灰粉比对苯丙乳液基水泥复合填缝料剪切性能的影响

制备了一种适用于机场水泥混凝土道面接缝的苯丙乳液基水泥复合填缝料(SCS),采用HS-3001B型剪切试验装置研究了不同灰粉比(水泥与无机粉料质量比)对SCS剪切性能的影响.结果表明:随着灰粉比增大,SCS的剪切强度及剪切模量显著提高,其剪切破坏形态由"内聚破坏"向"粘结破坏"转变,SCS在剪力作用下的负荷位移减小;适当增大灰粉比可显著提高SCS的剪切断裂伸长率、剪切峰值应变和剪切韧性;此外,结合扫描电镜分析可知,合理增大灰粉比可改善SCS的内部结构,进而提高其抗剪强度、剪切变形性能及剪切韧性.     

苯丙乳液基水泥复合道面填缝料力学性能研究

为解决机场道面接缝填缝料破坏失效问题,本研究制备了一种苯丙乳液基水泥复合道面填缝料,设计了四因素(粉液比、水泥比、分散剂掺量、成膜助剂掺量)三水平正交试验,开展了拉伸试验与剪切试验,系统研究了各因素对填缝料力学性能的影响规律.研究结果表明,以抗拉强度、拉伸模量、拉伸断裂伸长率、拉伸峰值应变为评价指标时,相比于水泥比、分散剂掺量、成膜助剂掺量等因素,粉液比对填缝料拉伸力学性能的影响最为显著.当粉液比位于0.30～0.55区间时,填缝料的强度性能随粉液比的增大而提高,变形性能随粉液比的增大而降低,当粉液比取0.40时,填缝料在拉伸荷载和剪切荷载作用下的强度性能较好,同时保持较好的变形能力,填缝料力学性能综合表现最佳.     

乳胶粉掺量对纤维素醚改性水泥浆体流变性能的影响

采用Anton Paar MCR 302型流变仪研究了乳胶粉掺量对纤维素醚改性水泥浆体流变性能和触变性的影响.结果表明,掺入乳胶粉的纤维素醚改性水泥浆体表现为剪切稀化的流变特性,当剪切速率较小时,浆体黏度下降显著.乳胶粉掺量越大,浆体基于Herschel-Bulkey模型拟合得到的屈服应力和黏度系数均越大.并且乳胶粉能...     

苯丙乳液水泥复合材料的拉伸力学性能

制备了一种苯丙乳液水泥复合材料(SCCM),并采用正交试验的方法对其拉伸力学性能进行了测试和分析.结果显示:粉液比决定了SCCM固化反应的形式,是影响其各项拉伸力学性能的主要因素;粉液比较低(0.45)时,随着水泥掺量的增大SCCM的变形能力和韧度变差,粉液比较高(0.65、0.85)时,随着水泥掺量的增大SCCM的强度、变形能力和韧度逐渐提高,粉液比越高提高越明显;滑石粉能提高SCCM的强度,重质碳酸钙能提高SCCM的变形性能和韧度;粉液比为0.65、水泥掺量为0.35、填料类型选用重质碳酸钙时,SCCM的各项拉伸力学性能均较好,具有很大潜力用作建筑接缝填缝材料.     

VAE乳胶粉改性水泥砂浆的配合比优化及抗冻性研究

以折压比、抗拉强度和黏结强度为评价指标,通过正交试验确定了醋酸乙烯-乙烯共聚乳胶粉(VAE乳胶粉)改性水泥砂浆配合比的较优方案。以较优方案为基础,研究了VAE乳胶粉掺量对砂浆力学性能和抗冻性的影响。结果表明,VAE乳胶粉改性水泥砂浆配合比的较优方案灰砂比为0.375,VAE乳胶粉掺量为10%(质量分数),水灰比为0.38。VAE乳胶粉可以显著提高砂浆的抗折、抗拉、黏结强度和韧性,随着VAE乳胶粉掺量(8%～12%)增大,砂浆的抗折、黏结强度和折压比均不断增大,抗拉强度不断减小,但仍显著大于普通砂浆;随着VAE乳胶粉掺量增大,砂浆的吸水率、质量损失率和强度损失率均不断减小;随着VAE乳胶粉掺量增大,抗压强度呈先增大后减小的趋势,当VAE乳胶粉掺量为12%时,砂浆的抗压强度开始低于普通砂浆。综合考虑砂浆的强度和韧性,VAE乳胶粉的较优掺量为8%～10%。     

