Distribution by Scientific Domains
Distribution within Polymers and Materials Science

Kinds of Molding

  • blow molding
  • compression molding
  • dynamic packing injection molding
  • injection molding
  • nuclear molding
  • packing injection molding
  • reaction injection molding
  • rotational molding
  • stretch blow molding

  • Terms modified by Molding

  • molding compound
  • molding condition
  • molding machine
  • molding process
  • molding technique

  • Selected Abstracts

    Manufacturing of Net-Shape Reaction-Bonded Ceramic Microparts by Low-Pressure Injection Molding,

    Nadja Schlechtriemen
    Reaction-bonded oxide ceramics based on intermetallic compounds are able to compensate the sintering shrinkage completely due to their high increase in volume caused by oxidation. Using low-pressure injection molding (LPIM) for shaping ceramics avoids needless materials loss and affords the manufacturing of complex formed structures. The combination of both, reaction-bonded ceramic and LPIM-processing, offers the manufacturing of ceramic microparts by keeping a high accuracy and replication quality. [source]

    A preliminary study on bladder-assisted rotomolding of thermoplastic polymer composites

    A. Salomi
    Abstract In this preliminary work, a new process is examined for manufacturing hollow parts from continuous fiber-reinforced thermoplastic polymer. The new process combines the basic idea of bag forming (or bladder-assisted forming) with the rotation of the mold for the processing of thermoplastic matrix composites. A pressurized membrane is used to compact the composite on the inner wall of a mold, which is placed inside a forced convection oven. The mold is removed from the oven for the cooling stage. The process was initially developed by using a thermoplastic pre-preg obtained using yarns of commingled E-glass fibers with isotactic polypropylene (iPP). A preliminary characterization of the thermoplastic composite showed that the material can be consolidated with pressures as low as 0.01 MPa, which is readily achievable with the process of this study. The design of the mold and membrane was carried out on the basis of both structural analysis of the aluminum shell and thermal analysis of the mold. The mold thickness is of great importance with respect to both the maximum pressure allowed in the process and the overall cycle time. Molding was performed on stacks of three and six layers of yarn, varying the applied pressure between 0.01 and 0.05 MPa and maximum temperature of the internal air between 185°C and 215°C. The composite shells obtained under different processing conditions were characterized in terms of physical and mechanical properties. Mechanical properties comparable with those obtained by compression molding and vacuum bagging were obtained. The maximum values obtained are 12.1 GPa and 290 MPa for the flexural modulus and the flexural strength, respectively. Furthermore, the results obtained show that mechanical properties improve with increasing the pressure during the cycle and with the maximum temperature used in the process. © 2007 Wiley Periodicals, Inc. Adv Polym Techn 26:21,32, 2007; Published online in Wiley InterScience ( DOI 10.1002/adv.20085 [source]

    Dynamic behavior of the flow field in a RIM machine mixing chamber

    AICHE JOURNAL, Issue 6 2009
    Ricardo J. Santos
    Abstract Dynamic behavior of the flow field in a Reaction Injection Molding, RIM, machine mixing chamber, having dimensions typically used in industrial machines, is studied from dynamic velocity data of Laser Doppler Anemometry, LDA, measurements and Computational Fluid Dynamics, CFD, simulations with a 2D model. This study is based on the spectral analysis of the dynamic flow field data. The typical frequencies, in the reactor flow field, are identified and its values are related to the identified flow structures. The differences between the typical frequencies from experiments and simulations are observed and justified on the basis of the 2D representation of a 3D cylindrical geometry. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

    Preparation and Characterization of a Large-Scale YBa2Cu3O7,x Superconductor Prepared by Plastic Forming without a High-Pressure Molding: Effect of Polyvinyl Alcohol (PVA) Addition on the Superconducting Properties

    Makoto Takahashi
    The preparation of large-scale YBa2Cu3O7,x superconductor samples was investigated. This method is based on plastic forming using a slurry consisting of YBa2Cu3O7,x particles and a sol solution made up of multimetallic hydroxide particles (YBa2Cu3(OH)x colloidal particles) and poly(vinyl) alcohol (PVA). The effects of adding PVA on the product, the crystallinity, and the superconducting properties of the sample were investigated. It was found that PVA acted as a protective colloid in the sol solution and stabilized YBa2Cu3(OH)x colloidal particles, and that the role of PVA changed from a thickener to a flocculant during drying so that the formability/workability of the green sheet sample was improved and large samples (about 80 mm × 80 mm × 3 mm) without large cracks were obtained after firing. The samples became superconducting at 91.5±0.5 K (Tcon) and the full transition temperature (Tcoff) was 88.5±1.5 K. The critical current density (Jc) of the sample prepared from the slurry containing 1 wt% PVA was 713±150 A/cm2 at 77 K. This Jc value was improved to 2300 A/cm2 by heat treatment at 773 K under an oxygen atmosphere. [source]

