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Totally found 505 items.

  • [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.
  • [期刊] Mechanical characterization of polymethyl methacrylate composites reinforced with surface-coated carbon fibers
    Using trihydroxy polyether polyol (PPG), diphenylmethane diisocyanate (MDI) as soft segment and hard segment, carbon fiber (CF) as reinforcement, and self-crosslinking CF/polymethyl methacrylate (PMMA) composite was prepared by prepolymer method. In this study, starch and octanoyl chloride were esterified to obtain esterified starch (SE). The fiber is then melt blended with PMMA matrix to prepare PMMA composite. Fourier-transform infrared spectroscopy (FTIR) and SEM were used to analyze and characterize the composites produced. The results show that the composite material was prepared by separately modifying the fiber with NaOH and SE, respectively. The mechanical properties of the composite materials prepared by the modified fiber are improved, and the fiber and the PMMA matrix showed better compatibility. The mechanism of comodified fiber enhanced the mechanical properties of its composites.
  • [期刊] Development characteristics of polymethyl methacrylate in alcohol/water mixtures: a lithography and Raman spectroscopy study
    Poly methyl methacrylate (PMMA) is the most widely used resist in electron beam lithography. This paper reports on a lithography and Raman spectroscopy study of development characteristics of PMMA in methanol, ethanol and isopropanol mixtures with water as developers. We have found that ethanol/water mixtures at a 4:1 volume ratio are an excellent, high resolution, non-toxic developer for exposed PMMA. We have also found that the proper methodology to use so that contrast data can be compared to techniques used in polymer science is not to rinse the developed resist but to immediately dry with nitrogen. Our results show how powerful simple lithographic techniques can be used to study ternary polymer solvent solutions when compared to other techniques used in the literature. Raman data show that both tightly bonded -OH groups and non-hydrogen bonded -OH groups play a role in the development of PMMA. Tightly hydrogen bonded -OH groups show pure Lorentzian Raman absorption only in the concentration ranges where ethanol/water and IPA/water mixtures are effective developers of PMMA, pointing to possible ordering or reduced amorphization due to the liquid state. The impact of understanding these interactions may open doors to a new developers of other electron beam resists that can reduce the toxicity of the waste stream.
  • [期刊] Electrical bistabilities and stabilities of organic bistable devices fabricated utilizing [6,6]-phenyl-C85 butyric acid methyl ester blended into a polymethyl methacrylate layer
    Organic bistable devices (OBDs) based on [6,6]-phenyl-C85 butyric acid methyl ester ([84]PCBM) embedded in a polymethyl methacrylate (PMMA) layer were fabricated by using a simple spin-coating technique. Atomic force microscope images showed that the surface roughness of the [84]PCBM:PMMA composite layer was uniform. Current density-voltage curves for the memory device showed a current bistability. The maximum ON/OFF ratio of the current bistability of the OBDs was as large as 103. Write-read-erase-read characteristics showed OBDs with rewriteable nonvolatile memories, and the retention time of the OBDs was about 104 s. The ON state and the OFF state for 20 randomly-chosen cells demonstrated the high reproducibility of the fabricated OBDs.
  • [期刊] Polymethyl Methacrylate Custom-Made Prosthesis: A Novel Three-Dimension Printing-Aided Fabrication Technique for Cranial and/or Orbital Reconstruction
    Background: Over the years, many materials have been used in orbital reconstruction and cranioplasty. Among the materials in current use, polymethyl methacrylate (PMMA) offers a high degree of compatibility with human tissue.
