Molecular Weight Polydispersity Effects on Diffusion at Polymer/Polymer Interfaces

The effect of molecular weight distribution (MWD) on diffusion at symmetric polymer/polymer interfaces is investigated by rheological tools. A new model allowing the determination of a self‐diffusion coefficient of polydisperse polymer systems is presented. The model is based on the double reptation theory and Doi and Edwards' molecular dynamics applied to A/A polymers brought into intimate contact in the molten state. The material parameters for the model are obtained from linear oscillatory shear experiments, in which the dynamic shear modulus is measured in parallel plate geometry under a small amplitude of deformation as a function of time and frequency for a sandwich‐like assembly. The experiments were conducted on polystyrene (PS) blends with constant weight average molecular weight (M_w) but with variable number average molecular weights (M_n). The measured self‐diffusion coefficients showed that the presence of short molecules in the blend increases the mean value of the self‐diffusion coefficient and the magnitude of such increase can be quantitatively evaluated by the proposed model.     

激光清洗轮胎模具新工艺

激光清洗轮胎模具的原理是利用模具基体物质与表面附着的污垢对某一频率的激光能量吸收系数的差别，使激光能量充分被表面附着的污垢所吸收，从而受热膨胀直至气化，所形成的气体被吸收利用而不损伤甚至强化模具基体，以达到绿色清洗的目的。本文从激光的特性、激光器简介、激光清洗原理以及激光清洗应用分析等方面对激光加工技术新应用进行了探讨。     

X-ray Photoelectron Study of Chemical Interactions at Ti/Polymer Interfaces

We have used X-ray photoelectron spectroscopy to study the chemical interactions at the interface formed during in situ deposition of Ti atoms on epoxy, triazine, and polystyrene surfaces. We find that for deposition on thick polymer films (1-2 mm) the primary component at the interface is TiO₂ with small amounts of titanium nitride and titanium carbide. The source of the oxygen in the TiO₂ is water or molecular oxygen dissolved in the polymer films. We also find that the Ti/triazine interface is more stable to heat treatment than the Ti/epoxy interface. This result is attributed to the higher glass transition temperature of triazine. For thin triazine films (～ 100Å) we observe that titanium carbide is the dominant product, with smaller amounts of oxide and nitride. Aging in air causes the carbide and nitride to convert to the more thermodynamically-stable oxide. Titanium carbide is also the primary initial species at the Ti/polystyrene interface.     

Aerosol and Solution Modification of Particle-Polymer Interfaces

In recent years several investigators have focused on the synthesis of uniformly and continuously coated particles to impart improved chemical stability, mechanical strength, morphology and/or dispersibility to powders required for preparing next-generation composities. This paper reviews two in situ reaction methods employed at Clarkson University to selectively coat individual particles having widely different shape, size and chemical composition. The aerosol procedure allows core particles to become coated using room temperature liquid-gas reactions. Alternatively, coating particles dispersed in a solvent containing reactive precursors is more applicable to industrial processing. Uniform, well-adhering coatings of polyurea on titania powder, of polydivinylbenzene on silica beads, and of carbon and boron nitride on silicon carbide whiskers were made by selecting the correct precursors and reaction chemistries. Qualitative assessment of adhesion between the coatings and cores is given.     

UGNX2．0的用户界面定制技术

对UG／Open MenuScript的语法进行了详细的讲解，介绍了环境变量的设置使得用户进行的二次开发可用。简略介绍了UG／Open UIStyler，讲解了几个关键点，重点介绍了对话框的互调问题。最后介绍了使用UGNX2．0的用户界面定制技术步骤。     

国产聚酯帘线应用于子午线轮胎的研究

采用山东安丘涤纶帘帆布厂生产的１０００Ｄ／３聚酯帘布，小批量试制１８５／７０ＳＲ１３、Ｐ２１５／７５Ｒ１５等规格的子午线轮胎。试验结果表明，只要帘布覆胶配方及轮胎结构设计合理，压延、成型及硫化等工艺条件适宜，国产聚酯帘线是小规格、薄胎体的轿车载车午线轮胎较理想的骨加材料。     

Tuning the Conductivity of Nanocomposites through Nanoparticle Migration and Interface Crossing in Immiscible Polymer Blends: A Review on Fundamental Understanding

This article critically reviews the detailed fundamental understanding of the influence of conductive nanoparticle migration on the localization, and hence, electrical conductivity of immiscible polymer blend nanocomposites. Three types of conductive nanoparticles, namely, spherical, tubular, and platelet, are discussed with respect to their migration and electrical conductivity of obtained nanocomposites. A complete migration process consists of bulk migration within one component, contact with the interface, and penetration to the other component. During processing, the wetting coefficient parameter is the main thermodynamically controlling factor for nanoparticle localization. However, kinetic effects, such as mixing sequence and intensity, viscosity ratio, size and shape of the nanoparticles, and mixing time, can play a substantial role in determining the final locations of nanoparticles. Moreover, the rate of migration varies with the surface chemistry of the nanoparticles. It has been reported that nanoparticles in a more viscous phase move slower compared with a low viscous phase. Furthermore, nanoparticles having high aspect ratios and surface polarities compatible with the other component migrating faster. It is established that immiscible polymer blend nanocomposites with a “double percolation” structure having higher conductivity with nanoparticles are localized at the interface of the co‐continuous blends.     

