曲率对PE管材环向拉伸强度的影响

选用环向拉伸试验的方法对高密度聚乙烯（PE-HD）管材环向拉伸的强度进行检测,主要研究拉伸试样在试验进行过程之中曲率的改变对环向拉伸强度的影响,整个试验过程采取多个平行试样进行试验,用以取得准确的试验数据来确定试验结果,并就曲率对PE-HD管材环向拉伸强度影响的变化规律进行研究探讨。结果表明,同一外径的PE-HD管材,随着环向拉伸试样在试验中曲率的减小,环向拉伸强度数值减少可达10 %。     

PVC-O管材在非开挖工程中应用的可行性分析

测试了PVC-O管材的拉伸性能、环向拉伸强度、环刚度,进行了落锤冲击试验、韧性破坏试验、粘接强度试验和弯曲试验,并与PE管材、M PP管材进行了性能对比,分析了其应用在非开挖施工中的可行性。结果表明:PVC-O管材的性能完全满足非开挖施工的要求,具有抗拉、抗压、抗冲击、施工速度快、成本低等优点。     

大口径低熔垂管材专用料开发和加工应用

介绍了中国石油吉林石化公司PE100级大口径低熔垂管材专用料JHMGC100S-LS的开发和应用情况。通过优化生产工艺条件,使产品的熔融指数更稳定,拉伸屈服应力、拉伸断裂标称应变、简支梁冲击强度等重要指标不断提升。结果表明,JHMGC100S-LS的抗熔垂性能良好,生产出的产品外观良好,能够满足大口径管材生产需要。     

简讯

德意利新品管材生产线通过专家鉴定 日前青岛德意利集团3种新产品通过了由青岛科教局组织的成果鉴定。专家们一致认为,德意利集团研制的大口径中空壁缠绕管材生产线、大口径中空壁缠绕管材和PVC-U内螺旋中空壁管材生产线3种产品,各项技术指标均达到国际先进水平,具有较好的社会效益、环境效益和经济效益。 专家们认为,该公司生产的大口径中空壁缠绕管材符合     

双向拉伸薄壁管成型中冷却条件的影响分析

围绕双向拉伸薄壁管工艺技术中冷却条件对某些变形参数,如轴向拉伸比、环向扩张比、壁厚分布、强度等的影响进行了综合分析。数据说明拉伸后的快速冷却有利于管的尺寸稳定和直线度改善。拉伸时的自然冷却会产生不均匀的产品,快速水冷却拉伸工艺能显著改善管的耐环境应力开裂性,成倍提高其强度。轴向拉伸比和环向扩张比要合理匹配。     

塑料管材双向拉伸技术的研究进展

介绍了材料的自增强机理和可用来双向拉伸的材料,并介绍了几种国内外主要的双向拉伸技术和装置,以及各自的工作原理和工艺流程,讨论了双向拉伸技术对管材性能的影响,最后通过数据分析得出：拉伸取向在提高管材的强度和韧性的同时,减小了管材的壁厚。     

TA16钛合金管材拉伸性能及组织研究

对大变形轧制的TA16钛合金管材在不同温度下进行热处理,分析热处理温度对管材室温拉伸性能和显微组织的影响,选择最优工艺对管材进行热处理,测定室温拉伸性能及工艺性能。并对管材进行不同温度高温拉伸,分析温度对管材高温拉伸性能和拉伸断口形貌的影响。结果表明:在600~750℃热处理时,管材强度和塑性随着温度升高呈下降趋势,晶粒逐渐长大。在100~350℃高温拉伸时,管材强度随温度升高而降低,拉伸断口均出现颈缩,表现出塑性断裂特征。     

PVC管材开发新动向

随着PVC管材市场的扩大,国外在管材的加工工艺方面也进行了大量的改进工作,推出了一些新型管材。国外生产厂家为了降低管材成本,降低管材噪音,开发了芯层发泡管;采用共挤出法使低发泡PVC管材内外表面覆盖一层不发泡的PVC,其韧性比不发泡管材更好,耐磨损,隔音效果好,并有较好的承载能力,比实芯壁管材可节约25％～40％的树脂。为了降低大口径管材的生产成本,国外还开发了径向有增强筋的薄壁大口径管材。这种管材比旧工艺节约树脂40％,生产方法简单,首先挤出加工成T型型材,然后缠绕焊接成带加强筋的管材,一次加工成型,具有与旧工艺生产的管材相同的强度,且管重大为减轻,安装方便,管径可达500mm。其次开发了空芯壁的大口径管材,管径最大达1.5m。其生产方法是先挤出加工成矩形空芯型材,然后螺旋缠绕并用红外线焊接成管材,加工速度与普通挤出管材的速度相同,并可节约50％～60％的树脂,管材有实芯壁管材一样的强度和韧性。为了减少挤出加工PVC管材的气泡,国外普遍采用了表观密度为0.6g/cm3以上的PVC树脂,解决了疏松型树脂喂料量不足的问题,提高生产效率25％左右。为了提高管材质量,国外还生产出一种新型锥形双螺杆 挤出机。在生产大口径管材时,不使用高表观密度的球形树 脂,而使用通用疏松型树脂也能生产出高质量的大口径管 材,解决了使用一般挤出机喂料量不足、管材易产生气泡的 问题。这些新技术、新设备的出现为我国PVC管材的大发 展铺平了道路。(塑市)     