丁苯乳液和乳胶粉对水泥水化产物形成的影响

用X射线衍射对晶态水化产物钙矾石(AFt)和Ca(OH)2进行表征,用环境扫描电镜观察水化硅酸钙(C-S-H)凝胶的变化,结合铝酸三钙(C3A)和硅酸三钙(C3S)的变化,分析丁苯乳液和乳胶粉对72 h内水化产物的影响.结果表明:丁苯乳液和乳胶粉促进了水泥浆体中AFt的生成,乳胶粉的效果更明显.丁苯乳液增加了AFt在浆体中的稳定性.丁苯乳液和乳胶粉使Ca(OH)2的生成量减少,乳液的效果更明显;延缓了水泥浆体中C-S-H凝胶的形成.水化72h时,改性浆体结构与未改性浆体差别不大,只是水化产物表面覆盖了一层聚合物薄膜.     

粉磨细度和石膏掺量对水泥性能的影响

众所周知，增加水泥的比表面积可以提高水泥的强度。如果在增加比表囱积的同时适当增加石膏用量，水泥强度可以得到进一步的提高（图１）。 但是，石膏用最增加后会不会延长石膏的反应时间、引起后期膨胀而损害水泥的安定性是一个问题。胶砂膨胀试验表明，在增加比表面积的前提下，即使水泥中ＳＯ３高达５．２３％，膨胀也大部分在一大就已经完成（图２）。由于水泥颗粒的细化，更多的Ｃ３Ａ在早期就进行了反应，ＳＯ３人概在早期就基本上被消耗完毕，因此直至３３０天也没有出现更大的膨胀。受研究手段限制，对５６天时出现的少量膨胀增加…     

和物夹层材料对减振复合钢板拉伸剪切性能的影响

高聚物夹层厚度为０．１５ｍｍ的减振复合钢板拉伸剪切特性与高聚物本身的拉伸变形规律一致,其破坏形态为高聚物内聚破坏;炕聚物夹层厚度为０．１０ｍｍ的复合钢板具有较高的拉伸剪切强度,其破坏形态为钢板与高聚物夹层间的类似界面破坏。聚氨酯和氯丁橡胶改性酚醛树脂含有极性基团,用它们分别作夹层制成的复合钢板具有较高的拉伸剪切强度;增加钢板表面粗糙度,有利于提高钢板和高聚物间的结合力。     

苯丙乳液改性高强水泥基材料性能及机理

苯丙乳液作为聚合物改性材料已经在水泥基材料中得到应用,而对其改性机理尚不清楚.本文测试了苯丙乳液改性高强水泥基材料的工作性、凝结时间及力学性能,利用微量热仪法与X射线衍射(XRD)分析了苯丙乳液对水泥基材料水化的影响,通过扫描电镜(SEM)及能谱分析(EDS)研究了其微观结构.研究结果表明,苯丙乳液延缓了水泥基材料的水化与二次水化反应,苯丙乳液能有效改善高强水泥基材料界面结构与水泥石结构.苯丙乳液与水泥或其水化产物间存在化学反应的可能性.     

用于可再分散乳胶粉的阳离子苯丙乳液的合成

采用种子乳液聚合法,以十六烷基三甲基溴化铵(CTAB)为乳化剂,偶氮二异丁眯盐酸盐(AIBA)为引发剂,引入亲水性阳离子单体甲基丙烯酰氧乙基三甲基氯化铵(DMC)及功能性单体丙烯酰胺(AM)〔m(DMC)∶m(AM)=1∶1〕来制备用于可再分散乳胶粉的阳离子苯丙乳液。探讨了聚合反应温度、乳化剂用量、引发剂用量、种子单体用量、阳离子单体用量等对乳液及可再分散乳胶粉性能的影响。确定最佳配方和工艺条件为:聚合反应温度为(80±2)℃、DMC添加量为2%(以主要聚合单体质量计,下同)、CTAB用量为2%(以单体总质量计,下同)、AIBA用量为0.53%(以单体总质量计,下同)、种子单体用量为10.0%(以单体总质量计,下同)。在该工艺条件下,合成的阳离子苯丙乳液粒径大小和分布适中、性能稳定,由其所制得的可再分散乳胶粉含水率低、平均粒径小、再分散性优良。     

