. It is found that increasing the temperature would decrease the δ2's of these polymers with a common rate of 0.02 (J/mL)1/2/K. A semiempirical model is proposed to rationalize the present finding satisfactorily. © 1995 John Wiley & Sons, Inc.

Allyl esters of palm olein, palmitic, and oleic acids were synthesized by transesterification and esterification methods using KOH and absolute H2SO4 as catalysts, respectively. Three allyl esters, namely, allyl palmitate, allyl epoxystearate, and epoxidized allyl ester of palm olein, were successfully polymerized in the presence of t-butyl perbenzoate at 120°C to obtain oligomers with the average number of backbone atoms approximately equal to the number of skeletal atoms of the long-dangling side chains. The kinetic data of polymerization were conformed to the rate equation proposed by other workers. No oxirane cleavage was detected during the chain reaction. The melting behavior of these comb-shaped polymers was compared with that of their respective allylic monomers. The polymer of epoxidized allyl ester of palm olein exhibits a glass transition temperature at 204.4 K. The critical molecular weights of the polymers of allyl esters investigated are predicted to be not lower than 104.

The thermodynamic interaction parameter, χφ, for a low-density polyethylene in p-xylene, ethylbenzene, and n-octane has been determined over a range of segment fraction, φ2, from 0.2 to 0.7 using the melting point depression method. Taking advantage of a unique feature of polyethylene, a new procedure has been proposed for evaluating the equilibrium melting points from data obtained by differential scanning calorimetry. The experimental χφ-φ2 relations conform well to the recent equation-of-state theory of polymer solutions. The exchange parameters of the model X 12 and Q 12 are accessible by a nonlinear leastsquares algorithm. Apparently, the observed small values of χφ for the foregoing dispersion force interactions are originated from the negative contribution of the effective interaction energy as concluded by the present findings.

A Study of Temperature Dependence of Thermodynamic Interactions in Polymer Solutions of Infinite Dilution by Equation-of-State Theory

Based on the Saito's model for random chain scission, a novel procedure is developed to determine the activation energy of polymer degradation process. Basically, this is a simple viscometric technique which yields reliable results. In fact, it is superior to the existing viscometry which has been widely used to study the kinetics of random scission. The present method is successfully applied to the thermal degradation of natural rubber, polycarbonate, and poly(tetramethylene oxide) in bulk.

The weight-average molecular weight is estimated by an extrapolation technique based on a linear relation between the viscosity-average molecular weight Mv and a Mark–Houwink–Sakurada constant. This method may also be used to assess the unperturbed dimensions of polymers. If the Mv data are known with high accuracy, then the straight line may be stretched to reach the number-average molecular weight confidently. The slope of the linear plot is associated with the molecular weight distribution and as such can be utilized to compute the polydispersity index.

A simple, inexpensive glass viscometer can be constructed to time the rate at which a rod falls into a liquid held in a concentric closed-end glass cylinder. This equipment can be used to measure absolute values of apparent viscosities of Newtonian and non-Newtonian fluids. Calibration is not required. The technique is an adaptation of a method used previously with polymer melts at elevated temperatures. The present article describes the modifications needed for lower-viscosity fluids, such as paints, and validates the flow analysis with results of study of a characterized Newtonian fluid.

A new semi-empirical equation proposed by us recently for evaluating the intrinsic viscosity of polymer solutions from the viscometric data of moderately concentrated solutions is successfully extended to the higher concentration region in which the critical concentration can be determined. Values of viscometric parameters for various polymer-diluent systems are reported by the present analysis. It is shown that the critical concentration can be used to estimate the unperturbed parameter and its physical significance is discussed.

A rigorous statistical method is established to compute the rate constants of the bimolecular decomposition of redox catalysts used to initiate polymer chains. Results obtained for the systems styrene-dimethylaniline-benzoyl peroxide and acrylamide-thio-glycollic acid-potassium bromate compare favorably with those reported by other workers. The merits of this error-in-variable technique, which outperforms conventional nonlinear least-square analysis and the dead-end polymerization method, are discussed.

A semiempirical equation is developed to compute the unperturbed parameter from the critical concentration of polymer solutions derived from the viscometric and kinetic data. This equation gives satisfactory results for various vinyl polymers including poly(vinyl chloride), polystyrene and poly(methyl methacrylate) among others that follow the Schulz molecular weight distribution function. It is found that the segments of a Gaussian polymer chain are associated with an equal number of foreign segments near its center of mass, when the polymer solution has attained a uniform segment density at the critical concentration. The effect of molecular weight distribution on the present studies is significantly large that it merits an empirical treatment. Defects of the model is also discussed.

A novel method developed to evaluate the unperturbed parameter Kθ from the viscometric data of dilute polymer solutions can be considerably simplified by making the reasonable assumption that the Huggins' constant under theta conditions, kHθ, is equal to ½ for a number-average degree of polymerization of over about 2000. Two linear equations are derived pertaining to the present analysis, one to deal with the experimental data, and the other specially to estimate the intrinsic viscosity [η]θ which corresponds to κHθ. All calculations were done by the linear least-squares method. The Kθ was computed by the Mark–Houwink–Sakurada equation. It is shown that reliable results on Kθ can be obtained for polystyrene and poly(vinyl acetate).

The classical expression for estimating the polymer-solvent interaction parameter χ from melting point data of the solvent is refined by considering χ to be concentration-dependent. Differential scanning calorimetry (DSC) measurements are performed on blends of cis-polyiso-prene-dimethyl terephthalate (DMT) and trans-polyisoprene–DMT. It is found that the presence of DMT would not affect the DSC events of the polyisoprenes appreciably. However, in both cases, the melting point of DMT decreases, and the rate of depression increases with increasing proportions of polymer. These DSC data are analyzed by the proposed procedure. The results on the interaction energy density parameter are presented as a function of the blend concentration, and rationalized by the specific interactions between different moieties on the component molecules. The limitations of the present technique are discussed.

