Influence of Poly(vinyl chloride) on Natural Rubber/Chlorosulfonated Polyethylene Blends

Blend of natural rubber (NR) and chlorosulfonated polyethylene (CSM) was so interesting due to binding of the good oil resistance of CSM, the good mechanical properties and low cost of NR. However, due to the different polarities of two rubbers, phase separation and inferior properties of NR/CSM blend were obtained. The practical way to improve its properties is the addition of the third component to bind both phases of the blend. Effects of poly(vinyl chloride), PVC as compatibilizer on cure characteristics, morphology, mechanical properties and automotive fuel resistance of NR/ CSM blend were investigated. In this contribution, NR/CSM blend with blend ratio of 50/50 was prepared using a two-roll mill, and then vulcanized in a compression mold at 160°C. The PVC content was varied from 1 to 7 phr. It was found that the usage of 7 phr PVC led to improve interaction between NR and CSM phases. Therefore, increase in cure characteristics, mechanical strength and automotive fuel resistance of the blend was observed.

Natural Rubber/Fluoro Elastomer Blends: Effect of Third Component on Cure Characteristics, Morphology,Mechanical Properties, and Automotive Fuel Swelling

The natural rubber (NR) was mixed with fluoro elastomer (FKM), due to the difference of polarity in NR and FKM made this blend incompatible so the third component was used. NR/FKM blended with the blend ratio of 70/30 was prepared by using a two-roll mill and vulcanization in a compression mold at 180℃ using peroxide as a curative agent. Epoxidized natural rubber (ENR) or polyisoprene-graft-maleic acid monomethyl ester (PI-ME) was used as a third component. The curing characteristics, morphology, mechanical properties, and automotive fuel swelling were investigated. The results indicated that the scorch time and cure time of the blend rubbers were longer as adding ENR or PI-ME. Both mechanical properties and automotive fuel resistance of the blend rubbers were found to increase with adding ENR in rubber blend. Conversely for adding PI-ME, automotive fuel resistance of the blend rubbers was found to decrease progressively with increasing PI-ME content.

Improved Automotive Fuel Resistance of Natural Rubber/Chlorosulfonated Polyethylene Blends by Blending Epoxidized Natural Polymer

The natural rubber (NR) was mixed with chlorosulfonated polyethylene (CSM), due to the difference of polarity in NR and CSM made this blend incompatible and the third component was used. Epoxidzed natural rubber (ENR) was used as a third component. NR/CSM blended with the blend ratio of 50/50 was prepared by using a two-roll mill and vulcanization in a compression mold at 160°C. The ENR content was varied from 1 to 7 phr. The curing characteristics, morphology, mechanical properties, and automotive fuel swelling were investigated. The results indicated that the cure time of the blend rubbers was shorter as adding ENR. The mechanical properties of the blend rubbers were not affected by ENR content. However, automotive fuel resistance of the blend rubbers was found to increase with adding ENR in rubber blend.

Development of Biobased Poly(Lactic Acid)/Epoxidized Natural Rubber Blends Processed by Electrospinning: Morphological, Structural and Thermal Properties

This article reports the production of electrospun fibers from blends of poly(lactic acid) (PLA) and epoxidized natural rubber (ENR) solutions. The produced fibers were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). SEM images showed the reduction in fiber size with ENR content of up to 25% in the mixture PLA/ENR. FTIR analysis revealed a possible interaction between carboxylic group of PLA and epoxi group of ENR. Thermal analysis showed the increase of the crystallinity fraction with ENR content and a decrease in thermal stability of eletrospun mats with the addition of ENR. The dynamic mechanical properties showed an enhancement of the stiffness of PLA/ENR blends with the increase of ENR content, which can support the production of interesting materials for tissue engineering based on renewable and biocompatible polymers. The reported properties indicate the possibility to use such fiber mats as potential materials in tissue engineering.

Investigations on the Performance of the Blending Natural and Artificial Graphite for Lithium ion Battery

In this work,it was found that the improved battery performance such as thermal stability and cycle performance with the blending of nature and artificial graphite.

