AN EXPERIMENTAL STUDY OF HOLE PRESSURES FOR POLYMER MELTS

A slit die apparatus is used to measure hole pressures for two polymer melts.Hole pressures up to 110kPa are determined and shear rates reach 200 s~(-1).Viscosity data obtained from the same apparatus agreewell with the values obtained from a cone-and-plate rheometer or a capillary rheometer.The hole pressuresobtained by direct measurements are all positive and increase with increasing shear stress.The values of the firstnormal stress difference obtained from hole pressures according to the Higashitani-Pritchard(HP)theory are ofthe right order of magnitude,but appear to be on the low side when compared with values obtained from a cone-and-plate rheometer or with values obtained via exit pressures.It is believed that the hole pressure is a measureof fluid elasticity,but cannot yield accurate values of the first normal stress difference according to the HP theory.     

RHEOLOGICAL BEHAVIOR OF POLYMER MELTS (Ⅰ)UNIFIED MOLECULAR THEORY OF NON-LINEAR ISCOELASTICITY WITH CONSTRAINTS OF GAUSSIAN CHAIN ENTANGLEMENT FOR POLYMER MELTS

An approach with statistical mechanics and a unified molecular theory of non-linearviscoelasticity with constraints of Gaussian chain entanglement for polymer melts were proposed.Amultimode model structure for a single polymer chain with tail segments and N reversibleentanglement sites on the test polymer chain was developed.The probability distribution function ofthe end-to-end vector for a single polymer chain at entangled state and the viscoelastic free energyof deformation for polymer melts were calculated.Four types of stress-strain relationship and mem-ory function were derived from this theory.The above theoretical relationships were verified by experi-mental data of PS(polystyrene)and LDPE(low density polyethylene)melts.     

聚合物熔体窄缝脉动挤出行为的光散射研究

利用聚合物熔体的双折射性质,对振动力场作用下窄缝挤出模头中的聚合物熔体脉动挤出行为进行光散射研究,用光弹性图像和光强度矩阵来表征聚合物熔体受到的剪切应力。振动力场的引入使光弹性图像和光强度矩阵发生了规律性变化。结果表明,振动力场使聚合物熔体剪切应力减小、表观粘度降低,最终使得挤出压力降低、产量提高。     

COMPUTATIONAL CLARIFICATIONS OF EXPERIMENTAL BLEND MORPHOLOGY TRANSITIONS IN IMMISCIBLE POLYMER MELTS ORGANIZED BY CHAOTIC ADVECTION

Chaotic advection has been used recently to organize immiscible polymer melts into thousands of alternating thin layers and controllably obtain from layer breakup a wide variety of useful derivative blend morphologies. Experiments suggested that morphology changes in the multiple layers occur progressively, volumetrically, and interactively via gradual layer refinement and the formation and growth of holes (i.e., ruptures). To theoretically evaluate the experimental findings and also clarify morphology development in multilayer melts, interactive hole growth in multiple layers and associated morphology transitions have been investigated for experimentally observed random and ordered-hole arrangements using the lattice Boltzmann method (LBM). Results also provide a three-dimensional generalization to multiple layers of prior studies focused on hole growth in thin film coatings.     

COMPUTATIONAL CLARIFICATIONS OF EXPERIMENTAL BLEND MORPHOLOGY TRANSITIONS IN IMMISCIBLE POLYMER MELTS ORGANIZED BY CHAOTIC ADVECTION

Chaotic advection has been used recently to organize immiscible polymer melts into thousands of alternating thin layers and controllably obtain from layer breakup a wide variety of useful derivative blend morphologies. Experiments suggested that morphology changes in the multiple layers occur progressively, volumetrically, and interactively via gradual layer refinement and the formation and growth of holes (i.e., ruptures). To theoretically evaluate the experimental findings and also clarify morphology development in multilayer melts, interactive hole growth in multiple layers and associated morphology transitions have been investigated for experimentally observed random and ordered-hole arrangements using the lattice Boltzmann method (LBM). Results also provide a three-dimensional generalization to multiple layers of prior studies focused on hole growth in thin film coatings.     

CO2气体进入挤出聚合物熔体时的气泡形态

讨论了泡沫塑抖连续挤出成型过程中的合理进气条件,分析了不同进气位置、喷嘴结构和螺杆转速等对气泡形态的影响.     

