Influence of polymer dispersants on dispersion stability of nano-TiO_2 aqueous suspension and its application in inner wall latex paint

The effects of SN5040 and polyethylene glycol（PEG） individually and in combination on the dispersion stability of nano-TiO2 aqueous suspension were investigated by ultraviolet-visible absorption spectroscopy. The adsorption mechanism of these dispersants was detected by zeta potential, isothermal absorption and FTIR analysis. It is found that SN5040 is superior for stabilizing nano-TiO2 in aqueous suspension to PEG in basic region, and the optimum mass fraction of SN5040 addition is 3%. In the case of NaCl addition, the optimum value increases with .the increase of NaCl concentration in the solution. When the mixture of SN5040 and PEG is employed, the antagonism appears preponderant. When SN5040 and PEG are added sequentially, the synergistic reaction takes place. The synergistic reaction can be attributed to the mechanism that PEG adsorption decreases the electronic repulsion between SN5040 molecules, which results in the increase of SN5040 adsorption density. PEG is adsorbed by the interaction with the pre-adsorbed SN5040 layer. Furthermore, the modified inner wall latex paint with well dispersed nano-YiO2 suspension is endowed with excellent ultraviolet absorption and antibacterial properties.

Wall slip behavior of polymer melts on capillary rheometer

Wall slip behavior of three commercial polymer melts polypropylene(iPP),low-density polyethylene(LDPE)(branched chains) and high-density polyethylene(HDPE)(linear chains) were studied by using a capillary rheometer with twin bores at different temperatures.The results show that a sudden first-stick-then-slip transition was observed for HDPE and a first-slip-then-stick transition was observed for LDPE and iPP as the shear rate sweep was done in an increased order,which shows that the chain structure has an obvious effect on the wall slip behavior of polymers.The critical shear stress for the onset of stick-slip transition increases linearly with temperature for HDPE,which accords with the disentanglement mechanism proposed by Brochard and de Gennes.While the extrapolation length used to quantify the magnitude of the transition remains about 0.05-0.09 mm for HDPE at 150-230 ℃.Also the relationship between the critical shear stress for the onset of wall slip and the molecular mass for polymer samples agrees with the disentanglement model of Brochard and de Gennes.The onset of slip-stick transition for LDPE and iPP at a critical shear stress may be interpreted as the shear thinning of the polymer chains at high shear rates,preventing further development of wall slip behavior.

COALESCENCE INDUCED GRADIENT MORPHOLOGY NEAR A WALL IN PHASE SEPARATED POLYMER BLENDS DURING QUIESCENT ANNEALING

A fast coalescence mechanism is proposed to account for the wall effect on the formation of gradient morphology in phase separated polymer blends during quiescent annealing. The existence of solid wall with high polarity is believed to change the potential field around the dispersed particles near the wall. This additional potential interaction between the solid wall and the dispersed particles causes faster coalescence of the dispersed particles near the wall than in the bulk. The gradient phase morphology thus formed can be predicted by combining the wall-particle interaction and the touch-coalescence mechanism. The effect of interfacial tension on the gradient morphology is also discussed.

SEGMENT DENSITY PROFILES OF COMPACT POLYMER CHAINS CONFINED BETWEEN TWO PARALLEL PLANE WALLS

We use the pruned-enriched Rosenbluth method to investigate systematically the segment density profiles of compact polymer chains confined between two parallel plane walls. The non-adsorption case of adsorption interaction energy ε = 0 and the weak adsorption case of ε= -1 are considered for the compact polymer chains with different chain lengths N and different separation distances between two walls D. Several special entropy effects on the confined compact polymer chains, such as a damped oscillation in the segment density profile for the large separation distance D, are observed and discussed for different separation distances D in the non-adsorption case. In the weak adsorption case, investigations on the segment density profiles indicate that the competition between the entropy and adsorption effects results in an obvious depletion layer. Moreover, the scaling laws of the damped oscillation period Td and the depletion layer width Ld are obtained for the confined compact chains. Most of these results are obtained for the first time so far as we know, which are expected to understand the properties of the confined compact polymer chains more completely.

