轻卡车架电泳漆膜附着力不良的原因分析及解决方案

针对某轻卡车架电泳漆膜附着力不良的问题,通过涂装线现场调查及缺陷样品微观形貌分析,得出基板表面涂油量过高、除油不净、氧化膜的存在等都会引起磷化成膜不良,最终导致电泳漆膜附着力不良.通过严格管控基板油品和涂油量,以及将基板更换为水洗抛丸热轧钢板,问题得以解决.     

表面处理对铝合金健身器材抗腐蚀性能的影响

研究了锆化液pH值和锆化时间对5083合金表面锆化膜电化学性能的影响,并在最优成膜工艺下分析了膜层的显微形貌和腐蚀性能。结果表明,当锆化处理时间为2.5min,锆化液pH=4.5时,5083合金表面锆化膜具有最佳的耐蚀性能;锆化处理2.5min可以在5083合金试样表面形成致密的网状锆化膜,锆化膜厚度约在60μm～80μm,与5083合金基体结合良好,成膜过程中Zr元素优先在第二相颗粒处形核;在2mol/L HCl和2mol/L H_2SO_4溶液中,优化工艺下锆化膜试样的耐腐蚀性能都要优于5083合金基体,浸泡腐蚀失重测试结果与极化曲线测试结果一致。     

面向气体分离膜应用的多孔陶瓷基体研究

在众多基体材料中,多孔陶瓷由于化学和热稳定性较好而成为气体分离膜基体材料的首选,但一般陶瓷基体表面粗糙并存在裂纹、针孔等缺陷,增加了气体分离膜的制备难度,并对分离膜的性能产生不利的影响。笔者采用溶胶—凝胶法对多孔陶瓷基体表面进行修饰,有效地降低了表面粗糙度,同时把基体渗透率调整到适宜值,以得到面向气体分离膜应用的多孔陶瓷基体。     

平板膜污泥浓缩临界通量与膜渗透性能研究

研究了不同浸泡条件、污泥含量、曝气量和膜龄对平板膜污泥浓缩( MST)临界通量和膜渗透性的影响,并通过环境扫描电镜检测分析长期运行平板膜的表面损伤情况.结果显示,良好贮存条件及低污泥含量的操作条件有助于提升临界膜通量与起始膜渗透性;曝气量升高,膜渗透性提升且稳定性增强;随着膜龄增加,膜渗透性能变差;无机颗粒摩擦与清洗会增加平板膜表面粗糙度,降低膜渗透性能,NaClO清洗对膜面损伤甚为严重.     

锆盐封孔对建筑铝合金阳极氧化膜耐蚀性能的影响

为了改善建筑常用6463铝合金的耐蚀性能,在其表面制备阳极氧化膜,然后采用氟锆酸钾溶液对阳极氧化膜进行封孔处理.研究了锆盐封孔对阳极氧化膜的微观形貌、表面成分和耐蚀性能的影响,并与沸水封孔和镍盐封孔进行了对比.结果表明:锆盐封孔对阳极氧化膜微观形貌的改善效果明显好于沸水封孔,阳极氧化膜中引入Zr元素,质量分数约为19....     

螺旋槽液膜密封端面空化发生机理

液膜中空化的发生直接影响着密封流体动压润滑性能,基于质量守恒的JFO边界条件,建立考虑表面粗糙度的螺旋槽液膜密封物理模型,经坐标变换将不规则物理域转换成规则计算域,采用有限控制体积法离散控制方程并求解,分析了膜厚、表面粗糙度、螺旋槽功用（上游泵送和下游泵送）、螺旋槽开槽位置及空化压力对液膜中空化发生的影响。结果表明：较小膜厚工况易促生空穴,而较大膜厚易削弱空穴,且随着膜厚增大,表面粗糙度的影响降低甚至被忽略;当密封为上游泵送型时,空穴区周向宽度明显大于下游泵送型,而螺旋槽位置对空化的影响与螺旋槽功用密切相关;选取较小空化压力使空穴缩减,而较大者反之,且后者对提升液膜承载有利。     

镀锌钢板表面耐腐蚀稀土镧盐转化膜的制备

采用稀土镧在镀锌钢板表面制备耐腐蚀的转化膜,通过交流阻抗、失质量和盐雾实验检测镧盐转化膜的耐腐蚀性能,实验结果表明:试样表面生成镧盐转化膜后,其阻抗值相对于空白试样大幅度提高,腐蚀速率降低近1个数鼍级,抗白锈时间达到54 h;原子力显微镜检测结果显示镧盐转化膜由大量无定形的固体颗粒沉积而成,膜质不均匀;EDS能谱检测结果表明镧盐转化膜由O、Fe、Zn和La元素组成.     

