Injection Moulding Method Research Articles

Fabrication of Free-Form Channels by a combined process of Metal Injection Molding and Sacrificial-Core Method

Fabrication of Free-Form Channels by a combined process of Metal Injection Molding and Sacrificial-Core Method

Mechanical and thermal properties of nanosized titanium dioxide filled rigid poly(vinyl chloride)

Nano-sized rod-like titanium dioxide (TiO2) filled rigid poly(vinyl chloride) (PVC) nanocomposites were prepared by using injection-molding method. Vicat, Charpy impact and tensile tests as well as thermogravimetric and dynamic mechanical analyses were used to characterize the structure and properties of the nanocomposites. The results showed that nano-TiO2 could improve Vicat softening temperature and also improve thermal stability of PVC during the stages of dehydrochlorination and formation of carbonaceous conjugated polyene sequences, which can be ascribed to restriction of the nanoparticles on the segmental relaxation as being evidenced by raises in glass transition and β-relaxation temperatures of PVC upon filling TiO2. Addition of TiO2 nanoparticles less than 40 phr (parts per hundreds of resin) could significantly improve impact strength of the composites while the TiO2 agglomeration at high contents leads to a reduction in impact toughness.

Moulding Properties of Highly-Filled Composites Based on Polypropylene and Wood Flour

This paper presents the results of studies of the moulding properties of highly-filled wood-polymer composites (WPCs) based on polypropylene. Studies were made of the properties of WPCs produced using an injection moulding method.

Study on the Preparation and Properties of CaZr<sub>0.9</sub>in<sub>0.1</sub>O<sub>3-α</sub> and BaCe<sub>0.85</sub>Y<sub>0.15</sub>O<sub>3-α</sub> Solid Electrolytes

CaZr0.9In0.1O3-α and BaCe0.85Y0.15O3-α two kinds of solid electrolytes were prepared, and the preparation conditions were determined. DSC-TG curves were used to illustrate the synthetic mechanism of CaZr0.9In0.1O3-α and BaCe0.85Y0.15O3-α, and XRD analyses indicate these two solid electrolytes are single phase after calcining at 1400°C for 10h. The isostatic pressing method and hot injection moulding method were used to prepare CaZr0.9In0.1O3-α and BaCe0.85Y0.15O3-α tubes. Through comparing the apparent density of sintered tubes, it is found that isostatic pressing shaping method is good for improving the compactness of CaZr0.9In0.1O3-α sintered tubes, and hot injection moulding shaping method is good for improving the compactness of BaCe0.85Y0.15O3-α sintered tubes.

Fabrication of Hydroxyapatite/Ethylene-Vinyl Acetate/Polyamide 66 Composite Scaffolds by the Injection-Molding Method

This research investigated the injection-molding techniques to produce hydroxyapatite (HA)/ethylene-vinyl acetate (EVA)/polyamide 66 (PA66) composite scaffolds. The effects of HA, EVA, azodicarbonamide (AC) content and shot size on the mechanical properties, pore morphology, porosity and crystallization behavior of the composite scaffolds were analyzed by XRD, DSC, SEM and mechanical test. The compressive modulus and strength of the HA/EVA/PA66 scaffolds with a pore size of 200–600 µm are close to the cancellous bone. Compared with common methods to fabricate scaffolds, this process makes the fabrication of composite scaffolds come true in a rapid and convenient manner.

Effect of industrial wood particle size on mechanical properties of wood-polyvinyl chloride composites

Wood-polyvinyl chloride (PVC) composites were prepared using industrial wood particles used for manufacturing three-layer particleboards. The effect of particle size (0.25–0.5, 0.5–1, 1–2, and 2–4 mm) on the mechanical properties of the composites was investigated. The effect of cross-section size (4×10, 6×15 and 8×20 mm2) of composite pieces made by an injection moulding method was also studied. Both the particle size and specimen cross-section area significantly influenced these properties. The tensile and flexural properties as well as the impact strength in general increased with increasing particle size, and decreased with increasing cross-section size.