A study on coherent structures and drag-reduction in the wall turbulence with polymer additives by TRPIV

An experimental measurement was performed us- ing time-resolved particle image velocimetry （TRPIV） to in- vestigate the spatial topological character of coherent struc- tures in wall-bounded turbulence of polymer additive solu- tion. The fully developed near-wall turbulent flow fields with and without polymer additives at the same Reynolds number were measured by TRPIV in a water channel. The compar- isons of turbulent statistics confirm that due to viscoelastic structure of long-chain polymers, the wall-normal velocity fluctuation and Reynolds shear stress in the near-wall region are suppressed significantly. Furthermore, it is noted that such a behavior of polymers is closely related to the decease of the motion of the second and forth quadrants, i.e., the ejection and sweep events, in the near-wall region. The spa- tial topological mode of coherent structures during bursts has been extracted by the new mu-level criteria based on locally averaged velocity structure function. Although the general shapes of coherent structures are unchanged by polymer additives, the fluctuating velocity, velocity gradient, velocity strain rate and vorticity of coherent structures during burst events are suppressed in the polymer additive solution com- pared with that in water. The results show that due to the polymer additives the occurrence and intensity of coherent structures are suppressed, leading to drag reduction.

Discussion on Anti-seepage Wall and Anti-seepage Technology of Water Conservancy Project

The water infiltration problem of water conservancy projects is one of the more common problems in the construction of water conservancy projects,which seriously affects the overall construction quality and safety of water conservancy projects.This article studies the causes of water infiltration in water conservancy projects and introduces related antiseepage technologies,hoping to be a reference for the implementation of anti-seepage projects.Through research,it is found that the factors that cause water infiltration in water conservancy projects include water conservancy project structural changes,environmental factors and construction factors.Relevant personnel can use concrete anti-seepage wall construction technology and high-pressure jet grouting technology to do the relevant anti-seepage work of water conservancy projects.

爆炸荷载作用下粘贴Polymer Sheet膜材砌体墙防护性能研究

以混凝土砌体墙爆炸试验为基础,借助LS-DYNA软件,分析混凝土砌体墙在爆炸荷载作用下的破坏机理及Polymer Sheet膜材加固后的防护性能。研究结果表明:爆炸荷载作用下,墙体背爆面跨中位置、迎爆面上下端部为危险截面,最易破坏;爆炸荷载的峰值压力不超过0.385 MPa时,砌块之间脱离和飞溅较少,可不进行防护;当峰值压力大于0.385 MPa时,随峰值压力增大,破坏部位脱离的砌块数量增多,飞溅速度加快,对建筑物内部人员及设施威胁增大,必须进行防护加固;峰值压力不超过0.95 MPa时,膜材能够很大程度上发挥防护作用,阻挡散落砌块的抛射;当峰值压力大于0.95 MPa时,膜材自身在锚固处断裂,墙体与断裂的防护膜以整体形式向建筑内部抛射,建议此时采用索膜防护体系,以提高防护效果;最后给出了Polymer Sheet膜材加固的砌体墙安全防护距离,以供设计参考。

The effect of cations on gelation of cross-linked polymers

The effects of different cation concentrations and types on rheological property and stability of Guar, Xanthan, and Partially Hydrolyzed Polyacrylamide(HPAM) cross-linked gels were analyzed through experiments. Also, a new approach was developed to reduce the negative effects of cation by application of multi-walled carbon nano-tubes(MWCNTs). The presence of cations in cross-linked gel system will reduce the viscosity of gel, the higher the cation concentration is, the lower the viscosity will be. The bivalent cation has a greater viscosity reduction effect on gel than monovalent cation. The stability of cross-linked gels is worse with cations, this situation becomes more serious under higher salinity. MWCNTs were added to HPAM gel, cross-linked by(3-Aminopropyl) triethoxysilane(APTES), they surrounded cations and removed them from polymers and reduced the reaction possibility. This method enhances the viscosity and breakdown pressure of cross-linked gels, improves the stability of HPAM cross-linked gel under different operating conditions, and can be applied to related drilling projects.