粉料组成对聚合物水泥防水涂料拉伸性能的影响

采用极限试验的方法确定了水泥、重钙、石英粉对聚合物水泥防水涂料涂膜拉伸性能的影响,影响程度排序为水泥>重钙>石英粉。试验表明,由水泥、重钙、石英粉组成的粉料体系中,在一定范围内随着水泥占比的提升,涂膜拉伸强度和断裂伸长率均呈先增大后减小的趋势;随着重钙占比的提升,涂膜拉伸强度和断裂伸长率均呈先增大后减小的趋势。此结论为不同季节调整涂膜拉伸强度和断裂伸长率提供理论依据。     

花岗岩石粉复合矿物掺合料对水泥胶砂性能的影响

研究了花岗岩石粉的流动度比、活性指数,及其掺量对水泥胶砂性能的影响,利用L9(34)正交试验,探究了花岗岩石粉复合粉煤灰和矿渣粉掺量对水泥胶砂性能的影响,以总功效系数d为评价指标。结果表明:花岗岩石粉具有潜在的应用价值,粉煤灰在多元矿物掺合料砂浆中对其性能是主要影响因素,其次是花岗岩石粉。     

Preparation and Properties of a Waterborne Contact Adhesive Based on Polychloroprene Latex and Styrene-Acrylate Emulsion Blend

Environmental protection and legislative pressure to eliminate the use of solvents in the adhesive industry have inspired the search for safer alternatives. In the area of contact adhesives, the waterborne route has proved to be of particular interest. Based on the synergistic effect of polychloroprene latex and styreneacrylate emulsion, a waterborne contact adhesive consisting of polychloroprene latex (PCL) and styreneacrylate emulsion (SAE) blend has been developed. In order to blend PCL with SAE easily and to accelerate the drying rate of the adhesive, boric acid was chosen for use in the PCL/SAE blend system. Effects of boric acid and SAE content on the properties of PCL/SAE blends, such as pH value, storage stability and set time, were investigated. At the same time, the effect of SAE content on the mechanical properties of PCL/SAE blend films was studied. The morphology of blend films was characterized by Atomic Force Microscopy. The adhesive performance of the waterborne contact adhesive was evaluated by peel and shear tests. The results showed that when the waterborne contact adhesive formulation contained 40 wt% styrene-acrylate emulsion (dry weight) and 1.25 wt% boric acid, it had a good shelf-stability, its set time was 5 min, and the blend film with this formulation was ductile and flexible with reasonably good tensile strength and very high elongation at break. And the blend films showed structure with a sea–island morphology. The waterborne contact adhesives derived from PCL/SAE blends were found to be comparable to the commercially available solvent-based contact adhesives. The synergistic effect of polychloroprene latex and styrene-acrylate copolymer emulsion was also discussed.     

Preparation and Properties of Siloxane-Modified Styrene-Acrylate Latex Particles with Core-Shell Structure

Siloxane-modified styrene-acrylate latex particles with core-shell structure were prepared by two-stage semicontinuous emulsion polymerization using a reactive surfactant. Effects of catalyst dosage, weight ratio of γ-methacryloxypropyltrimethoxysilane (MAPS) to hydroxyl silicone oil (HSO) and siloxane content on the grafting degree of siloxane were studied. The chemical components of the copolymer were characterized by Fourier transform infrared spectra. The micromorphology of latex particles was observed by transmission electron microscopy. The stability properties of emulsion were tested by Ca²⁺, centrifugal, and mechanical stability test. The latex film was studied by water contact angle, water absorption ratio and thermal gravimetric analysis. The results show that siloxane-modified styrene-acrylate latex with core-shell structure can be synthesized using reactive surfactant and the prepared emulsion presents excellent stability. By using hydroxyl silicone oil (HSO) to react with silane coupling agent MAPS during emulsion polymerization, HSO can be located in the side chain of the polymer and endow the latex film with excellent stabilities.     

