椎间融合器金属粉末注塑成型工艺参数研究

采用密炼机混炼不同配比的金属粉末与粘结剂的金属喂料,通过喂料流动性能对比试验,得到注塑成型试验所用的最佳喂料配方,喂料中不锈钢粉末的质量分数为0.926时,综合性能较好;利用所确定的喂料配方和已加工好的椎间融合器模具在阿博格精密注塑机上进行性能试验,分别控制注塑模具温度、喂料温度、注射压力进行注射,并对注射结果进行质量测量及注射时间记录,分析出此种配方最适合的注射工艺参数为:模具温度50℃;喂料温度180℃,且用注塑机控制4段加热区间为180,175,170和165℃;注射压力70 MPa。     

椎间融合器金属粉末注塑成型精度测量实验研究

基于喂料流动试验确定的最佳喂料配方,在精密注塑机上用椎间融合器模具按照最佳注塑工艺参数进行注塑,并在1 350℃下烧结出椎间融合器。测量结果表明,椎间融合器的关键尺寸稳定,精度较高,达到使用要求。通过扫描电子显微镜观察,脱脂后金属粉末占坯体的比例很大,表明粘结剂基本脱除。3D测量激光显微镜观察显示最终烧结制品的表面平整,表面高度差在10μm以内,表面光洁度较好,证明基于此配方的不锈钢椎间融合器金属粉末注塑成型方法完全可行。     

椎间融合器金属粉末注塑成型最佳烧结温度实验研究

采用喂料流动性能试验得到的最佳喂料配方和试样模具进行椎间融合器金属粉末注塑成型最佳烧结温度试验研究。结果表明,该配方喂料的最佳烧结温度为1 350℃,在该温度下烧结的316L不锈钢的物理性能最优,拉伸强度为486.8 MPa,烧结相对密度达到96.6%。与传统机械工艺得到的316L不锈钢相比,材料的物理性能和金相组织均差异不大。     

椎间融合器金属粉末注塑成型模具设计研究

针对传统模具设计方法存在设计周期长、成本高并且质量难以保证的缺点,采用限元分析软件Moldflow和计算机辅助设计软件UG相结合的方法进行试样模具与椎间融合器模具的分析与设计,通过分析注射过程中的各种影响因素,得到注塑成型初步工艺参数。试样模具用于测量金属粉末注塑成型烧结后制品的力学强度及所用配方喂料的收缩率,根据在最佳烧结温度下的收缩率,反向放大椎间融合器模型模腔。本设计模具为后续的金属粉末注塑成型工艺参数试验研究奠定了基础。     

注塑工艺对聚丙烯EP548N光学性能的影响

采用不同的工艺条件对无规共聚聚丙烯EP548N进行注塑成型,测试注塑件表面光泽度、黄色指数和透光率,分析了注塑成型条件对制品光学性能的影响。确定聚丙烯EP548N的最佳注塑工艺为:熔体温度200℃,模具温度40℃,注射速度210mm/s、保压压力4.6MPa、注射压力4.9MPa,注塑工艺条件改变对聚丙烯EP548N注塑件透光率影响较小。     

注塑工艺对哑光PC/ABS冲击性能的影响

通过不同注塑工艺对哑光级聚碳酸酯(PC)和丙烯腈–丁二烯–苯乙烯(ABS)共聚混合物进行注塑成型,通过改变不同的注塑条件(注塑温度、模具温度、注塑压力、注塑速度),研究不同的注塑工艺对哑光PC/ABS材料抗冲击性能的影响。研究结果表明,注塑工艺变化,会引起材料冲击性能变化。其中注塑温度与模具温度对结果影响较大,注塑温度240℃,模具温度80℃时,哑光PC/ABS的冲击强度最高;在合适的注塑压力范围内,压力变化对材料冲击影响不大;合适的注塑速度范围内,注塑速度变化对材料冲击影响不大。工艺选择注塑温度240℃,模具温度80℃,注塑压力2.6~6.1 MPa,注塑速度13.9~32.3 g/s时,哑光PC/ABS冲击性能最好。因此,选用合适的注塑工艺可以提高材料的冲击性能。     

