AN EXPERIMENTAL STUDY OF POLYMER DIFFUSION IN CONCENTRATED SOLUTION: IMPLICATIONS FOR DIFFUSION IN POLYMERIZATION

The Trommsdorf or gel effect in free radical polymerization is due to the fact that the termination reaction becomes strongly diffusion controlled above a critical concentration associated with the onset of molecular entanglements. Therefore, an understanding of polymer self-diffusion in entangled systems becomes essential to understanding the Trommsdorf effect. Our group has previously proposed a molecular model for the gel effect which uses a specific theory for polymer diffusion (reptution). The present work represents an experimental attack on the same problem Experimental studies of polymer self-diffusion in entangled systems are scarce. Quasielastic light scattering from ternary systems composed of solvent(l)-polymer(2)-polymer(3), in which species (3) is isorefractive to the solvent (i.e. 0n/0c ₃ = 0), offers an attractive way to study the tracer diffusion coefficient of species (2) in a binary mixture of composition c ₃. In regimes of low momentum transfer (qR _G < 1,) where q is the scattered wave vector and R _G is the polymer radius of gyration, we have shown that the correlation function of the scattered electric field should decay with a single exponential decay time, given by (D₂₂ q ²)^?1 where D ₂₂(c ₂, c ₃) is the main ternary diffusion coefficient of component (2). Extrapolation to zero concentration of 2) at fixed concentration of (3) yields the tracer diffusion coefficient of (2) in the binary mixture of (1) and (3). The systems toluene(l)-polystyrene(2)-polymethylmethacrylate(3) (0n/0c ₃ ≈ 0.007 at 25°C) and toluene(l)-polystyrene(2)-polyvinylmethylether (3) (0n/0c ₃ ≈ 0.012 at 60°C) very nearly satisfy the above criteria. In both systems, we have found that the tracer diffusion coefficient of the polystyrene decreases with increasing concentration of the isorefractive polymer. Further studies have focused upon the dependence of the tracer diffusion coefficient upon polystyrene molecular weight, and upon the effect of incomplete index matching.     

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.     

玻璃纤维增强复合材料筋材连接试验研究

本文通过实验研究了由两种不同的粘结材料对玻璃纤维增强复合材料(GFRP)筋材的连接特性。研究表明采用环氧类树脂粘结剂进行钢套管和GFRP筋的连接,技术可行;环氧类树脂粘结剂的粘结滑移关系曲线上升段具有双折线特性。依据粘结滑移关系曲线,建议粘结强度设计值以屈服强度或控制变形量为确定标准,本试验建议取粘结极限强度的50%。提出了选择粘结剂的指标和温度影响、各种环境介质对其粘结性能劣化的影响试验要求。     

FRP材料耐久性试验研究

通过普通环境、碱环境和氯离子环境下CFRP的耐久性试验,研究腐蚀环境对CFRP的力学性能的影响.试验结果表明,碱环境下CFRP抗拉强度有下降趋势,弹性模量和极限应变基本保持不变;氯离子环境下,CFRP抗拉强度和弹性模量有增加趋势,极限应变基本保持不变.     

无约束气云弱点火爆炸压力实验研究

引　言在可燃气体的输送、贮存、加工和使用过程中由可燃气体泄漏而形成的气云爆炸已给人类社会造成了巨大的人员伤亡和财产损失 ,近年来发生在我国的几起重大气云爆炸事故无不令人触目惊心 ,可见研究气云爆炸成灾模式及防治技术具有重要的社会和经济意义 .要防治可燃气云爆炸给社会造成的巨大灾难 ,首先就要掌握气云爆炸的强度 .关于可燃气云爆炸的研究可分为两大类 :一类是针对军事领域研究由炸药点燃气云从而形成爆轰波的过程[1,2 ] ;另一类是针对工业领域研究弱点火 (通常指点火能量小于10 0Ｊ)条件下的工业气云的爆炸过程[3～ 5] ,这正…     

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.     

聚合物熔体挤出流动中的弹性行为

研究了聚合物熔体挤出过程中出口压力降ΔＰｅｘｉｔ与剪切应力τｗ和挤出胀大比Ｂ三者之间的关系。提出了描述这一关系的方程：ΔＰｅｘｉｔ＝τｗ（Ｂ＾４－１）＾０５／３。初步验证，用该方程计算的ΔＰｅｘｉｔ值与文献提供的毛细管挤出实测值有较好的一致性。     

AN EXPERIMENTAL STUDY OF CHEMICAL WAVE PROPAGATION

A study was made of chemical waves which were propagated through the coupling of diffusion and reaction in an isothermal multicomponent system. The waves traveled down small-bore tubing the end of which was attached to a stirred tank reactor in which an oscillating reaction was occurring. The stirred tank thus functioned as a wave source whose frequency could be controlled. Frequency and speed were measured in the tube. At a fixed position the wavelength (the quotient of speed by frequency) decreased with increasing frequency while the speed increased slightly. Neither frequency, speed, nor wavelength changed greatly as a wave propagated down the tube.     

