共查询到20条相似文献,搜索用时 15 毫秒
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采用环氧树脂-DDS固化体系作为胶接剂,探讨了各种金属表面处理方法、胶接时对胶接面施加的压力、胶层厚度等因素对胶接剪切强度的影响.结果表明,对不锈钢工件采用盐酸氧化法及草酸-硫酸氧化法进行表面处理,得到的胶接剪切强度最好;对铝合金工件采用硅酸磷酸钠法进行表面处理,得到的胶接剪切强度最高.胶接时对胶接面施加0.1~0.4Mpa的压力、胶层厚度在0.10~0.23 mm范围内时胶接效果最好.由于处理液对金属表面产生适度的化学腐蚀,改变了金属表面的物理化学性质,表现出更好的可浸润性和更强的表面吸附力,可以有效地提高胶接剪切强度. 相似文献
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The surface of high molecular weight polypropylene monofilament fibre was modified using a oxyfluorination method. The oxyfluorination treatment level was varied and a hydrolysis post-treatment was also applied. Contact angles of oxyfluorinated, hydro-lyzed oxyfluorinated and unmodified polypropylene fibres were obtained by dynamic contact angle (DCA) measurement using three liquids of known dispersion, acid and base surface free energy components. The surface free energies were then calculated according to the acid-base theory developed by Good, van Oss and Chaudhury. Surface oxyfluorination largely increased the acid and base components of the fibres' surface free energy compared with unmodified polypropylene fibres. The oxyfluorinated and unmodified polypropylene fibre surfaces were observed by Scanning Electronic Microscopy and Photoacoustic Infrared Spectroscopy. It was found that the surface oxyfluorination largely increases the roughness of the polypropylene surfaces and the carbonyl group content increases as the treatment level increases. The interfacial shear bond strengths between the cementitious matrix and the polypropylene fibres treated under various conditions were determined by embedded fibre pull-out tests. Results showed that the fibre surface oxyfluorination treatments increase the interfacial bond strengths. The correlations between the shear bond strengths and surface free energy components were established. Results showed that fibre/concrete interfacial bonding was best correlated with the acid component of surface free energy of polypropylene fibres. 相似文献
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木质素阳离子乳化剂的制备及其表面活性 总被引:10,自引:1,他引:10
先用环氧氯丙烷和三乙胺反应制备环氧丙基三乙基氯化铵中间体,再与木质素反应制得木质素季铵盐。中间体制备条件是温度45~50℃,时间3h,n(三乙胺)/n(环氧氯丙烷)=1~1 1。木质素季铵盐制备条件为温度50~55℃,时间2h,n(木质素)/n(中间体)=0 6~0 8,pH>10 5。产物的表面活性测定表明,不同接枝率的木质素季铵盐降低水溶液表面张力的能力相差不大,最低表面张力约为40mN/m。 相似文献
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《Journal of Adhesion Science and Technology》2013,27(10-11):1573-1590
Abstract In this paper we show that current abrasion surface preparation practices do not perform equally on all composite surfaces. The effect of abrasion on the adhesive bond strength of various carbon fiber (CF) composites was investigated. Cyanate ester composites were fabricated using a low, a high and an ultra high modulus carbon fiber (T300, M55J, K13C2U). XPS and contact angle measurements showed that the surface energy of all three composites increased due to the removal of contaminants as well as increased in surface roughness. However, the