长玻纤增强聚甲醛注塑成型工艺的研究

制备了长玻璃纤维(LGF)增强聚甲醛(POM)复合材料。通过6因素2水平的正交试验,探讨了注射压力、注射速度、模具温度、保压压力、保压时间、冷却时间等工艺条件对LGF增强POM复合材料的制品表观和拉伸强度的影响。结果表明:注射压力、注射速度、保压时间和模具温度等4个工艺条件对LGF增强POM制品表观和拉伸强度的影响最大,当注塑成型条件分别为料筒温度180¹90℃、注射压力60 MPa、注射速度60 mm/s、模具温度80℃、保压时间15 s时,制品具有最佳的表观和力学性能。     

聚碳酸酯注塑工艺条件研究

以双酚A型聚碳酸酯(PC)为原料,对其进行注射成型,主要探讨了注射成型温度对其成型性能和力学性能的影响,同时讨论了注塑压力及模具温度对其成型性能的影响。结果表明,随着注塑温度升高,PC试样的拉伸强度、弯曲强度、断裂伸长率及缺口冲击强度升高,当注塑温度超过290℃后,力学性能总体上变化不大,注塑温度过高或过低都会使试样透明性下降、缺陷增多,而过高或过低的注塑压力及模具温度均会劣化PC的成型性能。PC的最佳注塑工艺条件为注塑温度290℃,注塑压力100 MPa,模具温度100℃。对在最佳注塑工艺条件下注塑的PC试样通过退火的方式进行热处理,发现在一定范围内,随着热处理温度提高,PC试样的拉伸强度和弯曲强度总体上升高,断裂伸长率和缺口冲击强度下降。当对PC的强度要求较高而对韧性要求相对较低时,125℃是较为适宜的热处理温度;而当对其韧性和强度都有一定要求时,热处理温度不宜太高。     

厚壁聚丙烯管材塑料件的注塑工艺研究

通过改进厚壁聚丙烯(PP)管材塑料件的熔体温度、注塑压力、快速注射时间,慢速注射时间、冷却时间、模具温度、背压等注塑工艺条件,以减少塑料件气孔出现的几率。总结出这几个工艺条件影响因素大小,并确定了使厚壁PP管材内部出现气孔几率最小的最佳工艺参数:熔体温度为170℃,注塑压力为13 MPa,快速注射时间为0 s,慢速注射时间为120 s,冷却时间为120 s,模具温度为70℃,背压为1.5 MPa。在最佳工艺条件下,注塑的PP管材内部气孔出现的几率可降至2%左右。     

ABS扣板注射成型工艺参数优化分析

通过模拟真实注射条件,应用Moldflow软件对ABS扣板注射成型工艺参数进行了优化分析,得出影响注射成型顺利进行的主要因素,并模拟制定出扣板注射成型的最佳注塑压力、锁模力、模具温度、熔体温度、注塑时间、保压压力、保压时间和冷却时间。采用该注射成型工艺参数并结合合理的注塑模具能注塑出最佳的ABS制品,为注射成型的顺利进行提供指导依据。     

Spray Drying of Yogurt: Optimization of Process Conditions for Improving Viability and Other Quality Attributes

Plain yogurt was subjected to spray drying to determine the optimum processing conditions that yield maximum survival ratio of lactic acid bacteria, maximum overall sensory attributes, minimum color change, and acceptable moisture content. The inlet (150–180°C) and outlet air temperatures (60–90°C) and the feed temperature (4–30°C) were the independent factors. A pilot-scale spray dryer was used to conduct a set of drying experiments where the process conditions were selected according to central composite rotatable design (CCRD). The resulting yogurt powder at each condition was also subjected to the measurement of some physical properties (water activity, titratable acidity [lactic acid, %] and pH) to determine the effects of spray-drying conditions. The morphological structure of the powder was inspected by scanning electron microscopy (SEM) analysis. Optimization by the application of the desirability function method resulted in air inlet temperature of 171°C, air outlet temperature of 60.5°C, and feed temperature of 15°C as the optimum processing condition. The mathematical optimum condition was experimentally verified.     