AN EXPERIMENTAL STUDY OF CHEMICAL WAVE PROPAGATION

A study was made of chemical waves which were propagated through the coupling of diffusion and reaction in an isothermal multicomponent system. The waves traveled down small-bore tubing the end of which was attached to a stirred tank reactor in which an oscillating reaction was occurring. The stirred tank thus functioned as a wave source whose frequency could be controlled. Frequency and speed were measured in the tube. At a fixed position the wavelength (the quotient of speed by frequency) decreased with increasing frequency while the speed increased slightly. Neither frequency, speed, nor wavelength changed greatly as a wave propagated down the tube.     

AN EXPERIMENTAL STUDY OF GAS-FIRED INFRARED DRYING OF PAPER

Infrared heating/drying of paper is becoming very common in industry. However, there is a lack of fundamental information explaining the transport phenomena occurring within a paper sheet due to energy supplied by a gas-fired infrared emitter. This experimental study provides basic drying and temperature data for moist paper exposed to gas-fired infrared radiation energy. Two paper types, linerboard and bleached, at three basis weight levels, are used in this study.     

AN EXPERIMENTAL STUDY OF GAS-FIRED INFRARED DRYING OF PAPER

Infrared heating/drying of paper is becoming very common in industry. However, there is a lack of fundamental information explaining the transport phenomena occurring within a paper sheet due to energy supplied by a gas-fired infrared emitter. This experimental study provides basic drying and temperature data for moist paper exposed to gas-fired infrared radiation energy. Two paper types, linerboard and bleached, at three basis weight levels, are used in this study.     

聚合物气辅共注成型工艺的实验研究

针对气辅共注成型中多相分层流动存在着各分层界面应力间的相互耦合,使得其成型过程具有特殊的流动输运规律和动力学特征,对气辅共注成型工艺进行了系统的实验研究。通过实验研究了熔体注射温度、气体填充量和气体延迟时间3种工艺参数对气辅共注成型的影响规律,并在此基础上通过理论分析揭示了工艺参数对气辅共注成型的影响机理。     

下压式多段混合搅拌槽的实验研究

用饱和NaCl溶液作示踪剂,计算机动态数据采集,研究了0.65L下压式多段混合搅拌槽(DPSTMM)流通截面放大25倍、体积放大100倍后轴向扩散、混合时间准数以及单位体积能耗等的变化。对放大后的DPSTMM,在煤油/辛醇(体积比10:1)-醋酸-水体系中,应用串级萃取原理分析了实验测定的总效率,计算出了不同混合段数时的总传质系数K_(od)α。结果表明DPSTMM具有良好的流体力学性能和传质性能。     

接管轴向推力作用下开孔-补强区应力分布规律的试验研究

对接管轴向推力作用下圆筒形压力容器开孔－补强区的应力分布规律进行了试验研究．工作针对３台具有不同ｄ／Ｄ比的接管及标准补强圈补强的试验容器进行．研究结果表明，在补强圈补强的范围内，容器上的应力明显降低。但由于几何尺寸的变化及焊缝的加强作用，在补强圈外边缘特别在横向截面（θ＝９０°）内，容器中将出现一高的不连续应力，从而使该区域成为整个接管最危险的区域．     

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。     

AN EXPERIMENTAL STUDY OF AN INCLINED BUOYANT PLANE TURBULENT AIR JET

An experimental study of the effects of buoyancy forces resulting from temperature differences on the mean flow and turbulence characteristics of a plane turbulent jet discharged at an angle to the horizontal has been undertaken. The jets were generated by discharging air through a rounded nozzle which was 10 mm wide by 580 mm long. The discharged air could be heated and tests were undertaken with discharge temperatures of 20° and 40°C above the ambient air temperature at a single nozzle discharge velocity which gave a discharge Reynolds number of approximately 1700. Tests were undertaken with angles of jet discharge to the horizontal of 0°, 30°, 60° and 90°. Velocity and temperature measurements were undertaken using hot wire anemometers. Measurements of the mean velocity and temperature, the turbulence normal and shear stresses, the temperature fluctuation intensity and the two components of the turbulence heat flux were obtained. Profiles of these quantities were measured at six equally spaced positions to a distance of approximately 60 nozzle widths from the discharge plane. Measurements at much more closely spaced intervals were also taken along the jet “centre-line”, this being defined as the locus of the point of maximum velocity in the jet.     

PBT熔体的流变性研究

本文采用Instron毛细管流变仪,研究了不同温度下的PBT的流变性。其结果表明,PBT熔体为切力变稀流体,粘度与温度的关系满足Andrade方程E=A·Exp(E/(RT))。     

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。     

LLDPE在挤出加工中的弹性现象研究

使用Brabender PLD 651 挤塑仪配不同长径比、不同材质的毛细管流变口模,测定了几种LLDPE在一定温度下的挤出物胀大和熔体破裂的临界剪切应力,同时用Instron 3211毛细管流变仪做了对比实验。结果表明,毛细管口模的长径比达到一定值后,挤出物胀大随剪切速率的变化关系与长径比无关。这一长径比值又随毛细管口模材质而有所不同。对于一定长径比的毛细管流变口模,熔体破裂的临界剪切应力与挤出温度、口模材质无关。通过实验可知,采用提高口模温度、增加口模长径比或改变口模材质均能推迟熔体破裂现象的发生,从而提高了挤出加工的生产量。