The technical properties of glasses based on plastic clays

Glass and Ceramics -     

Exploration and appraisal of plastic sedimentary clays for the fine ceramics industry

The term ‘sedimentary plastic clays for the fine ceramic industry’ is discussed. The deposits of these kaolinite-rich plastic clays are classified into four types: (1) complex tectonic basins, (2) interactive multi-basin deposits, (3) large lens deposits and (4) recent lenses. The aims of exploration and appraisal are defined as (a) geological evaluation, (b) production planning, (c) clay component classification, (d) identification of marketing and blend parameters and (e) provision of information for investment decisions. These aims are common to all deposits and demand the rigorous testing of undisturbed sample, which generally achieved by core drilling. The variety of core drilling techniques used in the deposit is described. The application of these drilling techniques and the patterns of boreholes used, is related to the diversity of geological occurrence and characteristics of the four types of deposit in a series of case studies. It is concluded that, in spite of the aims of exploration and appraisal being coincident, the diversity of the occurrence has led to favoured core drilling techniques and borehole patterns in the various deposit types, in order to achieve those aims in the most cost effective manner.     

Fire performance studies on glass-reinforced plastic laminates

Polyester, epoxy and phenolic glass-reinforced laminates were compared in terms of their fire properties in the cone calorimeter. The presence of a gel coat on the polyester and epoxy products had some effect, mainly in the FR grades. The FR polyester with a brominated flame retardant showed a marked decrease in rate of heat release and in rate of smoke production. Aluminium hydroxide (commonly called alumina trihydrate of ATH) caused a significant delay in ignition time for the epoxy product and some reduction in rate of heat release but rate of smoke release was still relatively high. Phenolic laminates showed a long ignition time and relatively low rate of heat release (RHR). The peak RHR was further reduced by the presence of aluminium hydroxide and by changing the type of glass reinforcement. The influence of thickness was explored for a series of phenolic laminates in both cone calorimeter and the International Maritime Organization (IMO) surface flammability test. Ignition delay time was significantly affected and the cone calorimeter results showed that the shape of the RHR curve was also changed as the thickness increased. However, the heat release measurements in the IMO test were not sensitive enough to pick up the differences in this property. The type of substrate under the laminate significantly altered the burning rate but this may have been because they were not glued or mechanically fixed.     

Sintering studies of nano-crystalline zinc oxide

Sintering and grain growth of nano-crystalline undoped ZnO has been studied in detail over a wide range of temperature and holding time. Below 800 °C, sintering of over 70% theoretical density is not observed, irrespective of particle size. At 900 °C for 6 h, the nano-crystalline sample sinters to 99% of theoretical density whereas the density for as received sample is 93% of theoretical density. However, at 1300 °C or higher, the densification is found to be much faster and after a few hours becomes independent of holding time. Grain growth studies reveal a similar feature of attaining saturation over holding time. The average saturated grain size is found to be ∼1.5 and ∼2.2 μm at 800 and 900 °C, respectively, while at 1300 °C or higher, it is in between 12 and 13 μm.     

柱撑粘土合成柱化机理及应用研究进展

柱撑粘土是一种独特的二维类沸石材料,通常由大的水解无机金属阳离子与粘土层间的补偿阳离子电荷进行离子交换后在高温下脱水、脱羟基后制备而得。柱撑粘土由于其具有大的比表面积、孔容及层间距而被作为新型固体酸催化剂和吸附材料得到了越来越多的关注。概述了柱撑粘土的制备、柱化机理及作为石油催化材料和吸附功能材料的应用。     

IR studies of wood plastic composites

Wood plastic composites (WPC) of simul were prepared by gamma radiation using butylacrylate (BA) and methylmethacrylate (MMA) as the monomer and methanol as the swelling agent at 9:1 (v/v) ratio. IR spectra of simul, bulk polymer of BA (or MMA) film, and WPC of different polymer loadings ranging from 18 to 115% were studied. Increase of the characteristic peak intensity at 1735 cm^?1 (C?O vibration for acetyl groups) over that of 1620 cm^?1 (conjugated aryl carbonyl groups) along with the increase of polymer loading of simul with the monomer indicates that the graft copolymerization took place between the monomer and the simul wood matrix. © 1993 John Wiley & Sons, Inc.     