混凝土表面缺陷修饰涂料的研制及应用

针对混凝土施工中出现的色差、水纹、砂线和麻面等缺陷,通过原料选择和组分优化,研制了一种兼有防护性能的混凝土表面缺陷修饰涂料,测试了其关键性能,研究了涂刷该涂料后混凝土外观、抗渗性能和耐腐蚀性变化。结果表明:所研制的修饰涂料粘结强度为2.2 MPa,水接触角为126.22°;涂刷该涂料后,带缺陷混凝土与正常混凝土色差为3.93,混凝土3 h、24 h吸水率分别降低56%、60%,28 d、56 d电通量分别降低51%、43%,硫酸盐腐蚀条件下120 d强度衰减率仅2%,有效提升了带缺陷混凝土的表面质量。     

预制膜层对铝合金微弧氧化陶瓷层性能的影响

在硅酸钠电解液体系中,利用微弧氧化技术,对无预制膜层和含化学氧化膜或稀土转化膜的6061铝合金表面进行陶瓷化处理,研究了预制膜层处理对陶瓷膜层性能的影响。结果表明,预制膜层处理能够降低起弧电压,有利于膜层增厚和硬度提高。无预制膜的铝合金微弧氧化膜层表面呈现凹凸不平的多孔状结构,经预制膜层处理后,其表面粗糙度变小。微弧氧化后,铝合金表面膜层主要由α-Al2O3和γ-Al2O3晶体相组成,而含预制膜层试样中,硬度较大的α-Al2O3相的相对含量较高。与无预制膜层及含化学氧化膜的试样相比,稀土转化膜试样的膜层厚度和硬度最大,粗糙度最小,表面较大较深的孔洞缺陷减少。     

用电化学阻抗谱研究提高锆基无铬化学转化膜耐蚀性的方法

采用含1.4%(质量分数)ZRT-955陶化环保处理剂的水溶液(pH=4.5),在20°C下对Q235钢板表面锆化处理12 min,通过测量所得锆化膜在0.35%(NH_4)_2SO_4+0.05%NaCl的模拟汗液中的电化学阻抗谱(EIS),探索了烘干温度和缓蚀处理对膜层耐蚀性的影响。确定最佳烘干温度为180°C。采用硅氧烷酮类缓蚀剂对锆基转化膜进行后处理能够有效地提高其防腐性能。     

Effect of molecular weight on latex film formation: Photon transmission study

A UV-visible (UVV) technique was used to monitor the evolution of transparency during film formation from hard latex particles. Two different latex films were prepared from particles with high and low molecular weight (HM and LM) poly(methyl methacrylate) (PMMA) separately and annealed at elevated temperatures in various time intervals above the glass transition temperature (T_g). In both films, a continuous increase in the transmitted photon intensity (I_tr) was observed above 160°C as the annealing temperature was increased. However, the reflected photon intensity (I_rf) first decreased and then increased by showing a minimum in the same temperature range as the annealing temperature was increased. The increase in the transmitted photon intensity (I_tr) is attributed to increase in the “crossing density” at the junction surface. The activation energies for back-and-forth motion (ΔE_tr) were measured and found to be around 35 and 25 kcal/mol for the reptating polymer chain across the junction surface in the LM and HM films, respectively. The decrease in I_rf was explained by the void-closure mechanism, and the increase in the I_rf above 160°C was again attributed to the increase in the crossing density at the junction surface. Back-and-forth activation energies (ΔE_rf) were measured to be around 47 and 18 kcal/mol and the void-closure constants (B) were found to be around 24 × 10³ and 12 × 10³ K for the LM and HM film samples, respectively. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 339–351, 1998     

Do molecular weight determinations of coal-derived materials give meaningful answers?

The relation between number-average (M?_n) and weight-average (M?_w) molecular weights has been examined, and it was demonstrated how this can be employed to determine the self-consistency of results obtained for calculating molecular weights of chemically treated coals. The present method of calculation was calibrated against data of Katz et al., then applied to the data of Sun and Burk for g.p.c. fractions of alkylated coals. The newly calculated value for M?_w (3300) did not agree with Sun and Burk's value of 7882.     

清洗工艺对磷化膜膜重的影响

讨论了清洗工艺中一些常用清洗剂及清洗方式对磷化膜膜重的影响，并提出了相关的实验数据。     

碳纤维复合材料在液压油缸中的应用

碳纤维复合材料凭借优异的性能为不同场合的应用产生了积极的效应,在液压油缸上也受到广泛的关注。本文简述国内外碳纤维复合材料轻量化油缸的设计和工艺性的研究进展,并用碳纤维复合材料替代液压油缸部分金属组件,制造了碳纤维增强环氧树脂复合材料轻量化油缸。结果表明:碳纤维复合材料在结构和性能上具有很强的可设计性,既可降低液压油缸的重量,又能充分发挥复合材料高强度、耐腐蚀和疲劳性能。     

Photon transmission method for studying film formation from polstyrene latexes with different molecular weights

A photon‐transmission method was used to probe the evolution of transparency during film formation from polystyrene (PS) particles with different molecular weights. The latex films were formed at room temperature from the PS particles having two different average molecular weights and annealed at elevated temperatures in various time intervals above the glass transition (T_g). Onset temperatures (T_H) at given times (τ_H) for the optical clarity of films formed from low (LM) and high molecular (HM) weight PS particles were used to calculate the healing activation energies for the minor chains and found to be 22.0 ± 0.5 and 27.0 ± 0.6 kcal/mol, respectively. The increase in the transmitted photon intensity, I_tr, above the T_H was attributed to increase in the number of interfaces that disappeared. The Prager–Tirrell (PT) model was employed to interpret the increase in crossing density at the junction surface. The backbone activation energies (ΔE) were measured and found to be 127.8 ± 2.5 kcal/mol for a diffusing polymer chain across the junction surface for LM and HM latex films. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 866–874, 2000     

