Production of Fine Polymer Powder under Cryogenic Conditions

In order to produce fine polymer powders, a special and unconventional cryogenic grinding system was established using liquid nitrogen, where a jet‐vortex mill was used as the grinding mill. The major feature of this grinding process is that heat generation during the grinding period was eliminated. The results suggest that this cryogenic grinding system may be suitable for studying the grinding properties of polymeric materials. It may also be helpful in understanding mechanochemistry, e.g., the t‐P‐T conditions for different mechanochemical processes under cryogenic conditions (where T is the temperature, and P the pressure of the gas mixture in the grinding chamber). In addition, an Elbow‐jet classifier was attached to the jet‐vortex mill so that fine, medium and coarse products of polymeric powders could be obtained simultaneously. Chitin, a type of renewable natural polymer, was ground in the system and XRD analysis of ground powders showed they displayed highly activated properties. Unlike a high‐energy mechanical milling process, such as a vibratory (bead) mill which requires more milling time t, the final properties of the ground polymer in the cryogenic grinding system were highly dependent on the temperature in the chamber of the jet‐vortex mill. The grinding results of chitin also showed that the minimum diameters of the ground polymer products are larger than several tens of micrometers (e.g., 75 μm). The developed method offers a new choice for the production of materials, polymer modification (e.g., degradation), and recycling of wasted rubber and plastic.     

空气涡轮制冷机在粉碎EVA技术中的应用

低温粉碎是塑料,特别是低软化温度塑料超细粉碎的发展趋势。本文在深入研究了乙烯-醋酸乙烯共聚物（EVA）材料特性和粉碎机理的基础上,将空气涡轮制冷低温粉碎技术应用于EVA低温细碎中,有效地提高了EVA颗粒的超细粉碎效率;同时指出了该粉碎流程的关键技术及影响粉碎效果的主要因素,开辟了一条规模化、高质量、低能耗回收可再生塑料的新途径。此外,从能量守恒的角度出发,以工程应用为目标,对粉碎过程中的核心环节——冷冻和粉碎,初步进行了理论方面的计算分析。这些分析的结果有益于设备的完善及改进。     

Ultra-fine grinding mechanism of inorganic powders in a stirred ball mill

Recently, in various industrial processes, the need for fine particles, especially submicron-sized particles, has increased in the field of preparing raw powders such as fine ceramics and high value added products. Therefore, the research in fine grinding has gained more importance, especially, in submicron grinding. In the previous paper, a series of wet grinding experiments using inorganic powders by a stirred ball mill were performed. The grinding consumption power was measured, and the grinding rate constant, K, in the grinding kinetics equation was examined, based on a grinding kinetics analysis of experimental specific surface area with particle size distribution of ground products obtained under various grinding conditions. Also the effect of grinding aids on grinding rate constant K was investigated. It was confirmed that the grinding rate constant K, when using grinding aids improved by 1.95% and 25.6% for a 60 wt% and 70wt% slurry concentrate, respectively, when compared with the case of the absence of grinding aids. It was found that grinding aids have an important effect on increasing the grinding rate, especially for a slurry of high concentration.     

Hydrothermal pretreatment for the preparation of wool powders

Wool powders with low solubility could be easily prepared from wool fibers by combining hydrothermal pretreatment (HTP) and grinding processes. Transforming wool fibers into powders was the first step of exploiting wool as new materials such as bio‐thermoplastics. However, wool fibers were difficult to be prepared into powders only by grinding due to their toughness. This article used a chemical‐free method to obtain wool powders by grinding HTP‐treated wool fibers. Wool fibers after HTP at 130°C for 40 min or above were obviously easier to be broken into snippets with lengths of 25–150 μm after grinding for 1 min and shapeless super‐fine powders with diameters of 3–15 μm after ball milling for 10 min. Wool fibers after HTP were brittle mainly owing to decrease of α‐helices and S? S bonds. Combination of HTP and grinding could be an eco‐friendly and feasible treatment to prepare wool powders on industrial scale. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40173.     

Thermolysis of scrap tire using supercritical toluene

With toluene in the supercritical state, scrap tire was decomposed into low molecular weight hydrocarbon liquid and solid residual. The experiment was carried out at 523.15, 573.15 and 623.15 K and pressures of 5, 10, and 15 MPa. The liquid and solid residual products were further separated by a simple filtering method. The reaction time, tire weight and the amount of the solvent were determined for the optimal thermolysis. The decomposition percent and TGA were used to evaluate the decomposition characteristics in terms of temperature and pressure. The GC-MS was applied to the decomposed liquid products from the various conditions. The average molecular weight of the decomposed liquid products tended to become lower with the increasing temperature.     

