凝胶渗透色谱在酚醛树脂合成中的应用

利用凝胶渗透色谱法(GPC)讨论了流速及酚醛树脂样品浓度等对测试结果的影响,建立了最佳测试条件:流速1 mL/min,样品浓度(6±1)g/L。跟踪测定了碱催化酚醛树脂合成过程中的分子质量及其分布变化情况。结果表明:通过GPC图谱可直观地了解不同合成阶段树脂分子质量及其分布状况,同时GPC谱图可作为判定树脂质量的依据。     

Analysis of phenol-formaldehyde resols by gel permeation chromatography

The chromatographic analysis of resol solutions in tetrahydrofuran solvent, by means of a set of columns packed with crosslinked polystyrene gels, has been carried out with adequate resolving power for a clear-cut qualitative or semiquantitative differentiation between various types of resols to be practicable. The resulting chromatograms, which show the distribution of different constituents by molecular size, could be interpreted by the use of reference substance and by calibrating the system with a number of compounds of known structures. The method has been used to investigate the way in which various reaction parameters (nature of catalysts, proportion of starting material, treatments undergone by the resols) affect the composition of resols. Different commercial products have been thus characterized. It has also afforded an insight into the progress of the polycondensation reaction as a function of time and helped to state the reactivity of different groups and unblocked ring positions. Thus, an hydroxymethyl group appears to be more reactive in the para than in the ortho position. Otherwise the reactivity of unblocked ring positions would be enhanced by an hydroxymethyl group in the ortho rather than para position.     

Block copolymer molecular weight determination via gel permeation chromatography: Choosing a combining rule

We present a method for accurately determining the true molecular weights of narrow‐distribution block copolymers, using only a basic gel permeation chromatograph (GPC) equipped with a refractive index detector and calibrated with polystyrene standards. Our approach is based on the well‐known observation that GPC calibration curves for different homopolymers in good solvents are essentially parallel, allowing the curves for different polymers to be described by simple hydrodynamic equivalence ratios r_B versus polystyrene. We present values of r_B, in both toluene and tetrahydrofuran, for various polydiene and hydrogenated polydiene homopolymers commonly incorporated into commercial styrenic block copolymers. These values of r_B must be combined to yield the hydrodynamic equivalence ratio of the block copolymer, from which the block copolymer's true molecular weight can be determined. Three combining rules proposed in the literature are tested against a series of symmetric polystyrene–polybutadiene diblock copolymers of varying molecular weight. A simple linear combining rule accurately represents the results. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2056–2069, 2001     

凝胶色谱法测试PVC树脂平均分子质量及分子质量分布

叙述了凝胶色谱法的测试原理,介绍了用凝胶色谱测试PVC树脂平均分子质量及分子质量分布的方法。     

Prediction of molecular weight distribution of cellulose by using the rheological method

In this article, a rheological method that can predict the molecular weight distribution (MWD) of polymer was introduced. Using this method, the MWDs of four cellulose samples were compared from rheological data of the cellulose / N‐methyl morpholine N‐oxide (NMMO) / H₂O solutions. The MWDs of cellulose also were determined by gel permeation chromatography (GPC) calibrated with narrow distribution polystyrene standards, using 0.5% lithium chloride (LiCl) in N,N‐dimethylacetamide (DMAc) as the eluent. Comparison of the results from rheology and GPC showed that the MW and MWD of cellulose could be roughly inferred from their rheological data. Although the differential MWD obtained from the rheological method was bell shaped and can not reflect the fine characteristics of cellulose as GPC, it may be feasible to compare the MWDs of cellulose by using the rheological method. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 598–603, 2004     

Molecular weight distribution of polyacrylonitrile produced in supercritical CO2

An effectively linear molecular weight calibration curve of polyacrylonitrile (PAN) was obtained using a copolymer standard with a single broad molecular weight distribution. The molecular weights and molecular weight distributions of PAN obtained from precipitation polymerization of acrylonitrile in supercritical CO₂ were quantitated by the calibration curve. The effects of monomer concentration, initiator concentration, the CO₂ pressure, and the total reaction time on the molecular weight and molecular weight distribution were studied in detail. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2338–2341, 2002     

GPC技术在合成纤维相对分子质量及其分布测试中的应用

综述了凝胶渗透色谱(GPC)技术在腈纶、涤纶、聚酰亚胺纤维、氯纶、氨纶、尼龙纤维和聚乙烯醇纤维的相对分子质量及其分布测试中的应用的研究进展.重点对各合成纤维的GPC测试条件进行了总结,揭示了色谱条件的优化机理,并对GPC方法开发方向及在合成纤维工业中的进一步应用提出了建议.指出在以后的合成纤维生产和研究过程中,可以挖掘...     

