金属注射成型用水溶性粘结剂的研究

介绍了一种金属注射成型用水溶性粘结剂的制备方法，该粘结剂使用方便且安全无毒，用于金属注射成型时可用水作溶剂脱除，从而使成本大大降低。     

陶瓷注射成型粘结剂现状及发展趋势

本文重点介绍了陶瓷注射成型粘结剂的种类,特性及脱脂技术,比较了目前几种粘结剂体系的优缺点,指出了今后粘结剂发展方向和趋势。     

陶瓷注射成型粘结剂现状及发展趋势

本文重点介绍了陶瓷注射成型粘结剂的种类、特性及脱脂技术;比较了目前几种粘结剂体系的优缺点,指出了今后粘结剂发展方向和趋势。     

注射成型氧化铝陶瓷工艺研究

研究了氧化铝陶瓷注射成型工艺过程,包括粘结剂的选择、粉末装载量的确定及热脱脂工艺的研究。探讨了注射压力、注射温度和模具温度等注射成型工艺参数对试样性能的影响,得到了一条优化的氧化铝注射成型工艺路线。     

陶瓷的注射成型技术

陶瓷注射成型技术可解复杂形状的高性能陶瓷元件的大批量生产难题,并且产品尺寸精度高,表面条件好,论述了瓷注射成型工艺中粘结剂选取,注射成型,脱脂等步骤,并提出了将来的研究方向。     

塑料与金属薄壳注射成型新技术

介绍薄壳的概念及其在工业生产中的地位及薄壳制品的设计要点,并就目前要用的高压注射成型方法进行了分析,还阐述了成型薄壳的多浇口技术,气辅成型技术,半固态金属注射成型技术。     

Sialon陶瓷注射成型的溶剂脱脂研究

在Sialon陶瓷注射成型中,以蜡基粘结剂的溶剂脱脂为研究对象,考查了注射成型中溶剂脱脂工艺的脱脂温度、脱脂时间、试样厚度、溶剂加入方式及表面积与体积之比等参数对试样脱脂的影响,对溶剂脱脂过程中可溶组元的最大脱除率作了初步的分析,并用SEM观察了不同脱脂率的形貌的变化。结果表明：在40℃下采用纯的三氯乙烯对试样进行脱脂,当PW的脱出率在75%以上时,连通孔道基本形成,坯体在后续热脱脂和烧结中不会变形。     

粉末注射成型技术及其发展

塑料制品加工技术和金属制品加工技术是各领域技术相互借鉴的典范。众所周知，塑料中的聚四氟乙烯因为熔体黏度过大，无法通过液态进行成型加工，从而借用了金属的粉末冶金烧结技术进行加工。这种冷压烧结技术只限于制造形状比较简单的制品。塑料的注射成型工艺具有一次性成型形状复杂制品的能力，而且产品尺寸精度很高，几乎不需要后加工，所以，塑料制品代替金属的机械零部件成为近几十年来的一种重要发展，而且这种发展远还没有结束。但是，金属毕竟具有其自身的优点，有一些金属零件（例如强度要求和耐热要求特别高的零件）并不能轻易被塑料所取代。当这些零件形状复杂时，传统金属加工工艺面临很大的困难。     

聚合物动态注射成型技术

介绍聚合物动态注射成型技术以及实现该技术的塑化注射装置。注射成型加工过程中使注射螺杆产生轴向脉动的激振力，可以利用电磁、机械、液压等方式来产生。电磁式振动塑化注射装置结构紧凑、振动频率高；模块化设计的液压激振装置结构简单，输出功率高，方便对传统塑料注射机进行改造。新技术具有加工能耗低制品质量高等特点，通过控制振动频率与振幅可以对制品的质量进行调控。     

聚合物塑化注射成型过程的研究

全面分析了聚合物塑化注射成型的工作周期与机理,阐述了聚合物塑化注射成型过程的控制策略,并揭示了聚合物注塑成型技术及其装备的发展现状与前景。     

Effect of microcrystalline wax on the solvent debinding of the Sr-ferrite ceramics prepared by powder injection molding

Powder injection molding (PIM) opens new possibilities to process complex Sr-ferrite components for magnetic applications. In the present study, new binder system with the addition of microcrystalline wax (MW) was used for the Sr-ferrite powder injection molding. The optimum binder composition was determined based on rheological measurement, mircrostructure observation by SEM, thermal change by DSC and debinding process. The results indicated that MW with 10 vol.% addition in the binder system containing high density polyethylene (HDPE), paraffin wax (PW) and stearic acid (SA) decreases the defects of the green parts after solvent debinding because the distribution of the binder system between the Sr-ferrite particles becomes more homogeneous. Using the proper binder system containing MW, the defect-free and dense Sr-ferrite ceramics can be prepared after solvent and thermal debinding and sintering. Based on the experimental results, the effects of MW microcrystalline wax on the solvent debinding of the Sr-ferrite ceramics were detailed discussed.     

Powder injection molding of complex-shaped aluminium nitride ceramic with high thermal conductivity

Aluminum nitride (AlN) is a promising material for heat sinks and microelectronic applications because of the advantages of high theoretical thermal conductivity, high mechanical strength, good electrical insulation, low dielectric constant and low thermal expansion coefficient. However, the difficulties in shaping complex-shaped parts with a high thermal conductivity have retarded the wide applications of AlN ceramic. Herein, we design a new binder system containing resin components and adopt the powder injection molding technology to fabricate complex-shaped AlN parts. After the debinding process, the special binder system would produce residual carbon, which could react with Al₂O₃ and result in decreasing oxygen impurity and forming the yttrium-rich aluminates. The yttrium-rich aluminates can accelerate the densification of AlN ceramic and fasten the oxygen on the triangular grain boundary, leaving the clean grain boundary beneficial for high thermal conductivity. The as-prepared AlN parts with complex shape possess a high thermal conductivity of 248 W m⁻¹ K⁻¹.     