Pyrolysis of scrap tire rubbers: Relationships of process variables with pyrolysis time

The functional relationships of industrially interesting variables such as pyrolysis temperature, heating rate, and sample size with pyrolysis time were explored to provide basic information on designing energy efficient processes. Pyrolysis kinetics of scrap tire rubbers tested in this study were investigated to formulate the functional relationships of pyrolysis temperature and heating rate. The pyrolysis time decreases exponentially with increasing pyrolysis temperature and heating rate, indicating high activation energies of pyrolysis reaction of the scrap tire rubbers tested in this study. The effect of heat transfer on the pyrolysis kinetics was evaluated by seeking the functional relationship between the sample size and pyrolysis time.The pyrolysis time increases linearly with increasing sample diameter. The slope of the straight line is proportional to the specific heat of the sample.     

轮胎硫化过程的数值模拟

介绍了利用有限元法对轮胎硫化过程进行数值模拟的基本原理和方法,并采用MARC有限元分析软件分析了半钢子午线轮胎175/70R13在硫化过程中各部位的受热历程,计算结果与轮胎硫化实时测温结果相当吻合,同时给出院 轮胎硫化过程中不同时刻的温度场分布云图,可以看出轮胎各部位的硫化历程差别较大,胎冠和胎肩的升温度速度小于胎侧和胎圈,胎肩、胎冠及胎趾的降温速度缓慢。     

Effects of Coarse Particles on the Gelcasting of Ceramic Foams

In order to study the effects of coarse particles on the gelcasting of ceramic foams, a coarse powder with a similar sintering ability as that of fine powder was designed. It was prepared by grinding the presintered foams manufactured using fine powder and by sieving with 200-mesh sieves. The resultant coarse powder was mixed with the fine powder to manufacture ceramic foams by direct foaming and the gelcasting method. The viscosities of suspensions with different fractions of coarse powder were close to each other at high shear rates. The flexural strength of the foams obtained by the mixed powders was about 10 MPa, which was about 25% lower than that obtained by the fine powder, while the permeability of the foams by mixed powders was about 30% higher than that without coarse powder. On the other hand, both the flexural strength and the permeability of the foams by the mixed powders had no clear relation with the fraction of coarse powder when it varied in the range of 5%–40%.     

Investigation into the removal of sulfur from tire derived fuel by pyrolysis

There is growing interest in the use of scrap tires as both a fuel and a feed material for petroleum feedstocks due to their abundance and their chemical composition. However, the sulfur content of scrap tires is a potential obstacle to scrap tires utilization as a fuel. In this paper, the partitioning of sulfur was investigated from the two major pyrolytic products from passenger car tires, liquid oils and solid chars, and the potential of producing a low sulfur char for fuel applications. The removal of sulfur during tire pyrolysis offers the greatest potential for the separation of sulfur products from the evolved gases and vapors. The influences of heating rate and pyrolysis temperature were investigated from 325 to 1000 °C, a range where substantial devolatilization occurs. The pyrolysis char and derived oil were analyzed for sulfur, and compared to the original parent sulfur content in tire derived fuel (TDF) samples. The results of sulfur determination verify that the overall desulfurization from the pyrolysis reaction is essentially unaffected by the heating rate but is affected by the ultimate pyrolysis temperature.     

Application of grinding kinetics analysis of inorganic powders by a stirred ball mill

The need for ultra fine particles has been increasing in the preparation field of raw powders such as fine ceramics and high functional products. A series of wet grinding experiments were carried out on inorganic powders such as calcite, pyrophyllite and talc by a stirred ball mill. The grinding rate constant K’ in the equation of grinding kinetics was examined based on the grinding kinetics analysis as the same type of function of a previous paper on a vertical type planetary ball mill. The experimental particle size distribution of the ground products was obtained in various grinding conditions. The grinding rate constants K and K’ were expressed by empirical equation involving experimental conditions by a stirred ball mill. The empirical equation on the grinding rate constant was expressed in terms of a function involving the ball diameter of grinding balls, the median diameter of feed material, and Bond’s work index of material, in the experimental conditions. The values of empirical constants C1 and C₂ were 21.13 and 0.0109 on K, while C₁ and C₂ were 120.99 and 0.0192 on K′, respectively. And the particle size distribution of ground products of each test material for a given grinding time was found to be expressing the selection function (the specific rate of breakage) which was obtained from the grinding kinetics analysis. In this study, the grinding rate change on calcite and pyrophyllite was similar at the same experimental operation condition. However, in the case of talc, it was observed that the grinding rate was not increased compared with other samples.     

