Influence of CaO-based expansive agent,superabsorbent polymers and curing temperature on pore structure evolution of early-age cement paste

Cracks easily generate in concrete at early age owing to the shrinkage deformation.CaO-based expansion agent(CEA)and superabsorbent polymers(SAP)have been extensively used for the mitigation of concrete shrinkage.The macroscopic properties of concrete are highly determined by the microstructure.In this study,the influence of CEA and SAP addition on the pore structure evolution of cement paste under different curing temperatures was evaluated via low-field nuclear magnetic resonance spectroscopy.Test results indicated that,in cement paste,a higher CEA content led to a higher porosity and a larger most probable pore diameter(MPPD).Meanwhile,SAP addition increased the porosity and MPPD of CEA cement paste at early age but decreased them after 7 d,and a higher SAP content always brought a higher porosity and MPPD.Furthermore,the addition of SAP led to a lower porosity and MPPD of CEA cement paste than that of plain cement paste after 14 d.Moreover,the porosity and MPPD of CEA cement paste decreased first and subsequently increased as the curing temperature raised.

Experimental Study of Concrete Column Shape Modification Using Fiber Reinforced Polymer Composite Shells and Expansive Cement Concrete

Fiber Reinforced Polymer （FRP） composites are an effective material for strengthening circular concrete columns. The effectiveness of FRP confinement for square and rectangular columns is greatly reduced due to stress concentrations at the sharp comers and loss of the membrane effect at the fiat sides of the cross-section. Shape modification can eliminate the effects of column comers and flat sides, and thereby restore the membrane effect and improve the compressive behavior of FRP-confined square and rectangular concrete columns. Shape modification using chemical post-tensioning, achieved by using expansive cement concrete, is described and several mix designs for obtaining the optimal level of expansion are presented. In addition, parametric studies regarding the optimal geometry of the shape-modified cross-section are presented utilizing the analytical model.

Research Progress of Polymer Fire Extinguishing Gel and Its Application in Forest Fire Prevention

The paper summarizes the structure and water-absorbing mechanism,classification,and preparation method of polymer fire extinguishing gel,and prospects for its application in aerial firefighting,forest ground fire extinguishing,opening of firebreaks,and mitigating human casualties in forest fire extinguishing.

Single long-polymer translocation through a long pore

This paper theoretically studies the free energy and conformational entropy of a long polymer threading a long nanopore （no/N ≥0.1） on external electric field. The polymer expanded model is built in this paper, that is, a single long polymer chain with N monomers （each of size a） threading a pore with no monomers can be regarded as polymer with N ＋ no monomers translocating a 2-dimension hole embedded in membrane. A theoretical approach is presented which explicitly takes into account the nucleation theory. Our calculations imply that, the structure of polymer changes more acutely than other situation, while its leading monomer reaches the second vacuum and its end monomer escapes the first vacuum. And it is also shown that the length scale of polymer and pore play a very important role for polymer translocation dynamics. The present model predicts that the translocation time depends on the chemical potential gradient and the property of the solvent on sides of pore to some extent.

Novel protection systems for the improvement in soil and water stability of expansive soil slopes

To improve the soil and water stability of expansive soil slopes and reduce the probability of slope failure,novel protection systems based on polymer waterproof coatings(PWC)were used in this study.Herein,three groups of expansive soil slope model tests were designed to investigate the effects of polyester nonwovens and PWC(P-PWC)composite protection system,three-dimensional vegetation network and PWC(T-PWC)composite protection system,and nonprotection on the soil and water behavior in the slopes under precipitation–evaporation cycles.The results showed that the moisture change of P-PWC and T-PWC composite protected slopes was significantly smaller than that of bare slope,which reduced the sensitivity of slope moisture to environmental changes and improved its stability.The soil temperature of the slope protected by the P-PWC and T-PWC systems at a depth of 70 cm increased by 5.6℃ and 2.7℃,respectively.Using PWC composite protection systems exhibited better thermal storage performance,which could increase the utilization of shallow geothermal resources.Moreover,the maximum average crack widths of the bare slopes were 7.89 and 3.17 times those of the P-PWC and TPWC protected slopes,respectively,and the maximum average crack depths were 6.87 and 3 times those of the P-PWC and T-PWC protected slopes,separately.The PPWC protection system weakened the influence of hydro–thermal coupling on the slopes,inhibited the development of cracks on the slopes,and reduced the soil erosion.The maximum soil erosion of slopes protected by P-PWC and T-PWC systems was 332 and 164 times lower than that of bare slope,respectively.The P-PWC and T-PWC protection systems achieved excellent"anti-seepage and moisture retention"and anti-erosion effects,thus improving the soil and water stability of slopes.These findings can provide important guiding reference for controlling rainwater infiltration and soil erosion in expansive soil slope projects.