    Refractive Index Drop Observed After Precision Molding of Optical Elements: A Quantitative Understanding Based on the Tool,Narayanaswamy,Moynihan Model

    Ulrich Fotheringham
    The room-temperature refractive index is measured for three different prior cooling rates (approximately 10, 50, and 250 K/h) for two glasses especially developed for precision molding. The empirical logarithmic relationship between the cooling rate and the refractive index is also reproduced for the comparatively high cooling rate of ca. 250 K/h. The same relationship is found in a simulation of these cooling rates by the semiempirical Tool,Narayanaswamy,Moynihan model for structural relaxation, with the necessary parameters obtained from differential scanning calorimetry and temperature jump experiments. The measured and the simulated refractive indices coincide within the limits of experimental error. The results demonstrate that the index drop, which is observed when these glasses are first cooled at a regular optical cooling rate (e.g., 2 K/h), and then precision molded (typical cooling rate 1000 K/h), can be understood considering the concepts of structural relaxation. [source]

    Microtransfer Molding of Gelcasting Suspensions to Fabricate Barrier Ribs for Plasma Display Panel

    Jooho Moon
    We have developed a new fabrication technique for the barrier ribs of a plasma display panel (PDP). The rib structure was formed on a glass plate by microtransfer molding a gelcasting suspension with a flexible soft mold. A well,dispersed gelcasting suspension of the glass frit was placed on the photolithographically patterned mold, followed by gelation and drying while pressed with a top glass plate. The rib structure replicated by micromolding was significantly influenced by the gelation kinetics, the green strength of the gelled body, and the mold release process. It was demonstrated that the box,type array of 1176 wells in the patterned area of 6.5 cm × 6.5 cm could be produced using the current method. [source]

    Biomimetic Polymer Nanostructures by Injection Molding

    Nikolaj Gadegaard
    Abstract The nanometer scale topography of self-assembling structural protein complexes in animals is believed to induce favorable cell responses. An important example of such nanostructured biological complexes is fibrillar collagen that possesses a cross-striation structure with a periodicity of 69 nm and a peak-to-valley distance of 4,6 nm. Bovine collagen type I was assembled into fibrillar structures in vitro and sedimented onto solid supports. Their structural motif was transferred into a nickel replica by physical vapor deposition of a small-grained metal layer followed by galvanic plating. The resulting inverted nickel structure was found to faithfully present most of the micrometer and nanometer scale topography of the biological original. This nickel replica was used as a die for the injection molding of a range of different thermoplastic polymers. Total injection molding cycle times were in the range of 30,45 seconds. One of the polymer materials investigated, polyethylene, displayed poor replication of the biological nanotopographical motif. However, the majority of the polymers showed very high replication fidelity as witnessed by their ability to replicate the cross-striation features of less than 5 nm height difference. The latter group of materials includes poly(propylene), poly(methyl methacrylate), poly(L -lactic acid), polycaprolactone, and a copolymer of cyclic and linear olefins (COC). This work suggests that the current limiting factor for the injection molding of nanometer scale topography in thermoplastic polymers lies with the grain size of the initial metal coating of the mold rather than the polymers themselves. [source]

    Investigations into the Chemical Modification of Polyolefin Surfaces by Radical Reactions during Molding

    Jürgen Nagel
    Abstract The surfaces of polyolefin parts are usually modified by separate processing steps. In this paper, we investigate how an in situ surface modification of polyolefins could be realized during molding, based on radical reactions, by which a macromolecule with functional groups is grafted to the polyolefin surface. The temperature of the melt is used to initialize the reactions. The different steps of the radical reaction chain were analyzed using model reactions. A modifier composition consisting of dibenzoylperoxide, potassium persulfate and poly(vinyl alcohol) revealed to be suitable. This composition was used for injection molding experiments. The bondability of the injection molded parts was largely enhanced. [source]

    Optimization of cure kinetics parameter estimation for structural reaction injection molding/resin transfer molding