Effects of Surface Modifications on the Peel Strength of Copper Based Polymer/Metal Interfaces with Characteristic Morphologies

This paper summarizes a study on the effect of changes in surface chemistry on the peel strength of copper/polymer interfaces. Two different surface topographics were created and evaluated, one produced by cleaning and etching in sodium persulfate, the other by etching then mechanically roughening using 180 grit sandpaper. Both surfaces were then oxidized in an alkaline/oxidizing treatment to form cupric oxide. Ion implantation and benzotriazole priming modified the surface chemistry of the cupric oxide samples. After lamination to form an epoxy/copper interface, peel strength measurements were taken. The results showed that ion implantation degraded the peel strength while priming with benzotriazole improved the peel strength compared with the unmodified cupric oxide. In a separate comparison study, peel strength measurements were taken on interfaces formed from copper oxides with the same oxide structure but with widely different gross morphologies, “As laminated” adhesive strength was virtually the same. The bonded interfaces were aged at elevated temperature and the peel strength obeyed first order degradation kinetics. Two terms can be determined from the degradation studies, the first is the long term peel strength, A(∞), and the other is Ω, the degradation rate with units of time^-1. A value of A(∞) was 3.0 lbs/in for etched copper interfaces while A(∞) was 0.5 lbs/in for the sanded interfaces.     

Fracture and Contact Adhesion Energies of Mica-Mica, Silica-Silica, and Mica-Silica Interfaces in Dry and Moist Atmospheres

A study is made of the factors that contribute to the energy of mica-mica, silica-silica, and mica-silica interfaces in the presence of moist atmospheres. Energies are measured using brittle fracture and contact adhesion techniques. Both "virgin" and "healed" interfaces are investigated, with special attention on the latter. The fracture and adhesion data overlap, reflecting a common underlying separation process by "sharp-crack propagation." The study identifies several contributors to the interface adhesion energies. At virgin mica-mica and silica-silica interfaces the energy is determined by primary ionic-covalent attraction, and by the screening of this attraction by condensed moisture from the atmosphere. At healed interfaces the energy depends on both environmental interaction and "lattice" coherence. At retracted cracks in mica-mica most of the virgin ionic attraction is retained. On misorienting separated cleavage halves prior to recontact the interaction energy drops substantially: in "dry" atmosphers (relative humidity <5%) a portion of the Coulombic interaction persists in the form of "macroscopic domains" of electrostatic charge, attributable to long-range order in the cation sublattice; in "wet" atmospheres (relative humidity >50%) capillary forces dominate. The dissimilar mica-silica system exhibits the same dominance by capillary forces in wet atmospheres. However, in dry atmospheres the adhesion energy becomes inordinately high, from spontaneous transfer of electronic charge from one surface to the other. The implications of these observations concerning mechanical properties of brittle ceramics are discussed.     

Polymer Hydrogels: A Review

This review encompasses definitions, classification, main properties, and application of polymer hydrogels. Raw materials and preparation techniques of polymer hydrogels were described. The factors that affect absorption capacity and swelling properties of polymer hydrogels were reviewed. PHG materials are defined as a viscoelastic network structure, swellable and not soluble in water with high absorbent capacity, which may reach 1000 g/g of their dried weight to be termed “superabsorbent polymer hydrogels”. PHGs have the ability to release absorbed fluids under certain circumstances.     

废轮胎热解资源化研究新进展

用热解法处理废旧轮胎能够实现能源的最大回收有价值产品的充分再利用,代表了当今废旧轮胎处理的发展方向。本文重点介绍了废轮胎的热解机理,热解动力学,热解过程控制及其产品特性的研究进展,并对今后废轮胎热解资源化研究发展方向提出了建议。     

A Rheological Model for the Interface of Immiscible Polymer Melt in Blending Process

We used an area density tensor as an interface variable of immiscible polymer blend. A phenomenological model for the evolution of such area density tensor in flow fields was established based on the concept of non‐equilibrium thermodynamics of complex polymeric fluids, without the limitations of passive mixing. Phase deformation, break up, relaxation, coalescence effect, as well as non‐affine deformation of the dispersed phase with matrix are all considered in the model. The model predictions show that interfacial slip greatly affects the morphology evolution. The influences of other factors, such as volume fraction, shear rate, interfacial tension, and viscosity ratio, on interfacial area development are also discussed.     

In Situ Characterization of Interfaces between Liquid Tin–Vanadium Alloys and Alumina by Neutron Reflection Spectroscopy

The composition and structure of interfaces between single crystal Al₂O₃ (sapphire) samples and liquid Sn–V alloys, containing 1% and 3% V, have been characterized in situ at high temperature using neutron reflection spectroscopy. Measurements made at 900°C are shown to be consistent with a thin (10–25 nm) AlV₂O₄ layer forming at the solid/liquid interface, with possibly a thinner layer of enhanced V content adjacent to the liquid, to promote wetting. After longer time exposure to temperature this interface layer roughens and a more complex interface structure occurs.     