Powder injection moulding of metallic and ceramic micro parts

Industrial use of micro components is determined by the availability of efficient manufacturing techniques. While micro injection moulding of plastic is common practice, metal and ceramic powder injection moulding (PIM) still is under development. High-pressure and low-pressure injection moulding methods complement each other ideally, covering the entire spectrum from prototype to large-scale production. With high-pressure PIM, micro gear wheels with diameters <300 μm can be fabricated using LIGA mould inserts. Densities between 97 and 99% of the theoretical values are achieved. Apart from oxide ceramics, metal materials like copper or powder metallurgical steels like 17-4PH or 316L are often applied. Multi-component injection moulding requires less mounting steps and, hence, offers decisive advantages for effective production of interesting material combinations like electrically conductive/insulating or hard/ductile. Studies relating to the fabrication of immobile as well as mobile shaft-wheel components were performed. Other activities focussed on in-mould labelling with foils containing ultra-fine particles to improve surface quality and detail accuracy. Low-pressure injection moulding allows for the manufacture of small series within 1–4 weeks at low cost. However, the process has features which are not compatible with high-pressure PIM. Although use of a low-viscous feedstock is associated with various benefits, low-pressure injection moulding has not met with acceptance in micro moulding.

Fabrication of a Nanosize Pattern Embedded Plastic Chip via an Injection Molding Method for Application to an Optical Biosensor

Abstract We demonstrate a commercialized injection molding method for nano patterning of polymethyl methacrylate (PMMA) for the purpose of mass production of a label-free optical biosensor chip. Scanning electron microscope (SEM) images clearly show uniform nanopattern transfer on the plastic chip fabricated by an injection molding method. A uniformly deposited silicon nitride layer having a high refractive index by a plasma enhanced chemical vapor deposition (PECVD) technique is also observed. A unique characterization method is described wherein optical resonance reflection is used accurately and quickly to characterize the geometrical sensor structure. The authors anticipate that this robust method will provide an excellent means of producing an optical resonance reflection biosensor (ORRB).

Effects of replacing metal powder with powder space holder on metal foam produced by metal injection moulding

Porous metal has a high strength-to-weight ratio and can be produced by various methods. Powder metallurgy using a powder space holder, which is one of the metal foam fabrication techniques, can produce complex parts with a well-controlled foam structure. This work employed the metal injection moulding method with the use of a powder space holder, which was PMMA. The volume fraction of PMMA was varied from 0% to 50% to replace the metal volume fraction, while the binder volume fraction was kept constant. The results show that when more PMMA is added, the mixture of metal powder, binder and PMMA has higher wettability and became less viscous and more difficult to mix effectively and to inject. In addition, there were two competing shrinkages during sintering, which were the shrinkage due to the consolidation of the powder during sintering, which was always present, and the shrinkage of the foam structure after the power spacer was removed, which was a function of the volume fraction of PMMA. All results can be divided into two regions, which are the first region (0–35% PMMA) and the second region (35–50% PMMA). In the first region, as the volume fraction of PMMA increased, the sintered density and mechanical properties decreased, and the porosity per area decreased. For the second region, the sintered density and mechanical properties improved and the porosity per area increased as more PMMA was added. The original shape of the parts could not be retained in the second region. Microstructural observations supported these findings.

Physico-mechanical Properties of Maleic Acid Post Treated Jute Fiber Reinforced Polypropylene Composites

During the past decade, increasing environmental awareness has renewed the interest in natural fiber reinforced thermoplastics. In current work, injection-molding method was utilized in manufacturing polypropylene (PP) composites reinforced with 20, 25, 30, and 35 wt% jute fibers. In order to increase the adhesion between the jute fiber and PP matrix, manufactured composites were post treated with maleic acid. Microstructural analysis and mechanical testing were subsequently carried out. Post treated specimens yielded better mechanical properties compared to the raw ones, while 30% fiber reinforced composites had the optimum set of mechanical properties. According to the authors, chemical modification of the PP matrix may improve mechanical properties at higher fiber content by having better interfacial bonding between the PP matrix and maleic acid post treated jute fiber.