THE INFLUENCE OF POROUS MEDIA ON THE FLOW OF POLYMER MELTS IN CAPILLARIES†

Porous media placed in the entrance of capillaries were found to reduce the pressure drop across the capillaries (?P_c) by a factor of two or three for polystyrene. The reduction in ?P_c was found to be a function of the distance of the porous media from the capillary entrance, the type of porous media, the length of the capillary, and the rheological properties of the polymer melt. No significant reduction in ?P_c was observed for a polymer melt such as polyethyleneterephthalate (PET) which is nearly devoid of memory. The apparent shear rate for the onset of melt fracture was extended by a factor of three when polystyrene passed through the porous media before entering the capillary. No significant difference in die swell values was observed with the use of porous media in the entrance of the capillaries. The mechanism which accounts for these phenomena is believed to be associated with the break up of the entanglement network in the porous medium which temporarily changes the rheological properties of the polymer melt.     

聚合物熔体与CO2气泡在螺旋流场中的动态特性研究

利用自行设计的长方形可视化流道进行了大量的试验，观察CO2气泡在聚合物熔体中的动态特性，分析了CO2气泡与聚合物熔体在螺旋流场及组合流场中的形态及变化。通过改变加工条件及控制参数，利用可视化流道和机头，观察并摄取了熔融聚合物中气泡的形态、变形、破裂等动力学现象，从实验观察角度出发，总结出CO2气泡在螺旋流场中的形态、分布，大小及变形等的影响因素。     

水泥预分解系统粉尘与碱、氯、硫融体的粘结特性及其对结皮的影响

采用化学试剂和生产原料,研究了预分解系统内粉尘与碱、氯、硫等单一或复合低温融体之间的粘结特性。结果表明：作为低温融体,KCl和混合融体KCl K2SO4 Na2SO4粘(融)结粉尘的粘结能力最强,对结皮堵塞的影响最大;其次是CaCl2,Na2SO4和混合融体CaCl2 K2SO4 Na2SO4;而单一的K2CO3和K2SO4对结皮的影响较小。作为粉尘,CaSO4最容易被各种融体粘结形成坚硬结皮;C2S与CaCO3较容易被融体粘结形成疏松结皮;CaO,Al2O3,MgO,Fe2O3,SiO2不易被融体粘结。分解率高(98％)的生料不容易被融体粘结;分解率低的生料较容易被粘结形成结皮。因此,提高入窑生料分解率不会增加而是可减少结皮堵塞的几率。     

无机纳米粒子在聚合物熔体中分散机理及表征

讨论了聚合物基纳米复合材料的熔融共混制备过程及其特点。分析了无机纳米粒了在聚合物熔体中的分散机理和相关的理论模型．以及分散程度的定量表证。     

振动对聚合物流变性能的影响

综合了国内外的一些实验结果,介绍了几种不同的振动形式对聚合物流变性能的影响,并且运用了高分子链及链段运动理论,分析说明了振动会导致聚合物的表观粘度降低、流动指数n增大及模口压力降低,表现在实际加工中则是流率增加,加工能耗减少,而且制品质量提高。     

纯振动场作用下聚合物粘弹性能的微观研究

通过对聚合物大分子与其他低分子的比较．指出了聚合物大分子具有独特分子结构、大的相对分子质量和长的分子链．以及由此引起的一系列特有的物理化学性能。从微观的角度解释了振动场作用下、聚合物大分子的运动情况．提出了聚合物大分子在振动状态下的橡皮筋模型．比较了直接加热与纯振动场作用下两种不同换能方式对聚合物同体材料塑化性能的影响，得出了纯振动场作用比直接加热更能促进聚合物材料塑化的结论。按照橡皮筋模型的原理．建立了广相应的力学模型。运用偏微分方法对该力学模型讲行求解，找出了振动场对高聚物的作用机理。     

ON THE RHEOLOGICAL BEHAVIOUR OF FILLED POLYMER MELTS†

The viscosity of polymer melts increases when adding fillers. Experiments were conducted with styrene—acrylonitrile copolymers filled with various amounts of glass beads and short glass fibres on a rotational and a capillary rheometer. Further from literature some representative equations have been compiled describing the influence of fillers on the viscosity. Applied to the experimental results it was found that the relative viscosity (R, i.e. the ratio of the viscosities of the filled and unfilled melts, shows a pronounced dependence on the shear rate ? but not on the shear stress t.     

