Small range 文档类型:"3"

Totally found 3032 items.

  • [期刊] Optimum creep lifetime of Polymethyl Methacrylate (PMMA) tube using rheological creep constitutive models based on experimental data
    In this paper, the creep behavior of Polymethyl Methacrylate (PMMA) is investigated both experimentally and numerically at different temperatures (30, 40 and 50 degrees C) and stress levels. The experimental results show that PMMA has a nonlinear viscoelastic behavior. Hence, to model the creep behavior of PMMA, three types of constitutive models have been proposed: a) the generalized time hardening model, b) Burgers model, c) modified Burgers model. It was found that the generalized time hardening model, which has extensive applications in commercial softwares, predicts the creep behavior of PMMA at higher stress levels but it deviates from the experimental results at lower stress levels. Although, Burgers model predicts the creep behavior of PMMA, to improve the accuracy of the model a modified version of Burgers model has been proposed, which demonstrates very good consistency with the experimental data over the whole range of applied stresses and temperatures. Finally, the results are used to estimate the optimum creep lifetime of a rotating pressurized tube. A set of diagrams, which can be used in industry, have been produced based on each model.
  • [期刊] Generalized regression and feed forward back propagation neural networks in modelling flammability characteristics of polymethyl methacrylate (PMMA)
    The capability of artificial neural networks in predicting microscale combustion calorimeter (MCC) parameters of polymethyl methacrylate (PMMA) was carried out in this study. Using values of sample mass and corresponding heating rate, feed forward back propagation (FFBP) and generalized regression neural network (GRNN) models were developed to predict MCC parameters. On the whole, GRNN outperformed FFBP in predicting HRC data while FFBP model saw an improvement over GRNN when estimating pTime. It was also discovered that GRNN obtained better THR, pTemp and pHRR predictions during training but generated a relatively poor correlation when estimating the testing data. Sensitivity analysis on the ANN models revealed that heating rate had a more significant effect on the models' outcome. Also, the ANN models observed the least error deviation when compared with HRC results for PMMA from structure-property models. Hence, ANN presents a reliable method for predicting flammability characteristics of PMMA from MCC test.
  • [期刊] Creep buckling analysis of PMMA (polymethyl methacrylate) pressure vessels for application in neutrino detectors
    Polymethyl methacrylate (PMMA) has recently been used to build the pressure vessels for application in neutrino detectors. For thin-wall vessels under external pressure, they may undergo buckling failure. Taking the creep behavior of PMMA into consideration, buckling analysis of PMMA pressure vessels has not yet been studied. In this paper, creep tests of PMMA immersed into liquid scintillator were performed. Creep damage constitutive model for PMMA under multi-axial stress state was derived and incorporated into ABAQUS by developing a CREEP subroutine. Then creep buckling analysis of spherical pressure vessels for neutrino detector was conducted. Double failure criteria were proposed to judge whether the creep buckling occurred or not. Finally, the relationship between the maximum stress on the vessel and the creep buckling time was revealed. The research results can be used to predict the service lifetime and guide the stability design of PMMA pressure vessels in neutrino detectors.
  • [期刊] Dielectric characterization of polyvinyl chloride/polymethyl methacrylate (PVC/PMMA) blends by TSDC technique
    The present work focuses on the study of polyvinylchloride/polymethyl methacrylate (PVC/PMMA) blends. Films with different weight ratios of PMMA were prepared. The ATR-FTIR spectroscopy was used to study their miscibility. The TSDC was applied to study dielectric properties. The TSDC spectra of miscible blends (<= 60 wt% of PMMA) have a single peak whose position is intermediate between the one of the two pure polymers as well as the activation energy, the fragility index and the compensation temperature were deduced using the fractional polarization technique. The maximal dielectric losses, which increase with the increase of PMMA content, are in the vicinity of the glass temperature.
  • [期刊] REMOVAL OF AGGREGATES FROM MICRON-SIZED POLYMETHYL METHACRYLATE (PMMA) LATEX BEADS USING FULL FEED DEPLETION MODE OF GRAVITATIONAL SPLITT FRACTIONATION (FFD-GSF)
    Split-flow thin cell (SPLITT) fraclionation (SF) provides separation of colloidal particles or macromolecules into two fractions. A gravitational SF(GSF) system was constructed and Us applicability was tested for removal of aggregates from mass-produced polymelhyl methacrylate (PMMA) latex beads. The full-feed depletion (FFD) mode of GSF (FFD-GSF) was found to be a simpler alternative to the conventional mode for removal of the aggregates. Unlike in the conventional mode, where two inlets are used for feeding of the sample suspension and the carrier liquid respectively, only one inlet (for the sample feeding) is used in the FFD mode, allowing easier control of the flow rate. Also the sample suspension is not diluted during FFD mode operation. Aggregated particles were found only in one of the two fractions, allowing removal of the aggregates. The sample was continuously fed into the GSF system, showing potential application to a large quantity operation for removal of the PMMA aggregates.
