The effect of composition on the properties of nylon 612 copolymers

The series of nylon 612 copolymers was synthesized from caprolactam (C) and laurolactam (L) at 145°C. The 50/50 C/L molar ratio copolymer was found to have the minimum melting temperature (T_m ) for the series. The glass transition temperatures (T_g 's) of the copolymers were affected by the crystallinity of the copolymers. The T_g was at a minimum for the 50/50 copolymer for crystalline samples. However, for amorphous samples there was a decrease in T_g with increasing L content. Percent crystallinity was determined by differential scanning calorimetry and X-ray techniques. It was found that the degree of crystallinity was at a minimum for copolymers of 70/30 to 40/60 C/L ratios. Coefficients of linear thermal expansion (CLTE) were obtained for the copolymers at 10°C intervals from 20 to 70°C for dry and from 20 to 50°C for samples conditioned at 50% relative humidity and 50°C. The dry samples gave lower initial values, but had a greater temperature dependence than the conditioned samples. As expected, the CLTE was found to be lowest for samples exhibiting the highest crystallinity. The tensile strengths and moduli decreased rapidly with increasing L up to the 70/30 C/L ratio after which they remained relatively constant. Elongations reached maximums between 70/30 and 40/60 C/L ratios. An inverse relationship was found between crystallinity and impact strength.     

Evaluation of a model for predicting the air-permeability of needle-punch and calendered material

The proposed model has limited use for evaluating the effect of the needle-punching and calendering regimes on the air-permeability of the material. It is somewhat difficult to correct the model to consider the effect of changes in thickness during needle-punching and calendering. The limited use of the model is due to the use of the filling factor and thickness of the material as the structural parameter.     

Suitability of Zavadov deposit dolomites for use as raw material

Conclusions Investigations of raw Zavadov deposit dolomite showed that in strength it belongs to the dense varieties of dolomite with a fine crystalline structure. The weight % of the basic component (dolomite) is 88–98%. The impurities are calcite, quartz, clay particles, and iron oxides.By firing the dolomite in the form of the previously separated 5–25-mm fraction at 1700–1750°C it is possible to provide sintering of practically all of the samples. The use of preliminary grinding and briquetting improves sintering but does not provide significant advantages in comparison with firing in granular form. The addition of scale causes an improvement in sintering and an increase in the resistance to hydration.The resistance of hydration after firing at 1750°C in storage in air of samples Nos. 4–17 was satisfactory while the dolomite of samples Nos. 1–3 hydrated significantly more rapidly. With the addition of 1% scale and firing at 1700°C in storage in air the resistance is significantly greater.As the result of the investigation it was established that the dolomite, with the exception of individual samples, meets the requirements of Industry Standard 14-84-82 for raw metallurgical dolomite for patching and filling the sills of hearth furnaces and also for firing for metallurgical dolomite. A further improvement in dolomite quality is pssible with selective mining and benefication of it.Translated from Ogneupory, No. 2, pp. 36–40, February, 1987.     

Chromium powder as a reference material for the quality control of particle-size measurement by laser diffraction

Chromium is an important alloying element for aluminium melts. During aluminium cast house practice, chromium is mainly added to melts of aluminium in the holding furnace as tablets or minitablets (compressed compacts of chromium and aluminium powders). Particle-size analyses of chromium powder used as raw material can routinely be carried out by laser diffraction to assure correct packing. Factors affecting the laser diffraction analysis were studied by means of designed experiments in order to improve and control the quality of such particle-size measurements. Moreover, a laboratory reference material based on chromium powder was produced to assure the quality control of particle-size measurements. The material was carefully handled (collection, pre-treatment and preservation) and its homogeneity and term stability were verified. Laser diffraction analyses were validated against sieve-type measurements for the same material.     

Flexible graphite modified by carbon black paste for use as a thermal interface material

Polyol-ester-based carbon black pastes are used to either coat or penetrate flexible graphite, thereby increasing the thermal contact conductance of flexible graphite between copper surfaces. Paste penetration by up to an effective paste thickness (the volume of the penetrated paste divided by the geometric area of the flexible graphite) of 5 μm increases the conductance by up to 350%, 98% and 36% for thicknesses of 50, 130 and 300 μm, respectively. Paste coating up to 10 μm increases the conductance by up to 200%, 120% and 65% for thicknesses of 50, 130 and 300 μm, respectively. The paste penetration is more effective than the paste coating in enhancing the conductance, when the thickness is below 130 μm. At thickness ?130 μm, paste penetration and paste coating are similarly effective. These results stem from the relatively low interfacial thermal resistivity provided by paste penetration and the relatively high through-thickness thermal conductivity provided by paste coating. Paste penetration decreases the thermal conductivity of flexible graphite, but paste coating does not affect the conductivity. Both penetration and coating decrease the interfacial resistivity. The highest thermal contact conductance is 1.4 × 10⁵ W/m² K, as provided by paste-penetrated flexible graphite of thickness 26 μm.     

