Preparation and Tribological Properties of Polyamide 11/Graphene Coatings

Polyamide 11/graphene coatings were prepared through a spraying method with as-prepared organophilic graphene. The tribological results showed that the wear life of composite coatings was obviously higher than that of neat Polyamide 11 coating; however, the values of friction coefficients had hardly changed. The optimal content of graphene in the range of our experiments was 0.4 wt%, and the wear life of the composite coating increased by 460%–880% compared with that of pristine Polyamide 11 coating. The morphology of worn surface for both pristine Polyamide 11 and the composites coatings was studied, and the wear mechanisms were discussed.     

Study on development of polyamide gears for improvement of load-carrying capacity

In polyamide based gears, thermal damage of the gear tooth surfaces occurs during gear meshing due to accumulated heat in the tooth body. In the experimental study reported in this paper, polyamide gear teeth have been modified in order to distribute the generated heat on the tooth surface by means of drilled cooling holes at different locations on the gear tooth body. The main aims of this paper were to study the effect of cooling holes on the accumulated heat on the tooth surface and on the measured wear. It was shown that the drilled cooling holes on the tooth body decreased the tooth surface temperature and led to an increase in the load carry capacity and improved wear resistance. Geometrically modified gears have showed an improved service life and a decreased surface temperature.     

芳纶电缆水下电连接器密封技术研究

芳纶电缆是一种新型电缆,具有质轻、强度高等优点,但常因连接密封技术问题影响其使用。本文介绍了芳纶电缆连接器的密封结构及设计和制造中的关键技术。地连接的可靠性和水密性进行了分析及试验,并提供了设计方法和腾技术参数。     

Investigation of gear performance of MLNGPs as an additive on polyamide 6 spur gear

Molded plastic gears have long provided an alternative to metal gears in lightly loaded drives. They transmit power quietly and often without lubrication in numerous applications, furthermore decrease the quantity of parts and oppose chemicals in numerous applications. Previously, plastic gears were restricted to to 0.25 hp because of varieties in their properties and uncertainties about how they react to natural conditions such as moisture, temperature and chemical. Today, better molding controls combined with design practices that more accurately encompass environmental factors have boosted plastic gear drive capacity to 1.5 hp. Using reinforcement this is standout amongst the most practices to enhance the gear performance.

This study estimated the effects of multilayer graphene nanoplatelets (MLNGPs) as an additive on polyamide 6 (PA6) spur gear performance. These include strength, elastic modulus, thermal stability, dynamic mechanical analysis, moisture absorption, and wear characteristics.The nanocomposite gear was made by melt mixing method and injection moulded into thick flanges. The flanges were machined using CNC milling machine to produce spur gear. The wear experiments were performed at a running speed of 1400 rpm and at torques of 13 and 16 Nm with different concentration 0, 0.1, 0.3 and 0.5 wt% MLNGPs using test rig. The result showed that 0.3% of MLGNPs is the optimum concentration. Young's modulus increased up to 40%, Vickers microhardness value increased up to 25%, storage modulus E’ is increased up to 37% and glass transition temperature is increased up to 14%. On the other hand TGA result shows that the Tonest increased up to 7.5% and Td increased up to 2%, and wear decreased by 35% at 16 Nm and 54% at 13 Nm.     

Influence of Processing Variables on Dynamic Mechanical Response of Laser-Sintered Glass-Filled Polyamide

For establishing selective laser sintering in manufacturing technology, a wide knowledge about the influence of processing variables on the quality of sintered part is mandatory. In this regard, this article addresses the influence of key process parameters (i.e., bed temperature, laser power, beam speed, hatch distance, hatch length) on the dynamic mechanical properties of laser-sintered glass-filled polyamide specimens to enhance their service life. A face-centered central composite design of response surface methodology was employed to gather data, and mathematical models were developed to investigate the effects and interactions of selected input processing variables on the different performance characteristics. Experiments revealed that dynamic mechanical properties reduced with decrease in bed temperature. This was due to nonuniform fusion of powder particles and increased porosity. Specimens fabricated at high energy density (ED) were strong, solid, and isotropic but become weak, porous, and anisotropic, as the ED decreased. Poor material integrity and weak interparticle bonding were the main reasons of low dynamic mechanical strength. In addition, microstructural analysis was also performed to examine the surface morphology of sintered specimens. Further, optimum working conditions for producing parts with maximum dynamic mechanical response were determined.     

