热塑性复合材料本构方程及应用

近年来,许多新型复合材料不断涌现,如热固性复合材料和热塑性复合材料等。这些材料在航空、航天、建筑等领域得到日益广泛的应用。因此,对这些材料力学性能的研究已引起国内外高度重视。本文根据弹性理论,考虑到流体不可压缩的条件,分析热塑性复合材料的力学性能,得出粘性各向异性、横观各向同性材料本构关系;通过细观力学研究,导出材料的粘性参数η11,η12,η22,η23;通过对层合板力学变形的研究,导出粘性各向异性层合板的膜应力和应变速率之间的关系及其实际粘性参数η-ij′,并对所得结果进行讨论。     

聚醚多元醇／液化MDI反应的化学流变性研究

采用自制的恒扭矩粘度计，通过测量聚醚多元醇／液化ＭＤＩ反应过程中绝热温升和恒扭矩电机转速，得到了反应注射成型中反应程度α和相对粘度ηｒ的关系，。利用反应程度α与时间ｔ的关系得到了反应动力学方程为ｄα／ｄｔ＝ｋ（１－α）＾３。并提出了很好描述化学流变性的具有较简单形式的经验方程ｌｎηｒ＝０．０９１α／０．６９－α。     

XP—1型高速卷烟胶粘剂的制备

采用复合改性技术，制得的ＸＰ－１型高速卷烟胶具有初粘性高，干燥速度快，粉接强度高，胶质细腻，废品率低的特点，可以满足车速在６０００～８０００支／分钟的要求。     

油品芳烃含量对充油1，2－聚丁二烯橡胶流变性的影响

研究了油品芳烃含量为５１％～９０％时，充油１，２－聚丁二烯橡胶（１，２－ＢＲ）的流变性、门尼粘度ＭＬ１００℃（１＋４）、抗湿滑性和力学性能的变化规律。结果表明，在同一剪切速率γｗ下，高芳烃含量的充油１，２－ＢＲ与低芳烃含量的相比，表观粘度ηａ增大，流变曲线斜率小，非牛顿性较强。充油１，２－ＢＲ的ＭＬ１００℃（１＋４）、抗湿滑性及拉伸强度随油品芳烃含量的增高而增大。在相同γｗ下，充油１，２－ＢＲ的ηａ随温度的升高而下降，１３０℃时的ηａ比７０℃的下降约半个数量级。     

应用毛细管流变仪研究ABS／PVC塑料合金的稳定性

应用毛细管流交仪研究了ＡＢＳ／ＰＶＣ塑料合金的稳定性。发现合金的对数表观粘度（Ｉｎηａ）与受热时间（ｔ）之间为折线关系；对数稳定时间（Ｉｎｔ）与绝对温度的倒数（１／Ｔ）之间为直线关系。同时对合金的４种稳定体系作了稳定时间、分解速率以及颜色变化综合考查，确定了最佳稳定体系。     

高温法二醋片可纺性表征方法初探

本文利用毛细管流变仪研究几种醋片丙酮纺丝原液的流变性。分析了粘流活化能与可纺性的关系。认为ΔＥη可作ＣＡ－丙酮纺丝原液可纺性的表征参数。ΔＥη越小，可纺性越好。ΔＥη大于８０ＫＪ。ｍｏｌ＾－１时，可纺性差。     

ST 增粘油在高温状态下的流变特性

本文研究的 ST 增粘剂与150~#中极压荐生油配制的润滑油,在高温状态下的增粘性,η—T 关系符合η=exp(A+B/T)~2式;油品粘度与增粘剂 ST 浓度关系符合1gη=1gηo+kC,而流变形态满足1gτ=1gK+n1gr。该油品用于轧钢机摆动台齿轮润滑取得较为理想的效果。     

立构嵌段聚丁二烯的研制 Ⅴ．立构三嵌段聚丁二烯的合成及动力学行为

以α－甲基萘锂（α－ＭＮＬｉ）为引发剂、二哌啶乙烷（ＤＰＥ）为调节剂、环己烷为溶剂的丁二烯负离子聚合体系，研究了ＤＰＥ／α－ＭＮｌｉ、聚合温度与聚合物１，２－结构含量关系，合成出１，２一结构近１００％的１，２－聚丁二烯（１，２－ＰＢ）和１，２－１，４－１，２－ＰＢ。反应动力学研究表明：１，４－ＰＢ与１，２－ＰＢ中单体浓度与反应速率呈一级方程关系；４０℃时，生成１，４－ＰＢ的反应动力学方程式为－ｄ［Ｍ］／ｄｔ＝０．２８［Ｃ］￣０．５［Ｍ］；ＤＰＥ用量增大，表观增长反应过度常数Ｋ＿ｐ￣η减小；求得不同条件下的表观增长活化能。     