    POLYMER COMPOSITES, Issue 6 2001
    Robert J. Duh
    A numerical method is proposed for polymer kinetic parameter estimation of either Structural Reaction Injection Molding (SRIM) or Resin Transfer Molding (RTM). The method simulates either radial flow or axial flow of reactive resins through a fiber preform inside a mold cavity. This method considers a non-isothermal environment with different inlet boundary conditions. Based on the molding conditions, this method can find the best values of chemical kinetic parameters by comparing the simulated temperature history and the experimental temperature history. Since the kinetic parameters are estimated with the real molding conditions, the simulations using these parameter values can have better agreement with molding data than those parameters which are obtained from idealized conditions such as Differential Scanning Calorimeter (DSC). The optimization approach was verified by estimating kinetics parameters for RTM data available in the literature. Temperatures predicted by the optimized kinetics parameters are compared with experimental data for two different molding conditions: injection of a thermally activated resin into a radial mold under constant pressure flow, and injection of a mix activated resin into a radial mold under constant volume. In both cases, the optimized kinetics parameters fit the temperature data well. [source]

    Investigation of unsaturated flow in woven, braided and stitched fiber mats during mold-filling in resin transfer molding

    POLYMER COMPOSITES, Issue 4 2001
    J. Slade
    In Resin Transfer Molding (RPM), which is a process to manufacture polymer composites, the impregnation of fibrous reinforcement In the form of mats by a thermosetting resin is modeled as the flow of a Newtonian liquid through a single length-scale porous medium. While this approach is sufficiently accurate for random fiber-mats, it can lead to appreciable errors when applied to woven, braided, or stitched fiber-mats that contain two length scales. This work investigates the primary factors governing the isothermal unsaturated flow through such dual-scale porous media. Two studies were conducted to better understand this phenomenon: the first experimenatally investigated the flow, while the second theoretically modeled the flow and identified important parameters affecting such a flow with the help of dimensionless analysis. In the first study, one-dimensional constant injection rate experiments were performed using various fiber mats. The unsaturated flow behavior of various mats was characterized using a constant "sink" term in the continuity equation. Results indicated that for a given fiber-mat, the magnitude of the sink effect was a function of the capillary number. In the second study, a numerical model was developed to describe flow through dual-scale preforms in which the two flow domains, the inter- and intra-tow regions, were coupled. We identified a dimensionless number called the sink effect index , that characterizes the magnitude of liquid absorption by the tows and is a function of the relative resistance to flow in the tow and inter-tow regions, and the packing density of the tows. The parametric study of this index with the help of numerical simulations reveals its influence on the flow and identifies the distinct transient and steady-state flow regimes. [source]

    A full 3D finite element analysis of the powder injection molding filling process including slip phenomena

    C. J. Hwang
    A full 3D finite element analysis system has been developed to simulate a Powder Injection Molding (PIM) filling process for general three-dimensional parts. The most important features of the analysis system developed in this study are i) to incorporate the slip phenomena, the most notable rheological characteristics of PIM feedstock, into the finite element formulation based on a nonlinear penalty-like parameter and ii) to simulate the transient flow during the filling process with a predetermined finite element mesh with the help of a volume fill factor and a melt front smoothing scheme. The treatment of the nonlinear slip boundary condition was successfully validated via a steady state pipe flow. For the purpose of comparisons, not only the numerical simulations but also experimental short-shot experiments were performed with two 3D mold geometries using two typical materials of slip and no-slip cases. The good agreements between the numerical and experimental results indicate that the melt front tracking scheme successfully simulates the transient filling process. [source]

    Thermal Sensor to Monitor Mechanical Properties in Polymer/Fiber Composite Molding