纵论注射成型技术

以注射成型技术在橡胶行业的发展现状为依据,从工作原理、生产工艺、产品质量、生产效率等几个方面着手,对模压成型技术和注射成型技术进行了比较,阐述了注射成型技术的优越性。同时,针对推广注射成型技术遇到的困难,提出了注射成型技术在橡胶行业的推广过程中所需要解决的一系列问题。     

Gas-assisted powder injection molding: A study on the effect of processing variables on gas penetration

Parts of polypropylene and of a stainless steel powder feedstock were molded by means of gas-assisted injection molding in epoxy cavities made by stereolithography. The design of the experiment method using the Taguchi L₉ array was implemented to test the effect of gas pressure, gas delay time, shot size and melt temperature on gas penetration depth and residual wall thickness. Simulations were conducted and compared with direct experimentation. Simulation predicted that the shot size was the only significant factor when processing polypropylene and the powder metal feedstock. The experiment showed that shot size and gas delay time were significant when processing polypropylene; and shot size, gas pressure, and melt temperature were significant factors when processing the powder metal feedstock. The residual wall thickness could not be controlled by the processing variables used in this study as the S/N ratios calculated were very small.     

气辅成型工艺的研究

介绍了气体辅助注射成型技术工艺参数的确定和成型材料的选择原则,讨论了成型过程中出现的主要缺陷及其原因和解决方法。     

注射成型中聚合物剪切诱导结晶行为的三维模拟

在考虑剪切导致分子链取向并升高其平衡熔点的基础上,建立了基于Nakamura方程的剪切诱导结晶动力学模型。在WLF-Cross黏度模型中引入结晶对黏度系数的影响,构建了考虑结晶的注射成型过程模型。采用改进的有限体积法对聚合物剪切诱导结晶行为进行了三维数值模拟,模拟中耦合了流动场、熔体压力、温度、诱导时间与结晶度。结果表明,本方法可清晰模拟出注射成型过程中聚合物的三维“喷泉”流动行为以及3层“皮-芯”结晶结构,同时,诱导结晶时间指数与相对结晶度的模拟结果与理论及实验结果吻合。     

注射成形磁体的粘结剂

论述了粘结剂在注塑磁体中 的作用及粘结剂应有的性能 。分析了三种常用的注塑磁 体粘结剂 。探讨了粘结剂的 开发方向。     

Toward a viscoelastic modeling of anisotropic shrinkage in injection molding of amorphous polymers

A novel approach to predict anisotropic shrinkage of amorphous polymers in injection moldings was proposed using the PVT equation of state, frozen‐in molecular orientation, and elastic recovery that was not frozen during the process. The anisotropic thermal expansion and compressibility affected by frozen‐in molecular orientation were introduced to determine the anisotropy of the length and width shrinkages. Molecular orientation calculations were based on the frozen‐in birefringence determined from frozen‐in stresses by using the stress‐optical rule. To model frozen‐in stresses during the molding process, a nonlinear viscoelastic constitutive equation was used with the temperature‐ and pressure‐dependent relaxation time and viscosity. Contribution of elastic recovery that was not frozen during the molding process and calculated from the constitutive equation was used to determine anisotropic shrinkage. Anisotropic shrinkages in moldings were measured at various packing pressures, packing times, melt temperatures, and injection speeds. The experimental results of frozen‐in birefringence and anisotropic shrinkage were compared with the simulated data. Experimental and calculated results indicate that shrinkage is highest in the thickness direction, lowest in the width direction, and intermediate in the flow direction. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2300–2313, 2005     

An analytical approach to relating powder characteristics and rheological properties of powder injection molding feedstocks

This study quantitatively analyzes the relationship between the material structure (powder characteristics) and flow properties of highly filled compounds. The model parameters are the powder particle-size distribution and its volume fraction in a compound. The simulated material structure is developed using the Hard Spheres Model, from which the structural functions in terms of the statistical distribution of inter-particle distances and the histograms of effective volumes of groups of close particles are calculated. A close similarity between simulated and real functions was obtained. The results obtained imply that numerical modeling might serve as a reliable and sensitive approach for analyzing the influence of powder particle-size distribution on the ability to process highly filled compounds.     

Time-dependent properties of bimodal POM — Application in powder injection molding

Powder Injection Molding is applied for manufacturing complex and precise components from metal, ceramics or cemented carbide powder. It basically consists of mixing the powder and a polymeric binder, injecting this mixture in a mold with the desired form, debinding and then sintering. Among the debinding techniques applied, catalytic debinding of polyoxymethylene (POM) stands out due to the high debinding rates and low risk of cracking. In this work, the potential use of a bimodal POM-based material as the main binder component was evaluated by comparing its thermal and time-dependent properties to a standard monomodal POM. In addition, the potential optimization of this bimodal material was investigated by preparing five new formulations of bimodal POM with higher concentration of short polymeric chains (wax). This work has shown that macroscopic properties of POM are sensitive to the addition of these short chains. For instance, the magnitude of the complex viscosity for the commercial bimodal material was found to be more than 67% lower than for the monomodal POM in the whole range of frequencies studied. Finally, a new formulation of bimodal POM was suggested with 8% of added wax concentration (in weight), resulting in a material with very fine structure that has shown even better flowability than the commercial bimodal POM, without compromising its thermal and mechanical properties.