CONSEQUENCES OF A CONFORMATIONAL CHANGE OF FLEXIBLE MACROMOLECULES ON THE NON-NEWTONIAN BEHAVIOUR OF THEIR SOLUTIONS

The shearthickening behaviour of flexible macromolecules in dilute solutions in a simple shear flow is predicted under the assumption of a transconformation from a random coil to a deformed coil at a critical shear rate. Some numerical results for polydisperse solutions in a constant shear rate flow, and monodisperse and polydisperse solutions in a Poiseuille flow are presented     

湿纺生产再生二醋纤烟用滤嘴丝束的研究 第1报 醋酸纤维素—丙酮溶液的流变性质

纺丝原液的可纺性优劣对纺丝生产工艺的影响非常大。原液的可纺性又与其流变性质有密切关系,因而研究纺丝原液的流变性质具有十分重要的意义。本文利用旋转粘度计研究了浓度为20～32％的几种废醋纤烟用滤嘴丝束(WCA)一丙酮纺丝原液在20～50℃范围内的流变性质,叙述了原液浓度和原液温度与非牛顿流动指数、结构粘度指数和粘流活化能的关系。讨论了纺丝原液组成对原液流变性质的影响。试验发现该WCA一丙酮纺丝原液的非牛顿流动指数(n)为0.7998～0.9332;结构粘度指数(△η)为4.5～7.25;粘流活化能(Eη)为11.2～30.3;极限零切变粘度与原液浓度的关系为η_0∝4.6～5.9。试验结果表明,WCA一丙酮纺丝原液中的三醋酸甘油酯起到了增溶作用,可以降低原液粘度。     

明胶大分子的还原性与抽提的关系

用不同抽提次序的一系列明胶样品，用电位法测定了它们的还原性，用氨基酸分析仪测定了蛋氨酸，蛋酸亚砜和砜的含量，用ＳＤＳ－ＰＡＧＥ电泳法测定了它们的不同构象组份的相对含量。发现：明胶的还原性随帛提次序的增加出现一极大值，而这个极大值与α１，α２和α１／α２的比值互呈正行性的对应关系。仔细考察和对比α１和α２的一极构型表明：α１，α２含有较多的Ｍｅｔ。这个极大值的出现，是与第２道抽提出来的明胶中含有较多     

冶金渣非牛顿流变特性对其泡沫化的影响

实验得到的冶金过程熔渣的一维本构方程和发泡性能方程都是幂律型的．本文对温度和添加物引起熔渣流变特性变化的原因进行了分析．对比熔渣的流变特性和发泡高度曲线,发现除加入较大颗粒的焦炭外,两者的变化趋势非常一致．对Ｆｒｕｅｈａｎ泡沫化指数不适合非牛顿流体熔渣的原因进行了解释。     

EFFECT OF DEFORMATION SEQUENCE ON RHEOLOGICAL BEHAVIOUR AND MECHANICAL DEGRADATION OF POLYMER SOLUTIONS

The flow behaviour of polymer solutions of non-hydrolyzed polyacrylamide and Xanthan was investigated in two rectangular and similar plexiglas models containing 3 cylindrical enlargements of the same dimensions. These three enlargements were located successively at the mid point of the first model length, whereas they were equally spaced along the second one. Only non-hydrolyzed polyacrylamide polymer solutions have shown viscoelastic behaviour in these plexiglas models. However, the behaviour of these polymer solutions in the first model was different from that in the second one.

The multipass mechanical degradation of the non-hydrolyzed polyacrylamide polymer solutions was studied extensively in the two plexiglas models. It was shown that, at high flow rates, the multipass mechanical degradation was stronger in the second model than in the first one. The mechanical degradation in model 1 converges with that in model 2 as the flow rate decreases.

The difference in flow behaviour and mechanical degradation of the same polymer solutions in the used plexiglas models was ascribed to the different times allowed for polymer solutions to relax prior to extension in the tested flow fields.     

THE BEHAVIOUR OF ADHESIVELY BONDED BEAMS VERSUS THEIR WELDED EQUIVALENT

The study aims to produce a design guide for the calculations of stresses and deflections of adhesively bonded beams fabricated from steel adherends using a structural epoxy adhesive. Such design calculations already exist for welded but not for bonded beams. Small models based on beams with a T-section profile, at various beam lengths, are formulated. A key to these calculations is the determination of the adhesive/adherend interface factors/coefficients, to correct the estimated values of stress and deflection from three-point bending conditions. This article presents the methodology for evaluating bonded beams in relation to equivalent welded (solid) beams. This includes mechanical testing, an analytical method based on beam and sandwich theory, and finite element techniques. Results from these techniques are presented and compared and values of the coefficients for T-section beams are determined.     

改善维纶染色性能的研究

本文对改善维纶染色性能进行了研究,提出了低温高酸缩醛化新工艺,较详细地阐述了新工艺的小试及生产性试验情况。研究结果表明:采用反应温度为45℃,硫酸浓度为350g/L,甲醛浓度为20g/L,硫酸钠浓度为60g/L的醛化工艺能较有效地提高维纶的染色性能(色泽深度能提高10—30%);同时,纤维主要物理机械性能均能达到常规短纤维一等品水平,且生产工艺简单可行。     

INFLUENCE OF NON-NEWTONIAN FLOW BEHAVIOUR ON MASS TRANSFER INBUBBLE COLUMNS WITH AND WITHOUT DRAFT TUBES†

Gas hold-up and mass transfer were examined in a column with and without a draft tube. It was found that the introduction of a draft tube increases the gas hold-up but decreases the volumetric mass transfer coefficient in Newtonian fluid systems. For non-Newtonian fluid systems, both parameters were increased by the presence of the draft tube. Empirical correlations are proposed for the gas hold-up and the volumetric mass transfer coefficient in the bubble column with Newtonian and non-Newtonian fluid systems. The correlations are in general agreement with the data in this work and in the literature. They should be useful for design and scale-up purposes. It was also found that introduction of an ancillary impeller improves the mass transfer in non-Newtonian fluids due to the break-up of large bubbles.     