PP/EVA/沸石共混体系流变性能研究

采用3211型毛细管流变仪，研究230℃下乙烯－醋酸乙烯共聚物（EVA）单一体系及聚丙烯（PP）／EVA／沸石共混体系的表观粘度（ηa）和EVA的用量、EVA中醋酸乙烯酯（VA）含量、不同性质偶联剂改性沸石粉体等的相互影响规律。结果表明：对于纯EVA体系而言，熔体的ηa随共聚体系中VA含量的增加而增加，且均高于本研究所用PP熔体的ηa；其变化趋势同VA含量没有明显的线性关系，同熔体流动指数测试结果有相同的趋势。在PP／EVA沸石共混体系中，共混溶体的ηa均高于PP／沸石共混体系。对沸石表面采用极性化改性，所得共混溶体的ηa有所降低，证明采用不同偶联剂对粉体表面改性可以导致共混体系中不同结构的形成。     

普通工业玻璃退火与应力的几个问题：Ⅱ在退火温度范围内恒温下玻璃中应力

探讨了玻璃在退火时应力松弛的机理，提出研究应力松弛规律必须在恒温条件下（静态条件）和变温下（动态条件下）两个方面来讨论。文中深入地对静态条件下应力松弛计算作了探讨。指出了著名的Ａｄａｍｓ公式１／σ－１／σ０＝Ａｔ的不足。文中从Ｂｏｌｔｚｍｅｎ公式出发利用已知的粘度与温度的加和关系计算了以退火温度范围内粘滞流动活化能△Ｅη和应力松弛活化能△Ｅα，并由此导出了应力松弛时间τ与温度关系的计算式，进而又推     

Determination of the elastic component for polymeric melt under steady shear flow

Steady state shear flow in rectilinear coordinates can be generated by a direct shear rheometer. The rheological behavior of polymeric melts under shear flow can be characterized by the inception of steady shear flow and stress relaxation after cessation of steady shear flow. Experiments were performed for bisphenol A polycarbonate with various mol wts. The elastic components, such as the primary normal stress differences and the elastic recoverable shear strain of the polymeric melts, can be determined from the shear moduli. © 1993 John Wiley & Sons, Inc.     

Review of the hierarchical multi‐mode molecular stress function model for broadly distributed linear and LCB polymer melts

We developed a novel Hierarchical Multi‐mode Molecular Stress Function (HMMSF) model for linear and long‐chain branched (LCB) polymer melts implementing the basic ideas of (1) hierarchical relaxation, (2) dynamic dilution, (3) interchain tube pressure, and (4) convective constraint release. With a minimum number of nonlinear free parameters and remarkable quantitative predictions of the rheology of polymer melts, this model is an outstanding option for the simulation of different processing operations in the polymer industry. The excellent predictions of this model were demonstrated in uniaxial, equibiaxial, and planar extensional deformations for linear and LCB melts, as well as in shear flow for a LCB polymer, with a minimum number of adjustable free nonlinear material parameters, that is, one in the case of extensional flows, and two in shear flow. In this contribution, we review the development of the HMMSF model and present a reduced number of well‐defined constitutive relations comprising the rheology of both linear and LCB melts. We also extend the comparison of model and data to cover the shear flow of a linear polymer melt. POLYM. ENG. SCI., 59:573–583, 2019. © 2018 Society of Plastics Engineers     

注射成型中模腔内振动剪切流动的理论模型

采用Ｌｅｏｎｏｖ本构模型,首次研究了在注射成型中模腔内聚合物熔体的振动剪切流动时所产生的振动剪切应力。结果表明,振动剪切应力的振幅随着聚合物熔体的粘度,振动频率和应变振幅的增加而增加,随着熔体温度的增加而减小。     

振动剪切流场中聚合物熔体的动态黏度计算方法——黏性耗散法

基于剪切功率的耗散机理,提出了一种计算振动剪切流场中聚合物熔体动态黏度的黏性耗散法,并建立了理论模型。运用黏性耗散法,计算了简单振动剪切流场中Maxwell流体的动态黏度,得到了与传统方法相一致的结果,从而验证了理论模型的正确性。通过讨论振动叠加流场中Maxwell流体的动态黏度,分析了黏耗散法的应用局限性。最后,通过动态流变实验,发现黏性耗散法对于小振幅范围的振动剪切流具有较好的预测能力。     

The viscosity of monomolecular melts of poly(vinyl chloride)

PVC melts are predicted to be homogeneous with single molecules as the stable flow units (monomolecular melts) at corresponding values of high temperatures and/or high shear stresses. Under these conditions, it is found that the zero shear viscosity in simple shearing flow of rigid compounds depends on the average molecular weight by weight to the 3.5 power for molecular weights between 24,000 and 100,000. All data measured under conditions where monomolecular melts are predicted fall on a master curve of reduced viscosity versus reduced shear rate when a relaxation time proportional to η0/c²T is used. It is, therefore, concluded that monomolecular melts of PVC compounds follow the same structure–viscosity relations as found for other linear melts in viscometric flow.     