  • [期刊] Mechanical properties characterization of polymethyl methacrylate polymer optical fibers after thermal and chemical treatments
    This paper presents the dynamic mechanical analysis (DMA) in polymer optical fibers (POFs) made of Polymethyl Methacrylate (PMMA) that were submitted to different thermal and chemical treatments, namely annealing and etching processes. The prepared samples were submitted to stress-strain cycles to evaluate the Young's modulus of each fiber. Also, test with constant stress and temperature variation were performed to estimate the thermal expansion coefficient of the fibers submitted to each thermal and chemical treatment. The samples were also tested under different temperature, humidity and strain cycle frequency conditions to analyze the variation of their mechanical properties with these parameters. Results show that the thermal and chemical treatments lead to a reduction of Young's modulus and an increase of the thermal expansion coefficient, which can produce sensors based on intensity variation or fiber Bragg grating with higher dynamic range, stress and temperature sensitivity. Furthermore, the etching and annealing resulted in fiber that presents lower Young's modulus variation with temperature, humidity and strain cycling frequency in most cases. However, the annealing made under water and the combinations of etching and annealing resulted in POFs with higher modulus variation with humidity, which enable their application as intensity variation or FBG-based sensors in humidity/moisture assessment
  • [期刊] Controlled Release of Necrostatin-1 from Calcium Phosphate-Polymethyl Methacrylate Bone Cement
    Objective : To evaluate the release of Necrostatin-1 (Nec-1) in bone cement mixed by different proportions of calcium phosphate cement (CPC) and polymethyl methacrylate (PMMA) in vitro , and to optimize the mixture proportion of CPC-PMMA. Methods : CPC and PMMA powderare mixed at the ratio of 0:1, 1:1, 2:1, and 3:1, with 5.18 mg of Nec-1 as 4 groups (0:1 group, 1:1 group, 2:1 group, 3:1 group). The mixed bone cement samples are produced by same standard (height of 12 mm and an inner diameter of 6 mm). All the bone cement samples are tested by X-ray diffraction,compression test, solidification time, electron microscope scanning and the detection of Nec-1 release in vitro . The activity of releasing Nec-1 was deteted by culturing with MC3T3-E1 cells and then necrotic apoptosis cells were tested via Flow cytometry. Results : Nec-1, CPCand PMMA do not affect each other's material generation after the analysis of their mixture structure. With the increase of the proportion of CPC, the compressive strength of CPC-PMMA bone cement mixed with Nec-1 is gradually reduced and the time of solidification is prolonged. The distancebetween the PMMA particles in 0:1 group, 1:1 group, 2:1 group, and 3:1 group are about 0 μ m, 100–200 μ m, 100–400 μ m, 100–400 μ m, respectively. By comparing the cumulative release of Nec-1 in the four groups, the release of 0:1 groupis at the lowest level, and the rank of release rate is 3:1 group>2:1 group>1:1 group. It is clear that the release of Nec-1 is fast in 5 days in each group, become slower from 5 to 19 days and continuously decelerate after 19 days. The amount of Nec-1 release reaches the highest pointat 19 days. The cumulative release concentration of Nec-1 of 0:1 group, 1:1 group, 2:1 group and 3:1 group in 59 days are 13.72 um/L, 286.66 um/L, 405.96 um/L and 553.77 um/L, respectively. The cumulative release percentages are respectively 0.34%, 7.17%, 10.15% and 13.84%. Through testingthe necrotic apoptosis cells via Flow cytometry, the releasing Nec-1 still remains activity. Conclusions : This study has verified that CPC-PMMA bone cement mixture has a better comprehensive performance than simple PMMA bone cement, and established a methodology for detection of Nec-1release in bone cement in vitro . In this study, Nec-1-CPC-PMMA bone cement mixture with the CPC to PMMA ratio of 3:1 showed the optimal compressive strength and coagulation time. And the mixture can release Nec-1 stably and the releasing Nec-1 maintains activity, thus this configurationwould be an ideal choice for the preparation of a new type of Nec-1-CPC-PMMA bone cement.]]>
  • [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] Toughness of Scots pine - polymethyl methacrylate composite
    A series of 1,600 samples of the sapwood of Scots pine (Pinus sylvestris), part of them in natural state, but majority subjected to polymerization with various level of impregnation with methyl methacrylate, were tested for toughness on Charpy's impact machine. The goal of the experiment was to investigate how polymerization improves toughness and, additionally, how exposure to low temperatures and to the action of seawater influences this property of the material tested. It was found that within impregnation levels and temperatures tested variability of toughness due to these two factors is almost linear and in practical considerations may be predicted based on an empirical formula. It was also found that exposure to the action of seawater weakens the material. To verify anisotropy of toughness in the plane perpendicular to the grain all samples were consistently cut out such that one pair of opposite lateral faces were tangent to the growth rings. Half of the whole set of samples was fractured with an impact directed perpendicular to the growth rings and the other half with an impact directed in the tangential direction. The results show that although in general toughness is slightly higher in the direction perpendicular to the growth rings than in the tangent direction, the difference may be neglected in practical considerations. POLYM. COMPOS., 40:811-822, 2019. (c) 2018 Society of Plastics Engineers
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