挤出条件对聚苯乙烯熔体流动行为的影响

应用毛细管流变仪，考察了挤出条件对通用型聚苯乙烯（ＰＳ６６６）和高抗冲聚苯乙烯（ＰＳ４７０）熔体流动行为的影响，实验发现，后者的末端效应较前者显著，且其熔体的切性亦高于前者；而前者熔休的温粘性则高于后者，两试样熔体的剪切流动大体上服从幂律。此外，口型入口角对两试样熔体流动行为的影响是明显的。     

由聚合物熔体的动态流变学性质测定分子量分布

根据聚合物熔体的流变学性质(如动态弹性模量G’(ω),应力松弛模型G(t)等)估算聚合物分子量分布,是近几年发展起来的一种测量分子量分布的新方法。本文着重介绍这种流变学方法使用的原理、估算方法及应用结果。虽然由于所提出的理论不够完善而使得测量结果与用体积排除色谱(SEC)表征的结果存在一定的误差,但对那些溶解困难和维持溶解状态所需条件苛刻的聚合物,如聚氟化物等来说,却是一种简单、快捷而且较为准确的测量方法。     

铁磷熔体的氧化还原态和导电性能

用电导率电池测量了含钠铁磷模拟放射性核废料（HLW）熔体的电阻率,并分析了相应玻璃的Moessbauer谱,计算了铁离子的价态和氧化还原比,分析了温度、时间和氧化钠含量对熔体电阻率和玻璃氧化还原比的影响。结果发现：在Na2O含量低的熔体中,升温和降温过程的电阻率的变化是不可逆的：随着Na2O含量增加,不可逆性消失,熔体的电阻率随时间轻微下降。同时发现：Na2O3含量低的铁磷熔体的导电机理是电子性的,并且氧化还原比解释了其电阻率－温度曲线的不可逆性。铁磷模拟HLW熔体的电阻率类似于相近Na2O含量的钠铁磷系统熔体的电阻率。     

Fe-Mn-C三元金属熔体作用浓度计算模型

根据含化合物的金属熔体结构的共存理论，推导了Fe－Mn－C金属熔体作用浓度计算模型，计算的碳作用浓度NC'与文献实测的碳活度aC相符合，从而证明所得模型可以反映Fe－Mn－C金属熔体的结构本质．同时模型揭示了锰含量XMn对标准态转换系数LC的影响规律．     

高铬铁基熔体中磷和铬的热力学性质的研究

通过Fe－Cr－C系中碳的溶解平衡实验和铝、磷在BaO－BaCl2渣和Fe－Cr－C—P系间的分配平衡实验，心别测定11723K时三元系中碳的溶解度和个街时铬、磷在渣余间的浓度关系根据实验结果，应用热力学理论求得了和，并提出厂适用于高铬含碳铁基熔体中格和磷的活度系数计算式     

玻璃微珠填充聚合物复合材料界面

阐述了聚合物/无机粒子复合材料界面层及其优化设计的重要性；总结出复合材料的界面理论；介绍了玻璃微珠表面处理常用的几种方法，包括偶联剂处理。等离子体辐射引发聚合及弹性体包覆，并对其表面化学接枝聚合进行了评述，根据玻璃微珠自身所具备的形状单一，各向同性等特点，指出采用适当的表面处理有助于对其复合材料界面层的设计与研究。     

DRYING OF SOLVENT COATED POLYMER FILMS

The ability to predict the drying behavior of coating is of great importance to the coating industry. For this purpose, the model developed by Vrentas and Vrentas has been used to predict the concentration profile as well as the thickness and the temperature change of the polymer film as a function of time. The model incorporates the coupling between heat and mass transfer and diffusion induced convection which occurs when a single layer of a binary polymer solution is dried in a convection heated oven.

The model was solved numerically by using the finite difference approximation and it was applied to the well characterized polyvinylacetate(PVAC)-toluene system. The effects of operating conditions on