Mechanical Properties of Ni-Free High-Nitrogen Austenitic Stainless Steel Made by Metal Injection Molding with Nitrogen Absorption Method

Microstructure and mechanical properties of high nitrogen steels containing 17Cr-12Mn-3Mo produced by means of metal injection moulding and nitrogen absorption methods were examined. The compacts were sintered at 1300°C, then furnace-cooled to 1200°C and were held at that temperature for 2 to 20 hrs. Subsequently, they were furnace-cooled. Thereafter, solution treatment was done at 1200°C. The solution treated compacts held at 1200°C for above 5 hrs had homogeneous microstructure. Increasing the holding time at 1200°C, ferrite phase disappeared due to the increment of nitrogen content and grain size became larger. Lattice constant of austenite phase also increased. Yield and tensile strength increased with increasing nitrogen content. Yield and tensile strength of the compact held at 1200°C for 10 hrs were 758 MPa, 1172 MPa respectively and elongation was 41 %. However, ductile-brittle transition (DBT) behaviour was seen, and the DBT temperature of every compact was about -20°C. From the fracture surface analysis, brittle fracture surface was identified as (111).

3D Reconstruction and Manufacture of Real Abdominal Aortic Aneurysms: From CT Scan to Silicone Model

Abdominal aortic aneurysm (AAA) can be defined as a permanent and irreversible dilation of the infrarenal aorta. AAAs are often considered to be an aorta with a diameter 1.5 times the normal infrarenal aorta diameter. This paper describes a technique to manufacture realistic silicone AAA models for use with experimental studies. This paper is concerned with the reconstruction and manufacturing process of patient-specific AAAs. 3D reconstruction from computed tomography scan data allows the AAA to be created. Mould sets are then designed for these AAA models utilizing computer aided designcomputer aided manufacture techniques and combined with the injection-moulding method. Silicone rubber forms the basis of the resulting AAA model. Assessment of wall thickness and overall percentage difference from the final silicone model to that of the computer-generated model was performed. In these realistic AAA models, wall thickness was found to vary by an average of 9.21%. The percentage difference in wall thickness recorded can be attributed to the contraction of the casting wax and the expansion of the silicone during model manufacture. This method may be used in conjunction with wall stress studies using the photoelastic method or in fluid dynamic studies using a laser-Doppler anemometry. In conclusion, these patient-specific rubber AAA models can be used in experimental investigations, but should be assessed for wall thickness variability once manufactured.

Sulphur dioxide plasma modification on poly(methyl methacrylate) for fluidic devices

Abstract We developed a sulphur dioxide plasma modification on a poly(methyl methacrylate) (PMMA) material for fluidic electrophoresis devices. The inner surface of the PMMA channel of a chip was modified by using sulphur dioxide plasma treatment. Contact angle measurements indicated that the buffer solutions were able to fill the capillary because of the hydrophilic property of the internal surface of the chip. XPS analysis indicated that the sulphur dioxide plasma treatment introduced a negative charge originating from the dissociation of the hydrogen atoms of sulphonic groups. Since this introduced a negative charge originating from strong acid sulphonic groups onto the surface of the channel, the electroosmotic flow (EOF) was observed to be large (∼7 × 10−4 m2 V−1 s−1) and stable over a wide range of pH (4–10). The chip was fabricated by using plastic injection moulding methods for enabling the mass fabrication and disposable use of chips. The separation method is based on the net electric charge of the material, which enables the separation of identical samples on the basis of both isoelectric points and molecular weight. Two synthetic peptides with similar isoelectric points and molecular weights but different net charges were selected as model protein samples for the separation. The sample peptides were detected under fluorescence microscopy. The resulting electropherograms obtained by using the sulphur dioxide plasma-treated PMMA chip demonstrated that the two peptides were separated and that the migration time of the peptides was correlated with the net charge.