浅析轮胎内衬层产生气泡的原因及解决措施

从内衬层胶料使用的原材料,内衬层胶料混炼工艺及内衬层压延工艺等多个环节分析了轮胎内衬层产生气泡的原因,并提出了相应的解决措施。     

Fatigue and Durability of Silane-Bonded Epoxy/Glass Interfaces

Fatigue (slow) crack growth in epoxy/glass interfaces bonded with the silane coupling agent 3-aminopropyltriethoxysilane was studied under static and cyclic loading at 23°C, 95% RH using the double cleavage drilled compression test. Crack growth rates under cyclic loading were significantly greater than under static loading, in contrast to crack growth rate results in monolithic glass. After aging up to 34 h at 94°C in distilled water, the silane-bonded epoxy/glass specimens exhibited somewhat greater resistance to fatigue crack growth than the unaged samples; however, after aging at 98°C in distilled water and at 70°C in an aqueous KOH solution at pH 10, crack growth became cohesive and exhibited fractal behavior. Mechanisms for fatigue crack growth at silane-bonded epoxy/glass interfaces are proposed.     

Fatigue and Durability of Silane-Bonded Epoxy/Glass Interfaces

Fatigue (slow) crack growth in epoxy/glass interfaces bonded with the silane coupling agent 3-aminopropyltriethoxysilane was studied under static and cyclic loading at 23°C, 95% RH using the double cleavage drilled compression test. Crack growth rates under cyclic loading were significantly greater than under static loading, in contrast to crack growth rate results in monolithic glass. After aging up to 34 h at 94°C in distilled water, the silane-bonded epoxy/glass specimens exhibited somewhat greater resistance to fatigue crack growth than the unaged samples; however, after aging at 98°C in distilled water and at 70°C in an aqueous KOH solution at pH 10, crack growth became cohesive and exhibited fractal behavior. Mechanisms for fatigue crack growth at silane-bonded epoxy/glass interfaces are proposed.     

我国工程子午胎的现状及发展趋势

分析了我国工程子午胎发展的背景和现状,结合国际市场和形势,对我国子午胎的战略定位和发展趋势以及企业发展提出了建议。     

Investigation of Processes Occurring at the Metal/Polymer Coating/Electrolyte Interface

The methodical approach and the cell to study electrochemical processes occurring during cathodic disbondment of a polymer coating are worked out. They permit one to investigate the role of each process separately when supervising the metal substrate potential, electrolyte and polymer coating composition at a metal/polymer/electrolyte interface. The cathodic disbondment of ethylene-vinyl acetate copolymer, polyisoprene and poly(vinyl chloride) coatings are studied. It is found that the cathodic disbondment rate for ethylene-vinyl acetate copolymer coatings depends on double layer parameters at the interface. These parameters are determined by specific volume charge of hydrated cations of the electrolyte, potential of the substrate, the presence of oxygen, surface active substances, etc. Based on the data of IR spectroscopy in internal reflection applied to disbonded films, it is established that during the cathodic disbondment an electron transfer to polymer functional groups, as well as an attacking of the adhesion bonds by active intermediates of oxygen reduction, occurs resulting in an electrochemical degradation of the polymer and an adhesion loss. It is shown that the electrochemical transformations at the steel/poly(vinyl chloride) interface can lead to the appearance of new adhesion bonds, increasing adhesion strength and decelerating the cathodic disbondment.     

Molecular Momentum Transport at Fluid-Solid Interfaces in MEMS/NEMS: A Review

This review is focused on molecular momentum transport at fluid-solid interfaces mainly related to microfluidics and nanofluidics in micro-/nano-electro-mechanical systems (MEMS/NEMS). This broad subject covers molecular dynamics behaviors, boundary conditions, molecular momentum accommodations, theoretical and phenomenological models in terms of gas-solid and liquid-solid interfaces affected by various physical factors, such as fluid and solid species, surface roughness, surface patterns, wettability, temperature, pressure, fluid viscosity and polarity. This review offers an overview of the major achievements, including experiments, theories and molecular dynamics simulations, in the field with particular emphasis on the effects on microfluidics and nanofluidics in nanoscience and nanotechnology. In Section 1 we present a brief introduction on the backgrounds, history and concepts. Sections 2 and 3 are focused on molecular momentum transport at gas-solid and liquid-solid interfaces, respectively. Summary and conclusions are finally presented in Section 4.     

Interfaces in repair,recycling, joining and manufacturing of polymers and polymer composites

A basic set of 10 thermoset polymer–polymer interfaces has been identified to play a vital role in the technical and economic aspects of composite manufacturing (RIM/RTM, compression molding, autoclave lamination), recycling, repair, welding, and joining of polymer composites. Knowledge of the chemical interactions and molecular connectivity at these interfaces and their influence on processability and mechanical properties of the polymers and polymer composite is essential, and has been the focus of this research. Presented in this report are the results of an exploratory study performed to understand the interactions at the polymer–polymer interface and their influence on the interfacial fracture toughness of a thermoset vinyl ester, which is widely used in liquid molding applications. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 775–785, 1999