PVC-UH管材用于给水管网建设

<正>新疆中泰集团库尔勒石油石化产业园日前正在建设的工业供水工程首次采用PVC-UH管材,用于给水管网建设。这种管材是新疆中恩高科技管业有限公司生产的高性能硬聚氯乙烯管材,环保无毒,输送水质达到直饮水标准,且耐水压、抗冲击,拉伸强度优于常见管道材料。其制造原料通过定级,并加入铅盐稳定剂,质量得到保证,生产配方绿色环保。     

PVC—U压力管静液压强度预控新方法

介绍了两种PVC-U压力管静液压强度预控新方法,即管材环向拉伸屈服强度测试法和长期抗蠕变性能测试法.此两种新方法简单易行,可操作性强,适应面广,运行成本低,能正确指导PVC-U压力管材的配方设计,有效地进行产品质量监控.长期抗蠕变性能试验还为管材长期静液压强度的验证提供了可能.     

Enthalpies of vaporization of oligomers of poly(hexamethylene sebacate) and esters of alkylcarboxylic acids

Enthalpies of vaporization for esters covering a molecular weight range of about 74–939 g/mol · [monocarboxylics; linear esters of sebacic series; branched esters of triglyceride series; and, oligomer esters of poly(hexamethylene sebacate)] and a temperature range of about 273.15–523.15 K have been empirically fitted to within about 5% to an equation of the following form: ΔHv(T,M) = S(T)f(M) + I₀(T), where S(T) = C Ln(T) + K₀, I₀(T) = aT + b₀, and f(M) = M/(1 + a₀M), M is the molecular weight (molar mass); T is in degrees Kelvin; and, C, K₀, a, b₀, and a₀ are constants. These results were used to determine the heat capacity difference, ΔC_p = C_p(l) − C_p(g), and compared to calculated values from functional relationships of C_p(l) and C_p(g), l is liquid g is gas. The heat capacity difference results in conjunction with C_p(l) were used to empirically calculate the heat capacity of the gas, C_p(g), over the molecular weight and temperature ranges investigated and compared to a group contribution method. The functional forms for ΔHv(T,M), ΔC_p(T,M), C_p(l), and C_p(g) were also found to be applicable for n-alkanes. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 731–746, 1998     

Assessment of the activities of catalysts for the hydrocracking of coal by means of hydrogen evolution

A close relation has been found between hydrogen evolution from coal-catalyst and pitch-catalyst systems and catalytic activities of liquefaction reactions. A MoO₃?TiO₂ catalyst has the highest activity and the order of activity of the catalysts for hydrogen evolution is: MoO₃?TiO₃> MoO₃?SiO₂>10% $\text{Fe}{}_2\text{O}{}_3\text{TiO}{}_2\text{?AI}{}_2\text{O}{}_3\text{>}\text{coal alone}$. The same trend was observed for benzene-soluble materials for the hydrocracking of Akabira Coal.     

Peculiarities of establishment of steady-state frontal polymerization of vinyl monomers

Frontal radical polymerization of vinyl monomers in non-stationary mode is investigated theoretically. It is shown that the formation and the time of establishment of steady-state polymerization heat autowaves considerably depend on the initial temperature, T_i. When T_i is less than the adiabatic heating temperature (T_a), the excess heat and relatively high conversion foster front formation before the non-stationary one. Whereas, for T_i > T_a, steady-state frontal polymerization regime is established, when the heat flow from the outer source is considerably less than the heat evolving due to the chemical reaction.     

Chemical assessment of the zinc status of some soils of the semi-arid region of India

To find critical tissue levels of Zn for wheat, and to evaluate various chemical extractants, a screen-house experiment was conducted on 21 diverse soils representing semi-arid regions in Haryana State, India. The extractants differed in the amounts of Zn extracted and the order was: 0.1 N HC1 > EDTA-NH₄OAc > EDTA-(NH₄)₂CO₃ > DTPA + CaCl₂. The amounts (mg kg^–1) of extractable Zn associated with a yield reduction of 20% were: DTPA + CaCl₂, 0.60; EDTA — (NH₄)₂CO₃, 0.80; EDTA-NH₄OAc, 0.92 and 0.1 N HCl, 1.20. The corresponding critical Zn concentration in ten weeks old plants was found to be 17 mg gm^–1. The DTPA + CaCl₂ method gave the best correlation (r = 0.85) between extracted Zn and Bray's per cent yield. It is recommended for assessing Zn status of soils of semi-arid region.     