Molecular weight distributions in novolac type phenol-formaldehyde polymerizations

In the acid-catalysed condensation polymerization of phenol and formaldehyde, the ortho and para positions of the phenol ring are known to exhibit different reactivities^1,2. Along with this on polymer molecules, the internal sites have lower reactivity due to molecular shielding. To model the novolac formation, five reactive sites have been proposed³ and their reactivities are assumed to be completely determined by the site involved. To find the molecular weight distribution (MWD) of the polymer from this information, a given polymer chain has been assumed to consist of these sites in the same relative ratio as in the reaction mass. A mass balance, on polymer molecules of given size, has been made and solved numerically as a function of time. The sensitivity analysis has been carried out to show that the MWD is little affected by the variation of reactivities of the internal sites. The reactivity of para external positions and the ratio of phenol and formaldehyde, however, play a major role in determining the MWD.     

凝胶色谱法测定木素分子量及其分布

综述了凝胶色谱法测定本素分子量及其分布的方法和取得的进展。新型高效凝胶位的出现,使凝胶色谱法可以测定多种本素分子量。用凝胶色谱法测定木素的分子量,需要根据样品的性质选择色谱技、流动相和标样,并通过实验确定合适的色谱条件。本素样品可能需要经过适当的预处理以适应色谱柱和流动相的要求。     

Comparison of molecular weight distribution models for polymers characterized by g.p.c.

A semi-empirical model which employs polynomials based on general free radical polymerization kinetics, is developed to describe the molecular weight distribution data as well as to evaluate the average molecular weights of a variety of commercial thermoplastics including polystyrene, poly(methyl methacrylate) and low density polyethylene. These novel expressions are equally applicable to a natural rubber sample with a bimodal distribution. Least-squares methods for the classical Schulz and Flory distribution functions are introduced to handle the g.p.c. data of the above polymers. Comparison of the results collected from various analyses indicates clearly that the polynomial model is the most versatile one in the sense that it can be utilized to smooth out satisfactorily the molecular weight distribution data of many polymers. In general, the Wesslau distribution function is particularly good for the highly branched polyolefin and the Schulz model is fairly effective for the addition polymers of moderately sharp molecular weight distribution, presumably with $\text{M}\text{?}{}_{\mathrm{<mtext>w</mtext>}}\text{M}\text{?}{}_{\mathrm{<mtext>n</mtext>}}\text{=3.0}$. However, the Flory and Tung distributions are found to be rather inferior in the present studies. On the basis of the current findings, a new procedure is suggested to facilitate the computations of the true average molecular weights from g.p.c. data directly.     

Kinetics of petroleum pitch polymerization by gel permeation chromatography

The thermal polymerization kinetics of petroleum pitch molecules with molecular weights (MW) between 400–2000 were studied utilizing gel permeation chromatography (GPC). Two distinctly different reaction mechanisms of the petroleum pitch were observed from the GPC curves during transformation of the pitch to mesophase and semi-coke. When mesophase is forming in the pitch, molecules in the MW range of 400–700 were the most reactive, while molecules with MW greater than 1200 were essentially unreactivc. This lack of reactivity of the larger molecules ensures that the mesophase remains highly fluid during its formation. A change in reaction mechanism occurs after the mesophase has solidified as a result of the thermal polymerization reactions. At this stage, there is an abrupt decrease in the reactivity of molecules with MW less than 1100 and the reactivity of all measured molecules is the same. This significant kinetic change is due to a physical phenomenon in which solid state reactions occur in the infusible (vitrified) polymerized pitch. The significantly reduced reaction rates occurring in petroleum pitch after vitrification are similar to the results observed for other thermosetting materials.     

Molecular weight distribution of polyphenylene sulfide by high temperature gel permeation chromatography

Poly(phenylene sulfide) (PPS) has been characterized using a novel high temperature gel permeation chromatograph (GPC). Samples were injected in slurry form at ambient temperature, and redissolved by an in-line precolumn heater at 250°C. A viscometer consisting of a capillary tube with inlet and outlet taps connected to a sensitive differential pressure transducer was used as sole detector, with deflections converted to concentration using the column calibration. Columns and viscometer were operated at 210°C. Universal calibration was carried out using intrinsic viscosity/molecular weight relations for polystyrene and PPS, determined by light scattering. Satisfactory operation was confirmed by agreement between intrinsic viscosity calculated from GPC with independently measured values, and comparisons with melt flow data. Samples of PPS tested were found to be of relatively narrow distribution, with M_w/M_n typically less than two.     