表面更新型搅拌釜中非牛顿流体脱挥特性的研究

探讨了高粘流体脱挥过程的容积传质系数,提出用氧探头放在气相测试的方法,建立并求解了测定模型,利用该法测定了双轴表面更新釜中采用三种不同型式的桨搅拌非牛顿流体时的脱挥性能,对结果作了关联,并对各种桨型的脱挥性能进行了评价。     

丙纶BCF在热空气变形中的受热过程与物理性质变化

分析了丙纶BCF在热空气变形时的传热情况。对变形管内丝温的理论计算表明:变形管内丝表面和丝芯温度均以相似的规律——近似指数规律变化,丝在变形管内所达到的温度,超过了丝的软化点而低于丝的熔点。另外,还研究了经BCF变形后丙纶部分物理性质的变化情况。     

轧制工艺对柔性石墨力学性能的影响

研究了柔性石墨生产过程中初压力、轧制方向、轧制咬入角和轧制辊径等因素对其宏观力学性能的影响,结合对不同密度的柔性石墨取向度的分析,对柔性石墨的强度机制作了进一步的探讨。     

氧化剂对柔性石墨材料力学性能的影响研究

采用液相氧化法制备可膨胀石墨，在10MPa下压制柔性石墨试样并测定其抗拉强度和抗压强度，考察了氧化剂的氧化性和氧化程度对柔性石墨力学性能的影响，探讨了柔性石墨的微观结构和内部孔结构与其力学性能的关系。结果表明：柔性石墨材料的抗拉强度和抗压强度随氧化剂氧化性的提高而增大，氧化程度过高和过低都不利于获得高力学性能的柔性石墨材料。通过工艺优化可得到抗拉强度为4．02MPa、抗压强度为52．3MPa的高性能柔性石墨。膨胀石墨的微观结构和内部孔结构对柔性石墨的力学性能有较大的影响，膨胀率较高的膨胀石墨孔隙细长、孔径较大、开孔数量较多，在压制过程中孔隙内的气体容易排除，所得柔性石墨的气孔数目少，体积小，因而具有较高的力学性能。     

THE EFFECT OF TEMPERATURE ON FLUIDIZED BED BEHAVIOUR

Most published correlations for the minimum fluidizing gas velocity have been derived from tests under ambient conditions and increasing discrepancy is found in their application over wider ranges of operating conditions. Up to 1000°C the Ergun equation is reliable but it requires a knowledge of the particle shape factor and bed voidage for its application. Bed voidage is found to vary with temperature for laminar gas flow conditions.

Paralleling changes in gas flow conditions with operating temperature are changes in bed-to-surface heat transfer coefficients. There is a distinct transition from the interphase gas convective to the particle convective component of heat transfer being the dominant mechanism as the operating temperature increases and Re_mf reduces through 12,5 at Ar ∼ 26000. This is thought to be a consequence of change in bed bubbling behavior.     

THE EFFECT OF TEMPERATURE ON FLUIDIZED BED BEHAVIOUR

Most published correlations for the minimum fluidizing gas velocity have been derived from tests under ambient conditions and increasing discrepancy is found in their application over wider ranges of operating conditions. Up to 1000°C the Ergun equation is reliable but it requires a knowledge of the particle shape factor and bed voidage for its application. Bed voidage is found to vary with temperature for laminar gas flow conditions.

Paralleling changes in gas flow conditions with operating temperature are changes in bed-to-surface heat transfer coefficients. There is a distinct transition from the interphase gas convective to the particle convective component of heat transfer being the dominant mechanism as the operating temperature increases and Re_mf reduces through 12,5 at Ar ～ 26000. This is thought to be a consequence of change in bed bubbling behavior.     

聚酯的摩尔质量与机械性能研究——Ⅰ.动态力学性能

应用粘弹谱仪考察了不同摩尔质量的聚酯(PET、PBT、PBT/PET)的动态力学性能,结果表明摩尔质量增大将提高其模量,但亦导致结晶速度变慢,使测得的模量反而比摩尔质量较低的试样小.     

柱色谱法及其在高分子领域中的应用——第二讲 柱色谱在高分子领域中的应用

本文介绍柱色谱法在高分子领域中的应用,用一系列单体、溶剂、助剂、齐聚物和高聚物等的色谱分析实例说明。同时对反相色谱、裂解色谱和化学降解色谱分别作了讨论。     

使用过程中碳化硅匣钵显微结构的变化

利用扫描电子显微镜对某窑具厂制造的SiC质匣钵进行了显微结构分析，并通过与德国的SiC质匣钵比较。得出了匣钵开裂的原因是SiC颗粒被氧化变小，针状莫来石长大、粗化，玻璃相增多。由此提出了延缓开裂的办法。     

HA－PP改性丙纶流变行为的研究

对成孔剂（ＨＡ）－聚丙烯（ＰＰ）改性丙纶的流变行为进行了考察和研究。结果表明：共混ＨＡ使改性丙纶表现粘度下降；粘流活化能上升；流变指数值增大；挤出膨化现象变小，可纺性得到改善。