粉末注射成型新技术

通过代替传统的生产工艺，粉末注射成型的应用范围得到大大的提高，近年来，已能生产重量最大为300g，壁厚较大的复杂金属制件。     

褐煤无黏结剂成型理论的粉体工程分析

在分析多种褐煤无黏结剂成型假说的基础上,提出了影响褐煤成型特性的其他内因。介绍了褐煤无黏结剂成型的粉体力学模型,同时对无桥、液桥、固桥3种黏结类型下的平均颗粒抗拉强度的计算公式进行了推导。探讨了在褐煤成型过程中,不同阶段相应的主要黏结力,并得出褐煤型煤最终产品的强度取决于颗粒间形成的固桥黏结力。研究表明:确定合理的外部条件,使颗粒间形成合适的固桥黏结力,即可满足褐煤运输和加工利用所需强度。     

注射压塑成型工艺

注射压塑成型是在加工压注塑基础上发展的一种先进加工技术,其特点是：可获得较高的流动距熟／壁厚之比,可降低夹昆力和注射压力,加工过程中材料应力较低,有利于模制大型零件。     

Characterisation of micro gears produced by micro powder injection moulding

The paper describes the fabrication of micro gears of diameter and height 1 mm by micro powder injection moulding. 316L stainless steel powder of 2.4 µm (d₅₀) is mixed with a multi-component wax-based binder system. The feedstock is then injection-moulded into micro gears followed by debinding and sintering. The microstructure of the micro gear at its tooth and hub is studied by electron backscattered diffraction. The average grain size at the hub is ~ 5 µm. However, a high content of annealing twin and a significant grain growth is found at the tooth.     

陶瓷材料挤出成型工艺与理论研究进展

挤出成型在各种陶瓷成型工艺中被认为是最合适生产等截面制品的低成本工艺。挤出成型可以在低温、低压下由陶瓷粉体混合物挤出长的线材、管材或片材。近年来 ,挤出成型在陶瓷及复合材料的制备工艺中受到越来越多的重视 ,目前的研究与开发工作主要集中在各种挤压浆料的制备、挤压新工艺的应用开发 ,对挤压过程的理论分析研究以及理论对工艺、设备开发的指导等方面     

国外汽车构件特殊成型技术

本文就汽车工业应用塑料特殊成型技术生产构件的状况作一概述。论述了各种特殊注射成型工艺生产的塑料构件在汽车设计制造方面的应用，指出其优点及发展趋势。     

高温煅烧制作石英纳米粉体的研究

根据高温煅烧使石英碎裂的原理,选用天然高纯石英为实验材料,从室温开始以30℃/h速率升温,升至1 460℃,接着保温72 h,然后以30℃/h速率降温至室温。将煅烧过的石英以250 r/m in在行星式高能球磨机中研磨2 h。经原子力显微镜、成分测试等手段分析,石英粉平均粒径为43 nm,纯度由99.51%提高至99.97%。     

Influence of powder morphology on properties of ceramic injection moulding feedstocks

The powder-binder-mixture is the most critical aspect in the injection moulding processing chain, because the feedstock properties determine the success of the following steps, i.e. excellent flowability in the injecting phase and high green strength during debinding. Therefore, nearly spherical particles which pass each other easily in the feedstock stream are advantageous. The applicable particle size is limited in order to reach high solids loadings which are connected with the specific powder surface. According to this, in this study a very unfavourable powder was introduced into a feedstock. The investigated β-alumina powder consists of plate-like primary particles and has a specific surface of 25 m²/g. During mould filling the particles orient in the feedstock stream which affects the debinding and sintering behaviour and is the source of defects. The influence of the plate-like shape on defect formation is demonstrated in comparison to spherical-shaped particles having the same specific surfaces.     

Effects of oxidation on the strength of debound SiC parts by powder injection moulding

In order to increase the production efficiency of powder injection moulding for SiC parts, thermal debinding was performed in air furnace without gas shield. Bending tests were performed to evaluate the strength of samples debound under different temperatures. The effects of oxidation on debinding process were also analyzed. Analysis indicates that air could accelerate the debinding rate of green parts without defects occurring. The bending strength of debound samples increases from 6.55 MPa to 11.58 MPa as the pre-sintering temperature increases from 550 °C to 850 °C. On the other hand, the bending strength of the samples pre-sintered at 1200 °C in argon atmosphere is only 11.52 MPa. It was found that, blanks have enough strength for transport after being pre-sintered in air atmosphere at 850 °C. The technology could reduce the requirement for heating equipment and enhance the efficiency of debinding for SiC parts.     

不饱和聚酯模塑料的研制

参照客户提供的样品性能配制了不饱和聚酯模塑料,通过DSC、TG等手段对比研究了2种材料的各种性能。结果发现:2种模塑料的物理和电气性能相近,固化起始温度相似,0~410℃的耐热行为相近,410~700℃自制模塑料的耐热性优于客户样品。现场注塑试验表明,2种材料注塑工艺调整不明显。因此,自制的不饱和聚酯模塑料完全可以替代客户样品。     

Micro powder injection moulding of alumina micro-channel part

A feedstock consisting of submicron alumina powder and a formulated binder, was developed to fabricate alumina micro-channel part by micro powder injection moulding. During small scale-mixing, the mixing torques of feedstocks with four different powder loadings were used to establish a suitable powder loading. The thermal and rheological properties of the selected feedstock were examined and used to establish conditions for large scale mixing, debinding and injection moulding. The micro-channel parts were pressureless sintered at different temperatures. The results showed that the moulded, debound and sintered micro-channel parts had good shape retention. The dimensions of the micro-channel part changed with the different processing steps. High densification of the micro-channel parts was achieved at sintering temperatures of 1350 °C and above. Above 1350 °C, the grain grew significantly with increasing the sintering temperatures and thus it led to a decrease in the microhardness.     