Capillary extrusion flow curves of four anionic and five polydisperse polystyrenes have been measured at five temperatures between 170 and 237°C. The non‐Newtonian flow curves of the narrow distribution polymers can be represented by a common master curve in terms of the viscosity ratio (η/η0) and the product of shear rate and a relaxation time. The polydisperse polymers do not yield a single flow curve. Current molecular and semiempirical models do not yield master curves which fit the experimental plots. Exceptions are Pao's model for monodisperse polymers and an empirical relation presented in this article which fits the data of the five commercial polymers studied. The existence of a general theory which represents experimental polymer flow curves satisfactorily has yet to be demonstrated. An acceptable model should predict rheological parameters correctly and should also show why experimental data for polymer melts scatter rather severely. Such scatter often reflects lack of control of an important e...

A three-parameter equation is put forward to evaluate the [η] of polymer solution from a wide range of concentrations, up to a relative viscosity of 100. The equation is tested by viscometric data of polystyrene, poly(vinyl chloride), poly(1-vinylnaphthalene), poly(2-vinylnaphthalene), and poly(4-vinylbiphenyl) at different temperatures and in a variety of solvents including mixed solvents. A statistical method is employed to analyze the experimental data. It is found that the values of [η] obtained by the new equation are consistently lower than those derived from the Huggins equation. However, the discrepancy is not more than 3% on average, and it does not affect the values of Mark-Houwink constants significantly. Other parameters of the equation are also computed.

A new approach pertaining to the hole and lattice theories of polymeric systems is developed to interpret the universal inverse relationship between the glass transition temperature (Tg) and the difference in thermal expansion coefficients for liquid and glassy polymers (δ α). The success of this particular theoretical consideration rests upon the familiar hypothesis of the iso-free volume state at Tg and the entropy contribution to the hole-polymer segment interaction energy. Based on the experimental data available, we have established the free volume fraction at Tg, vg = 0.025, which is identical with the assessment of the empirical Williams-Landel-Ferry (WLF) equation for the temperature-dependence shift factor aT. However, appreciably higher values of vg are reported by other contemporary models. The present findings justify an alternative form of the WLF equation with the product Tg, δ α playing the role of δ α. The universality of this novel expression is demonstrated, by means of statisti...

The general validity of four single-point methods for intrinsic viscosity ([η]) determination is verified to be unacceptable even for dilute polymer solutions. Also, a direct method based on a truncated version of Huggins equation is shown to be less practical in that it involves advanced experimentation and is valid only at sufficiently low concentrations. In view of the shortcoming and sophistication of the above procedures, an effective approach is introduced to resolve these problems. This novel computation expresses the Huggins coefficient in terms of [η], and the associated equations are calibrated against the polymer system of interest. This procedure is tested using various polymer solutions with results compatible with those acquired by other means. The advantage of the proposed technique is discussed.

A linear equation is proposed to quantify the glass transition behavior of miscible polymer blends in terms of the polymer-polymer interaction density parameter whose values are obtainable from the melting point depression method. This practical model is successfully applied to four series of binary polyblends containing poly(hydroxy ether) of biphenol A, poly(vinyl chloride), poly(vinylidene fluoride), and poly(2,4-dimethyl-1,4-phenylene oxide) as the common components. Each of these groups of polymer systems exhibits a distinct type of intermolecular interaction that can be characterized by the two coefficients of the model equation. In connection with the present analysis, three novel expressions are introduced for describing the glass transition temperature—composition relations of the polymer systems of interest.

An inexpensive, accurate falling coaxial cylinder viscometer is described. Viscosities can be measured at shear stresses at least as low as 103 dynes per cm2 and flow curves can be obtained with shear thinning fluids. Data for a polystyrene and a polyethylene polymer coincide with those from other techniques and with corresponding literature values. The lower Newtonian viscosities pf both polymers were experimentally accessible, and it is shown that estimation of ηo by extrapolation from viscosities in the non-Newtonian region may be subject to errors of uncertain magnitude. Shear history of the sample affects the Newtonian and low shear viscosities of high molecular weight polymer melts. On decrit un viscosimetre non-coǔteux dans lequel on peut determiner avec exactitude le temps de chute d'un cylindre coaxial dans un fluide. On peut mesurer des viscosites correspondent a des efforts de cisaillement aussi faibles que 103 dynes au centimetre carre et peut obtenir des courbes d'ecoulement pour des fluides dont la viscosite est reduite par le cisaillement. Les resultats obtenus dans le cas de deux polymeres (polystyrene et polyethylene) concordent avec ceux qui proviennent d'autres methodes et avec les valeurs correspondantes qui ont ete publiees. On a pu determiner experimentalement les viscosites newtoniennes plus faibles des deux polymeres et demontre que l'estimation de ηo par extrapolation des viscosites dang le secteur non-newtonien peut ětre sujette a des erreurs dont l'importance est aleatoire. Le degre de cisaillement auquel ont ete soumis les echantillons affecte les viscosites newtoniennes et a cisaillement faible des polymeres fondus qui possedent un poids molceulaire eleve.

The specific volumes of anionic polystyrenes with molecular weights between 9,000 and 700,000 have been measured at 170–237°C. The volumes attributable to end groups differ between anionic and thermally initiated polystyrenes. Uncertainties in average molecular weights of short chain polymers have a critical influence on conclusions as to the influence of molecular weight and temperature on polymer melt density and related phenomena.