硫含量对GCr15轴承钢摩擦学性能影响的试验研究

冶炼了3炉不同硫含量的GCr15轴承钢,采用MM-200、MPX-200和Falex摩擦磨损试验机对其进行了不同条件下的摩擦磨损试验,研究了硫含量对GCr15轴承钢摩擦学性能的影响规律。结果表明,随着硫含量的增加,GCr15轴承钢的摩擦系数降低,耐磨性能和抗咬合性能提高。作者根据金相分析、电子探针线扫描和电解分离法的测试结果指出,硫在GCr15轴承钢中主要是以化合态的形式存在,并对其作用机理进行了初步探讨。     

Simultaneous measurement of transient stress and flow birefringence in one-sided compression (biaxial extension) of a polymer melt

Summary Investigation of time dependent behaviour of a polystyrene melt is carried out with the aid of a new apparatus for biaxial extension. Use is made of the method of two impinging fluid streams guided by lubricated trumpet shaped metal walls. The flow birefringence is measured in the plane of symmetry and, at the same time, the force is measured which tends to separate the trumpets. The linear stress-optical relation turns out to be valid in this new flow geometry. An accurate value for the stress-optical coefficient can be determined from the relaxation experiments. The stress build-up as calculated from the optical measurements, is compared with the pertinent result of the theory of linear viscoelasticity. For the desired interconversion of dynamic moduli use is made of the approximation by Schwarzl and Struik. The steady state measurements are checked by the results of the non-linear model of Acierno et al.With 16 figures and 2 tables     

The steady shear viscosity of filled polymeric liquids described by a linear superposition of two relaxation mechanisms

Filled polymeric liquids often exhibit apparent yielding and shear thinning in steady shear flow. Yielding results from non-hydrodynamic particle—particle interactions, while shear thinning results from the non-Newtonian behavior of the polymer melt. A simple equation, based on the linear superposition of two relaxation mechanisms, is proposed to describe the viscosity of filled polymer melts over a wide range of shear rates and filler volume fraction.The viscosity is written as the sum of two generalized Newtonian liquid models. The resulting equation can describe a wide range of shear-thinning viscosity curves, and a hierarchy of equations is obtained by simplifying the general case. Some of the parameters in the equation can be related to the properties of the unfilled liquid and the solid volume fraction. One adjustable parameter, a yield stress, is necessary to describe the viscosity at low rates where non-hydrodynamic particle—particle interaction dominate. At high shear rates, where particle—particle interactions are dominated by interparticle hydrodynamics, no adjustable parameters are necessary. A single equation describes both the high and low shear rate regimes. Predictions of the equation closely fit published viscosity data of filled polymer melts. n power-law index - n ₁,n ₂ power-law index of first (second) term - shear rate - steady shear viscosity - ₀ zero-shear rate viscosity - _{0, 1}, _{0, 2} zero-shear rate viscosity of first (second) term - time constant - ₁, ₂ time constant of first (second) term - µ _r relative viscosity of filled Newtonian liquid - ₀ yield stress - ø solid volume fraction - ø _m maximum solid volume fraction     

Delamination of sodium montmorillonite in PA6 in the presence of melamine polyphosphate

This study describes the influence of melamine polyphosphate (MPP) flame retardant addition on layered structure of virgin sodium montmorillonite (MMT) in PA6/MMT system obtained in extrusion process. It was found that the extrusion of the PA6/MMT binary system in co‐rotating twin screw extruder gives intercalated clay nanocomposites, while during extrusion of ternary PA6/MMT/MPP composite, full exfoliation of clay was obtained in the system. Structure of the composites was proved utilizing wide angle X‐ray scattering and transmission electron microscopy techniques. Exfoliation of MMT in ternary PA6/MMT/MPP system was also confirmed by rheological studies (viscosity and creep measurements) which were carried out using rotational rheometer. Young's modulus of PA6/MMT/MPP was found to be ~25% greater comparing to PA6/MPP of the same filling level. Cone calorimetry experiments proved decrease of heat release rate peak of PA6/MMT/MPP by ~55% comparing to PA6/MPP with the same total filling level. Copyright © 2017 John Wiley & Sons, Ltd.     

