The Role of Interfacial Interactions in the Toughening of Precipitated Calcium Carbonate–Polypropylene Nanocomposites

This paper investigates the effect of the interphase properties and the interfacial interactions between matrix and filler on mechanical properties of precipitated calcium carbonate (PCC)–polypropylene nanocomposites. PCC particles were coated with stearic acid (SA). The weight ratio of SA on the particles (w _SA) ranged from 0 to 0.135 g SA/g PCC. The introduction of PCC particles resulted in an increase in stiffness and yield stress compared with the pristine polymeric matrix and, at the same time, it increased the impact resistance. The maximum improvement in the impact behaviour was achieved for the composites with w _SA =0.045 corresponding to the theoretical monolayer ratio. A decrease in interfacial interactions between monolayer coated PCCs and the matrix with respect to the uncoated particles was observed by using a semi-empirical equation developed by Pukànszky. The low degree of interfacial interactions between particulate filler and matrix allows a matrix–particle debonding phenomenon, as shown by scanning electron microscopy analysis. Extensive plastic deformations were evident as well, promoting an improvement in toughness. The thickness of the interphase between particles and matrix was evaluated by using the Shen–Li model which is based on the hypothesis of a non-homogeneous interphase. It results that the thickness increased in the order uncoated < monolayer coated < 3% SA coated ? 13.5% SA coated particles. The thinner and stronger interphase found for the composite with uncoated particles can be explained with the high interaction between matrix and filler and the consequent low mobility of the polymeric chains.     

Numerical simulation of micro-scratch tests for coating/substrate composites

In this paper the micro-scratch test is simulated by ANSYS finite element code for thin hard coating on substrate composite material system. Coulomb friction between indenter and material surface is considered. The material elastic-plastic properties are taken into account. Contact elements are used to simulate the frictional contact between indenter and material surfaces, as well as the frictional contact after the detachment of coating/substrate interfaces has taken place. In the case of coating/substrate interfaces being perfectly bonded, the distributions of interfacial normal stress and shear stress are obtained for the material system subjected to normal and tangential loading. In the case of considering the detachment of interfaces, the length of interfacial detachment and the redistribution of stresses because of interfacial detachments are obtained. The influences of different frictional coefficients and different indenter moving distances on the distributions of stresses and displacements are studied. In the simulation, the interfacial adhesion shear strength is considered as a main adhesion parameter of coating/substrate interfaces. The critical normal loading from scratch tests are directly related to interfacial adhesion shear strengths. Using the critical normal loading known from experiments, the interfacial adhesion shear strength is obtained from the calculation. When the interfacial adhesion shear strength is known, the critical normal loading is obtained for different coating thicknesses. The numerical results are compared with the experimental values for composite materials of thin TiN coating on stainless steel substrate.     

Stabilization of solvent-impregnated resins (SIRs) by coating with water-soluble polymer and chemical cross-linking and its application in mercury removal

Stabilization of solvent impregnated resins was achieved by the formation of a surface coating with the absorptive layer of poly(vinyl alcohol) and cross-linking with the protective layer of vinyl sulphone (VS). Amberlite XAD-4 and vinyl sulphone proved to be effective matrix and cross-linking agents, respectively, in the preparation of a protective layer of SIRs containing Cyanex 923 as extractant. The stabilized SIRs were characterized by the amount of vinyl sulphone contributing to the N and S content in the stabilized resin as well as to its operational stability. Optical and single electron microscope pictures were used to examine the appearance and the morphology, respectively, of the external protective barrier of SIR. Batch and column mode of sorption/elution studies for the removal of mercury from aqueous solution at pH 4 were carried out with Cyanex 923 containing SIR coated with PVA cross-linked with VS. Stabilized SIR was found to be effective for the mercury removal and showed great stability during the batch recycle runs. Elution of mercury from SIR was quantitatively achieved with 3M HNO₃. Kinetic and column performances were influenced by the degree of cross-linking of resin coating. Chemical stability and sorption capacity of stabilized SIR remained almost constant after several recycle runs whilst uncoated SIRs lose extractant with time as confirmed by efficiency studies.     

Effects of hygrothermal ageing and thermal shock on reliability of interfacial adhesion between black oxide coated copper substrate and epoxy resin

Black oxide is a conversion coating applied onto the Cu substrate to improve the interfacial adhesion with polymeric adhesives. A comprehensive study was made to characterize the black oxide coating and the corresponding interfacial adhesion with various types of polymeric resin, aiming to optimize the oxide processing conditions. The reliability of adhesion performance of the coating was evaluated before and after accelerated hygrothermal ageing, such as temperature cycling, pressure cooker test, and moisture sensitivity test followed by thermal shock. The moisture resistance of the substrate with black oxide coating was much higher than the bare Cu substrate, during both the moisture absorption and desorption processes. Thermal cycling alone did not change significantly the adhesion performance of any of the substrates studied. Pressure cooker test was detrimental to adhesion performance of oxide coated Cu substrates. Nevertheless, the residual interfacial bond strengths were consistently much higher for the black oxide coated substrates than the bare Cu surface. Significant delamination occurred between the bare Cu and the moulding compound after the moisture sensitivity test followed by thermal shock, whereas there was virtually no delamination on the black oxide coated samples under the same ageing condition, confirming the higher reliability of interfacial adhesion performance for the latter.     