凝胶渗透色谱法测定聚丙烯腈共聚物的平均分子量及分布的研究

通过一系列的条件试验，确定了最佳的凝胶渗透色谱（Gel Permeation Chromatography简称GPC）试验条件。采用宽分布的聚丙烯腈共聚物（Polyacrylonitrile简称PAN）标准样品，通过编制的计算机程序，模拟计算出PAN的GPC校正曲线方程，对宽分布的标准样品进行重复测定。重现性试验结果符合误差要求。本方法快速准确，可满足生产和科研的需要。     

Can porosity properties of particles really be determined by inverse gel permeation chromatography?

Inverse gel permeation chromatography can be fruitfully used for the texture determination of porous mineral beads. However for swelling macroporous gels the same procedure may lead to flagrant errors, which are pointed out on some examples. Thermodynamic considerations explain such results and some ways to take into account perturbing effects are suggested.     

薄膜专用PP树脂加工性能的凝胶渗透色谱评价

用凝胶渗透色谱测定了不同批号的薄膜专用聚丙烯(PP)树脂T38F的相对分子质量及其分布,评价了产品的相对分子质量及其分布对加工性能的影响.测定结果的重复性和再现性良好.根据分析结果调整相关工艺条件后生产的PP T38F能够满足用户的加工要求.实验结果表明:薄膜专用PP树脂的重均分子量(Mw)控制在(25.0～29.0)...     

凝胶渗透色谱联用技术测定树脂分子质量

介绍了当前凝胶渗透色谱法测定树脂分子质量及其分布的情况,并将凝胶色谱柱与不同的检测器相连,如与黏度计、静态光散射、质谱技术、核磁共振等联用的方法,并且比较了它们用于测定树脂分子质量时各自的特点。     

凝胶色谱法测定聚丙烯腈聚合物的相对分子质量及其分布

通过一系列的试验,确定了最佳的凝胶色谱试验条件:采用含有0.025 mol/L KNO_3的DMF为流动相;样品质量浓度为1 mg/m L,进样量200μL;柱温采用80℃,采用窄分布的聚苯乙烯为标样绘制标准曲线,然后采用纯PAN标样校正仪器。该方法快速准确,具有良好的重现性,可满足生产和科研的需要。     

凝胶渗透色谱法测定瓶级PET切片相对分子质量的制样方法优化

样品制备是凝胶渗透色谱(GPC)测定瓶级PET切片分子质量的一个关键因素,样品剪切方法的差异、烘箱温度的误差、加热时间的变化、溶剂和溶解方法选择的不同等都有可能影响到测试的结果。通过优化以上这些因素可以使得测试结果更为准确。     

A study of micelles in a base lubricating oil by gel permeation chromatography

Micellar solutions of two polystyrene-poly(ethylene/propylene) block copolymers in a base HVI lubricating oil were studied by gel permeation chromatography (g.p.c.). The Styragel columns employed in the work were calibrated using polyisobutylene fractions. At 50°C each copolymer solution gave a single sharp peak which was well within the resolution of the columns, indicating that the micelles were able to enter the pores of the Styragel and elute through the columns as stable particles. Analysis of the chromatograms showed that the micelles had narrow size distributions. Light scattering provided a method of determining the weight-average molecular weights and apparent mean-square radii of gyration of the micelles. Molecular weights determined from g.p.c. using the universal calibration procedure were in fair agreement with the light scattering values. Unfortunately g.p.c. experiments attempted over the range 75°–150°C were unsuccessful because the Styragel strongly absorbed the copolymer at these higher temperatures.     

聚丙烯腈原丝相对分子质量及其分布的测试

采用凝胶渗透色谱仪（GPC）测定了聚丙烯腈（PAN）原丝的相对分子质量及其分布,对比了国产PAN原丝与进口原丝分子量及分布的差异,结果表明,相对于进口PAN原丝,国产PAN原丝相对分子质量分布较宽,并可能存在凝胶或微凝胶现象。最后分析了测试过程中的主要影响因素及其解决方法,提出严格控制实验和环境条件,注意仪器的保养和监控,是确保测试结果准确性的关键。