Preparation of regioisomers of structured TAG consisting of one mole of CLA and two moles of caprylic acid

TAG (MLM) with medium-chain FA (MCFA) at the 1,3-positions and long-chain FA (LCFA) at the 2-position, and TAG (LMM) with LCFA at the 1(3)-position and MCFA at 2,3(1)-positions are a pair of TAG regioisomers. Large-scale preparation of the two TAG regioisomers was attempted. A commercially available FFA mixture (FFA-CLA) containing 9-cis, 11-trans (9c, 11t)- and 10t,12c-CLA was selected as LCFA, and caprylic acid (C₈FA) was selected as MCFA. The MLM isomer was synthesized by acidolysis of acyglycerols (AG) containing two CLA isomers with C₈FA: A mixture of AG-CLA/C₈ FA (1∶10, mol/mol) and 4 wt% immobilized Rhizomucor miehei lipase was agitated at 30°C for 72 h. The ratio of MLM to total AG was 51.1 wt%. Meanwhile, LMM isomer was synthesized by acidolysis of tricaprylin with FFA-CLA: A mixture of tricaprylin/FFA-CLA (1∶2, mol/mol) and 4 wt% immobilized R. miehei lipase was agitated at 30°C for 24 h. The ratio of LMM to total AG was 51.8 wt%. MLM and LMM were purified from 1,968 and 813 g reaction mixtures by stepwise short-path distillation, respectively. Consequently, MLM was purified to 92.3% with 49.1% recovery, and LMM was purified to 93.2% with 52.3% recovery. Regiospecific analyses of MLM and LMM indicated that the 2-positions of MLM and LMM were 95.1 mol% LCFA and 98.3 mol% C₈ FA, respectively. The results showed that a process comprising lipase reaction and short-path distillation is effective for large-scale preparation of high-purity regiospecific TAG isomers.     

The influence of structure order on the kinetics of dehydroxylation of kaolinite

The structural order of kaolinite is an important factor that shows a substantial effect on the processes which take place during the thermal treatment of kaolin. The influence of structural order on the dehydroxylation process was investigated by simultaneous thermogravimetry and differential thermal analysis (TG-DTA). The thermal analysis was performed on the samples with gradually decreasing structural order prepared by milling procedure. The apparent activation energy of dehydroxylation process decreases with decreasing structural order according to the exponential function. The extrapolation of experimental data leads to the estimation of apparent activation energy of 76.6 kJ mol^?1 and of frequency factor of 0.12 × 10⁴ s^?1 related to completely disordered form of kaolinite, while the ordered form shows the apparent activation energy of 216.17 kJ mol^?1 and the frequency factor of 9.26 × 10⁴ s^?1. The relationships between features such as the infrared pattern of treated material, the degree of structural order and the apparent activation energy were established.     

Preparation of superacid of iron-supported zirconia for reaction of butane to isobutane

A highly active superacid of 2 wt% Fe-supported ZrO₂ for the skeletal isomerization of butane to isobutane was obtained by sfexposing Fe₂O₃/ZrO₂ to 1 N H₂SO₄ followed by calcining in air at 700°C for more than 24 h; the Fe₂O₃/ZrO₂ was prepared by impregnating zirconia gel with a solution of Fe(NO₃)₃ followed by drying at 300°C (2 wt% Fe). A much lower activity was observed with the opposite procedure, where the first impregnation was sulfation of the gel, followed by a second impregnation with the iron compound. It was proved from analysis of the sulfur content in the catalysts that residual sulfur species were not related with generation of the superacidic sites. XPS showed the catalyst to be Fe₂O₃ supported on ZrO₂.Superacids by metal oxides, VIII. For previous publications VI and VII in this series see refs. [10,11].     