不同粘结剂含量对金属喂料流动性能的影响

通过密炼机混炼出不同比例金属粉末与粘结剂的金属喂料,对不同粘结剂含量的金属喂料进行喂料流动性能对比实验,对比金属粉末含量对喂料熔融指数的影响及不同金属粉末含量在不同温度下表观粘度随剪切速率的变化,得到最佳注塑成型实验所用的最佳喂料配方。结果表明,随着粘结剂含量的增加,金属喂料的流动性能一直提高。在达到金属粉末质量分数92.6%之前,熔融指数急剧上升,当达到92.6%后,熔融指数缓步上升。     

Effects of spray-drying operational parameters on the quality of freshwater mussel powder

In this paper, the operating parameters of spray drying after a series of pre-processing were investigated and the properties and qualities of the freshwater mussel meat (FMM) powder were also analyzed. The considerable optimum conditions of spray drying were as follows: the inlet and outlet air temperature of the both deodorization were 180 °C and 80 °C, respectively; the optimum feed concentration for composite deodorization (CD) FMM powder was 30%, and for stewing deodorization (SD) FMM powder 27%; on top of all that, the feed temperature was 50 °C, 45 °C, respectively. In the later analysis, FMM powder was shown to be rich in protein and glycogen, up to 52.7%, 27.71% and 53.4%, 27.69%; meanwhile both the contents of essential amino acids (EAAs) in FMM powders were as high as 44%, which were close to the pattern of FAO/WHO. Thus the FMM powder of the both kinds, namely CD and SD FMM, were thought to be acceptably edible resources with high nutrition for human.     

Metal adhesive properties of polyamides having the 2,3‐bis(1,4‐phenylene)quinoxalinediyl structure

Polyamides were synthesized by interfacial polycondensation of 2,3‐bis(4‐chloroformylphenyl)quinoxaline (BCFPQ) and several aliphatic diamines using a phase transfer catalyst, and their adhesive property for stainless steel was investigated. The inherent viscosity of the obtained polyamides ranged from 0.37 to 1.24 dL g⁻¹. The glass transition temperatures of the polyamides ranged between 154 and 201°C, and their thermal decomposition temperatures were above 450°C. The polyamides were soluble in several organic solvents, including m‐cresol, N‐methyl‐2‐pyrrolidone (NMP), and formic acid. The adhesive property for stainless steel was examined by a standard tensile test. One member of the series, polyamide P8, derived from BCFPQ and 1,8‐octanediamine, displayed high tensile strength with values of 232 kgf cm⁻² at 20°C, 173 kgf cm⁻² at 120°C, and 137 kgf cm⁻² at 180°C. Thus, the tensile strength of P8 decreased at 180°C, but the decrease was much smaller than that of an epoxy resin in wide use as a metal adhesive. Heat distortion temperature, measured by thermal mechanical analysis, of P8 was 191°C. This suggested that P8 possessed high thermal resistance in metal adhesives. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1366–1370, 1999     

Spray Drying of Elderberry (Sambucus nigra L.) Juice to Maintain Its Phenolic Content

Spray drying was studied with Elderberry (Sambucus nigra L.) juice using a Buchi B-290 spray dryer. Different inlet temperatures ranging from 70°C to 120°C and two feed flow rates of 180 ml/hr and 300 ml/hr were considered for the experiment. The operating parameters were optimized in terms of total phenolic content retention, color, and powder recovery. The inlet temperature of 80°C with feed flow rate of 180 ml/hr gave high phenolic content retention with good color but lower recovery of the dried powder, i.e., less than 50%. To increase the recovery percentage during the drying process, the elderberry juice was spray dried with five different wall materials, i.e., soya milk powder, soya protein powder, isolated soya protein, gum acacia, and maltodextrin. Wall materials were evaluated in terms of total phenolic content retention, color of the powder, and mass recovery percentage. The gum acacia and maltodextrin gave better results and high recovery percentage, i.e., more than 70%. The best three combinations were stored under three different storage conditions in three different packagings to monitor the stability of the phenolic content and color of the powder.     