    David Rouison
    Abstract Multi-layered samples of 1) continuous fiber axially aligned and 2) random oriented mat glass fiber composites were manually prepared for a fiber content ranging from zero to 20% (vol.). The uniaxially aligned samples displayed linear relations between both normalized elastic modulus and normalized thermal conductivity, and fiber content, for axially applied load and heat flux. For the random mat composite samples, similar results were obtained, with symmetry displayed in the plane of the mat. In both cases, measured axial thermal conductivity permits an evaluation of the axial elastic modulus. The Mathis surface probe used (US patent #5,795,064) is demonstrated as a non-intrusive indirect method of obtaining thermal conductivity for heat flux parallel (i.e. axial or transverse) to the plane of a sample. The method shows potential for use as an in-line monitoring device for the mechanical properties of molded composites. Des échantillons multicouches de composites (1) de fibres continues alignées dans le sens axial et (2) de fibres de verre en natte orientées aléatoirement, ont été préparés manuellement pour une teneur en fibre comprise entre 0 et 20 % (vol.). Pour les échantillons alignés dans le sens uniaxial, on montre l'existence de relations linéaires entre la teneur en fibre et le module élastique normalisé et entre la teneur en fibre et la conductivité thermique normalisée, pour une charge et un flux de chaleur appliqués dans le sens axial. Pour les échantillons de composite en natte aléatoire, des résultats similaires ont été obtenus, avec une symétrie observée dans le plan de la natte. Dans les deux cas, la conductivité thermique axiale mesurée permet une évaluation du module élastique axiale. On démontre que la sonde de surface Mathis utilisée (brevet US # 5,795,064) constitue une méthode indirecte non intrusive pour obtenir la conductivité thermique pour un flux de chaleur parallèle (c.-à-d. axial ou transversal) au plan de la surface de l'échantillon. La méthode montre du potentiel en tant que dispositif de surveillance en ligne pour les propriétés mécaniques des composites moulés. [source]

    Cytopathological diagnosis of adult retinoblastoma in a vitrectomy specimen,

    Maria E. Orellana M.D.
    Abstract Retinoblastoma (RB) is extremely rare in adults. We describe a case of RB diagnosed by cytology in a vitrectomy specimen of a 23-year-old patient who presented with diminished visual acuity and retinal detachment in the absence of a clinically-visible mass. Cytological examination of the vitreous fluid showed clusters of loosely cohesive atypical cells with high nuclear to cytoplasmic ratio and "salt and pepper" chromatin pattern in a background of normal neuronal retinal cells. Nuclear molding was present as well as numerous apoptotic bodies. The cells were focally positive for epithelial markers and showed strong and diffuse positivity for neuroendocrine markers. Ki-67 stained 90% of the "atypical cells" nuclei, in contrast to nonneoplastic retinal neuronal cells, which were negative for the marker. A diagnosis of RB was rendered, and subsequently was confirmed in the enucleation specimen. The cytological differential diagnosis is discussed as well as the role that cytology and immunohistochemistry can play in differentiating neoplastic cells from normal retinal cellular elements in vitreous fluid specimens. Diagn. Cytopathol. 2010. © 2009 Wiley-Liss, Inc. [source]

    Differential diagnostic features of small cell carcinoma in the uterine cervix

    Min Jung Kim M.D.
    Abstract Small cell carcinoma (SMCC) of the uterine cervix is rare and known to be an aggressive tumor, but there are only few reports on the cytologic features of cervical SMCC. This rare small cell lesion should be distinguished from malignant lymphoma (ML), squamous cell carcinoma in situ (SCIS), and chronic lymphocytic cervicitis (CLC). By clarifying cytologic features and reevaluating the significance of cervical cytologic smears to reveal these cervical lesions, we can improve the diagnostic specificity and patient's outcome. The clinical record and available cervical smears from 13 cases of SMCC, four cases of malignant lymphoma, 20 cases of SCIS, and five cases of CLC were analyzed. The cytologic differential diagnostic points of SMCC were nuclear molding and smearing (100%), salt and pepper chromatin (100%), exudative and necrotic background (91.7%), various architectures including individual cells (83.3%), tight clusters (75%) and feathering and strip (50%), and inconspicuous nucleoli (75%). Early diagnosis of the cervical SMCC by cytology and treatment is important for better outcome of patients. Diagn. Cytopathol. 2008;36:618,623. © 2008 Wiley-Liss, Inc. [source]

    Fine-needle aspiration of metastatic prostatic neuroendocrine carcinomas: Cytomorphologic and immunophenotypic features

