Navegando por Palavras-chave "High density polyethylene"

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    Effect of PANI on Thermal, Mechanical and Electromagnetic Properties of HDPE/LLDPE/ PANI Composites
    (Univ Fed Sao Carlos, Dept Engenharia Materials, 2018) de Faria, Patrick Valadao [UNIFESP]; Backes, Eduardo Henrique; Montagna, Larissa Stieven [UNIFESP]; Pinto, Simone de Souza [UNIFESP]; Pessan, Luiz Antonio; Rezende, Mirabel Cerqueira [UNIFESP]; Passador, Fabio Roberto [UNIFESP]
    In this work, polyaniline (PANI) in emeraldine-base form, synthesized by chemical oxidation polymerization, was protonated with hydrochloric acid (HC1) Composites based on high-density polyethylene (HDPE) and linear-low density polyethylene (LLDPE) blends with PANI were prepared in molten condition using a torque rheometer The effect of compatibilizer agent (maleic anhydridegrafted high density polyethylene, HDPE-g-MA) and different contents of PANI on the blends-based composites was also investigated Thermal, mechanical, and electromagnetic (electric permittivity) measurements and morphological aspects of the composites were evaluated The addition of PANI content in the composites decreases the degree of crystallinity of HDPE and LLDPE blends, which implies that PANI particles make it difficult for co-crystallization to occur in the HDPE and LLDPE, respectively On the other hand, the addition of compatibilizer agent in the HDPE and LLDPE blends increased the degree of crystallinity The complex parameters of permittivity in the frequency range of 8.2 to 12.4 GHz vaned as a function of the PANI content m the blend It was also observed that the compatibilizer agent increased the composite stiffness and decreased the electric permittivity values This result shows that the increasmg rigidity of the molecular structure of the polyethylene matrix hindered the dissipation of the electromagnetic energy in the sample.
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    Effect of pulse repetition rate and number of pulses in the analysis of polypropylene and high density polyethylene by nanosecond infrared laser induced breakdown spectroscopy
    (Elsevier B.V., 2012-02-01) Leme, Flavio O.; Godoi, Quienly; Kiyataka, Paulo H. M.; Santos Junior, Dário [UNIFESP]; Agnelli, Jose A. M.; Krug, Francisco J.; Universidade de São Paulo (USP); Universidade Federal de São Carlos (UFSCar); Inst Tecnol Alimentos; Universidade Federal de São Paulo (UNIFESP)
    Pulse repetition rates and the number of laser pulses are among the most important parameters that do affect the analysis of solid materials by laser induced breakdown spectroscopy, and the knowledge of their effects is of fundamental importance for suggesting analytical strategies when dealing with laser ablation processes of polymers. in this contribution, the influence of these parameters in the ablated mass and in the features of craters was evaluated in polypropylene and high density polyethylene plates containing pigment-based PbCrO4. Surface characterization and craters profile were carried out by perfilometry and scanning electron microscopy. Area, volume and profile of craters were obtained using Taylor Map software. A laser induced breakdown spectroscopy system consisted of a Q-Switched Nd:YAG laser (1064 nm, 5 ns) and an Echelle spectrometer equipped with ICCD detector were used. the evaluated operating conditions consisted of 10, 25 and 50 laser pulses at 1, 5 and 10 Hz, 250 mJ/pulse (85 J cm(-2)), 2 mu s delay time and 6 mu s integration time gate. Differences in the topographical features among craters of both polymers were observed. the decrease in the repetition rate resulted in irregular craters and formation of edges, especially in polypropylene sample. the differences in the topographical features and ablated masses were attributed to the influence of the degree of crystallinity, crystalline melting temperature and glass transition temperature in the ablation process of the high density polyethylene and polypropylene. It was also observed that the intensities of chromium and lead emission signals obtained at 10 Hz were two times higher than at 5 Hz by keeping the number of laser pulses constant. (C) 2011 Elsevier B. V. All rights reserved.