  • [期刊] Reduced graphene oxide/polymethyl methacrylate (rGO/PMMA) nanocomposite for real time gamma radiation detection
    Novel 3 dimensional radiation sensors using reduced graphene oxide (rGO) nanoflakes in polymethyl methacrylate matrix as sensing material were synthesized and fabricated to measure the dose rate of gamma radiation. A detailed characterization of the prepared reduced graphene oxide using X-ray diffraction (XRD), thermal gravimetric analysis (TGA), atomic force microscopy (AFM), Field Emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR) and High-resolution transmission electron microscopy (HRTEM) is presented. Reduced graphene oxide-polymethyl methacrylate composite was prepared using methylene chloride solvent-assisted dispersion of nano flakes of reduced graphene oxide in the polymer matrix. The gamma sensor mainly consists of polymethyl methacrylate/reduced graphene oxide (rGO/PMMA) nanocomposite as the sensing material and two silver coated glass electrodes to make a conductive cell. Real time dose rate information of the nanocomposite such as linearity response to dose rate and sensitivity are investigated. rGO/PMMA based gamma sensors show better performance at a standard bias voltage with respect to graphene oxide (GO) dosimeters. The response to dose rate is linear in the range of 50-130 mGy/min and the sensor array can be introduced for gamma radiation application dosimetry in diagnostic activities.
  • [期刊] Polymethyl methacrylate (PMMA) point of care for ABO-Rh(D) blood typing
    Polymethyl methacrylate (PMMA) based point of care (POC) for ABO-Rh(D) blood grouping by the naked eye was investigated. PMMA substrate was covalently linked with carboxyl methyl dextran (CMD) and coupled to the blood group specific antibodies anti A, anti B, and anti D, which were patterned into "A", "B", and "+". The red read out color originated from the color of hemoglobin in the ABCs. The major human blood group, ABO-Rh (D), was successfully sorted using these patterns. PMMA strip-based assays for blood grouping by the naked eye resulted in correct blood group identification of all 74 samples in comparison to slide agglutination test. The determination of captured RBC Rh(D) required a longer reaction time with immobilized anti D antibody on the PMMA substrate than other blood groups to produce sufficient color for unambiguous visual identification. The proper RBC concentration was found to be higher than 1% v/v for naked eye detection. The dilution of blood sample is playing a crucial role in reducing interference from blood proteins during detection. A used of undiluted blood sample for the testing should be avoided. The proper blood dilution was found to be 10% or 1:10 dilution. The proposed technique presents a quick, cheap, simple, and almost instantaneous assay for blood grouping.
  • [期刊] REMOVAL OF AGGREGATES FROM MICRON-SIZED POLYMETHYL METHACRYLATE (PMMA) LATEX BEADS USING FULL FEED DEPLETION MODE OF GRAVITATIONAL SPLITT FRACTIONATION (FFD-GSF)
    Split-flow thin cell (SPLITT) fraclionation (SF) provides separation of colloidal particles or macromolecules into two fractions. A gravitational SF(GSF) system was constructed and Us applicability was tested for removal of aggregates from mass-produced polymelhyl methacrylate (PMMA) latex beads. The full-feed depletion (FFD) mode of GSF (FFD-GSF) was found to be a simpler alternative to the conventional mode for removal of the aggregates. Unlike in the conventional mode, where two inlets are used for feeding of the sample suspension and the carrier liquid respectively, only one inlet (for the sample feeding) is used in the FFD mode, allowing easier control of the flow rate. Also the sample suspension is not diluted during FFD mode operation. Aggregated particles were found only in one of the two fractions, allowing removal of the aggregates. The sample was continuously fed into the GSF system, showing potential application to a large quantity operation for removal of the PMMA aggregates.
  • [期刊] REMOVAL OF AGGREGATES FROM MICRON-SIZED POLYMETHYL METHACRYLATE (PMMA) LATEX BEADS USING FULL FEED DEPLETION MODE OF GRAVITATIONAL SPLITT FRACTIONATION (FFD-GSF)
    Split-flow thin cell (SPLITT) fraclionation (SF) provides separation of colloidal particles or macromolecules into two fractions. A gravitational SF(GSF) system was constructed and Us applicability was tested for removal of aggregates from mass-produced polymelhyl methacrylate (PMMA) latex beads. The full-feed depletion (FFD) mode of GSF (FFD-GSF) was found to be a simpler alternative to the conventional mode for removal of the aggregates. Unlike in the conventional mode, where two inlets are used for feeding of the sample suspension and the carrier liquid respectively, only one inlet (for the sample feeding) is used in the FFD mode, allowing easier control of the flow rate. Also the sample suspension is not diluted during FFD mode operation. Aggregated particles were found only in one of the two fractions, allowing removal of the aggregates. The sample was continuously fed into the GSF system, showing potential application to a large quantity operation for removal of the PMMA aggregates.
  • [期刊] Influence of Adding Nano Graphene and Hybrid SiO2 - TiO2 Nano Particles on Tribological Characteristics of Polymethyl methacrylate (PMMA)
    Tribological characteristics of pure poly(methyl methacrylate) (PMMA) reinforced with nano graphene and hybrid dioxides nano particles, SiO2 - TiO2, with weight fraction of 0.2%, 0.4%, 0.6%, 0.8% and 1% were investigated. Durometer device, Shore D, is used to measure the hardness. Friction and wear of composites is examined on the reciprocating tribometer. Based on the experiments, it can be concluded that hybrid of the nano dioxides NH-NG-PMMA composite gives the best tribological characteristics. The minimum weight loss ratio is observed by adding hybrid dioxides of 0.4 wt.%. In addition, the hardness of the nanocomposite increases by 18% more than pure PMMA.
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