Flow activation volume of polystyrene/multiwall carbon nanotubes composites

We applied the rate theory of plastic deformation to evaluate the flow activation volume in polystyrene melts and in its composites with different concentrations of multiwall carbon nanotubes. The experiments consisted in the analysis of a perturbation induced to the melt by varying the shear rate of a monotonic test at a melt state with nearly constant viscosity. The variation consisted on the application of shear steps with lower shear rate during short-time intervals. The material’s response to the perturbation allows a flow activation volume to be evaluated. For the pure polymer, the flow activation volume compares to the volume of a tube confining the chains, confirming the validity of tube model. Addition of nanotubes to the melt affects the melt response in the high temperature flow region, resulting in the development of a plateau in G′(ω). This plateau is linked to interactions of chains with nanotubes. However, the flow activation volume was not affected by the addition of nanotubes, suggesting that tube model holds also for composites of polymer melts with carbon nanotubes.     

A model viscoelastic fluid

Shear stress and first normal stress difference data are presented for materials which exhibit a constant viscosity and yet at the same time exhibit elasticity levels of the same order as polymer melts. Flow pattern observations in circular die entry flows in conjunction with independent shear and normal stress measurement strongly suggest that these fluids would make excellent model fluids for melt studies. Studies in which the influence of elasticity in the absence of shear thinning and fluid inertia can easily be made. Furthermore it is clearly shown that a realistic solution to the die entry flow problem is not obtained using second order flow theory. In the second order region the secondary cell is observed to be almost identical in size to the cell observed for an inelastic Newtonian fluid in creeping flow. Marked growth in the secondary cell as a function of elasticity is not observed until the shear rates exceed the region of second order behavior. This growth in cell size as a result of elasticity is followed at higher shear rates by a spiraling flow instability like that observed for some polymer melts.     

Rheology of polymer melts in high shear rate

Little is known of the rheology of polymer melts in the high shear rate up to 10⁶ s^?1 or more. A specially designed high-shear-rate rheometer was developed, by which the rheology of polymer melts for shear rates up to 10⁸ s^?1 can be investigated. Two non-Newtonian regions and a transition or the second Newtonian region were observed in the wide range of shear rates up to 10⁷ s^?1. The observed flow curves for various polymer melts are classified into three typical patterns. One is the flow curve typically shown of high-density polyethylene in which a clear second Newtonian region appears after the first non-Newtonian region. The second is the typical flow curve of polystyrene in which a “transition region” appears instead of the second non-Newtonian region. The third is the flow curve shown of acrylonitrile-styrene copolymer, which exhibits behavior between the two types. A generalized flow curve is proposed to explain the observed flow behaviors of various polymers over a wide range of shear rates. The flow behavior in high shear rate results from high orientation and scission of polymer molecules.     

A constitutive theory for polyolefins in large amplitude oscillatory shear

A versatile transient network theory has been used as a framework for the interpretation of large amplitude oscillatory behavior of polyolefin melts in terms of their entanglement kinetics. The model reasonably describes all previously published measurements of the large amplitude oscillatory shear behavior on melts. Seven polyolefins are examined, three new materials and four previously studied. A qualitative difference in the nonlinear behavior in large amplitude oscillatory shear has been identified between the polyethylenes examined and the two other polyolefins, polystyrene and polyisobutylene.     

Rheological properties of glass bead-filled low-density polyethylene composite melts in capillary extrusion

The melt flow of glass bead-filled low-density polyethylene composites in extrusion have been observed by using a capillary rheometer to investigate the effects of temperature, shear rate, and filler content on the rheological properties of the melts. The results show that the melt shear flow obeys a power law, and the dependence of the apparent shear viscosity, η_app, on temperature is in accord with an Arrhenius equation. At the same temperature and shear rate, η_app increases slightly with increasing the volume fraction of glass beads, but the flow behavior index decreases with increasing filler content. In addition, the first normal stress difference of the melts linearly increases with increasing wall shear stress. Good agreement is shown with the N₁ calculated with the equation presented in this article and the pressured data from the sample melts. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1451–1456, 1999