考虑化学反应的高聚物压密劈裂注浆仿真研究

考虑浆液化学反应原理,综合运用扩展有限元理论、修正剑桥模型和高聚物浆液膨胀力计算模型,建立了模拟高聚物在土体中压密劈裂注浆动态过程的二维仿真分析方法。通过模型试验验证了所提出方法的适用性,进而分析了浆液膨胀力、浆脉形态、土体孔隙比随时间变化规律及注浆孔埋深、土体断裂韧度对浆脉扩展过程的影响。结果表明:受高聚物化学反应进程驱动,在浆液与土体耦合作用下,浆液膨胀力初期随时间近似呈线性增长,达到峰值后快速下降并趋于稳定;浆脉长度和宽度发展速度不同步,裂缝启裂至二次扩展阶段,浆脉长度基本保持不变,宽度线性增大,裂缝二次扩展后,浆脉长度近似线性增大,而宽度增长速率趋缓;受浆液挤密作用影响,裂缝两侧一定范围内土体孔隙比显著降低,沿垂直于裂缝面方向,距注浆孔中心越近,孔隙比越小;孔隙比随时间整体呈下降趋势,随着裂缝的扩展和后期膨胀压力的下降,紧邻裂缝面两侧土体孔隙比有一定恢复,随后趋于稳定;随着注浆孔埋深和土体断裂韧度的增加,浆脉长度逐渐减小,宽度不断增大,两者变化速率基本保持不变;浆脉扩展稳定时间随埋深的增大而提前,随断裂韧度的增大而延后。

液滴微流控技术制备纳米聚合物微球及性能评价

以改性聚丙烯酰胺作为分散相单体,3#白油和十二烷基硫酸钠(SDS)作为连续相,通过液滴微流控技术制备出一种纳米聚合物微球PQM-1。优化了PQM-1的制备条件,并评价了其吸附性能。结果表明:随着单体浓度和交联剂用量的逐渐增大,PQM-1的膨胀倍数逐渐减小;随着引发剂用量的逐渐增大,PQM-1的膨胀倍数逐渐增大。推荐最佳的单体浓度为25%,最佳的交联剂的用量为3%,最佳的引发剂的用量为3%。当亚甲基蓝溶液浓度为50mg/L,吸附时间为2h时,PQM-1对亚甲基蓝的吸附效率可以达到98.7%,吸附性能较好。

环状聚合物的制备技术

环状聚合物的分子链不存在末端,减少了分子链间的缠结,因此,环状聚合物常表现出一些独特的性质,具有广泛的应用前景。本文首先简要介绍了环状聚合物的研究背景及意义,然后对近年来环状聚合物的制备技术进行了分类并举例评述,最后展望了环状聚合物未来的研究方向。本文为新型功能性聚合物材料的研究和开发提供借鉴。

多功能压裂液稠化剂的合成和性能评价

为满足压裂作业对压裂液增稠性、耐盐性、地层低伤害和破乳助排一体化的需求,采用丙烯酰胺和丙烯酸钠作为稠化剂主体,引入耐盐单体、防膨单体和破乳助排功能性单体,制得多功能型聚合物稠化剂。实验结果表明:在2-丙烯酰胺-2-甲基-丙磺酸单体质量分数为4.5%时,多功能稠化剂耐盐效果最好;以新疆油田FN区块净化水为水源配制压的裂液具有良好的耐温耐剪切性能,在140℃,170 s^(-1)条件下剪切120 min,黏度为80 mPa·s,且压裂液破胶彻底,破乳助排性能显著,可以满足矿场施工要求。

