A one-point intrinsic viscosity method for polyethylene and polypropylene

A statistical analysis of dilute solution viscosity data for a wide range of polyethylene and polypropylene samples in Decalin at 135°C has shown that the Martin equation fits the experimental data better than the Huggins equation at higher values of [η]c. A grand average k of 0.139 is applicable to both polymers. Based upon this, tables have been calculated permitting the ready determination of [η] from a single relative viscosity measurement at a known concentration. The Martin equation has been put into a universal form, permitting [η] to be calculated from a measured η_sp if k and c are known. Graphs relating η_sp to [η] are included for use of the Martin equation over wide ranges of both k and c. It was found that the Solomon and Ciuta equation fits the experimental polyethylene and polypropylene data, and the reasons for this are discussed.     

Viscosity properties of aqueous solutions of carboxymethylcellulose and hydroxyethylcellulose blends

The possibility of using hydroxyethylcellulose (HOEC) as a modifier polymer for regulating crosslinking processes in Na-carboxymethylcellulose (CMC) solutions was established. The effect of differences in the conformation of the macromolecules of miscible polymers not only on the intensity of intermolecular interaction but also on structuring of the solution was revealed. The decrease in the total concentration of components of the solution and the molecular mass of one of the miscible polymers causes the appearance of individuality of the macromolecules, confirmed by the deviation of the thermodynamic characteristics of viscous flow from additivity. __________ Translated from Khimicheskie Volokna, No. 1, pp. 11–14, January–February, 2007.     

An alternative method for evaluation of intrinsic viscosity

An alternative method for determination of intrinsic viscosities is described which evolves from the application of l'Hǒpital's rule to the expression defining the intrinsic viscosity. The method yields independent evaluations of the intrinsic viscosity and does not involve extrapolation beyond the range of experimental data or rely on a theoretical expression associated with such extrapolations. The application of the method is illustrated and comparisons are included with the results obtained by traditional approaches.     

聚合物特性黏度称重增浓外推测试新方法

根据黏度测量基本原理建立了聚合物稀溶液特性黏度测试新方法——称重增浓外推法。使用这种方法测定了一系列刚性链大(键共轭结构聚合物的特性黏度,其比浓黏度ηsp/c以及比浓对数黏度In(ηr/c)分别与浓度的关系曲线均呈现良好的线性关系。和传统的稀释外推法以及单点法如Maron法、Solomon-Ciuta法和算图法相比,称重增浓外推法具有数据可靠、准确、低有机溶剂消耗和操作连续省时等优点。     

PET特性黏度分析离群值的判定方法

结合PET生产检验实例,使用方差分析发现特性黏度数据之间存在显著性差异,而使用国标中离群值检验判别法发现离群值的判定结论相反,在结论矛盾的基础上分析指出应正确识别系统误差及随机误差,合理应用各种检验方法,同时指出离群值判定方法与方差分析的结合使用有助于提高离群值判定的科学准确性。     

A new analytical method to calculate intrinsic viscosity and viscosity constants of polymer–solvent systems

Experimental viscosities were measured by Schott Gerate viscometer at 30 °C for polystyrene–chloroform and polycaprolactum–benzene systems. These data were analyzed by a newly developed analytical method to calculate intrinsic viscosity and viscosity constants. The analytical method was compared with the graphical as well as the least squares methods and the new analytical method is better than the graphical method because it avoids personal errors that might arise in reading the intercept and slope values from the reduced viscosity versus concentration plots. Furthermore, the analytical method is as effective as the least squares method, but provides better insights while choosing the experimental viscosity values. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 283–290, 2002     

超高相对分子质量聚乙烯特性黏数的测试方法

采用毛细管黏度计法测定超高相对分子质量聚乙烯(UHMWPE)的特性黏数([η]),对[η]的准确测定的影响因素进行了探讨。结果表明:以十氢萘为溶剂,使用前进行蒸馏提纯;在配制UHMWPE溶液时,加入质量分数为0.2%的抗氧剂1010,按预溶胀、溶胀、溶解3步骤进行溶解,溶解温度150℃,溶解时间0.5 h,配制UHMWPE溶液浓度为100~600 mg/L;严格控制温度(135±0.2)℃,所测UHMWPE的[η]平行性较好,相对标准偏差为1.08%。     

Practical use of intrinsic viscosity for polyethylenes

Although usually derived from measurements at several concentrations, intrinsic viscosity (IV) can be determined with good precision from a single measurement. IV tends to be a regular and distinct function of melt index (MI) for each family of high-density polyethylenes. The tendency to regularity suggests a use in routine control, uniform production being marked by a small scatter about the IV–MI line. The distinctiveness marks one family of medium high and high-density resins from another, and becomes a rapid means of identifying the production method of a resin. Further, IV at a given MI correlates roughly with properties, and can be used to characterize a resin. These attributes of the IV–MI relationship arise from the correlation of IV a t a given MI with width of molecular weight distribution. Such width varies considerably among commercial high-density polyethylenes, causing a commensurate variation in IV. Among low-density polyethylenes the IV–MI relationships is less useful, being confused by long-chain branching.     