废弃轮胎的热解回收技术

从反应温度、反应时间、催化剂等热解条件对废弃轮胎热解产品产量的影响、热解的产物分析及其应用、废弃轮胎中硫的迁移等方面进行了详细论述。指出反应温度是轮胎热解的主影响因素。热解后,一般得到质量分数为10%～30%的气体、38%～55%的油相产物及33%～38%的固相产物,这些产物均具有较高的热值,可以作为燃料。此外,还可以分离回收液相中的具有较高附加值的化学物质;固相产物以炭黑为主,经处理后可以作为炭黑回用或吸附剂使用。同时还对废弃轮胎热解产物中硫的转化分布进行了讨论。最后对废弃轮胎的其他处理回收技术进行了展望。     

Copyrolysis of scrap tires with waste lubricant oil

Two different types of scrap tires, passenger car tire (PCT) and truck tire (TT) with waste lubricant oil (WLO) were copyrolyzed in a fixed bed reactor at the temperatures of 550, 650 and 800 °C under nitrogen atmosphere. Copyrolysis products were investigated comparatively. The gaseous products were analyzed by GC–TCD. The physical and chemical properties of copyrolysis oils were characterized by means of ASTM methods, GC–FID, GC–MS, and ¹H NMR. In addition, boiling point distributions of hydrocarbons in copyrolysis oils were determined by using simulated distillation curves in comparison with commercial diesel. An increase in the temperature had no effect on the product distributions of copyrolysis and the composition of copyrolysis oils. However, the types of scrap tires strongly effected the product distributions and compositions of copyrolysis oils. Copyrolysis of PCT/WLO produced less amount of liquid and more amount of solid residue than that of copyrolysis of TT/WLO. However, the naphtha and aromatic content in oils from copyrolysis of PCT/WLO was found more than that of TT/WLO. The amount of aromatic content in copyrolysis oils found to be less than that of scrap tire derived oils. By comparing the copyrolysis oils with commercial diesel, copyrolysis oils contained lighter fraction than that of commercial diesel whereas the specific gravities and viscosities of copyrolysis oils were higher than that of commercial diesel.     

Copyrolysis of scrap tires with waste lubricant oil

Two different types of scrap tires, passenger car tire (PCT) and truck tire (TT) with waste lubricant oil (WLO) were copyrolyzed in a fixed bed reactor at the temperatures of 550, 650 and 800 °C under nitrogen atmosphere. Copyrolysis products were investigated comparatively. The gaseous products were analyzed by GC–TCD. The physical and chemical properties of copyrolysis oils were characterized by means of ASTM methods, GC–FID, GC–MS, and ¹H NMR. In addition, boiling point distributions of hydrocarbons in copyrolysis oils were determined by using simulated distillation curves in comparison with commercial diesel. An increase in the temperature had no effect on the product distributions of copyrolysis and the composition of copyrolysis oils. However, the types of scrap tires strongly effected the product distributions and compositions of copyrolysis oils. Copyrolysis of PCT/WLO produced less amount of liquid and more amount of solid residue than that of copyrolysis of TT/WLO. However, the naphtha and aromatic content in oils from copyrolysis of PCT/WLO was found more than that of TT/WLO. The amount of aromatic content in copyrolysis oils found to be less than that of scrap tire derived oils. By comparing the copyrolysis oils with commercial diesel, copyrolysis oils contained lighter fraction than that of commercial diesel whereas the specific gravities and viscosities of copyrolysis oils were higher than that of commercial diesel.     

A novel composite diamond-containing dispersed material of natural and synthetic diamonds powders and abrasive tools made of it

A two-stage process of producing a novel composite material based on fine-dispersed powders of natural diamonds and mesh grinding powders of synthetic diamonds. At the first stage of producing the components mixture is compacted and at the second stage it is sintered in a gas-thermal reactor of the physicochemical synthesis plant at a temperature of 1100–1200 °C and below ambient pressure in the methane atmosphere. The values of the morphometric characteristics and the uniformity of abrasive powders in these characteristics produced from the new diamond-containing material, their physico-mechanical and electrophysical properties were studied. The results of the use of these composite powders in grinding wheels for machining a hard alloy are discussed. A substitution of powders of the new composite material for synthetic diamond mesh powders in the cutting layer of a standard grinding wheel makes it possible to essentially (more than by a factor of 3) increase the wear resistance of the tool.     

