On the single-point determination of intrinsic viscosity

In the present paper we have analytically derived a single-point equation for determining the intrinsic viscosity of a polymer. It is observed that the proposed equation gives a much better agreement with the extrapolated value of [η] over a wide range of concentration for good as well as poor polymer–solvent systems.     

PET切片特性黏度测定方法的探讨

通过准确测定pET切片特性黏度溶剂在25℃时的密度,计算出25 mL该溶剂的准确质量,实现了用称量溶剂质量的方法替代恒定温度下移取溶剂体积的方法,使得测定聚酯特性黏度的方法更加准确,简便了操作;在日常分析过程中,对溶剂苯酚/1,2-二氯苯(质量比:1:1)与苯酚/1,1,2,2-四氯乙烷(质量比:1:1)测定聚酯切片特性黏度结果进行跟踪比对,2种溶剂测定结果一致,证明苯酚/1,2-二氯苯(质量比:1:1)溶剂可以作为测定PET切片特性黏度的溶剂。     

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.     

聚合物特性黏度与在线黏度测量相关性实例分析

通过不同配方的特性黏度和在线黏度的实测案例,对特性黏度和在线黏度测量结果的相关性、数据转换和偏差进行分析,结果表明,聚合物特性黏度和在线黏度测量值之间有很好的相关性,通过适当的数据转换,在线黏度计可用于快速、实时、连续测量特性黏度。     

熔体流动时间法测定PBT树脂特性粘数的研究

开发了一种新的特性粘数分析方法 ,该方法采用熔体流动时间计算特性粘数 ,与经典特性粘数分析方法有很好的相关性且具有分析时间短、费用低、无污染等优点。     

A critical approach to viscosity index

The viscosity index (VI) is a useful tool for lubricant users and refiners, since it is a measure of the effect of temperature changes on the viscosity of the oil. However, it was found that the viscosity index does not correlate with the flow activation energy E_a, which is the theoretically defined dependence of the viscosity on temperature. In this way, two oils may have the same flow activation energy but a viscosity index varying by up to 120. We therefore believe that the VI does not always give a proper representation of the effect of temperature on the kinematic viscosity.¹³C NMR spectroscopy was used to identify the molecules with a high VI. Twenty different oil samples produced from eight different vacuum gas oils with viscosity indices ranging from −104 to 146 were analyzed and key parameters identified for high VI molecules: long alkyl chains, methyl branching in the centre of the molecule, low content of aromatic compounds, no ethyl branching and no tertiary carbons.A correlation based on four selected peaks was developed, giving a very good prediction of the viscosity index.     

Determination of intrinsic viscosity by single specific viscosity measurement

Single point determination of intrinsic viscosity saves considerable amount of time, effort and materials. Quite a few equations are available in the literature which require relative viscosity of the polymer solution at a single concentration for calculation of [η]. A comparative assessment of the applicability of two such equations and that of a proposed one has been made by using reported data as well as the practical data on viscosity of alkyd solutions in different solvents. It is inferred from the findings that, for good results from single point methods, the concentration should not be the sole criterion, as suggested by earlier workers; η_sp may also be considered as one of the criteria. The single point technique is found to be applicable to alkyd solutions in different solvents.     

Comparison of various solvents for determination of intrinsic viscosity and viscometric constants for cellulose

Different solvents used to determine the intrinsic viscosity and the viscometic constants, a and K, published in the literature for cellulose, were compared. The various parameters affecting the viscometric constants were also evaluated. The main conclusions obtained from the experimental data available in the literature are that (1) the intrinsic viscosities in various solvents are ordered as follows: [η]_LiCl/DMAc > [η]_NH3/NH4SCN ≥ [η]_FeTNa > [η]_CED > [η]_Cadoxen > [η]_Cuoxam; (2) the reported intrinsic viscosities and molecular weights for cellulose are lower than the true value due to degradation of cellulose in the solvents; (3) the rate of degradation was the smallest in LiCl/DMAc and NH₃/NH₄SCN, moderate in cadoexn and FeTNa, and the highest in CED and cuoxam; (4) the plot of log K versus exponent a was linear and inversely related; (5) the curve was used for estimation of the constant K for cellulose in a solvent (NH3/NH4SCN) with a known exponent a; and (6) among various reported solvents, LiCl/DMAc and NH₃/NH₄SCN are advantageous over other solvents because of a complete dissolution of the polymer with a negligible reduction in its intrinsic viscosity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2189–2193, 2002     

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.     

The effect of shear rate on the molecular weight determination of acrylamide polymers from intrinsic viscosity measurements

The rheological response of dilute solutions of high molecular weight polyacrylamides at low shear rates has been measured using a capillary viscometer that provided for a fivefold variation in shear rate at each concentration. The non-Newtonian effects were found to be significant for polyacrylamides with number-average molecular weights exceeding 10⁶. The molecular weight average–intrinsic viscosity relationship most widely used in the literature, [η] = 6.80 × 10^?4M , was found to be valid when [η] was measured at high shear rates where the polymer solutions approached Newtonian behavior. A new relationship was developed relating M _n to the intrinsic viscosity extrapolated to zero shear rate.     

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.     

Determination of intrinsic viscosity of polyelectrolyte solutions

Intramolecular hydrodynamic contribution η_intra/C to the reduced viscosity η_SP/C of polyelectrolyte solutions is derived as a function of polymer concentration C by separating the theoretically calculated intermolecular electrostatic contribution η_inter/C from the observed reduced viscosity, assuming an additivity, η_SP/C=η_intra/C+η_inter/C. The resulting intramolecular part η_intra/C reflects nearly the net effect of the polyion conformation; it increases monotonously with decreasing polymer concentration and levels off to a constant in sufficiently dilute concentrations. The leveling-off value of η_intra/C corresponds to the intrinsic viscosity [η]. From the estimated values of [η], the ionic strength I dependence of the polyion conformation has been visualized, resulting in a similarity between two relations, η_intra/C vs. C and [η] vs. I.     

聚酯特性粘数测试方法的比较

阐述了相对粘度仪法和传统玻璃毛细管粘度仪法的测试原理,实验验证了Y501相对粘度仪和LAUDACD30粘度仪测试结果的差异性。结果表明其差异性不大,相比LAUDACD30粘度仪,5（501相对粘度仪的测试精度及自动化程度更高、有利环保,更具有实用性和快捷性。     

Prediction of solubility parameter from intrinsic viscosity

Polymer for coating such as epoxy and alkyd resin use additives for enhancing physical properties, hardening acceleration, and decreasing viscosity. Therefore, diluent selection is important for blending of additives in the resin. The choice of these solvents is determined by comparing the solubility parameters. In this study, it is a measure of the intrinsic viscosity of epoxy resin by Ubbelohde viscometer and epoxy resin is calculated solubility parameter through intrinsic viscosity. The epoxy and alkyd resins’ solubility parameters were calculated from their intrinsic viscosities to be epoxy resin (${\delta }_{2d}=16.55$, ${\delta }_{2p}=5.98$, ${\delta }_{2h}=6.53$) and alkyd resin (${\delta }_{2d}=19.11$, ${\delta }_{2p}=3.96$, ${\delta }_{2h}=4.86$), respectively. Their total solubility parameters were calculated to be epoxy resin (${\delta }_{2t}=18.77$) and alkyd resin (${\delta }_{2t}=20.11$), respectively.     

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.