lap shear strength degraded sharply for a number of cases, irrespective of roughness, depending on the fiber used. Composites utilizing lower modulus carbon fibers increased in adhesive bond strength following abrasion in comparison to composites with higher modulus fibers. As the modulus of the fiber and the abrasive grit size increased, the degree of degradation caused by abrasion was shown to increase significantly. Scanning electron microscopy (SEM) and profilometry measurements showed the development of an abrasion-affected zone that was especially prevalent for higher stiffness composites. The failures for the higher modulus specimens were caused by subsurface damage located a few fiber diameters below the abraded surface. However, an alternate technique using atmospheric plasma surface treatment exhibited efficient removal of contaminants while showing no degradation of bond quality when treating these ultra high modulus composites. 相似文献
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应用Washburn浸渍理论(penetration theory)和van Oss-Chaudhury-Good组合理论(combining rules)及柱状灯芯技术(column wicking technique),对木质素及磺化木质素的表面能进行了估算和比较。结果显示,未经处理的木质素的表面能约21~22 mJ/m2,而磺化过程增加了表面能,主要原因是磺化使木质素的极性得到加强。红外光谱测定也证实了这个结果。 相似文献
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以酶解木质素(EL)、尿素(U)、甲醛(F)和三聚氰胺(M)为原料,采用碱反应工艺制备了酶解木质素改性三聚氰胺脲醛树脂(ELMUF)。分别考查了EL用量对制备的ELMUF树脂的固化时间、固化温度、游离甲醛量及其制备胶合板胶合强度和甲醛释放量等性能的影响,随着EL用量的增加,ELMUF树脂游离甲醛量从0.26%逐渐降低至0.12%,固化时间从96 s逐渐延长至152 s,黏度由86 mPa·s迅速升高至1 140 mPa·s。通过DSC测定不同EL用量的脲醛树脂固化过程,结果表明:随着EL用量的增加脲醛树脂的反应活性逐渐降低,固化温度由120.6℃逐渐升高至132.0℃,对热压工艺要求更加苛刻。 相似文献
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碱木质素改性及其产物表面活性的研究 总被引:3,自引:1,他引:2
通过将竹材碱水煮烷基化、氧化,提高其余水性能,以达到改善其表面活性的目的。先将碱木素的酚羟基与卤代烷烃反应醚化,带上亲油性的烷烃基,再用氧化剂如硝酸、高锰酸钾、高碘酸钠将其侧链氧化成羧基,加入NaOH中和后得到亲水性孩酸钠盐。考察了反应温度、溶液pH值对本素烷基化反应的影响,不同的氧化剂氧化对氧化产物结构及表面活性的影响。所得产物降低表面张力的能力超过了十二烷基磷酸钠及十二烷基苯磷酸钠,降低界面张力的能力与十二烷基苯磷酸钠接近。 相似文献
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木质素的氢解及其合成环氧树脂探索 总被引:10,自引:0,他引:10
木质素是一种潜在的能在生产中利用的自然资源。对自制的木质素在一定的条件下。进行氢解反应,得到了羟基数量提高到约为2倍量的氢解木质素,提高了木质素的活性.使其易于和环氧氯丙烷在氢氧化钠的催化作用下发生环氧化作用。本文对木质素进行了化学改性和合成环氧树脂的探索。用红外光谱和核磁共振对改性产物和环氧树脂加以表征。 相似文献
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采用曼尼希反应,将玉米芯木质素改性制备木质素胺(AL),然后与水性聚酰胺(PAE)、聚乙二醇二缩水甘油醚(PEGDE)混合,以豆粕粉为原料,通过AL/PAE/PEGDE改性制备高固体含量的豆粕基胶黏剂(豆胶)。对豆胶性能进行表征和测试,结果表明:复合改性豆胶固化后的红外谱图中酰胺Ⅰ带吸收峰由1632 cm^(-1)处蓝移至1640 cm^(-1),酰胺Ⅱ带吸收峰由1533 cm^(-1)蓝移至1538 cm^(-1),此现象说明固化豆胶中形成了结构致密相互交联的网状结构;热重分析结果也说明PAE、PEGDE、AL与蛋白质分子之间形成了结构更为致密的网络结构;流变行为分析显示固化豆胶具有假塑性流体的特征;改性豆胶含固体高达42.5%,而表观黏度仅为3746 mPa·s,具有较好的涂布性能,适于工业化应用;所得胶合板的胶合强度为0.86 MPa,合格率100%,符合国家Ⅱ类胶合板的标准要求(胶合强度≥0.70 MPa,合格率≥90%)。 相似文献
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以湖北稻草秸秆为研究对象,研究了超低酸水解木质纤维素的适宜条件,测定了适宜条件下的超低酸法水解15种不同种类秸秆的纤维素及半纤维素的转化率、还原糖得率及结晶度的变化。实验结果表明:秸秆投料量3 g、硫酸投料量45 mL(硫酸质量分数0.05%)、搅拌转速500 r/min、反应温度210 ℃、反应时间10 min为适宜的水解条件。对15种不同种类秸秆的水解结果统计得到,随着秸秆中木质素含量的增大,纤维素和半纤维素的转化率都逐渐降低,还原糖得率逐渐降低;通过SEM和X衍射分析水解前后的木质纤维素结构,得到了木质素影响水解过程的方式:1)木质素含量越大,纤维素的结晶度越大,纤维素的非晶化越困难,从而影响了纤维素的水解;2)原木质素不溶于反应体系且在酸性条件下相对稳定,富木质素层的木质素阻碍反应物与产物扩散,使富木质素层内的纤维素、半纤维素水解速率降低;3)木质素含量越高,木质纤维素的富木质素层越厚、强度越大,水解时难以从颗粒表面脱落,进一步降低水解速率。 相似文献