引发剂对核壳型复合乳液合成及性能影响的研究

采用半连续种子乳液聚合法合成了核壳型聚丙烯酸酯复合乳液,系统考察了引发剂(过硫酸铵)用量对乳液聚合过程中单体转化率、聚合稳定性、乳胶粒粒径及其分布、乳液黏度及Zeta电位的影响,探讨了其内在影响机制,并采用红外(FT-IR)、差示扫描量热(DSC)及透射电镜(TEM)对乳胶粒的结构进行了表征。结果表明:乳胶粒的Zeta电位随着引发剂过硫酸铵用量的增加而增大;合适的引发剂用量可使合成的复合乳胶粒粒径较小且粒径分布较窄;引发剂用量较大会使复合乳胶粒在聚合过程中发生聚并,但所得乳液在贮存过程中稳定性较好;当引发剂用量为0.4%～0.8%(占单体混合物的质量分数)时,单体均能参与反应,极少有残余,并且所得乳液呈明显的核壳结构。     

超细磷渣粉对水泥性能的影响

为了研究超细磷渣粉对水泥性能的影响,测试了普通磷渣,4 μm、2μm超细磷渣-水泥复合胶凝材料的标准稠度用水量、凝结时间、水化热、胶砂抗压强度.结果 表明:与纯水泥相比,超细磷渣掺入使复合胶凝材料标准稠度用水量增大5.6％～12.6％,凝结时间延长;普通磷渣-水泥复合胶凝材料相比于纯水泥水化速率缓慢,第二水化放热峰时间延迟8.26h;超细磷渣-水泥复合胶凝材料相比于普通磷渣-水泥复合胶凝材料水化放热速率增大,第二水化放热峰提前5.5h,超细磷渣-水泥复合胶凝材料120 h水化放热总量接近纯水泥;超细磷渣-水泥复合胶凝材料3d、7d抗压强度与水泥胶砂强度持平,28 d抗压强度超过水泥胶砂强度.超细化处置可增强磷渣的活性,促进磷渣本身的火山灰反应,提高水泥基材料性能,对实现磷渣的资源化利用具有重要意义.     

基于膨润土、粉煤灰的水泥复合土抗剪强度研究

为了研究基于水泥、膨润土和粉煤灰的水泥复合土抗剪强度特性,设计了水泥复合土配合比,并利用正交试验进行了水泥复合土的抗剪强度试验,得到了抗剪强度指标参数-黏聚力和内摩擦角,探讨了水泥掺量、膨润土掺量和粉煤灰掺量对水泥复合土强度指标(黏聚力和内摩擦角)的影响,建立了水泥复合土的黏聚力和内摩擦角随水泥、膨润土和粉煤灰等掺量变化的回归方程,以及水泥复合土抗剪强度的归回方程,试验结果表明:随着水泥、膨润土以及粉煤灰的逐步增加,其黏聚力均逐渐增大,而内摩擦角均逐渐降低.水泥掺量对黏聚力影响程度最大,对内摩擦角影响相对偏小.而粉煤灰掺量和膨润土掺量的影响基本相同,对内摩擦角相对较大,对黏聚力影响较小.     

Effects of Preform Shear on Tensile Properties of a Woven C/SiC Composite

This article addresses effects of weave defects in an angle‐interlock C‐fiber preform on the tensile properties of the resulting fully processed C‐fiber/SiC‐matrix composite. For this purpose, a preform was intentionally sheared in a controlled manner after weaving. The resulting distortions were quantified by analyzing high‐resolution images of the preform surface after the first step of matrix processing, while the tows were still clearly visible. Comparisons are made of tensile test results on specimens cut from this composite panel and from a pristine panel in select loading orientations. Strain maps obtained by digital image correlation are used to identify local strain variations that are attributable to weave defects. The results are discussed in terms of: (i) the shear‐normal coupling that arises in loading orientations of present interest, and (ii) the geometric effects of tow misalignment on tow continuity along the specimen gauge length. The composite is found to perform in a robust manner, in the sense that the tensile properties are not sensitive to the presence of the defects.