Experimental Investigation on Flexural Performance of Masonry Walls Reinforced with GFRP

This paper presents the results of a test program for flexure reinforcing characteristics of gless fiber-rein forced polymer（GFRP） sheets bonded to masonry beams. A total of eight specimens subjected to monotonic four-point bending were tested up to failure. These specimens were constructed with two different bond patterns. Six of these specimens were reinforced by using GFRP sheets prior to testing, and the remaining two were not reinforced. The test results indicate a significant increase in both load-bearing capacity and ductile performance of the reinforced walls over the unreinforced ones.

Effect of fiber angle on LYP steel shear walls behavior

Steel shear wall(SSW) was properly determined using numerical and experimental approaches.The properties of SSW and LYP(low yield point) steel shear wall(LSSW) were measured.It is revealed that LSSW exhibits higher properties compared to SSW in both elastic and inelastic zones.It is also concluded that the addition of CFRP(carbon fiber reinforced polymers) enhances the seismic parameters of LSSW(stiffness,energy absorption,shear capacity,over strength values).Also,stress values applied to boundary frames are lower due to post buckling forces.The effect of fiber angle was also studied and presented as a mathematical equation.

Polyaniline and multi-walled carbon nanotube composite electrode for rechargeable battery

The multi-walled carbon nanotube was introduced into the polymer matrix (PANI) to improve the electric conductivity as well as mechanical properties of the original polymer matrix.PANI/multi-walled carbon nanotube (MWCNT) composites were synthesized via ex-situ and in-situ polymerization to improve their electrical property.And the DC conductivities of PANI/MWCNT according to content and diameter of MWCNT were measured by four-point probe.The highest electric conductivity of PANI/MWCNT composite is 20 S/cm when 0.3% (mass fraction) MWCNTs with 10 nm in diameter and 15 μm in length are added in composite.

Synthesis,Crystal Structure and Thermal Property of a 2D Brick Wall Framework Constructed from a New Mononuclear Complex

One new coordination polymer with the chemical formula [CoCu2L2·K2·1.5C2H5OH]n（H4L = 2-hydroxy-3-[（E）-（{3-[（2-hydroxybenzoyl）amino]propyl}imino）methyl] benzoic acid） has been synthesized based on the slow diffusion method,and characterized by IR spectroscopy,thermalgravimetric and X-ray diffraction analysis.It crystallizes in the monoclinic system,space group P21/n with a = 11.98860（10）,b = 24.4279（3）,c = 14.9008（2） ,β = 104.7490（10）°,V = 4220.01（8） 3,Z = 2,Mr = 1009.94,Dc = 1.590 g/cm3,F（000） = 2056,μ（MoKα） = 1.649 mm-1,the final R = 0.0411 and wR = 0.1178 for 5920 observed reflections with I 2σ（I）.The compound possesses a 2D brick wall structure constructed from trinuclear units.

Rapid Repair of Earthquake Damaged RC Interior Beam-wide Column Joints and Beam-wall Joints Using FRP Composites