Mechanical performance studies on extruded cornstarch‐based plastic manufactures

Twin‐screw extrusion of cornstarch produces a strong, yet readily biodegradable plastic material. Because of the brittleness of these cornstarch plastics, ASTM standard methods did not apply, and an alternative sample grip was developed. A suitable method for the tensile testing of extruded cornstarch plastics of differing feed composition (amylose content, cross‐linking, plasticizer) and processing conditions (temperature) was developed, and quantitative values of tensile strength, strain, elastic modulus, and energy were obtained. The mean tensile strength of these materials ranged from 667 to 4148 psi, which is in the range of values for low‐density polyethylene and high‐density polyethylene. The high amylose content cornstarch plastics extruded at high temperatures demonstrated greatest strength. Wet/dry studies of the pure cornstarch materials showed them to degrade readily with extended exposure to water, but immersion in water for 1 h in room temperature (17°C) water did not, as measured by standard tensile tests, adversely affect their strength, but made them more ductile, less stiff and tougher. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2147–2154, 1999     

Sintering dense nanocrystalline 3YSZ ceramics without grain growth by plastic deformation as dominating mechanism

It is difficult to obtain nanocrystalline ceramic bulks due to its high surface activity at high temperatures. In the study, in order to achieve both high density and ultrafine morphology, the plastic deformation was induced by an ultrahigh pressure at a deliberately selected temperature, which was much lower than the threshold temperature for rapid grain growth. According to the ultra-high pressure route, nanocrystalline 3YSZ ceramics without grain growth were fully densified at 900?°C under 1.5?GPa. Both direct microstructural observations and calculation results proved that the plastic deformation including high temperature yield and sliding played a dominant role in densification during the sintering process.     

Application of high-speed centrifugation to studies of plastic spreads

Summary By means of the analytical ultracentrifuge the rate of separation of a plastic spread into liquid and solids phases was observed and the proportions of each phase determined. An estimate of the amount of true solids was complicated by the fact that the solids phase consisted of approximately one-half oil. In the preparative ultracentrifuge sufficient quantities of the oil phase were isolated for chemical analysis. Centrifugation at each of several temperatures and analysis of the oil and solids phases would yield a characterization of the different components which crystallize at various temperatures. By centrifuging the plastic spread with a layer of aqueous alcohol of density intermediate to the oil and solids, the solids phase was separated more nearly oil-free. The solids phase however still was not sufficiently pure to permit a chemical characterization representative of the solid component. Corrections can be made however for the effect of occluded oil. Presented at the American Oil Chemists' Society Meeting, New Orleans, La., May 4–6, 1953. One of the Branches of the Agricultural Research Service, U. S. Department of Agriculture.     

Numerical and experimental studies on the ejection of injection‐molded plastic products

Numerical and experimental studies have been conducted on the ejection stage of plastics injection molding process. A numerical approach is proposed to predict the ejection force from the mold‐part constraining and friction forces as the product cools in the mold cavity up to the moment of ejection. The finite element thermoviscoelastic solidification analysis has taken into account the stress and volume relaxation behavior of polymers under the cavity‐constrained condition. The predicted ejection force and its distribution over ejector pins are validated by injection molding experiment of rectangular boxes using a polycarbonate resin. Different cases of the ejector pin layout are evaluated to examine the effect of the number, location and dimension of ejector pins, so as to identify the balanced layout causing minimum stress and deformation to the product. The approach is also applied to another product geometry which shows complex distribution of the mold‐part constraining and friction forces and involves multi‐step operations in the demolding stage.