芳纶复合纸基摩擦材料的初步研究

本文采用高性能芳纶纤维和剑麻纤维为原料制备湿式成型纸基摩擦材料.初步探讨了原纸中两种纤维的配比、剑麻打浆度、芳纶纤维的长度和形态以及作为粘结剂的酚醛树脂的种类和上胶量等对纸基材料的力学性能和摩擦性能的影响,为进一步研究湿式成型纸基摩擦材料奠定基础.     

聚酰亚胺树脂提升对位芳纶纸性能研究

对位芳纶纤维分子链刚性结构以及纤维表面化学惰性导致纤维间的结合力较差,进而导致其机械性能较低。本实验利用高强、高模、耐高温性能优异的聚酰亚胺树脂溶液浸渍对位芳纶原纸,以此来增强对位芳纶纸基材料的力学性能及耐热性能。实验结果表明,浸渍后纸页抗张、撕裂指数比未经处理的纸样绝对值分别增大了32.9%和54.2%。XRD分析表明,浸渍后纸页的结晶度增大,这将有利于在纸页热压后提升其物理性能。SEM图显示由于聚酰亚胺树脂溶液的浸渍作用,对位芳纶浆粕和短切纤维在纸页的表面分布更加均匀,起到增强效果。TG分析表明,经过浸渍处理后,对位芳纶纸的最初分解温度达到500℃,显著提升了其耐温性能。     

混合纤维纸基复合摩擦材料的研究

对纸基纤维复合材料的成型及有关影响因素进行了初步研究.采用剑麻纤维与芳纶纤维为原料,针对原纸的抄造、纸页与树脂的复合条件、材料的热压及强度性质等进行了实验,探讨了原纸定量、原纸纤维配比、剑麻浆打浆程度以及浸渍液树脂浓度等因素对材料强度的影响.     

树脂浸渍对纸基摩擦材料性能的影响

分别以酚醛树脂、聚酰亚胺树脂、聚酰亚胺树脂和酚醛树脂复合共3种浸渍液来浸渍纸基摩擦材料原纸,研究了不同浸渍条件对热压前后手抄片抗张强度和热压后手抄片孔隙率的影响。结果表明,热压前后手抄片的抗张强度均随两种单一树脂浸渍液浸渍量的增加而增加;单一树脂浸渍时,手抄片的孔隙率随浸渍量的增加而降低;当两种树脂复合浸渍时,热压后的手抄片抗张强度和孔隙率均随聚酰亚胺树脂比例的增加而增加,且手抄片抗张强度和孔隙率均比单一酚醛树脂浸渍时有所提高。     

不锈钢纤维/玻璃纤维针刺毡增强摩擦复合材料的研发

采用非织造布针刺技术制作不锈钢纤维/玻璃纤维针刺毡作为增强材料,与硼改性酚醛树脂复合开发高性能摩擦材料。论述了不同树脂含量、不锈钢纤维含量、纤维毡定量和结构以及环境温度对增强摩擦复合材料力学性能和摩擦磨损性能的影响。研究结果表明,不锈钢纤维/玻璃纤维针刺毡增强摩擦复合材料具有良好的综合性能。     

对位芳纶纸的增强方法

为了获得更高机械强度和绝缘性能的对位芳纶纸基材料,本实验采用添加热塑性黏结纤维A、间位沉析纤维,利用酚醛树脂浸渍芳纶手抄原纸的方法,来增强纸页的各项性能指标。试验结果表明,这3种增强方式可以在大大改善芳纶纸机械性能的同时,并使其具有较好的耐压强度。扫描电镜观察,增强后的芳纶纸表面更平整,这是由于热塑性黏结纤维受热熔融将对位芳纶纤维粘接起来所致。     