    Guoping Cai M.D.
    Abstract Metastatic prostatic carcinoma may, in rare occasions, present as a neuroendocrine tumor. Its recognition is crucial to avert a wrongful exclusion of prostate as a primary site. We report five cases of metastatic prostatic neuroendocrine carcinoma diagnosed by image-guided fine-needle aspiration biopsy. The aspirate smears showed loosely cohesive or dyscohesive clusters of tumor cells with scanty (three cases) to moderate amount (two cases) of cytoplasm, speckled or coarse chromatin and inconspicuous nucleoli. Nuclear molding and necrosis were focally present in two cases. Immunohistochemically, the tumor cells were positive for synaptophysin or/and chromogranin, but negative for prostatic specific antigen and prostatic specific acid phosphatase. Review of prior prostate biopsies/resections revealed adenocarcinoma with focal neuroendocrine differentiation in all cases, with two cases being newly recognized on retrospective review. Confirming neuroendocrine differentiation in the prior biopsy/resection may help to establish a link between metastasis and prostate primary. Diagn. Cytopathol. 2008; 36: 545,549. © 2008 Wiley-Liss, Inc. [source]

    Desmoplastic round cell tumor of childhood: Can cytology with immunocytochemistry serve as an alternative for tissue diagnosis?

    Dr Brijal Dave M.D.
    Abstract There are limited reports on the cytology of desmoplastic small round cell tumors (DSRCT). Fine needle aspiration biopsy (FNAB) findings in seven aspirates from four cases of histologically and immunohistochemically confirmed cases were analyzed with the main intention of ascertaining if cytological diagnosis of DSRCT is possible. Also assessed were the immunocytochemistry(ICC) findings in these cases. The basic cytological impression was that of a cohesive small round cell tumor. Nuclei showed granular chromatin with grooves, nuclear molding and inconspicuous nucleoli. Stromal fragments were noted in all four cases. In two cases, awareness of cytological features in the appropriate clinical context led to a suggestion of the diagnosis of DSRCT on cytology itself. ICC on destained smears showed positivity for cytokeratin, epithelial membrane antigen (EMA), desmin and WT-1 in two cases. In conclusion, given the right clinical setting, a cytological diagnosis of DSRCT is plausible and in conjunction with ICC may help in documenting the polyphenotypic nature and thereby confirming the diagnosis. Diagn. Cytopathol. 2005;32:330,335. © 2005 Wiley-Liss, Inc. [source]

    Low-grade urothelial carcinoma: Reappraisal of the cytologic criteria on ThinPrep®

    Ph.D., Wei Xin M.D.
    Abstract The diagnostic criteria for low-grade urothelial lesions that have been described in the past were based on urinary specimens prepared by the cytospin method. Recognizing the recent popularity of the ThinPrep® methodology and the cytologic alterations it introduces to the cellular features, we sought to evaluate the reproducibility of these criteria in ThinPrep urinary samples. One hundred twenty-six ThinPrep urinary specimens with a tissue diagnosis of low-grade urothelial carcinoma (LGUC) and 45 negative controls were evaluated. Three pathologists blindly reviewed the slides separately and the consensus on each feature was used in the study. Logistic regression analysis was used to determine which criteria in combination were most predictive of low-grade urothelial carcinoma. All specimens were evaluated for the following 18 features: nucleus/cytoplasm ratio, irregular nuclear border, cytoplasm homogeneity, cell clusters, high cellularity, prominent nucleoli, granular nuclear chromatin, hyperchromasia, acute inflammation, vesicular chromatin, nuclear molding, nuclear eccentricity, elongated nuclei, necrosis, anisonucleosis, irregular bordered fragments, absent cytoplasmic collar, and peripheral palisading. High nucleus-to-cytoplasm ratio, irregular nuclear borders, and homogeneous cytoplasm (combination sensitivity of 59% and specificity of 100%) were the best predictive features for LGUC. Minor predictive criteria were eccentric nuclei and nuclear molding. ThinPrep provides well preserved, cleaner specimens without significantly altering the morphology. The three key criteria applied in cytospin specimens to diagnose LGUC were reproducible in ThinPrep specimens. Diagn. Cytopathol. 2003;29:125,129. © 2003 Wiley-Liss, Inc. [source]

    Morphologic predictors of papillary carcinoma on fine-needle aspiration of thyroid with ThinPrep® preparations