A New Method of Eddy Diffusivity Calculation for Droplets of a Venturi Scrubber

An analytical model using eddy diffusivity is applied for predicting droplet concentration distribution and liquid film formation in a Venturi scrubber. By comparing experimental data of film formation reported in literature (Viswanathan et al., 1984) and the results obtained from this model, a semi‐empirical correlation for liquid droplets eddy diffusivity is obtained. The validity of this correlation is confirmed by obtaining good agreement between theoretical and experimental data of droplet concentration distribution and film formation in a Venturi scrubber (Viswanathan, 1998; Viswanathan et al., 1984).     

Influences of molecular weight and particle morphology on film processing properties of polyvinyl fluoride

To select a suitable kind of resin for preparing films, the melting point (T_m), thermal decomposition temperature (T_d), and stretch property of polyvinyl fluoride (PVF) as a function of the viscosity–average molecular weight (M_η) were investigated. The results showed that T_d and maximal stretch ratio of extrusion‐cast PVF films gradually increase with the increase of M_η. T_m also increases when M_η is below 400,000, but keeps invariable when M_η is beyond 400,000. Six different kinds of PVF resin samples in this article were classified into three types, according to their particle morphologies: (1) loose‐structured PVF (PVF‐A and G); (2) tight‐structured PVF (PVF‐F); and (3) intermediate‐structured PVF (PVF‐B, E, and H). The effects of the morphology on the solvent absorbability of PVF were studied. The results indicated that the loose‐structured PVF has better absorption capacity to solvent than does tight‐structured PVF. The processing temperature can be considerably reduced when N,N‐dimethylformamide (DMF) as a plasticizer was mixed with PVF, and the diminished magnitude depends on the absorption capacity of PVF to DMF. The evaporation of DMF is influenced by both molecular weight and particle morphology of PVF, and the final residue of DMF in the PVF/DMF mixture is dependent on the molecular weight of PVF. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1780–1786, 2006     

Effect of Drying Conditions on the Mechanical and Barrier Properties of Films Based on Chitosan

Films plasticized with glycerine were prepared using chitosan with two different molecular weights (Mw), 780 and 430 kDa. Films were obtained by drying at 80 and 40°C at 20 and 40% relative humidity (RH) in a climatic chamber. Drying kinetics were established by the measurement of the evolution of the actual temperatures of the film forming solutions. Chitosan Mw did not show any significant influence on drying kinetics. Drying temperature affected drying kinetics in a more intense way than drying RH. Maximum tensile strength (86 MPa) and elongation at break (56.5%) were obtained with slow drying cycles (lower drying T) and when higher Mw chitosan was employed. Minimum water vapor permeability (0.59 g · mm/kPa · h · m) was achieved for films dried at faster drying cycles (higher drying T). Chitosan Mw was not a significant factor affecting water vapor permeability.     

Molecular weight dependent changes with time during latex film formation: a photon transmission study

A photon transmission method was used to probe the change with time of transparency during film formation from latex particles. Two different latex films were prepared from high (HM) and low (LM) molecular weight poly(methyl methacrylate) (PMMA) particles, which were annealed at 10min time intervals at various temperatures above the glass transition T_g. The increase in the transmitted photon intensity I_tr is attributed to the increase in ‘crossing density’ at the junction surface. The back and forth activation energies (ΔE) were measured for HM and LM films and found to be around 29kcalmol^-1 and 53kcalmol^-1, respectively, for a reptating polymer chain across the junction surface. Monte Carlo simulations were performed for photon transmission through a rectangular lattice. The number of transmitted photons N_tr was calculated as a function of the mean free path of the photons. It was observed that N_tr increased similarly to I_tr as the square of the mean free path of the photons increased. © 1998 Society of Chemical Industry     

农膜用聚乙烯树脂分子结构与耐老化性能的关系

通过对低密度聚乙烯（PE_LD）、线形低密度聚乙烯（PE-LLD）、茂金属线形低密度聚乙烯（m-PE—LLD）、乙烯-乙酸乙烯酯共聚物（EVA）等原料直接吹塑农用棚膜进行农田扣棚试验和力学性能测试，分析了各种树脂对生产PE功能性农用棚膜的适用性，并尝试从各种树脂基础分子结构角度对农膜的耐老化性能进行解释。试验结果表明：m—PE-LLD附脂的力学性能明显优于PE-LD和EVA树脂，EVA树脂在透明性方面占有优势；在耐老化性能方面，m-PE-LLD和EVA树脂无论扣棚时间还是测试数据均比PE-LD要好，从连续取样测试数据看出PE-LD断裂伸长保留率下降趋势明显，而m-PE-LLD和EVA树脂则是拉伸强度保留率下降趋势明显。