Potential for use of crushed waste calcined-clay brick as a supplementary cementitious material in Brazil

The Brazilian ceramic industry generates large amounts of calcined-clay waste. This paper examines the factors that influence its potential for use as a partial replacement of Portland cement. Superplasticized mortars of equal workability containing ground crushed waste calcined-clay brick (GCWCCB) in the proportions of 10, 20, 30 and 40% as a cement replacement were analyzed through mechanical tests, pore structure characterization and durability tests. The results indicated the optimal percentages of substitution lies between 10% to 20%. The potential reduction of CO₂ emissions could be as high as 10% of current Brazilian cement industry emissions if this approach were to be fully implemented, and it could be eligible for “Clean Development Mechanism” credits under Kyoto protocol.     

涤纶长丝装置改纺锦纶长丝

将涤纶长丝装置改纺锦纶长丝 ,着重介绍了装置的切片输送加料系统、纺丝部分的单体抽吸装置及熔体预过滤器、卷绕头部分的电器仪表和压缩空气系统等设备的改造 ,改造后的装置可生产 90～ 186dtex锦纶长丝 ,且 POY合格品率大于等于 99.8%。     

Study of the possible use of intermediate flax as raw material for production of cellulose

In treating intermediate flax with concentrated solutions (greater than 5 M) of sodium hydroxide, crystalline regions of cellulose totally pass from modification CI to modification CII, despite the presence of contaminants (lignin, hemicellulose, etc.). The presence of hydrogen peroxide in basic solutions shifts the beginning of the CI CII phase transition toward higher concentrations of sodium hydroxide. A sufficiently high degree of purification of intermediate flax (~93% cellulose content) can be attained in two-step treatment including acid-peroxide cooking in the first stage and alkaline cooking in the second stage and in alkaline-peroxide cooking.Translated from Khimicheskie Volokna, No. 5, pp. 30–33, September–October, 2004.     

Efficiency of the use of silicon nitride ceramics as an armor material

The efficiency of the use of materials based on Si₃N₄ for armor is estimated experimentally in comparison with conventional alumina ceramics. It is shown that the studied compositions of monolithic and composite ceramics based on Si₃N₄ are 12–30% more efficient in ballistic applications than alumina ceramics. Monolithic high-density OTM-917 ceramics based on Si₃N₄ (PCS) is shown to have the highest physicomechanical properties among the studied materials. The choice of the composition depends on the requirements on the mass, size, and cost of the armor. The experimental results have been confirmed by tests for bullet and splinter strength. Translated from Ogneupory i Tekhnicheskaya Keramika, No. 6, pp. 9–12, June, 1997.     

硫化钙碳酸化制备硫化氢工艺参数的研究

研究了以磷石膏为原料烧制硫化钙和碳酸化硫化钙生产硫化氢的工艺路线,并用正交设计法找出了硫化钙碳酸化制备硫化氢的最优工艺参数.通过实验得到最优工艺参数为气流速度110个气泡/min、温度60℃、反应时间5 h,此时硫的转化率达93%.     

Methods for predicting size degradation of Western Canadian coals

Excessive size degradation of friable coal occurs during mining, handling and processing. This reduces the efficiency and increases the cost of coal preparation. Three methods are investigated aimed at predicting the degradation of friable Western Canadian coals. The methods include a tumbling test, scanning electron microscopy of coal micro-structure, and measurement of the ΔP index of gas desorption. Results indicate that rectilinear relations exist between the ΔP index and the amount of < 0.6 mm (28 mesh) coal generated during the tumbling test, and between the ΔP index and the amount of < 0.6 mm coal produced during the mining and handling of run-of-mine coals. The rate of gas desorption, which is indicated by the ΔP index, is dependent on the degree of fissuration of the coal which also leads to the friability of the coal. The relation between the ΔP index and the amounts of fines produced by degradation processes can be used for predicting, at the exploration or development stage, the amount of <0.6 mm material that will be produced from new seams.