STUDY ON THE PROPERTIES OF BLEND OF NATURAL RUBBER LATEX/METHYL METHACRYLATE GRAFTED RUBBER LATEX BY GAMMA RADIATION

Natural rubber latex （NRL） and methyl methacrylate （MMA） grafted rubber latex were blended in different ratios and irradiated at various absorbed doses by gamma rays from Co-60 source at room temperature. The tensile properties, swelling ratio and permanent set were measured. The maximum tensile strength and modulus at 500% elongation were obtained at an absorbed dose of 8 kGy. Modulus increases from 6.99 MPa to 9.87 MPa for an increase in proportion of MMA grafted rubber from 40% to 60% in the blend at similar absorbed dose. Elongation at break and swelling ratio decrease with increasing absorbed dose as well as the MMA grafted rubber content in the blends. The decreasing trend of permanent set is high up to 5 kGy absorbed dose, and beyond that dose, it becomes almost flat.

Preparation and Properties of PVC/ELNR-30 Blends

The mechanical and thermal properties of solution-cast blends of Polyvinyl chloride (PVC) and Epoxidized Liquid Natural Rubber having 30 mole % epoxidation (ELNR-30) have been examined using Zwick materials testing machine and heating in air circulating oven (200°C) at different time intervals respectively. The ELNR was prepared by oxidative degradation of natural rubber latex using Phenylhydrazine/Oxygen system and subsequent epoxidation with formic acid and 30% H2O2. Tensile strength of unblended PVC was 26.5 ± 0.5 MPa. The blends had lower tensile strength which decreased with increase in blend ratio of ELNR-30. Experimental data revealed that there was greater homogeneity in the PVC/ELNR-30 (80/20) compared with PVC/ELNR-30 (90/10). The PVC/ELNR-30 (80/20) also showed superior elongation at maximum (%) than the unblended PVC and PVC/ELNR-30 (90/10) in that order. Thermal stability decreased in the order PVC, PVC/ELNR-30 (90/10), PVC/ELNR-30 (80/20).

天然气管道掺氢输送研究现状与分析

天然气管道掺氢输送是实现大规模、远距离和低成本氢气运输的手段之一,但氢气掺入天然气管道给管线运行工况、安全维护等带来了不容忽视的影响,具有一定的安全隐患。为此,围绕国内外天然气管道掺氢输送的技术研究与工程应用现状,讨论了影响天然气管道掺氢安全输送的主要因素,即掺氢引起的天然气物性改变、氢致失效和掺混不均,以及掺氢管道泄漏扩散和燃爆的安全问题。结果表明,天然气掺氢后,对现有管材提出了新要求,需开展相关实验以揭示氢致失效机理,掺氢天然气管道停输后是否发生气体分层与管道是否发生氢致失效密切相关。掺氢天然气管道泄漏扩散及自燃的安全范围、发生燃爆所需的最小掺氢比及燃爆机理尚不明晰,实验研究与实际运营存在差距。针对天然气管道掺氢输送的规范、标准及相关监管政策仍处于发展阶段,需要结合系统的研究数据及实践进一步完善。以上结果明晰了掺氢输送存在的风险,可为大规模掺氢混输的工程推广与实际运营提供参考。

纯氢与掺氢天然气管道摩阻系数预测

纯氢与掺氢天然气管道是实现氢气长距离、大规模输送的最佳方式之一,其中摩阻系数是气体管道水力计算的关键参数,现有的经验公式不能满足预测掺氢天然气的摩阻系数要求。为改进传统的摩阻系数计算公式在纯氢与掺氢天然气管道系统的适用性,搭建了纯氢和掺氢天然气管输调压综合实验平台,开展纯氢和不同比例的掺氢天然气管输流动实验,根据实验采集的流量、温度、压力和管道的长度、管径等参数计算管道的摩阻系数,同时建立了摩阻系数与雷诺数、粗糙度之间的关系,并修正了传统摩阻系数公式,最后利用湖南省巴陵—长岭纯氢气管道的实际运行数据进行了验证。研究结果表明:①由于氢气与天然气物性差异较大,掺氢比会影响流动摩阻系数,相同条件下掺氢比越大摩阻系数越小;②传统摩阻系数计算公式存在30%左右的误差,创新提出的适用于纯氢和掺氢天然气的3段式摩阻系数经验公式,相对误差最大11.84%,能够有效降低误差;③与巴陵—长岭纯氢气管道实际的运行数据相比,修正后摩阻系数预测公式的平均误差为0.62%,该公式可以满足实际工程的误差要求。结论认为,得到的纯氢与掺氢天然气管道摩阻系数修正公式可应用于纯氢与掺氢天然气管道工程设计,具有重要的工程应用价值和前景。