    Yilin Zhang M.D.
    Abstract Although the cytologic features of papillary carcinoma of the thyroid are well-known, none is entirely specific. We conducted this study to determine the minimal criteria necessary to achieve 100% specificity for the diagnosis of papillary carcinoma on fine-needle aspiration (FNA). Forty patients with histologically confirmed papillary carcinoma and 17 patients with other thyroid lesions who underwent preoperative FNA at Beth Israel Deaconess Medical Center during a 4-yr period were included in the study. All cytology slides were prepared with the ThinPrep® processing technique. Various architectural and nuclear features were evaluated, with a score assigned to each feature, and correlated with the histologic diagnosis of papillary carcinoma. Intranuclear inclusions, papillary and/or sheet arrangements, nuclear grooves, powdery chromatin, nuclear molding, high cellularity, and small nucleoli were significantly associated with papillary carcinoma (P < 0.05). The requirement of any intranuclear inclusions and many nuclear grooves, or a minimum of sum of scores (of the above eight features) of 10, yields 100% specificity and approximately 70% sensitivity. Cases with fewer features can be reported as suspicious or indeterminate for papillary carcinoma. A quantitative/probabilistic approach in the reporting of thyroid FNA provides a practical guide for management of patients with thyroid nodules. Diagn. Cytopathol. 24:378,383, 2001. © 2001 Wiley-Liss, Inc. [source]

    Effect of Ti addition on magnetic properties of TbCu7 -type Sm-Fe-Co-Mn system nitrides

    Hiroshi Yamamoto
    Abstract To support the development of high-performance isotropic bonded magnets, experiments were carried out to investigate the effect of Ti addition on the magnetic properties of Sm-Fe-Co-Mn system nitride compounds with TbCu7 -type structure. Sm10(Fe0.9Co0.1)89.5,xMn0.5Tix (x=0 to 1.0) alloy ribbons were prepared by the single-roller rapid-quenching method. The effects of alloy composition and of heat treatment and nitriding conditions on the magnetic properties were examined. The optimum preparation conditions of the compounds were as follows. Composition: {Sm10(F0.9Co0.1)89Mn0.5Ti0.5}86.8N13.2; roller speed: 50 m/s; heat treatment: 700°C×60 min in high-purity Ar gas; nitriding conditions: 420°C×15 h in high-purity N2 gas. Typical magnetic properties of the obtained compound powders were Jr = 0.97 T, HcJ = 730.8 kA/m,(BH)max = 140.0 kJ/m3 (17.6 MGOe), Tc=500°C. XRD, TEM photographs, and recoil loops of the hysteresis curve demonstrated that this sample had the characteristics of an exchange spring magnet. The value of (BH)max for the isotropic compression molding bonded magnet prepared from the {Sm10(F0.9Co0.1)89Mn0.5Ti0.5}86.8N13.2 powder was 94.8 kJ/m3 (11.9 MGOe) at a bonded magnet density of 6.07 Mg/m3. The reversible temperature coefficient of Jr was ,(Jr)=,0.04%/°C and the temperature coefficient of HcJ in the range from 25°C to 125°C obtained by linear extrapolation was ,(HcJ)=,0.40%/°C. © 2008 Wiley Periodicals, Inc. Electron Comm Jpn, 91(7): 25,31, 2008; Published online in Wiley InterScience ( DOI 10.1002/ecj.10124 [source]

    Atmospheric molding of ionic copolymer MALDI-TOF/MS arrays: A new tool for protein identification/profiling

    ELECTROPHORESIS, Issue 24 2006
    Alexander Muck
    Abstract An atmospheric molding protocol has been used to prepare an ionic methacrylate-based copolymer sample support chips for MALDI (pMALDI)-MS by targeting selected groups of various monomers copolymerized during molding, namely, carboxy, sulfo, dimethylalkyamino, and trimethylalkylammonium groups. The new disposable array chips provide analyte-oriented enhancement of protein adsorption to the modified substrates without requiring complicated surface coating or derivatization. The MALDI-MS performance of the new ionic copolymer chips was evaluated for lysozyme, ,-lactoglobulin,A, trypsinogen and carbonic anhydrase,I using washing with solutions prepared in pH or ionic strength steps. On cationic chips, the proteins are washed out at pH lower than their pI values, and on anionic chips at pH higher than their pI values. The ability of the microfabricated pMALDI chip set to selectively adsorb different proteins from real samples and to significantly increase their MS-signal was documented for the transmembrane photosystem,I protein complex from the green alga Chlamydomonas reinhardtii. The proteins were almost exclusively adsorbed according to calculated pI values and grand average of hydropathy (GRAVY) indexes. The new disposable chips reduce manipulation times and increase measurement sensitivity for real-world proteomic samples. The simple atmospheric molding procedure enables additional proteomic operations to be incorporated on disposable MALDI-MS integrated platforms. [source]

    Manufacturing of Net-Shape Reaction-Bonded Ceramic Microparts by Low-Pressure Injection Molding,