Fabrication of Porous Zirconia Ceramics by Injection Molding Method

An innovative processing route for fabricating porous zirconia ceramics has been developed based on traditional injection molding method. Azodicarbonamide (AC) was used as the foaming agents and mixed with the zirconia powder and conventional binders (polypropylene, ethylene/vinyl acetate, paraffin wax and stearic acid). There were three stages in the foaming course: (1) Small bubbles nucleated when AC decomposed into N2 and CO in the barrel. (2) Viscosity and pressure drop led to the growth of the bubbles when the melt feedstock was injected into the die cavity. (3) The porous structure was kept in the solidified body. The AC content and injection parameters were optimized to control the pore density and size. The porous green body was debinded at the heating-up rate of 0.5 °C /min to 450°C and sintered at 1550°C. Samples with porosity of 40%-50% and pore sizes from 200-250μm were prepared when the addition of AC was 0.3% by weight. The results showed that ceramic injection molding method was also suitable for fabricating the porous ceramics.

TOUGHENING AND STIFFENING EFFECTS OF T-ZnOw WHISKERS ON POLYSTYRENE

The main subject of this work is about the effect of T-ZnOw on the toughness and stiffness of polystyrene (PS). In order to avoid the rupture of T-ZnOw during the melt processing, T-ZnOw/PS composites were obtained via the combination of solution blending and injection moulding methods. Although the tensile strength of the composites decreases slightly, the impact strength and tensile modulus increase with the increase of the T-ZnOw content in the matrix. The stiffness and toughness of the composites are enhanced simultaneously. SEM results of the impact-fractured surface show more polymer avulsions, ridges and micro-cracks formed in the T-ZnOw/PS composites, companied with pullout of T-ZnOw from PS matrix and local yielding of PS matrix around T-ZnOw during the impact processing. The possible reasons for the toughness increment of T-ZnOw/PS composites are attributed to the interfacial debonding, pullout of T-ZnOw from PS matrix, anchoring effect of T-ZnOw's special three dimensional structure, local yielding of PS matrix and the formation and propagation of micro-cracks.

Metal Injection Molding Method of Ni-Free Austenitic Stainless Steel II - Microstructure and Mechanical Properties

Microstructure and mechanical properties of high nitrogen steels whose chemical composition were Fe-17Cr-12Mn-3Mo and that was produced by using metal injection molding method and nitrogen absorption methods were examined. A compact which is furnace cooled from 1573 K has a brittle surface layer with high chromium and nitrogen contents but the surface layer disappears when the compact is held at 1473 K. The compact which is furnace cooled at 1473 K is observed precipitates in the grains and the grain boundary, while the compact which is quenched at 1473 K shows homogeneous microstructure. In the heat treatments at 1473 K for 2, 5, and 10 h, the nitrogen content becomes higher with increasing of holding time. In the holding times of 5 and 10 h, the microstructure is austenite. In the tensile tests, tensile strength becomes larger with increasing of nitrogen content. In the specimen which is conducted the heat treatment at 1473 K for 10 h, tensile strength is about 1,000 MPa and elongation is 80 %, which shows better balance of strength and elongation than SUS304 and SUS316 steels.

Dispersant selection for aqueous medium pressure injection moulding of anhydrous dicalcium phosphate

Injection moulding is an extremely versatile method for producing ceramic parts with complex shapes. However, there are many disadvantages associated with conventional injection moulding methods, which may include the requirement of high viscosity polymers, toxic solvents, high temperatures and pressures. In recent years, considerable attention has been directed towards the development of low/medium pressure injection moulding which is an alternative low-cost forming method using water and low melting point gelling food binders. The basic requirement for injection moulding is the preparation of a stable, well-dispersed slip, which is achieved by the selection of an effective dispersant. This paper details an investigation into the dispersing abilities of sodium citrate, sodium pyrophosphate and sodium carbonate in different concentrations (0.01, 0.1, 0.3, 0.5, 1 and 1.5 wt.%) in anhydrous dicalcium phosphate (DCPA) slips by studying the two main interlinking properties: electrophoretic mobility and rheology. Furthermore, the effects of temperature on the behaviour of the dispersants are also investigated. The results obtained showed that the optimum dispersant was sodium citrate at a concentration of 0.3 wt.% which yielded the greatest viscosity decrease (95.6%) relative to the slip without dispersant and showed the best stability over the injection temperature range.