Photo-induced alignment behavior of azobenzene compound in thin film

Photo-induced molecular alignment behavior of spin-coated poly(4,4′-azobenzene pyromellitamic acid) (PAA(azo)) film was investigated by Fourier transform infrared spectroscopy measurement, atomic force microscope and transmission electron microscope observation. As-spun PAA(azo) flm was found to be smooth and uniform with an amorphous structure. Upon irradiation of linearly polarized ultraviolet light, the molecular ordering and crystallization were induced, and the film surface was roughened slightly. The PAA(azo) film converted to poly(4,4′-azobenzene pyromellitimide) (PI(azo)) film with higher ordering and crystallinity by subsequent thermal treatment. The PI(azo) film was useful as an active layer to introduce the molecular alignment of copper phthalocyanine (CuPc).     

Water and toluene barrier properties of a polyamide 12 modified by a surface treatment using cold plasma

CF₄ and CO₂ plasma treatments have been used to modify the barrier properties of a polyamide 12 (PA12) towards permeant molecules, which present opposing characteristics: water and toluene. The surface modifications were observed by atomic force microscopy, X-ray photoelectron spectroscopy and surface Gibbs function measurements. Both treatments lead to different surfaces; one is rather hydrophobic (with CF₄) whereas the other is more hydrophilic (with CO₂. The effect of this modification on permeametric properties has been investigated by liquid water and liquid toluene permeation measurements. Our results show opposite effects of the two treatments. CF₄ plasma treatment leads to a reduction of water and toluene permeability. With CO₂ plasma treatment, in terms of permeation, two different behaviours were observed, an increase and a decrease of permeancy for water and toluene respectively. These results are in full agreement with those obtained for the surface characterization, and confirms change in the polymeric surface affinity for the permeant leading to a variation of the materials permeancy.     

纳米磷灰石晶体/聚酰胺复合骨组织工程支架材料的研究

采用常压共溶、共沉淀和水热处理的方法制备了纳米磷灰石晶体／聚酰胺复合骨组织工程支架材料。纳米磷灰石在复合材料中含量高达60wt％(重量比),纳米磷灰石和聚酰胺之间有化学键结合,材料的力学性能接近自然骨水平。复合材料可加工成块状多孔体,材料的孔隙率为55％-70％,平均孔径为300μm,多孔支架不仅有大孔,而且大孔壁上含有丰富微孔,是一种非常有发展前景的组织工程材料。     

Solid State Shear Milling to Prepare Magnesium Hydroxide Flame-Retardant Polyamide 6 with High Performance

A novel processing method, that is, solid state shear milling (S3M), was adopted to compound high loading inorganic flame-retardant magnesium hydroxide with polyamide 6 by using our self-designed pan-mill equipment. S3M can effectively pulverize PA6, increase the interfacial interaction of the resin and magnesium hydroxide, and achieve their even blending, thus effectively controlling the state of the dispersion phase in solid state. With the co-milled composite powder as flame retardant master batch filled in original PA6 pellets, it can greatly improve the compatibility of the system, modify the distribution process of magnesium hydroxide, and decrease the dispersion phase size in the following melt processing. As a result, S3M technology can remarkably increase the melt flowability of the composite materials, and obtain obviously enhanced flame retardance and mechanical performance, thus providing an effective solution to the poor processibility and deteriorated performance of magnesium hydroxide flame-retardant PA6 obtained through direct melt processing.     

Thermal and mechanical properties of polyamide 11 based composites reinforced with surface modified titanate nanotubes

The preparation of polyamide 11 (PA11) based composites reinforced with pristine and surface-modified titanate nanotubes (TTNT) is reported. Twin-screw melt compounding was used to produce composites with up to 2 wt% of TTNT. To enhance dispersion and TTNT compatibility with the thermoplastic, these were modified with cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulphate (SDS). Fourier transform infrared spectroscopy and thermogravimetry were used to demonstrate that surface modification prior to composite processing was successful, while scanning transmission electron microscopy combined with energy-dispersive X-ray analysis confirmed the retention of surfactants on TTNT in composites. Nevertheless, scanning and transmission electron microscopy revealed incomplete dispersion of TTNT inside polyamide. The improved wettability on the TTNT–PA11 interface was observed for composites comprising surface-modified TTNT. Consequently, these composites exhibited better thermal and mechanical properties than those containing pristine TTNT. A significant rise of the decomposition temperature was detected in composites containing TTNT modified with CTAB, while the uppermost increment of the storage and Young’s modulus (of about 35% and 26%, respectively) was achieved in the composite comprising 0.5 wt% of TTNT modified with SDS. The increase of the nanofiller content improved the yield strength and led to the drop in the strain at break.