ADHESION OF ELASTOMERS: DWELL TIME EFFECTS

The strength of adhesion of elastomers to rigid substrates generally increases with time of contact. This effect has been studied for samples of butyl and chlorobutyl rubber adhering to some rigid substrates. The peel strength increased continuously over long periods of contact until in some cases failure became cohesive within the elastomer layer. At higher temperatures the strength increased more rapidly, consistent with the WLF relation governing molecular motions. It is postulated that slow molecular rearrangements occur at the interface and increase the bond strength. A criterion for the observed transition from interfacial to cohesive failure is suggested.     

Reuse of reverse osmosis membranes in advanced wastewater treatment

In areas where tap water has a high salt content, wastewater is not appropriate for reuse in agriculture, particularly for sensitive crops. One alternative is reduction, via desalination, of the brackish character to the secondary effluent. A filtration stage is also required before desalination. On the other hand, used reverse osmosis membranes can be recycled and used as filters in the advanced treatment stage in order to reduce suspended matter contained in the secondary effluent—one advantage being the environmental recovery of solid waste. Used membranes can be treated with strong chemical oxidants to peel off the active separation layer in order to transform them into microfiltration or ultrafiltration elements. Preliminary tests have been carried out with 8″ elements, aimed at comparing membrane performance before and after the peeling process. An index denoted as peeling effectiveness (high flux, high salt passage) is used for comparison. It was soon observed that potassium permanganate was more effective than others, together with sodium hydroxide. Doses around 1000 mg/L KMnO₄ provided the best results. It was also concluded that membrane cleaning, done with sodium bisulphite prior to peeling, was better when recirculating the cleaning solution around the membrane rather than soaking it. Next steps in the research will test the actual filtration capability of the peeled membranes in actual wastewater.     

The effects of oxide film and annealing treatment on the bond strength of Al–Cu strips in cold roll bonding process

In this study the influence of Al₂O₃ coating and post-rolling annealing on the bond strength of dissimilar Al–Cu strips was investigated. For this purpose different degrees of thickness of Al₂O₃ film on Al strips were coated using anodizing process. Anodized aluminum and copper strips were then cold-rolled at different reduction levels. To investigate the effect of annealing treatment on bond strength after cold rolling, selected strips were annealed. Peeling test was used to investigate the effect of ceramic-based oxide film on bonding strength of Al–Cu strips. It was found that bond strength was improved after applying higher reductions and was decreased dramatically by providing oxide film. However, by increasing the thickness of oxide film up to a certain value (20 μm), bond strength was increased after which it was decreased. A decrease in bond strength was observed by post-rolling annealing.     

The effect of rippled graphene sheet roughness on the adhesive characteristics of a collagen–graphene system

A great amount of effort has been made in order to reach a more precise understanding of the adhesion phenomenon that happens as a vital component of several biological systems. Therefore, a firm understanding of the important factors that influence this phenomenon is of special importance in triggering the adhesive characteristics of different biological, bio-inspired and synthetic materials in fields such as tissue engineering.In this study the adhesive characteristics of a multi-material system consisting of the frequently used synthetic material, graphene, in the form of armchair-configuration sheets, and an important biological filament which is type 1 Collagen consisting of 3 alpha helices, has been studied in detail. The main emphasis of this study is placed on understanding the effects of the roughness characteristics of the inorganic elements which are the graphene sheets on the overall adhesive features of the system which are quantified within the framework of two main criteria: adhesion energy and peeling force. At first, the methodology used in order to obtain graphene sheets with various roughness values is described in detail. The abovementioned criteria are then evaluated through Molecular Dynamics (MD) modeling of the system in the NAMD simulation software environment and various simulation scenarios are studied.     

铝基刚挠结合板制作工艺探讨

金属铝基由于其良好的散热性能，广泛应用于LED方面；但随着PCB技术进一步向短、小、轻、薄的方向发展，其平面安装技术在安装空间方面受到了极大的限制，因此，如何实现金属基板三维折叠安装成为业界新的研究课题。对铝基＋软硬结合板的制作工艺进行了可行性探讨，通过铝基表面复合处理工艺＋纯胶预贴局部撕胶十二氧化碳激光切割技术有效实现了金属铝基与挠性电路的有机结合，满足了客户对金属基板实现三维安装的特种需求。     

核桃脱青皮机脱皮辊数值仿真与力学特性分析

为分析核桃脱青皮机中的关键加工部件脱皮辊的结构强度和振动特性,计算确定并模拟了脱皮辊的各项参数。将建立好的脱皮辊UG模型导入ANSYS进行静力学分析和模态分析。结果表明:脱皮辊可以在有效剥离核桃青皮的同时还能将脱净后的核桃向出料口方向输送;脱皮辊在工作状态下的最大变形为0.814 mm,等效应力为5.25 MPa,在负载情况下的最大等效应力远小于材料的屈服强度;分析得到脱皮辊的前6阶固有频率分别为0.846 3、51.287、172.07、183.62、186.66、242.33 Hz,远大于核桃脱青皮机的工作频率。结果显示该脱皮辊的刚度和强度完全满足要求,且在正常工作的情况下不会发生共振,为进一步研制核桃脱青皮机提供了数据支撑和科学依据。     

化学剂去皮法分离香豆胶

本文报道化学剂去皮法分离香豆胶的室内实验研究结果。将香豆用化学剂浸泡、清水冲洗除去种皮，再用机械方法将去皮香豆分离为内胚乳和胚。分出的内胚乳片即香豆胶片，种皮和胚为下脚料。香豆胶的收率可高达３３％－３８％，且较纯净，不含杂质。用双化学剂脱皮后分离出的香豆胶片，其增粘能力高于现行行业标准对一级香豆胶粉规定的指标。从工艺技术、经济等方面考察，该法可以实现工业化。以去皮所用某些化学剂处理目前市售香豆胶片，可使其增粘能力接近和超过瓜尔胶片。     

东风4 7215内燃机车凸轮轴失效分析

通过对失效凸轮轴的外观、化学成分、金相组织和力学性能等综合分析研究，认为在凸轮轴热处理工艺上存在缺陷，淬火层过薄或未淬火、接触应力过大是导致凸轮轴出现麻点、剥离的主要原因，提出了预防凸轮轴失效的措施及改进建议。     

同步及异步固相轧结铜铝铜复合材料的比较研究

以实验结果为基础，本文对同步及异步固相轧结铜铝铜复合材料时的轧制压力，轧制力矩，塑性变形功率及产品的剥离强度进行了较全面的比较，结果表明：异步轧结较同步轧结能提高产品的剥离强度，同时降低轧制压力及轧制能耗，但两辊侧的轧制力矩存在较严重的不均匀分配。     

脱皮处理对藜麦粉物化特性及结构的影响

为探究脱皮工艺对藜麦粉物化特性及结构的影响,采用差示扫描量热仪、扫描电镜和傅里叶红外光谱等对比脱皮处理前后和传统制粉工艺对藜麦粉的理化性质的变化;结果表明:脱皮处理工艺可以保留藜麦粉中的营养成分,降低其非营养成分含量;藜麦粉热糊稳定性升高;藜麦颗粒脱皮处理后保持完整的粒形;无新特征峰出现;说明脱皮处理对于改善藜麦粉的加工特性效果明显,为藜麦的营养成分、物化特性及结构提供参考。