柴油引燃甲烷/氢气混合燃料发动机实验与仿真研究

基于光学发动机研究了5%柴油燃料比下,氢气比对柴油引燃甲烷/氢气混合燃料发动机的燃烧过程的影响。燃烧过程的自然光度图像由高速摄像机记录。结合光学实验结果,模拟微量柴油点燃甲烷和氢气混合物的燃烧过程。研究不同氢气配比下燃烧过程中缸内温度、OH基团和燃烧组分的变化过程。研究结果表明:氢气比的增加促进了燃烧,点火延迟时间和燃烧持续时间显著缩短,燃烧放热阶段提前;混合燃烧过程中首先在圆柱体边缘形成低温点,火焰在短时间内随着温度的升高而膨胀;在相同的氢气比下,随着进气压力的增加,点火延迟期减小;氢气比例的增加使得主要放热率波峰升高并变窄,逐渐从双峰放热变为单峰放热过程。

埋地掺氢天然气管道泄漏扩散数值模拟研究

为减少掺氢天然气在输送过程中因泄漏引发的安全问题,基于流体力学及多孔介质理论,采用Fluent软件建立城市埋地掺氢天然气管道泄漏扩散的三维数值模型,分析掺氢比例、泄漏孔径、管道压力、管道埋深和土壤类型等因素对掺氢天然气泄漏量及甲烷、氢气爆炸下限竖直方向上扩散距离的影响。结果表明:掺氢比例越大,掺氢天然气泄漏量越小,甲烷爆炸下限等值线扩散至地表所需时间越长,而氢气则相反;泄漏孔径10 mm时的泄漏量约为孔径5 mm时泄漏量的2倍,泄漏孔径20 mm时的泄漏量约为10 mm时泄漏量的2倍,且泄漏孔径越大,甲烷和氢气的爆炸下限等值线到达地表所需时间越短;管道压力越大,掺氢天然气泄漏量越大且扩散速度越快,危险系数越高;管道埋深1.1 m泄漏量最大,其次为1.4、0.8 m,埋深越浅,甲烷和氢气的爆炸下限等值线到达地表所需时间越短;土壤类型对掺氢天然气的泄漏扩散有重要的影响,土壤类型为粉质砂土时,掺氢天然气泄漏量及扩散速度最大,其次为壤土,最后为黏土。

掺氢输送管道材料的适应性及评价方法

天然气管网掺氢输送可有效解决氢能利用过程中的输送问题,但这会给管道带来安全风险。本文详细评述了掺氢输送管道金属和非金属材料的种类、适应性影响因素及其评价方法,建议完善和利用现有金属和非金属材料宏观性能表征及微观机理分析方法,结合实际工况环境及材料关键性能指标,建立掺氢输送管道的适应性评价方法和评价限值要求,并完善实际掺氢试运行评价方法和评判标准。本文可为天然气管网掺氢输送工程提供重要参考。

基于BOPPPS的融合式教学模式在天然药物化学中的应用

目的:探讨基于BOPPPS的融合式教学模式在天然药物化学教学中的应用效果。方法:以某医学院校药学专业2019级本科生为研究对象,其中2班学生为对照组(n=27),1班学生为试验组(n=29),2个班级的学生同一批教师授课。对照组采用传统教学方法,以课堂讲授为主,结合多媒体教学;试验组采用基于BOPPPS的融合式教学模式。比较2组学生的期末考试成绩,对2组教学效果及满意度进行问卷调查。结果:问卷调查结果显示,基于BOPPPS的融合式教学模式的教学效果得到了试验组96.55%学生的认可,试验组期末考试成绩高于对照组(P<0.05);试验组教学效果明显优于对照组(P<0.05),试验组学生满意度高于对照组(P<0.05)。结论:基于BOPPPS的融合式教学模式应用于天然药物化学教学中,学生的学习兴趣得到有效的激发,提高了教学质量。