    Nadja Schlechtriemen
    Reaction-bonded oxide ceramics based on intermetallic compounds are able to compensate the sintering shrinkage completely due to their high increase in volume caused by oxidation. Using low-pressure injection molding (LPIM) for shaping ceramics avoids needless materials loss and affords the manufacturing of complex formed structures. The combination of both, reaction-bonded ceramic and LPIM-processing, offers the manufacturing of ceramic microparts by keeping a high accuracy and replication quality. [source]

    A Soft Molding Process for Fabrication of Micromachine Parts from Stainless Steel Powder,

    Mohamed Imbaby
    This work introduces a valid approach to fabricate high quality micromachine parts from stainless steel powder using soft molding and powder metallurgy techniques. In soft molding, SU-8 and negative replicas micromolds are produced. A mixture of Duramax B-10007 and B-1000 is successfully used as a binder in the preparation of stainless steel slurry. Sintering in forming gas atmosphere is very effective of preventing the oxidation of the stainless. [source]

    Finite element and sensitivity analysis of thermally induced flow instabilities

    Jean-Serge Giguère
    Abstract This paper presents a finite element algorithm for the simulation of thermo-hydrodynamic instabilities causing manufacturing defects in injection molding of plastic and metal powder. Mold-filling parameters determine the flow pattern during filling, which in turn influences the quality of the final part. Insufficiently, well-controlled operating conditions may generate inhomogeneities, empty spaces or unusable parts. An understanding of the flow behavior will enable manufacturers to reduce or even eliminate defects and improve their competitiveness. This work presents a rigorous study using numerical simulation and sensitivity analysis. The problem is modeled by the Navier,Stokes equations, the energy equation and a generalized Newtonian viscosity model. The solution algorithm is applied to a simple flow in a symmetrical gate geometry. This problem exhibits both symmetrical and non-symmetrical solutions depending on the values taken by flow parameters. Under particular combinations of operating conditions, the flow was stable and symmetric, while some other combinations leading to large thermally induced viscosity gradients produce unstable and asymmetric flow. Based on the numerical results, a stability chart of the flow was established, identifying the boundaries between regions of stable and unstable flow in terms of the Graetz number (ratio of thermal conduction time to the convection time scale) and B, a dimensionless ratio indicating the sensitivity of viscosity to temperature changes. Sensitivities with respect to flow parameters are then computed using the continuous sensitivity equations method. We demonstrate that sensitivities are able to detect the transition between the stable and unstable flow regimes and correctly indicate how parameters should change in order to increase the stability of the flow. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Numerical simulation of mold filling in injection molding using a three-dimensional finite volume approach

    Rong-yeu Chang
    Abstract This work presents an implicit finite volume approach to simulate the three-dimensional mold filling problems encountered during the injection molding. The described numerical model deals with the three-dimensional isothermal flow of incompressible, high-viscous Newtonian fluids with moving interfaces. The collocated finite volume method and the SIMPLE segregated algorithm are used to discretize and solve the Navier,Stokes equation. In addition, a bounded compressive high-resolution differencing scheme is adopted to solve the advection equation to capture the interface on a Eulerian framework. This approach effectively solves the flow field in terms of CPU time and memory storage as well as the complicated three-dimensional melt front topology. Several two- and three-dimensional examples are presented to validate the presented approach and illustrate its capabilities. This method can more accurately predict the critical three-dimensional phenomena encountered during mold filling than the existing Hele,Shaw analysis model. The presented numerical approach has been proven to be a highly effective and flexible tool for simulating mold filling problems. Copyright © 2001 John Wiley & Sons, Ltd. [source]

    Texture Analysis and Finite Element Modeling of Operational Stresses in Ceramic Injection Molding Components for High-Pressure Pumps

    Martin Wenzelburger
    Texturization of microstructures in ceramic components during injection of thermoplastic feedstocks into the mold is a well-known problem in ceramic injection molding (CIM) technology. The influences of textures on the mechanical properties of components with anisotropic properties, which depend on crystallite structure and orientation, usually involve weakening of the structure by the formation of separation planes and accumulation of stresses, which can lead to crack initiation and subcritical failure. A light optical texture analysis technique was developed for the analysis of thin section preparations from optically anisotropic ceramic materials. An internal Al2O3 gear rim for high-pressure gear pumps that is manufactured by CIM was chosen for the evaluation of this technique. Components were produced from thermoplastic ceramic feedstocks with different rheological behavior. Thin sections were prepared from the sintered parts. The texture was analyzed by polarized transmission light microscopy of the thin sections and colorimetric analysis of the crystal orientation. For the evaluation of the component properties, function, and lifetime, operating tests on a test bench were carried out as well as finite element (FE) simulation of the stress distribution in the components under operational load with regard to the texturization. The results were used for the localization of stress gradients and their comparison and correlation to the texturization. The functionality of this texture analysis method was proved by the tests, and it is expected to be a convenient novel method for the analysis and optimization of the parameters in CIM processes and the design of injection gate and mold. [source]