A method for determination of thermodynamic and solubility parameters of polymers from temperature and molecular weight dependence of intrinsic viscosity

An equation using the temperature dependence of intrinsic viscosity of a polymer was proposed for the determination of the partial molar entropy and enthalpy changes of the polymer for mixing in dilute solution. It was found that the partial molar entropy change of a polymer for mixing at a given temperature is proportional to the hydrodynamic volume or segment number of the polymer. The partial molar enthalpy change of the polymer for mixing was determined from the thermodynamic equilibrium property of polymer phases. The solubility or cohesion parameter of a polymer fraction was calculated by using the partial molar enthalpy change and repeat unit volume of the polymer. The solubility parameter of high molar mass polymer at a given temperature was determined by extrapolating solubility parameter values of polymer fractions to high molar mass by using the solubility parameter-segment number relation of polymer fraction. This relation gives a straight line. The solubility parameter of the polymer at a given temperature and the effective interchange energy parameter for polymer-solvent pair were obtained directly from the intercept and the slope of this line, respectively. These equations were applied to the intrinsic viscosity-temperature data of polystyrene fractions in decalin solutions, and polystyrene fractions in decalin, cyclohexane and dioctyl phthalate solutions at the theta temperatures and in toluene solutions at the given temperatures. The results obtained in this study coincide with the literature values. In addition, it was given a relation, which is derived from the blob theory for the temperatures above the theta point, for the estimation of the thermodynamic parameters of polymers for mixing.     

Four modified sodium alginate/carboxymethylcellulose blends for prednisone delivery

Polysaccharides have been widely used for the development of drug delivery systems. These systems can be physicochemically modified to enhance their stabilities and control their drug release profiles. However, such modifications cannot alter their biocompatibility or toxicity. Herein, four structurally modified sodium alginate/carboxymethylcellulose blends are synthesized and loaded with prednisone, and the effects of the modifications on their hydrolytic degradation rates, biocompatibilities, toxicities, and drug release profiles are investigated. All the blends are ionically cross-linked with Ca²⁺ and Fe³⁺. Blend 1 is not modified further, blend 2 is additionally reinforced with 8% w/w of cellulose nanocrystals, blend 3 is treated with epoxidized linseed oil to develop a hydrophobic layer, and blend 4 is chemically cross-linked with epichlorohydrin. Blends 2 and 4 exhibit similar physicochemical characteristics, appropriate hydrolytic degradation rates and drug release patterns, as well as biocompatibility and non-toxicity. In-vitro studies using the osteoblasts and CAM assay demonstrate that blends 2 and 4 are also biocompatible and non-toxic. In contrast, blend 1 exhibits the highest drug release rate, followed by blend 3.     

Relation between intrinsic viscosity and molecular weight

The connection between intrinsic viscosity and number-average and weight-average molecular weight has been revealed by calculations from distribution curves. Log-normal distributions, and moderate variations thereon, were chosen as typical for polystyrene and other thermoplastics. Intrinsic viscosity and number-average molecular weight are unlikely to be related because of the highly disturbing effect of small variations in molecular weight distribution. Conversely, intrinsic viscosity is a good practical measure of weight-average molecular weight up to a ratio of 10 for weight-to-number average.     

高粘聚酯切片特性粘数测试方法的优化

针对高粘PET样品的特性,通过试验对比,对聚酯特性粘数分析测试方法中规定的样品粉碎时间及称样量进行了优化,得到了适用于高粘PET样品特性粘数测试的最佳测试条件。     

Ionotropic crosslinking of sodium carboxymethylcellulose and sodium carboxymethylcellulose-gelatin matrices and their erosion properties

Hydrophilic sodium carboxymethylcellulose (NaCMC) matrices were chemically modified into hydrophobic gels by ionotropic crosslinking with cupric or ferric ion under ambient temperature and pH. Insoluble matrices were also prepared using an interactive polymer gelatin in combination with NaCMC. These matrices underwent erosion at the crosslinks, followed by matrix erosion when released in water. The matrix erosion in water was influenced by the gelling agent, initial crosslinker density, and gelatin content in the insolubilized matrices. The apparent diffusion coefficients of fenthion ranged from 7.2 × 10^?9 to 175.6 × 10^?9 cm²/sec, with matrices prepared under different conditions. These erosion-controlled matrices can be used for the controlled release of various biologically active agents. © 1993 John Wiley & Sons, Inc.     

羧甲基纤维素钠接枝型高分子表面活性剂的合成及评价

运用正交试验法及主成分分析法研究了反应的温度、时间、配比3个主要因素对羧甲基纤维素钠接枝型高分子表面活性剂接枝率、单体转化率的影响,并就产物进行了相关基本物性分析。     

A critical evaluation of the single-point determination of intrinsic viscosity

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.     

One-point determination of intrinsic viscosity for polycarbonate,poly(phenylene oxide), and polyetherimide

Intrinsic viscosity determination for polymers can be simplified and considerable time and effort saved via a single measurement of relative viscosity at a known concentration. Several workers have proposed one-point intrinsic viscosity methods. Of the methods in the literature, two one-point methods were found to be as accurate as the multiple-point graphical extrapolation procedure. These two methods, one due to Solomon and Ciuta and a nomographic technique due to Khan and Bhargava, were successfully applied for the intrinsic viscosity determination of three polymers: polycarbonate, poly(phenylene oxide) and polyetherimide.