This paper studies the seismic performance of FRP-strengthened RC interior non-seismically detailed beam-wide columns and beam-wall joints after limited seismic damage.Four eccentric and concentric beam-wide column joints and two beam-wall joints,initially damaged in a previous study,were repaired and tested under constant axial loads(0.1fc′Ag and 0.35fc′Ag) and lateral cyclic loading.The rapid repair technique developed,aimed to restore the original strength and to provide minimum drift capacity.The repair schemes were characterized by the use of:(a) epoxy injections and polymer modified cementitious mortar to seal the cracks and replace spalled concrete;and(b) glass(GFRP) and carbon(CFRP) sheets to enhance the joint performance.The FRP sheets were effectively prevented against possible debonding through the use of fiber anchors.Comparison between responses of specimens before and after repair clearly indicated reasonable restoration in strength,drift capacity,stiffness and cumulative energy dissipation capacity.All specimens failed with delamination of FRP sheets at beam-column joint interfaces.The rapid repair technique developed in this study is recommended for mass upgrading or repair of earthquake damaged beam-column joints.

New Strategy for Chemically Attachment of Imine Group on Multi-Walled Carbon Nanotubes Surfaces: Synthesis, Characterization and Study of DC Electrical Conductivity

This paper used a new approach of preparing poly-composites by covalent linkage between the MWCNT’s by imine group. The Poly (Imine)/MWCNT Composite was synthesized by the solution blending method from reacted amino multi-walled carbon nanotubes (MWCNT-NH2) with Terephthalaldehyde (TPAL). The obtained poly-composite was characterized by FT-IR, UV-Vis, XRD, TEM, SEM, TGA, DSC and DC electrical conductivity. The formation of Poly (Imine)/MWCNT composite was confirmed. The DC electrical conductivity of poly-composites was within the range 2.3 × 10–4 - 5.3 × 10–4 S/cm due to the interaction between the nanotubes.

原材料对泡沫混凝土吸水性能的影响研究

通过测试吸水率、孔洞微观形貌,研究了矿物掺合料(矿渣粉、粉煤灰、硅灰)、聚合物乳液(氯丁胶乳液、苯丙乳液、硬质环氧乳液)、憎水剂(有机硅、硬脂酸钙)对泡沫混凝土吸水性能的影响,并对作用机理进行了阐述。结果表明:矿渣粉对吸水率的影响程度有限,粉煤灰可在一定程度上降低吸水率,硅灰的加入显著提高了吸水率;三种聚合物乳液对吸水率的影响程度由大到小依次为氯丁胶乳液>苯丙乳液>硬质环氧乳液;憎水剂能有效降低吸水率,其中硬脂酸钙的效果明显好于有机硅;憎水剂在合适掺量范围内能有效降低孔洞缺陷率,同时由于其本身具有较好的疏水特性,进而可显著降低材料的吸水率。

分子印迹电化学传感器对动物源性食品中氯霉素残留检测方法的建立与应用

实验将分子印迹技术与电化学工作站结合,利用多壁碳纳米管与金、铂纳米粒子对电极进行双敏化处理,用以增强玻碳电极表面电子转移速率,增强电化学传感器电流响应值,从而降低检测限。采用扫描电镜和电化学手段进行表征;通过吸附动力学试验与等温吸附试验对分子印迹修饰的电极进行研究,确定吸附性能,并对其选择性进行分析;以修饰后的电极检测实际样品鸡肉、鱼肉和牛奶中的氯霉素,分析其检测效果。结果表明,修饰后的电极表面具有杂乱的多壁碳纳米管状结构,从电化学循环伏安法(cyclic voltammetry,CV)、电化学阻抗谱(electrochemical impedance spectroscopy,EIS)可以清楚地看出电极的修饰效果,多壁碳纳米管与金、铂纳米粒子对电极表面电子传导速率的增强效果明显。分子印迹修饰对其结构类似物具有良好的选择性;传感器在氯霉素浓度为0.66~56.66µg/L之间呈现出良好的线性关系,R 2>0.99,检出限为0.45 nmol/L(0.146µg/L)。在对实际样品鸡肉、鱼肉和牛奶的检测中,氯霉素的回收率分别为83.72%~103.43%,相对标准偏差(RSD)为2.61%~6.03%,该结果满足GB/T 27404-2008定量分析检测要求(被测组分<0.1 mg/kg,回收率范围为60%~120%),且试验方法具有极低的检测限。