高性能复合纸基摩擦材料原纸抄造工艺的初步研究

采用碳纤维、短切芳纶纤维和芳纶浆粕、竹纤维以及海泡石绒为原料,通过湿法成形制备纸基摩擦材料原纸;探讨了原纸中海泡石绒对混杂纤维的分散作用,以及在羧基丁腈胶乳和阳离子聚丙烯酰胺(CPAM)的作用下对填料、摩擦性能调节剂的吸附和粘结效用。实验结果表明:海泡石绒对混杂纤维有良好的分散作用,并能改善浆料的留着和纸页的匀度。     

对位芳纶纸浸渍增强作用的研究

通过采用红外光谱、DSC-TG分析手段对4种聚酰亚胺树脂(PM1～PM4)的结构和热稳定性进行了分析；用聚酰亚胺树脂浸渍对位芳纶原纸，考察聚酰亚胺树脂的上胶量对对位芳伦纸强度性能的影响以及对位芳纶原纸与4种浸渍树脂的相容性。结果表明，PM1树脂的酰胺化程度较高，为带有胺端基芳香族聚酰亚胺，与对位芳纶分子结构相近，因此与对位芳纶原纸的相容性最好；聚酰亚胺树脂的上胶量随着树脂浸渍液质量分数的增大而升高，当PM1树脂浸渍液质量分数25%时，其上胶量达36.68%，对位芳纶纸的抗张指数为52.4 N·m/g，伸长率为0.8%，撕裂指数为43.1 N·m2/g，此时对位芳纶纸的强度性能最为理想。     

酚醛树脂对芳纶复合纸基摩擦材料的影响

本文采用高性能芳纶纤维和剑麻纤维为原料制备湿式纸基摩擦材料.初步探讨了酚醛树脂的种类和上胶量对纸基材料的强度性能和摩擦系数的影响.     

纤维表面改性对纸基摩擦材料原纸强度性能的影响

采用高温空气氧化法对碳纤维表面进行改性处理,同时采用磷酸氧化法对芳纶短切纤维表面进行处理,对改性前后的两种纤维分别进行表征;采用芳纶浆粕、竹浆、海泡石绒以及改性前后的碳纤维和芳纶短切纤维混合来抄造纸基摩擦材料原纸;探究纤维的表面改性处理对纸基摩擦材料原纸强度性能的影响。结果表明,改性后的纤维表面产生了很多沟壑,纤维表面粗糙程度增加,纤维表面的接触点和面积更多,结合力更大,同时引入了大量的活性基团;用改性纤维配抄的纸张层间结合强度比未改性纤维配抄的纸张层间结合强度提高了21%。     

摩擦片圈砂光机的研制

汽车自动变速器的摩擦片圈是传递动力的重要零件,它是由耐磨、耐热、高硬度的材料薄片冲剪成纸圈形状。摩擦片圈轻薄柔软,材料质脆而易折断,且精度要求高。为满足加工要求,研制了专用的砂光设备。本文阐述了专用砂光机的设计要点。     

Joining wood by friction welding

At the Chair of Timber Constructions of the Swiss Federal Institute of Technology in Lausanne (EPFL) tests were carried out to join wooden work pieces by friction welding without any additional welding deposit. It could be determined that this kind of technology, which is mainly used for thermoplastics and metal, can also be applied to wood. Tests were carried out to determine the influence of the processing parameters like welding pressure, frequency and amplitude of the circular movement on the welding process and the input of energy at the interface. In addition, the resistance of the joint was examined. The development of the shear strength during solidification of the interface as well as the shear strength achievable after a complete solidification of the interface was the objective of the examinations. Furthermore, the microstructure of the welded joint was studied to reveal the manner in which the thermally decomposed wood forms the connection between the welded pieces.     

Physical analysis of friction cooked RTE snacks

Extrusion is widely applied for production of ready to eat snacks. The existing technology is capital intensive and requires preconditioning the raw grains before extrusion, dedicated drying after extrusion and post extrusion addition of fat and sugar where required. A novel technology, friction cooking, has been developed to greatly lower capital costs and overcome the limitations of conventional extrusion. The production conditions (temperature and moisture content) and resulting physical properties from eight friction cooked raw grains were compared to the equivalent properties of conventionally extruded products from these grains. Properties were expansion ratio, bulk density, hardness and colour. Friction cooking temperatures were lower (60–98 °C versus about 150 °C), and products were softer but with a lower expansion ratio and higher densities. In friction cooking colour differences between raw grains and cooked product were minor. Many of these differences were attributed to lower temperatures and moisture contents in the friction process.     