Thermal stress-induced fracture of coating layer of galvannealed steel

The thermal stress-induced multiple fracture of the Fe-Zn intermetallic compound coating layer of galvannealed steel was investigated for samples with IF (interstitial free steel) and SPCC (steel plate cold commercial, Japanese Industrial Standard) as substrates. The analysis of the measured length of the multiply fractured coating layer showed that the fracture strength of the coating layer was 260–280 MPa and the residual stress around 720–740 MPa of the coating layer was reduced to around 130–140 MPa through the multiple fracture. The influences of the coating layer thickness and the stress–strain curve of the substrate on the multiple fracture behavior of the coating layer were also clarified.     

具有长侧链结构苯醌类化合物的合成及其成膜性质研究

应用经过改进的自由基烷基化新方法，合成了一系列的具有长侧链结构的苯醌类化合物。研究了这类化合物形成LB膜的性能和规律。讨论了醌类化合物的成膜性能与生物活性之间的关系。     

Physicochemical Investigations of Metolose Coating Films

In the course of film coat preparation it is very important to carry out preformulation investigations. The film formed by Metolose^® SM-4 polymer containing Macrogol 2000 (polyethylene glycol) as plasticizer showed structure changes depending on the concentration of the plasticizer during storage. This could be explained by the fact that the small quantity of plasticizer can be built in among the methyl cellulose molecules more easily, while the greater amount of plasticizer forms a separate phase in the beginning and can be built in into the film structure only later. On the other hand, the water bound by the hygroscopic property of the plasticizer can further influence the properties of the film as water also serves to function as a plasticizer. The increase in the quantity of the plasticizer enhanced the tensile strength of the film: the resulting film was less breakable and easier to handle mechanically. The studied films proved to be suitable for forming a protective coat of different solid dosage forms (pellets, tablets).     

Interpenetrating Polymer Networks

Interpenetrating polymer networks (IPNs) are a new class of polymer blends in network form in which at least one component is polymerized and/or cross-linked in the immediate presence of the other. IPNs possess several interesting characteristics in comparison to normal polyblends, because the varied synthetic techniques yield IPNs of such diverse properties that their engineering potential spans a broad gamut of modern technology. Interpenetrating polymer networks have shown excellent chemical resistance, hardness, elongation, tensile strength properties and higher compatibility. Hence, it can be concluded that using the IPN concept, it is possible to design the most desirable material for a specific end use requirement.     

Chemical treatment for improving wettability of biofibres into thermoplastic matrices

The use of biofibres as reinforcing agents for composite materials is one of the most promising areas of composite development, but the handicap of their hydrophilic nature has to be resolved to ensure stable composites. This article concerns the effectiveness of chemical modification using fatty acid derivates followed by graft copolymerisation with vinyl monomers to confer hydrophobicity and resistance to enzymatic degradation to biofibres. Oleoyl chloride was used as a fatty acid derivative to modify jute fibres leaving one double bond available for further co-polymerisation with styrene. The chemical modification was applied in swelling and non-swelling solvents and different extents of modification were obtained. The reaction was monitored by FTIR spectroscopy and the extent of modification was calculated from elemental analysis. The copolymerisation reaction was carried out from 2–3 molar% modified jute fibres resulting in highly hydrophobic jute fibres with large resistance to microorganisms. The copolymerisation reaction was also followed by FTIR spectroscopy and covering styrene ratios were deduced from elemental analysis. Additional investigations such as SEM, optical microscopy, enzymatic degradation and floatation techniques were used to support the efficacy of the proposed method.     

稀土配合物Et~2NC~6H~4CH=CHC~5H~4NC~1~6H~3~3Ln(TTA)~4(Ln=La,Nd,Dy,Yb)的合成、表征与成膜性能

合成了四(α-噻吩甲酰三氟丙酮)合稀土(La,Nd,Dy,Yb)酸(E)-N-十六烷基-4-[2-(4-二乙氨基苯基)乙烯基]吡啶四个新的稀土配合物。用元素分析、紫外可见光谱、红外光谱、小角X射线衍射、差热-热重分析和摩尔电导对配合物进行了表征。研究了它们的表面压-面积(π-A)等温线行为。研究结果表明它们具有良好的成膜(Langmuir)性能, La, Nd, Dy和Yb配合物零压分子平均截面积A~π~→~0分别为1.94,1.93,1,73和1.85nm^2/分子。