    Selenium-Based Glasses and Glass Ceramics Transmitting Light from the Visible to the Far-IR

    ADVANCED MATERIALS, Issue 1 2007
    L. Calvez
    An innovative glass/glass ceramic based on the GeSe2,Ga2Se3,CsCl system is reported. This material is the first reported glass/glass ceramic transparent from the visible to the far-IR, has improved mechanical properties over selenide glasses, and is compatible with high-precision molding, making it suitable for applications in thermal imaging. [source]

    Elastomeric Molds with Tunable Microtopography,

    ADVANCED MATERIALS, Issue 23-24 2004
    M. Hoffman
    Elastomeric "microtunable" molds (,TMs) whose microtopography can be tuned post-fabrication at certain pre-defined locations have been devised. Their features make them very attractive for the molding of complex microstructures. The Figure shows a scanning electron microscopy image of poly(dimethylsiloxane) double- replicas of a ,TM whose membrane contains a 1.18,mm spiral. [source]

    Stamps for Submicrometer Soft Lithography Fabricated by Capillary Force Lithography ,

    ADVANCED MATERIALS, Issue 13 2004
    M. Bruinink
    A convenient, inexpensive technique for fabrication of stamps for submicrometer soft lithography from masters with micrometer-size features is presented. Templates fabricated by capillary-force lithography are robust against replica molding of stamps. The Figure shows the resulting metal structure after employing such a second-generation stamp in microcontact printing of octadecanethiol and subsequent wet chemical etching of the underlying gold. [source]

    Adaptive geometry and process optimization for injection molding using the kriging surrogate model trained by numerical simulation

    Yuehua Gao
    Abstract An adaptive optimization method based on the kriging surrogate model has been developed to intelligently determine the optimal geometric dimensions and processing parameters for minimizing warpage in injection-molded components. The kriging surrogate model is a statistics-based interpolated technique that provides the approximate functional relationship between warpage and factors that influence warpage. In this study, it is used to be first trained by,and later replaced,the full-fledged, time-consuming numerical simulation in the optimization process. Based on this surrogate model, an adaptive iteration scheme that takes into account the predicted uncertainty is performed to improve the accuracy of the surrogate model while finding the optimum solution. The optimization process starts with a small number of initial training sample points and then adds additional key points during iterations by evaluating the correlations among the candidate points. As an example of validation and application, optimization of geometric dimensions and processing parameters for a box-shape part with different and stepwise wall thicknesses has been performed. The results demonstrate the feasibility and effectiveness of the proposed optimization method. © 2008 Wiley Periodicals, Inc. Adv Polym Techn 27:1,16, 2008; Published online in Wiley InterScience ( DOI 10.1002/adv.20116 [source]

    Visualization of the foaming mechanism of polyethylene blown by chemical blowing agents under ambient pressure

    Remon Pop-Iliev
    Abstract Understanding the fundamental mechanisms that govern the foaming process is the most essential universal prerequisite for developing effective processing strategies for fabricating high-quality foamed plastic products using any type of foaming technology. Despite chemically blown foaming of thermoplastics under atmospheric pressure has been successfully implemented in rotational foam molding over the last decade, the related open literature does not provide substantial research addressing the fundamentals of this unique foaming mechanism. The present study focuses on clarifying the fundamental foaming mechanisms that govern the successful manufacture of thermoplastic foams using a chemical blowing agent under low-pressure (atmospheric) conditions. The presented research is mainly based on observing a series of visualization experiments conducted using a custom-made visualization system including an optical microscope and a computerized CCD camera imaging system, which was utilized for investigating the behavior of foamable polyethylene samples prepared by using the compression-molding method. © 2008 Wiley Periodicals, Inc. Adv Polym Techn 26:213,222, 2007; Published online in Wiley InterScience ( DOI 10.1002/adv.20102 [source]