桥梁伸缩缝快硬聚合物水泥复合材料PCC研究

在保证伸缩缝正常使用功能的基础上,为解决受损桥梁伸缩缝快速修复的问题,文中以硫铝酸盐水泥与普通硅酸盐水泥为胶凝材料,并加入聚合物胶粉,通过调节灰砂比、外加剂及矿物掺合料,制备一种快速硬化的水泥基砂浆材料,即快硬聚合物水泥复合材料(PCC,Polymer Cement Composite),经试验测试,其5 h抗压强度达到32 MPa,28 d抗压强度达到60 MPa以上,干缩率小于0.4‰,是一种理想的桥梁伸缩缝快速修补料。

特低渗透油藏聚合物微球2.0驱油技术研究与应用

随着水驱开发的不断深入,优势窜流通道、剩余油分布日渐复杂,聚合物微球长周期注入后持续深部移动、进一步扩大波及体积作用有限,继续提升调驱效果难度大,需要尽快优化升级现有聚合物微球。本文在聚合物微球Ⅰ代产品的基础上进行优化升级,设计出具有延迟溶胀性的聚合物微球2.0,通过开展室内评价和5个井组现场应用,成功实现了聚合物微球结构的时序性演化,开发出具有延迟膨胀功能的聚合物微球2.0。该体系耐温性达到80℃以上、抗盐性达100000 mg/L以上,相比Ⅰ代体系,延迟膨胀时间提升3倍左右,有效解决了微孔细喉条件下持续深部运移的技术难题。

Conjugation expansion strategy enables highly stable all-polymer solar cells

The stability issue is one of the key factors hindering the commercial application of organic solar cells.All-polymer organic solar cell is one of the effective ways to solve the stability problem.In this work,we designed and synthesized two polymer donor materials PBDT and PDTBDT with different conjugation ranges,and demonstrated for the first time that extending the conjugation range of donor materials in all polymer solar cells can significantly improve device efficiency and stability.The experimental results of materials and devices show that PDTBDT with a larger conjugation range has stronger crystallinity and a more planar structure,which endows the active layer in its corresponding device with higher exciton dissociation probability,lower carrier recombination probability,more balanced charge transport properties and more favorable film morphology.As a result,the PDTBDT:PYF-T-o devices display an outstanding PCE of 13.38%,which is much higher than PBDT with smaller conjugation range based devices.Moreover,the PDTBDT:PYF-T-o device retains 0.86 of the initial PCE after over 500 h in the air atmosphere,exhibiting significantly improved stability.The improved stability is attributed to the enhanced moisture and air tolerance of active layer film thanks to the strong crystallinity of the donor material.These results demonstrate that the conjugation expansion strategy is one of the effective ways to obtain efficient and stable all-polymer organic solar cells.

聚合物的热膨胀

热膨胀既是聚合物的基本属性,同时也与聚合物结构与性能密切相关。本文在提出聚合物热膨胀产生机制的基础上,介绍了测量聚合物热膨胀的方法,讨论了热膨胀在聚合物基础研究中的应用,着重评述了热膨胀在PTC材料为代表的聚合物基复合材料设计中的重要价值。

偶氮染料掺杂的聚甲基丙烯酸甲酯薄膜的热光性质研究

本文演示了用阿贝折射仪测定染料掺杂聚合物薄膜热光系数的方法 ;通过改变掺杂体含量的方法 ,方便地实现了聚合物体系的折射率控制 ;通过热光系数的测量 ,计算了聚合物薄膜的热膨胀系数 ,并用以解释了聚合物薄膜的热光系数随掺杂体含量增加先增大后减小的实验观察 .

活性氧化镁补偿无机聚合物浆体收缩的作用机制

将活性氧化镁均匀分散于无机聚合物浆体中,以期快速、均匀补偿收缩.研究了掺活性氧化镁的无机聚合物浆体的形变、力学性能、结构与组成.结果表明:活性氧化镁掺量为6%时,无机聚合物浆体的28 d化学收缩降低10.7%,7 d自收缩降低72.1%,28 d干燥收缩降低20.0%,有效补偿了无机聚合物硬化过程中的体积收缩.颗粒细小的活性氧化镁在高碱度液相环境中与水反应生成晶体细小的蠕虫状Mg(OH)_2,在无机聚合物浆体中产生均匀微膨胀,细化了浆体孔径,并提高了无机聚合物的强度,实现了无机聚合物浆体收缩和氧化镁补偿收缩历程的匹配.