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掺杂炭纤维对乙苯脱氢催化剂性能的影响 总被引:1,自引:0,他引:1
在氮气保护及程序控温条件下,制备了具有一定孔隙的炭纤维掺杂的乙苯脱氢催化剂。通过对比表面积、孔隙度的测定,发现微孔数量随炭纤维加入量的增加而增加,炭纤维催化剂得到了活化。催化剂的扫描电镜分析、侧压强度及抗拉强度测试证明,炭纤维使催化剂的机械强度明显提高。乙苯脱氢实验表明,苯乙烯选择性随炭纤维的加量增大;乙苯的转化率则存在最大值。考虑机械强度与催化活性,加入6%炭纤维的催化剂最佳。 相似文献
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Yasumitsu Uraki Chinatsu Matsumoto Takuro Hirai Yutaka Tamai Makiko Enoki Hiroshi Yabu 《木材化学与工艺学杂志》2013,33(4):348-359
Abstract We have already fabricated honeycomb-patterned cellulosic films with cellulose I and II polymorphisms as a basal framework in order to create an artificial woody cell wall.[ 1 , 2 ] The adsorption of an isolated lignin, acetic acid lignin (AL), was attempted onto the honeycomb films not only to develop materials further mimicking the cell wall but also to elucidate the mechanical effect of isolated lignin on the tensile strength of the cellulosic architecture. The tensile strengths of honeycomb-patterned cellulosic films were improved by the AL adsorption. Although the cellulosic films without lignin weakened under high moisture content conditions as compared with those under the low content conditions, the lignin-adsorbed cellulosic film maintained significant tensile strength even under the high content conditions. This result suggests that lignin contributes to reinforce the mechanical strength of cellulose framework, in particular high moisture conditions. 相似文献
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NOTE The Application of Surface Analysis Techniques in the Adhesive Bonding of Oily Automotive Steel
There are fewer papers on the adhesive bonding of steel for structural applications than for aluminum and titanium alloys. However, the approach to the adhesive bonding of all three adherends has been similar, that is, the surfaces are pretreated prior to bonding. Trawinski, et al.1,2,3 reviewed several conversion coatings or etching processes used for steel. Haak and Smith4 selected two surface treatments among nineteen based on minimal cost, simplicity and good durability. Smith5 has reported work on stainless steel-epoxy bonds under hydrothermal stress. Bischof, et al.6 investigated the effect of surface pretreatment of steel on bonding strength obtained with polyvinyl chloride. Ziane, et al.7 identified four fracture zones resulting from shear loading of epoxy bonded galvanized steel following four different surface pretreatments. But in some cases, as in the automotive industry, there is a need to bond oily steel directly without surface pretreatment. Rosty, et al.8 have reported a study of the role of fillers and cure temperature on the shear strength of oily steel bonded with epoxy. None of the reported research utilizes both microscopic and spectroscopic techniques to analyze the fracture surfaces. 相似文献