钻孔桩施工用聚合物制备技术优化与应用研究

本文设计合成出一种用于钻孔桩施工的高效护壁聚合物PZH-4,并采用正交实验优化出其合成的最优条件,以N,N-二甲基丙烯酰胺、2-丙烯酰胺基-2-甲基丙磺酸、乙烯吡咯烷酮、丙烯酰氧乙基三甲基氯化铵为聚合单体,聚合质量比为3∶1∶1∶1且总占比为30%,引发剂浓度为0.2wt%、碳酰胺浓度为0.2wt%,余量为去离子水,在60℃下反应8h,可得到分子量高于1200万的PZH-4聚合物分子,且聚合物粉末通过140目过筛后可在清水中12s内充分溶解。其配制的泥浆体系在稠化性、含砂率、胶体率、失水量等方面效果极佳,远优于膨润土泥浆体系。同时,废弃聚合物钻孔泥浆体系可使用5%NaClO溶液与3%H_(2)O_(2)溶液高效处理。

上海轨道交通14号线穿越黄浦江段防汛墙的耐久性加固研究

对隧道保护范围内的防汛墙进行耐久性加固,可避免因防汛墙大修而给隧道带来的不利影响,保障隧道和防汛墙安全。以上海轨道交通14号线穿越黄浦江段防汛墙的耐久性加固工程为案例,分析了防汛墙耐久性影响因素,介绍了在防汛墙外立面采用“双层聚合物水泥防水砂浆+硅烷浸渍剂”加固方案的设计和施工过程,并通过结构复核和耐久性评定验证了该加固方案的合理性。研究思路可为类似堤防维修加固工程提供参考和借鉴。

受火RC剪力墙加固后的抗震性能试验研究

针对钢筋混凝土(RC)剪力墙受火后力学性能下降问题,对8榀RC剪力墙试件(包括4榀轴压试件和4榀低周反复加载试件)的抗震性能进行试验研究。通过低周反复荷载试验,对常温状态、四面受火后不加固、四面受火后粘贴角钢加固和四面受火后布置聚合物砂浆钢筋网加固四种工况下,试件的承载力、延性、耗能能力和刚度退化情况进行分析。结果表明:粘贴角钢加固法可显著提高剪力墙受火后的性能,加固后的耗能能力与无损剪力墙相近,但延性未能达到无损构件的水平;聚合物砂浆钢筋网加固法能在一定程度上恢复剪力墙受火的性能,但加固后的延性和耗能能力均无法达到无损构件的水平。

Structure and Dynamics of Confined Polymer Melts from Attractive Interaction to Repulsive Interaction Between Polymer and Smooth Wall

We studied the static and dynamic properties of unentangled polymer chains which have a variable strength of interaction with the confining smooth walls by means of the lattice Monte Carlo simulation based on the bond-fluctuation model, that is, investigated the wall-polymer interactions which systematically vary from attraction to repulsion. A critical value of attractive potential（ewe） is found to be -0.6kilT, and only below it can the adsorption layer of monomers be formed near the wall. At the critical point of attraction ewe, attractive interaction counterba- lances the wall-polymer excluded volume effect, which minimizes the confinement effects on both chain dimension and mobility. Influences on both chain dimension and mobility increase with the increasing of either attraction or repulsion imposed by the walls. Despite of the nature and strength of the wall-polymer interaction, with the decrease of film thickness, configurations more parallelly aligned and flattened are adopted by confined chains, and a systematic trend of deceleration is found. Variations of chain dynamics with both film thickness and wall-polymer interaction can be well explained by the corresponding changes in the confinement of the nearest-neighboring particles that surround the chains. Besides, the thickness of the interfacial layer inside polymer films, where chains adopt a flattened ＂pancake＂ shape, is about two times the bulk radius of gyratioia and independent of the wall-polymer interaction.