Warp breakage mechanism of friction spun yarns

Abstract

Warp breakage mechanism of Dref, ring, and rotor spun yarn is discussed using five different techniques,which include Weibull distribution, fatigue behavior, scanning electronmicroscopy studies, and analysis of structural distortion by digital image processing. In all types of yarn, failure occurs at minimum diameter. Interfibre slippage is a dominant factor for warp breakage and the slippage length is found to be highest for Dref yarns.     

Contact-crack problem with friction in spruce

This analysis presents of how friction in wood-to-metal interfaces can affect data from wedge-splitting tests on Double Cantilever Beam (DCB) spruce specimens. Cases evaluated were short cracks, and cracks emanating from a long notch. A numerical analysis is performed to clarify the influence of frictional characteristics at the wood-aluminium wedge interface on stress intensity factors. This demonstrates a correlation between fracture toughness (K_Ic) and contact friction (μ) in fracture mode I for short cracks. However, the effect of friction diminishes, when the crack tip moves away from the contact area. Analysis and conclusions are relevant to other situations where components develop cracks in close proximity to contact regions, for example, in predicting the strength with dowel fasteners.     

Contact-crack problem with friction in spruce

This analysis presents of how friction in wood-to-metal interfaces can affect data from wedge-splitting tests on Double Cantilever Beam (DCB) spruce specimens. Cases evaluated were short cracks, and cracks emanating from a long notch. A numerical analysis is performed to clarify the influence of frictional characteristics at the wood-aluminium wedge interface on stress intensity factors. This demonstrates a correlation between fracture toughness (KIc) and contact friction (μ) in fracture mode I for short cracks. However, the effect of friction diminishes, when the crack tip moves away from the contact area. Analysis and conclusions are relevant to other situations where components develop cracks in close proximity to contact regions, for example, in predicting the strength with dowel fasteners.     

织造过程中经纱承受的摩擦作用浅析

对织造过程中经纱与停经片、经纱与经纱间、经纱与综眼和钢筘之间的摩擦作用进行了简要分析,并分区探讨了打纬区、综框区、后梭口区和经停区经纱强伸性及表面毛羽的变化及其成因,确定了织造生产中经纱所承受的摩擦作用主要为经纱与钢筘间、经纱与经纱间的摩擦,这对于降低经纱织造断头、提高经纱的可织性、实现轻浆甚至不上浆织造具有指导意义.     

DREF摩擦纺与纱线特性的优化

摩擦纺对于产业用纺织品所需的新型纱线的开发提供了特殊的可能性.不同的纤维(包括短纤维)按照设计好的方式结合在纱线的横截面中,形成皮芯型多组分结构.描述了利用特殊的纺纱参数来设定纱线特性的技术和可能性及用摩擦纺纱线生产的主要产品.     

球阀摩擦阻力系数的研究

对饮料工业等卫生要求较高的管路系统中普遍采用的球阀,进行了研究,获得了局部阻力系数ζ与Re之间的公式.     

The role of friction in perceived oral texture

Instrumentally measured in vitro friction in semi-solid foods was related to oral texture sensations. Increased fat content resulted in lower sensations of roughness, higher sensations of creaminess, and lower friction, suggesting that lubrication is the mechanism by which fat affects oral texture in low fat foods. Starch breakdown by salivary amylase in low fat foods resulted in reduced friction, possibly through the release of fat from the starch food matrix, and the migration of fat to the surface of the bolus where it becomes available for lubrication. No evidence was found that salivary mucins or salivary viscosity play a role in lubrication. Astringent sensations may be related to reduced lubrication and increased friction caused by particles, either resulting from precipitation of salivary protein rich proteins or from flocculation of dead cells.