掺氢天然气管道故障树分析及建模软件开发

针对掺氢天然气管道可能存在的风险与隐患,分析国内外各类管道失效数据,建立了掺氢天然气管道故障树,共包含10个子树和148个底事件,在掺氢管道失效库基础上采用C#程序设计语言开发了掺氢天然气管道故障树建模软件;应用建模软件对已建立的掺氢天然气管道故障树进行分析。软件计算通过行列法求解出最小割集共189个,其中一阶最小割集106个,二阶最小割集83个;采用双循环法得到148个底事件结构重要度。分析得出防腐措施是否正常工作以及自然灾害是影响掺氢天然气管道安全运行的重要因素。

自然资源资产有偿使用的法治化构造

自然资源资产有偿使用是生态文明体制的改革重点。从基本属性、资源利用和表现形式三个方面廓清自然资源资产的概念内涵是建构自然资源资产有偿使用制度的逻辑起点。在宏观层面,公权力规制失范与私权利保障失衡是阻滞自然资源资产实现有偿使用的主要原因。在实践层面,价值核算体系混乱、使用范围模糊、使用方式粗放是推动自然资源资产有偿使用走向法治化道路的现实动因。以法治维度构造自然资源资产有偿使用制度,应以“公权管制”与“私权自治”为中心,准确释明自然资源资产的法律概念;明确允许有偿使用的自然资源资产范围;建立自然资源资产收益共享机制;完善自然资源资产有偿使用的程序性规则,为维护国家所有者权益和建设美丽中国提供制度保障。

高架火炬掺氢燃烧热辐射模拟研究

目的天然气掺氢后燃烧特性会发生改变,因此,有必要对掺氢天然气热放空过程进行研究,以确定掺氢输送条件下原有高架火炬适用的工况条件,从而确保天然气管输系统在掺氢输送时的安全。方法结合掺氢燃烧实验和CFD数值模拟,研究掺氢(摩尔分数0~20%)天然气进行扩散燃烧时燃烧特性及热辐射半径变化情况,揭示掺氢对燃烧热辐射半径的影响机理,明确API STD 521—2014《泄压和减压系统》中热辐射半径解析模型可用于掺氢天然气的计算。结果在等体积流量下,掺氢减小了热释放量从而减短了火焰长度,而在侧风作用下的火焰倾斜角几乎不变,因此缩小了热辐射半径;在等质量流量下,掺氢增加了热释放量从而增长了火焰长度,而火焰倾斜角变大,使得热辐射半径变化极小。同时,风速增大会导致热辐射半径扩大。结论在安全热辐射半径不变的前提下,按体积流量计算,掺氢条件下最多可提高19%~23%体积流量的放空量,火炬系统的排放效率有所提高;按质量流量计算,掺氢条件下高架火炬的质量流量放空量与掺氢前相比几乎保持不变。

使命与认同:清代西域满族居官文人诗作中的物我交融书写

清代西域满族居官文人深受朝廷倚重,且多熟谙汉语诗文创作,故仕宦期间以诗作表达其恪尽职守、践履西域的强烈使命感。西域满族居官文人的西戍诗歌亦表现出对治边理政的强烈责任感,将自然地理、人文景观书写与立功边塞豪情相融合形成物我交融的书写,诗作亦得江山之助,将豪迈超拔之气与闲适静谧之情相结合,塑造出靖边安国、建设西陲与体察民情等善理边政的主人翁形象。清代西域满族官员作为朝廷之重臣而竭尽忠诚,在西戍诗歌中寄寓忠孝情怀下的建功西陲之志,诗风雄健激昂,彰显清代西域满族居官文人的深厚文化底蕴,循此亦可寻绎清代满汉文化融合在西域边地的重大成效。