Dynamic mold surface temperature control using induction heating and its effects on the surface appearance of weld line

Electromagnetic induction heating combined with coolant cooling is used to achieve dynamic mold surface temperature control. A simulation tool was also developed by integration of both thermal and electromagnetic analysis modules of ANSYS, and capability and accuracy were verified experimentally. To evaluate the feasibility and efficiency of induction heating on the mold surface temperature control, a mold plate (roughly about an inset size of cellular phone housing) with four cooling channels was utilized for two demo experiments with varying mold surface temperature between 110 and 180°C, and 110 and 200°C, respectively. During induction heating/cooling, it takes 4 s to increase mold surface temperature from 110 to 200°C and 21 s for mold surface to return to 110°C. The mold plate surface temperature can be raised at about 22.5°C and cooled down at 4.3°C/s within the aforementioned temperature range. Mold plate temperature distribution exhibits good uniformity as well in all stages of the heating/cooling process. Finally, mold surface temperature of a double‐gated tensile test part mold was induction heated to above glass transition temperature for few seconds prior to melt injection. The surface mark of weld line was eliminated, and the associated weld line strength enhanced. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1174–1180, 2006     

Kneading and molding of ceramic microparts by precision powder injection molding (PIM)

This paper investigates the kneading and formability of microparts made using alumina in micro‐powder injection molding. In this study, quality feedstock with uniform powder dispersion was achieved when optimum kneading process was performed. In addition, the thin microplates were successfully manufactured using a custom‐made injection machine. Shrinkage was significantly reduced in microspecimens when the mold temperature was increased to 70°C. The results of flow visualization were conformed to that of experiments in this study. A very important result for flow visualization and experiment was molten polymer filled the cavity by shortest period producing a least shrinkage in microparts. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 892–899, 2006     

Production of injection molding tooling with conformal cooling channels using the three dimensional printing process

A Solid Freeform Fabrication Process called Three Dimensional Printing is applied to the fabrication of injection molding tooling with cooling channels which are conformal to the molding cavity. The tool is created by spreading layers of stainless steel powder and selectviely joining the powder in the layers by ink‐jet printing of a binder material. Unbound powder is removed from without and within the green part thus defined. The green part is sintered and infiltrated with a copper alloy to produce a fully dense tool. The infiltrant is kept out of the cooling channels by elevating the tool above the free surface of the pool of infiltrant in the crucible, thus creating a controlled negative pressure within the infiltrant. An upper limit to the separation of tooling cavity and cooling channel was derived based on transient heat transfer considerations. A tooling set was created to mold a split ring shape and conformal cooling channels were placed in both the cavity and core sides of the tool. The performance of this tool was compared against the performance of a tooling set with straight cooling channels. Thermocouples buried in the core and cavity showed that the conformal tool had no period of transient behavior at the start of molding, while the tool with straight channels took 10–15 cycles to come to an equilibrium temperature some 40°C above the temperature of the coolant. The conformal tool was also found to maintain a more uniform temperature within the tool during an individual molding cycle. The gap in the molded split rings did not change from cycle to cycle with the conformal tool, while it did with the conventional tool. A 2‐D finite difference model accurately captured the observed temperature histories of the mold with conformal cooling channels.     

Influence of injection temperature and pressure on the properties of alumina parts fabricated by low pressure injection molding (LPIM)

The quality of ceramics parts made by powder injection molding (PIM) method is influenced by a range of factors such as powder and binder characteristics, rheological behavior of feedstock, molding parameters and debinding and sintering conditions. In this study, to optimize the molding parameters, the effect of injection temperature and pressure on the properties of alumina ceramics in the LPIM process were thoroughly studied. Experimental tests were conducted on alumina feedstock with 60 vol% powder. Injection molding was carried out at temperatures and pressures of 70–100 °C and 0.1–0.6 MPa respectively. Results showed that increase in injection temperature and pressure and the resulting increase in flow rate leads to the formation of void which impairs the properties of molded parts. The SEM studies showed that injection at temperature of 100 °C results in evaporation of binder components. From the processing point of view, the temperature of 80 °C and pressure of 0.6 MPa seems to be the most suitable condition for injection molding. In addition, the effects of sintering conditions (temperature and time) on the microstructure and mechanical properties are discussed. The best final properties were found using injection molding under the above stated conditions, thermal debinding and sintering at 1700 °C during 3 h.