Supercritical extraction of scrap tire with different solvents and the effect of tire oil on the supercritical extraction of coal

Scrap tires are a growing environmental problem because they are not biodegradable. In this investigation, supercritical extraction of scrap tire and co-processing of coal with tire oil were studied. In the first stage, tires were extracted at 400 °C with a number of different solvents. The effects of the hydrocarbon and polar solvents used under the supercritical extraction conditions on the conversion and oil product of tire were determined, and it was observed that all volatile organic material of the scrap tire was converted to the liquid or gas product. In the second stage, coal and supercritical extracted tire oil (SCETO) samples were extracted with different solvents using various tire oil/coal ratios. In general, the use of tire oil generated an improvement for coal conversion. Further, the oil yield was higher than those of coal alone runs. The SCETOs were characterized using spectroscopic (FTIR) and chromatographic analytical techniques (GC–MS). GC–MS, and FTIR results showed that the oils are mainly comprised of alkyl aromatic species. A significant amount of alkyl-substituted phenol compounds was also found to be present in the oils.     

Ball-mill grinding kinetics of master alloys for steel powder metallurgy applications

The grinding kinetics of three newly developed master alloys for steel powder metallurgy applications were investigated using a laboratory ball-mill. Non-first order grinding kinetic is observed for the three master alloys as the breakage rate increases with grinding time due to the work hardening of the ductile phase in the microstructure. Agglomeration of fine particles is observed after a critical time at which d₉₀ reaches its lowest value (~ 30 μm). Critical times are related to the hardness and the microstructure of the different master alloys. Agglomeration of fine particles can be overcome with the use of a process control agent. In this study, the addition of stearic acid to master alloy powders prior to grinding successfully eliminates agglomeration for long grinding times (d₉₀ ~ 16 μm after grinding for 270 min).     

贝氏体-马氏体耐磨磨球的生产

利用铬钢边角废料生产贝氏体-马氏体耐磨磨球,该磨球具有优良的机械性能和较高的性能/价格比.论述了化学成分、热处理工艺对耐磨磨球的质量影响.     

子午线轮胎11R22.5的硫化仿真分析

利用ABAQUS软件对子午线轮胎11R22.5进行硫化仿真分析,通过模型建立、材料参数及边界条件赋予等,建立起了仿真分析的硫化温度场和程度场云图。通过与轮胎硫化测温实验结果对比得到,各测温点仿真分析的硫化温度和硫化程度与实验结果基本吻合,验证了此分析方法的可行性。对硫化过程中的初始条件、边界条件及材料参数因素进行分析,得出轮胎初始温度、外温和胶囊的导热系数对轮胎的硫化程度影响较大。总体来说,目前初步建立起轮胎仿真的分析平台,并可为轮胎硫化工艺的优化提出理论指导。     

Effects of boron addition and intensive grinding on synthesis of anorthite ceramics

Anorthite ceramics were synthesized starting from mixtures prepared by using mechanochemical methods with boron oxide addition. The raw materials used in this study were Sivas Kaolin, calcined alumina/Al(OH)₃ and calcite. Statistical experimental design techniques (SED) were used in order to determine and analyze the more important process variables for synthesizing anorthite ceramics. Phase characterizations of synthesized powders were performed by XRD using Cu Kα radiation. Microstructural characterization was performed by SEM. The results of screening experimental design clarified that the temperature was the most important process variable. Second most important process variable was grinding speed of starting mixture which was followed by additive amount and additive type. The effect of both additive use and grinding on anorthite synthesis helped decrease the synthesis temperature down to 900 °C.     

钡钛醋酸盐凝胶制备BaTiO3粉体

本文报道了用ｓｏｌ－ｇｅｌ法制备钡醋酸盐凝胶，并分别作高灼烧和水热处理制备ＢａＴｉＯ３粉体。通过对产物的表征，比较了这两种处理过程，进而对水热条件下陶瓷粉体的形成机理作了探讨。由于水热条件，凝胶在反应介质中溶解，进而结晶形成晶粒，因此所形成的ＢａＴｉＯ３晶粒线度小；线度分布范围窄。晶粒形貌完整，明显优于高温灼烧处理后得到的粉体。