Evaluation of methods of measurement of nitrogen in poultry and animal manures

Kjeldahl nitrogen (N), total N and forms of inorganic N (ammoniacal (NH₄)-N, nitrate (NO₃)-N and nitrite (NO₂)-N) were measured in a range of animal manures. The manures include fresh samples of poultry manure, sheep manure, horse manure, dairy slurry and pig slurry and composted poultry manure. Kjeldahl N was measured by standard micro-Kjeldahl digestion. For total N measurements, NO₃-N and NO₂-N were recovered during Kjeldahl digestion by pretreatments with various oxidizing and reducing agents. Inorganic forms of N were measured by extraction with 2M KCl solution.Kjeldahl digestion alone allowed measurement only of organic N and NH₄-N. Amongst various modifications to the Kjeldahl, pretreatment with either acidified (H₂SO₄) Zn-CrK(SO₄)₂ or acidified (H₂SO₄) reduced Fe achieved complete recovery of NO₃-N. Nitrite N was only recovered by first oxidising the NO ₂ ^- to NO ₃ ^- with KMnO₄ followed by reduction to NH₄-N with acidified (H₂SO₄) reduced Fe.More than 95% of the total N in fresh animal manure was present as organic N and NH₄-N which were recovered by the standard Kjeldahl digestion. In the case of fresh manures there was no difference between the amount of total N measured by the Kjeldahl digestion and its modified methods. However composting of poultry manure or drying of poultry manure, pig slurry and dairy slurry resulted in an increase in NO₃-N which was not recovered during Kjeldahl digestion alone. Under these conditions the total N could be measured by pretreating the samples with KMnO₄ and reduced Fe prior to Kjeldahl digestion.Drying of animal manures caused a decrease in organic N and NH₄-N, especially in poultry, pig and dairy manures. There was a slight increase in NO₃-N; but most of the decrease in N content with drying was attributed to the volatilization loss of ammonia (NH₃). Amongst various drying methods examined air drying caused maximum loss of N as NH₃ whereas freeze drying caused minimum loss of N. This suggests that fresh animal manures can be freeze dried for analysis of N which causes minimum loss of N.     

Estimation of the Surface Energy of Polymer Solids

The methods to estimate the surface tension of polymer solids using contact angles have been reviewed in the first part. They are classified into the following three groups depending on the theories or the equations applied: (1) the methods using the Young's equation alone, (2) the methods using the combined equation of Young and Good-Girifalco, and (3) the methods using the equations of work of adhesion. Some notes and comments are given for each method and results are compared with each other. The two-liquids method for rather high energy surface is also introduced.

Next, some new possibilities to evaluate the surface tension of polymer solids are presented by our new contact angle theory in consideration of the friction between a liquid drop and a solid surface. The advancing and receding angles of contact (θ _a and θ _r ) are explained by the frictional tension γ_F and accordingly two kinds of the critical surface tension γ_C (γ_Ca and γ_Cr ) are given.

This work has shown that one of the recommendable ways to evaluate γ_S is either the maximum γ_LV cos θ_a or the maximum γ_C using the advancing contact angle θ_a alone, and another way is the arithmetic or the harmonic mean of the γ_Ca and γ_Cr . A depiction to determine the γ_C such as ln(1 + cos θ₀ ) vs. γ_LV with cos θ₀ = (cos θ₀ + cos θ_r )/2 has also been proposed.     

Effects of preparation methods of support on the properties of nickel catalyst for hydrogenation of m-dinitrobenzene

Using tetraethyl orthosilicate (TEOS) as the precursor of silica, the silica aerogel and xerogel, which were used as supports of nickel-based catalysts for liquid hydrogenation of m-dinitrobenzene to m-phenylenediamine, were prepared by the sol-gel method combined with supercritical drying (SCD) and conventional drying, respectively. Then, a series of nickel-based catalyst samples supported on these supports were prepared by the incipient wetness impregnation method with an aqueous solution of nickel nitrate as well as lanthanum nitrate as impregnation liquids. Based on the characterization results of nitrogen adsorption-desorption (BET), X-ray diffraction (XRD), temperature programmed reduction (TPR), temperature-programmed desorption of hydrogen (H₂-TPD), and catalytic activity evaluation, the physico-chemical properties and catalytic performances of the catalysts were investigated. The results show that the nickel crystallites on the binary nickel catalyst using silica aerogel as support are of smaller particle size. However, compared with the sample supported on silica xerogel, the nickel catalyst supported on the silica aerogel exhibits lower activity and selectivity for the hydrogenation of m-dinitrobenzene because it has a lesser amount of active sites and weaker absorption ability to reactants caused by sintering of the nickel crystallites. The addition of promoter La₂O₃ could increase the activity and selectivity of the catalysts. Among all the nickel-based catalyst samples prepared, the La₂O₃ promoted ternary nickel-based catalyst supported on silica xerogel exhibits the highest activity and selectivity for the hydrogenation of m-dinitrobenzene to m-phenylenediamine, which could be attributed to its highest active surface area and appropriate absorption strength to reactants. Over this promising catalyst, the conversion of m-dinitrobenzene and the yield of m-phenylenediamine could reach 97.0% and 93.1%, respectively, under proper reaction conditions of hydrogen pressure 2.6 MPa, temperature 373 K, and reaction time 1 h. Translated from Journal of Chemical Engineering of Chinese Universities, 2006, 20(5): 723–727 [译自: 高校化学工程学报]