天然气中掺氢对计量物性参数的影响分析

在天然气管道中掺入氢气是进行大规模天然气输送的有效途径,但氢气会对管输水力和热力特性造成影响,进而影响与计量相关的物性参数。基于此,以常规天然气、页岩气及伴生气等三种典型气质组成为基础,系统分析了不同掺氢条件对管输温度、压力的影响及天然气物性参数的变化规律,探讨了天然气掺氢对计量分析的影响。结果表明,掺氢浓度与掺氢天然气温度呈反比,升高温度或降低压力可以减少掺氢天然气的沿程温降;采用GERG-2008方程计算压缩因子的结果准确度明显高于AGA8-92DC方程,随着温度降低、氢气浓度增加,计算结果误差明显增大。建议管道中掺氢浓度不应超过10%;并从改造气相色谱仪、加速标准气体制备、完善量值溯源和标准体系建设等方面入手,逐步实现掺氢天然气计量的标准化和工业化。

静置工况条件下掺氢天然气浓度分布规律

利用天然气管道进行掺氢输送已成为氢能及天然气输送领域的热点和重点,但当前业界对于掺氢天然气在管道输送和停输静置过程中是否会自发分层一直存在较大争议。为了厘清该问题,以掺氢天然气在管道中静置这一极端工况为例,基于热力学能量最小原理,推导了在重力场作用下掺氢天然气浓度分布数学模型,并采用Peng-Robinson真实气体状态方程对该数学模型进行了求解,最后研究了甲烷—氢气二元组分混合气体在4种典型场景高度和5种掺氢比下氢浓度随高度的分布规律。研究结果表明:(1)在重力影响下管道顶部和底部的氢浓度存在差异,但其受高度差的影响显著,对于米级的水平管道、几十米级的一般城镇楼宇天然气立管、百米级的高层楼宇天然气立管,氢浓度随高度变化的差异微小,可完全忽略氢分层;(2)对于千米级大落差的掺氢天然气管道,当掺氢比不超过20%时,氢分层仍可忽略,但当掺氢比很高时(例如50%)管道顶部和底部的氢浓度差将超过1%,此时需考虑工程实际情况评估能否忽略氢分层;(3)西气东输某管道考虑真实气体组成、掺氢比20%、管道落差200 m时,各气体组分的浓度随落差高度的分布规律揭示了在实际工程中此类落差高度的掺氢天然气氢分层可忽略。结论认为,对于掺混均匀的掺氢天然气在静置这种最容易发生分层的极端工况下,如果不存在千米级极端大落差和极端大掺氢比,掺氢天然气管道分层现象可完全忽略;该认识从理论上厘清了目前关于掺氢天然气分层现象的争议,对掺氢天然气管道安全输送具有重要指导意义。

掺氢天然气干气密封启动特性研究

为评估天然气掺氢对管线压缩机轴端干气密封性能的影响,提出一种考虑阻塞效应的干气密封性能数值预测模型,分析了不同掺氢比下干气密封的静态特性和启动特性。首先,采用空气介质螺旋槽干气密封的气膜压力分布和开启力实验数据,验证了数值模型的可靠性;然后,针对GE PCL800机型天然气管线压缩机螺旋槽干气密封,分析了4种掺氢比(H 2体积分数分别为0、10%、20%、30%)和5种进口压力(4、6、8、10、12 MPa)对干气密封开启力、泄漏量和气膜刚度等静态特性的影响规律;最后,分析了4种掺氢比和5种进口压力下,转速、进口压力、平衡比和弹簧比压对干气密封启动特性的影响规律。研究结果表明:所提出的干气密封性能数值预测模型能够可靠预测高压差下干气密封出口阻塞效应及其对密封性能的影响;掺氢比对干气密封开启力、泄漏量和气膜刚度等密封静态特性影响较小;干气密封开启临界转速随掺氢比的增加而增大(掺氢比增加30%时,开启临界转速增大8.51%~16.90%),因此天然气掺氢增大了干气密封的开启难度,需设计合适的平衡比和弹簧比压以保证干气密封顺利开启。该研究结果可为掺氢条件下天然气管线压缩机轴端干气密封的高效设计和可靠运行提供理论参考。