蓖麻油基巯烯基紫外光固化胶粘剂的研制与性能研究

以异佛尔酮二异氰酸酯(IPDI)、蓖麻油(CO)、丙烯酸羟丙酯(HPA)为原料,采用熔融缩聚法合成出端丙烯酸酯基预聚体;同时以CO和3-巯基丙酸(3-MPA)为原料采用酯化反应合成出端巯基光引发单体。将端不饱和双键聚氨酯丙烯酸酯预聚体与所制备巯基丙酸酯按一定比例复合,加入光引发剂,在紫外光照射下,预聚体中双键与光引发单体中巯基发生巯基-烯点击反应,制得聚氨酯丙烯酸酯固化膜。采用核磁共振氢谱(1 HNMR)、红外光谱(FT-IR)、热重分析(TG)和光量热系统(Photo-DSC)等手段对合成预聚体、巯基丙酸酯及固化膜结构和性能进行了分析表征。结果表明:在紫外光辐照下,预聚体中不饱和双键与巯基化合物中巯基间发生了自由基加成反应,固化时间在60s以内,且所制备UV固化膜具有良好的机械性能和热稳定性。     

耐磨环氧胶粘涂层冲蚀磨损特性的研究

本文对气固冲蚀和浆体冲蚀条件下耐磨环氧胶粘涂层的磨损特性进行了研究。结果表明,这种涂层的冲蚀磨损是由粘结剂的磨损和抗磨填料的磨损所组成;填料粒度和磨料粒度都对涂层的气固冲蚀磨损有影响,但在给定的试验条件下,填料粒度对涂层的浆体冲蚀磨损影响甚微。文章指出,耐磨环氧胶粘涂层在气固冲蚀和浆体冲蚀下的磨损机理相似,但磨损规律却有所不同;耐磨环氧胶粘涂层尤其适用于浆体冲蚀的场合,可以明显地提高机械过流部件的使用寿命。     

Linear elastico-viscous properties of molten standard polystyrenes

This paper contains an extensive presentation of dynamic mechanical data (complex moduli), as obtained on the melts of a series of standard polystyrenes of narrow molar mass distributions. It also shows the way of obtaining structural parameters (plateau modulus and friction factor) which are needed for an interpretation of these data in terms of simple theoretical models (Maxwell elements, Doi-Edwards model). A linear mixing rule is used for taking into account the finite width of the molar mass distributions.Dedicated to Prof. F. R. Schwarzl on the occasion of his 60th birthday     

On the bursting of linear polymer melts in inflation processes

Molten LLDPE and HDPE plates (thickness 2 mm) have been inflated into a circular cylinder (inner radius 31 mm) under isothermal conditions. Low deformation rates allow the plates to be inflated considerably into the cylinder, and at high inflation rates an early burst is observed.Axis-symmetric numerical simulation of the inflations have been performed, using a constitutive equation in the form of a separable memory integral where the strain dependence is described by the Linear Molecular Stress Function (L-MSF) model with dissipative convective constraint release. The material parameters in the constitutive model are obtained using liner viscoelastic (oscillatory shear) and uni-axial elongational measurements.The numerical simulations were performed for inflation of a flat plate and a perturbed plate, where a small circular cone was removed from the centre of the surface of the plate. This was done in order to investigate the stability of the inflations. It is shown that all of the inflations are hydrodynamically unstable, though the effect on the occurrence of the burst is limited. One exception is at slow inflation, where an unexpected burst may appear as a consequence of minute deviations from an ideal flat plate. All of the numerical calculations show quantitative agreement with the experiments for a wide range of experimental conditions. This strongly suggests that the initiation of the burst is a hydrodynamic phenomenon.The critical parameters in the inflation of molten linear polymers have been investigated using the Gel equation as a memory function (M(s)=Ans ^–(1+n)) and inflating the plate with a constant velocity for the top of the plate. The hydrodynamic burst in a linear polymer is mainly associated with the linear viscoelastic properties and only slightly with the non-linear strain dependence. Increased (linear) elasticity reduces the inflated volume, at the same inflation velocity, before the burst occurs. Furthermore, the critical parameter for the occurrence of the burst (whether or not the burst occurs) is related to the crossover point (G=G) in linear viscoelasticity.     

IUPAC-LDPE的流变性测试实验之间的相对滑动

以IUPAC—LDPE熔体在150℃下详细的流变学表征实验和毛细管挤出实验为基础考察了该熔体在挤出实验中的滑动问题．根据相对滑动特性给出了判断相对滑动存在和计算相对滑动速度的方法．用Wagner模型，PSM模型和Osaki模型计算的表观剪切速率，在10s^-1时的毛细管壁面剪切应力比毛细管挤出实验给出的应力值高出约15％-17％，这个结果意味着IUPAC—LDPE熔体在挤出实验中存在滑动现象．在表观剪切速率为0．1，1．0和10s^-1时，挤出实验条件下的流动与根据在旋转流变仪上测定的流变特性用PSM模型计算的流动相比，它们之间存在的相对滑动速度分别为0．004，0．071和1．343mm／s．用Wagner模型和Osaki模型计算的相对滑动速度与PSM模型的结果相近．