The role of interface modification on the mechanical properties of injection-moulded composites from commingled polypropylene/banana granules

Commingled polypropylene (PP)/banana granules were fabricated from slivers by mixing PP fibers and banana fibers by textile equipment. By twisting the sliver, the reinforcing fibers were compacted and bonded with the molten matrix material. PP/banana composites were prepared from commingled PP/banana granules by injection moulding method with special reference to the effect of maleic anhydride modified polypropylene (MAH-PP) concentration. The mechanical properties of the composites were found to depend on the concentration of MAH-PP. The tensile and flexural properties of the composites increased with the addition of MAH-PP up to 2 wt%. After 2 wt% addition of MAH-PP, these properties tend to be stabilized. On the other hand the unmodified composites showed the maximum impact strength. Fourier transform infrared spectroscopic (FTIR) analysis of the MAH-PP modified composites showed evidence of a chemical bridge between the hydroxyl group of the banana fiber and maleic anhydride of the MAH-PP through an esterification reaction. The feature peak of the esterification occurred in the range ∼ 1743 cm−1. In order to confirm the esterfication reaction further, FTIR spectra of the banana microfibrils and MAH-PP modified PP/banana microfibril composites were taken and compared. The tensile fracture surfaces of the unmodified and MAH-PP modified PP/banana composites were studied by scanning electron microscopy (SEM). An improvement in adhesion between the fiber and the matrix was observed in the case of MAH-PP modified composites. Two different processing methods, both injection and compression mouldings were performed to prepare the PP/banana composites. Tensile properties of the composites prepared by these two methods were compared. The enhancement of tensile properties for injection-moulded composites compared to the compression-moulded composites is owing to the occurrence of orientation, better mixing and interaction between the fiber and the matrix during injection moulding. Finally, experimental results of the tensile properties of the injection-moulded composites have been compared with theoretical predictions.

Influence of Binders on the Structure and Properties of High Speed-Steel HS6-5-2 Type Fabricated Using Pressureless Forming and PIM Methods

Based on the comparison of structures and properties of the HS6-5-2 high speed steels made with the powder injection moulding method, pressureless forming, compacting and sintering, and commercial steels made with the ASEA-STORA method, fine carbides spread evenly in the steel matrix were found in the structure of all tested high-speed steels in the sintered state. The use of a nitrogen atmosphere in the sintering process, causes the formation of fine, spherical MX type carbonitrides, stable in high sintering and austenitizing temperatures. The steels made with the pressureless forming method are characteristic of the lowest sintering temperature and the highest density, resulting from the high carbon concentration coming from the binding agent degradation. Moreover, the higher carbon concentration causes an increase in the retained austenite portion and a lower hardness after quenching and tempering. The heat-treated injection moulded steel attains hardness comparable to the commercial ASP23 type one, demonstrating the well-founded reasons for using the powder-injection moulding method for manufacturing the high-speed steel. The powder-injection moulding makes manufacturing tools possible with their final shape, i.e., leaving out the plastic forming and machining which is necessary for instance in case of the ASP 23 type steel. Furthermore, the degradation and sintering process time of the injection moulded steels is approximately 10h shorter than for steels made with pressureless moulding, which is due to the use of a two-component binding agent.

Characteristics of Titanium Parts Produced by Powder Injection Moulding

The production and characteristics of a part produced from titanium hydride (TiH2) powder using the powder injection moulding (PIM) method are described. Use of hydrogen as a temporary alloying element in titanium alloys is an attractive approach to enhance processability including sintering, compacting, etc., and also to improve final mechanical properties. In this paper, the mechanical properties are presented, based mainly on the uniaxial compression resistance of sintering parts. The PIM parts were formed using three different sintering temperatures to verify the influence of dehydrogenated processes on final mechanical properties.