纳微米聚合物微球的水化膨胀封堵性能

为改善聚合物微球的深度调剖效果,利用蒸馏沉淀聚合法制备纳微米聚合物微球,并利用激光粒度分析仪、微孔滤膜装置和驱替装置对纳微米聚合物微球的粒径、水化膨胀能力和变形封堵能力进行测试分析.结果表明:纳微米聚合物微球为较规则均匀的球形,粒径分布集中,具有良好的水化膨胀性能;随着盐矿化度增大,纳微米聚合物微球膨胀性能变差;随着温度升高,微球的膨胀性能变强;在氯化钙和氯化镁水型中,微球膨胀性能变差;在酸性和碱性环境中,微球膨胀性能变差;随着水化时间增长,微球的封堵性能和变形能力逐渐增强,对孔道产生有效封堵的同时又能变形通过孔道,在渗透率较低的岩心中具有更好的深度调剖效果.

SAP内养护剂改善膨胀混凝土性能及其机理研究

研究了SAP(超强吸水树脂)内养护剂对膨胀混凝土力学性能、变形开裂性能和耐久性能的影响,然后通过MIP,SEM,XRD等手段对其养护机理进行了微观分析.结果表明:掺加SAP可显著提高膨胀混凝土的早期膨胀值和限制膨胀率,降低膨胀与收缩变形的差值,且对强度、渗透性无不利影响.由于SAP具有吸水-释水功能,因此掺加SAP将有利于钙矾石的生成和水泥水化程度的提高,并能有效改善膨胀混凝土的孔结构分布.

生物可降解聚合物血管支架膨胀性能有限元分析

血管支架最有潜力的发展方向是生物可降解聚合物血管支架,而支架的膨胀性能直接影响血管支架的质量和应用.利用有限元方法,采用von Mises屈服和各向同性强化准则,通过与316L不锈钢和WE43镁合金两种支架材料进行对比,分析了聚左旋乳酸(PLLA)材料支架的膨胀性能.结果表明,PLLA新型血管支架具有良好的均匀膨胀性、轴向短缩性和柔顺性,但其回弹性能有待改善.

孔喉尺度聚合物弹性微球膨胀性能研究

孔喉尺度聚合物弹性微球具有在油藏岩石孔隙中运移、封堵、弹性变形、再运移、再封堵,及全程改变注入水渗流方向的特点。采用实验的方法分析了不同矿化度和温度下微球的吸水膨胀规律,提出了微球膨胀动力学方程,并绘制了微球膨胀倍数理论图版。微球膨胀机理为氢键形成、水解和渗透压差引起的扩散。微球的膨胀倍数随矿化度增大而减小,随温度的升高而增大,膨胀最终在溶剂化和次价键缔和的双重作用下达到平衡,且高温下矿化度对膨胀倍数的影响更显著,低矿化度下温度对膨胀倍数的影响更显著。利用微球膨胀动力学方程可以定量描述微球膨胀规律,而膨胀倍数理论图版有助于方便、快捷地确定不同温度和矿化度下微球的膨胀倍数,对设计与特定油藏岩石孔喉相匹配的微球体系具有重要意义。

温度对HMX基PBX炸药热膨胀系数和热导率的影响

用热膨胀仪和闪光导热仪研究了温度对HMX基PBX的热膨胀系数和热导率的影响。结果表明,在低于330K时,HMX基PBX的线膨胀系数约为5.34×10-5 K-1;在330～350K,线膨胀系数迅速增大到13.47×10-5K-1,随着黏结剂软化,线膨胀系数随之减小到8.04×10-5 K-1。在293～373K,HMX基PBX的比热容从0.978J.g-1.K-1线性增长到1.254J.g-1.K-1,但在343K附近黏结剂融化存在异常偏大值;HMX基PBX的热扩散率从0.256mm2.s-1下降至0.179mm2.s-1,通过比热和热扩散率实验数据计算获得的热导率从0.462W.m-1.K-1下降至0.406W.m-1.K-1。基于分子晶体传热理论模型建立了比热和导热系数的温度关系函数,HMX基PBX的导热机制符合两相串联模型。