三类热固性塑料性能与成型

通过性能测试,从结构与遥关系讨论了三类热固性模塑料的物理、机械、电气性能,以温度、压力、时间等工艺参数在注射成型加工中以热固性模塑料性能的影响,为注射成型加工和设计应用正确选择材料提供参数。     

Effect of a binder system on the low-pressure powder injection moulding of water-soluble zircon feedstocks

Micronized natural zircon sand powders were used as a raw material to conduct low-pressure powder injection moulding (LPPIM) processes. PIM could lead to new technological applications for this mineral, which has very stable dimensional behaviour with changing temperature. Zircon powders that have unconventional attributes for PIM (in terms of size and morphology) were mixed with poly(ethylene glycol) (PEG) based binders. Combinations of this water-soluble substance with different polymers, including low-density polyethylene (LDPE) and several types of acetate butyrate celluloses (CAB), were investigated. The influence of acetyl, butyryl and hydroxyl groups on the behaviour of the created feedstocks at different process stages and on the final piece properties were studied. The higher affinity of CAB with PEG and zircon powders compared with LDPE could result in improved densification and properties, but the butyryl, acetyl and hydroxyls groups affect the processability of these feedstocks.     

板材级ABS的产品性能及挤出成型工艺研究

对比并分析了国内市场常用板材级ABS树脂与通用级ABS树脂的性能特点,介绍了挤出板材的工艺流程和工艺条件,并对ABS板材挤出成型工艺的影响参数及控制要点进行了讨论,分析探讨了AgS板材从粒料干燥到板材冷却定型的各种工艺参数、影响因素及其控制要点,归纳总结了挤出成型ABS板材的各种质量缺陷、产生原因及其相应的对策措施。     

UHMWPE微孔滤板压制烧结模具设计

介绍一种压制烧结成型超高分子量聚乙烯(UHMWPE)微孔滤板的方法。针对高聚物微孔材料成型难点,重点设计了模内加热系统,给出了模具设计分析及详细计算过程,分析了其合理性,得出了此模具既达到制备UHMWPE滤板的要求,又符合微孔开孔成型标准的结论。     

Evaluation of the moulding process for production of short-fibre-reinforced C/C-SiC composites

For the production of C/C-SiC brake discs via the liquid silicon infiltration method (LSI), the hot pressing process is the state of art technique for the moulding of the CFRP composites. This technique consists of several manual steps which increase production cost. The overall cost can be reduced by implementing injection moulding process.In this paper the influence of the moulding process (hot pressing, injection moulding) on the properties of semi-finished and final products during the production of short-fibre-reinforced C/C-SiC composites by means of the LSI process are examined. The starting polymer is chemically characterised. Carbon-fibre-reinforced plastic (CFRP) composites are fabricated by hot pressing, as well as injection moulding process. The CFRP composites are converted into porous C/C composites by pyrolysis. Liquid silicon is infiltrated to form dense C/C-SiC composites, which are further investigated during the course of this paper. Significant differences in properties of the composites are discussed.     

环氧粉末涂料的固化动力学和固化工艺的研究

采用非等温示差扫描量热法(DSC)研究了E-12/双氰胺(固化剂)和E-12/双氰胺/2-甲基咪唑(促进剂)体系的固化反应动力学。采用Kissinger法和Crane公式对DSC数据进行处理,获得了固化反应动力学参数,应用热重分析(TGA)研究了固化产物的热稳定性。结果表明:双氰胺、2-甲基咪唑的最佳用量分别为环氧树脂质量的4%和0.4%,最佳固化条件为160℃/15min。E-12/双氰胺体系和E-12/双氰胺/2-甲基咪唑体系的表观活化能分别为105.12kJ/mol和70.62kJ/mol,固化反应级数n=0.92。起始分解温度约为410℃,促进剂2-甲基咪唑的加入对体系热稳定性没有影响。     

The effect of powder characteristics on pressure sensitivity of powder injection moulding compounds

Pressure effect on the rheological behaviour of powder-polymer compounds intended for powder injection moulding was determined. A single-piston capillary rheometer modified by addition of a second chamber with a restricting needle valve generating backpressure increasing the pressure in the melted material during the flow through the die was employed to determine pressure sensitivity coefficients. The results obtained for three compounds varying in the characteristics of powders used confirmed that compounds at the loading level close to the maximum packing are more sensitive to pressure than polymer binder. It is shown that pressure sensitivity coefficients of these materials are strongly dependent on powder characteristics — particle size and particle size distribution. The highest coefficient (32.9 GPa⁻¹) was found for compound containing broad particle size distributed powder having a perceptible portion of small particles.     

Powder injection moulding PIM of feedstock based on hydrosoluble binder and submicronic powder to manufacture parts having micro-details

Small and complex-shaped parts can be manufactured with powder injection moulding PIM process at a low cost in comparison to other traditional powder technologies. A variant of PIM process denoted as micropowder injection moulding (μ-PIM) has been recently developed in order to manufacture components having sub-millimeter dimensions or micrometer range structural details. PIM and μ-PIM are used for numerous applications in the field of electronics, defence and aerospace, medical industry. This contribution displays preliminary study on the feasibility to manufacture parts having micro-details by powder injection moulding from partially water soluble self-made feedstock. All process steps are investigated from feedstock preparation to sintering.