Glass Transition
Mostrando 13-24 de 249 artigos, teses e dissertações.
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13. Evaluation of Fracture Toughness of Ultraviolet-Irradiated Polycarbonate Using the Essential Work of Fracture Method
The essential work of fracture (EWF) method provides useful parameters to characterize the fracture toughness of polymers exposed to degrading environments under conditions associated with plane-stress state of failure. Exposure of polymeric engineering materials to ultraviolet (UV) radiation may produce macromolecular changes that impair their fracture toug
Mat. Res.. Publicado em: 26/07/2018
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14. Microscopía fototérmica para el estudio de transformaciones de fase
ABSTRACT A novel system allowing a high spatial resolution mapping of the thermal diffusivity as a function of temperature up to 1800 K is presented. The system is based on a photothermal technique recently developed by the group, consisting in measuring, with a probe laser beam, the curvature induced by local heating with a modulated pump laser. A microscop
Matéria (Rio J.). Publicado em: 19/07/2018
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15. Membranas Compuestas: propiedades superficiales y estabilidad térmica
ABSTRACT The composite membranes were manufactured with crosslinking poly(vinyl alcohol) on polyethersulfone porous membranes by coating process. PES membranes were exposed to air plasma for the purpose of surface modification. The coating of the support membrane was carried out by using a polymer matrix with a crosslinking agent. The physico-chemical proper
Matéria (Rio J.). Publicado em: 19/07/2018
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16. Estrategia para la optimización de un compuesto de caucho con aceite de soja utilizando diseños de experimentos
ABSTRACT When a rubber component is made, is necessary to start from a “rubber compound” which may be composed of one or more polymers and various additives or fillers. The development of an elastomer mixture to produce a compound with a specific end-use is complicated in the field of rubber technology. Therefore, the successful development of a compound
Matéria (Rio J.). Publicado em: 19/07/2018
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17. Structural, Optical and Thermal Characterizations of PVA/MAA:EA Polyblend Films
Films of polyvinyl alcohol (PVA), Methacrylic Acid - Ethyl Acrylate (MAA:EA) copolymer and their blends PVA:MAA:EA of composition 80:20, 60:40, 50:50, 40:60, 20:80 (wt %) were prepared by using the solution cast technique. The prepared films were investigated by structural, optical and thermal studies. X-ray diffraction (XRD) scans revealed the semicrystalli
Mat. Res.. Publicado em: 16/07/2018
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18. Frozen-to-jamming-to-fluid Transition of Weakly Sheared Granular Systems by Low-frequency Mechanical Spectroscopy
Granular matter usually displays frozen, jamming and fluidized states when submitted to an external vibration with increasing intensity. The dissipation properties of granular systems with three different millimeter-size glass grains (0.1, 0.5 and 1.9 mm) have been investigated by a modified low-frequency inverted torsion pendulum under a shear strain and an
Mat. Res.. Publicado em: 10/07/2018
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19. Effect of disinfection techniques on physical-mechanical properties of a microwave-activated acrylic resin
Abstract The effects of disinfection by microwave irradiation and immersion in peracetic acid on the physical-mechanical properties of a microwave-activated acrylic resin were evaluated. Specimens of acrylic resin were divided into a control group (specimens not disinfected) and 2 test groups subjected to one disinfection method: microwave irradiation at 85
Polímeros. Publicado em: 06/07/2018
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20. Manipulation of Glassy State in Amorphous Selenium by Low-temperature Internal Friction Measurements
We have studied the thickness and quench-rate dependent internal friction of amorphous selenium (a-Se) thin films deposited at room temperature. The internal friction of a-Se films exhibit a temperature independent plateau below 1 K followed by a broad maximum at 10 K. The plateau, which is seen in almost all amorphous solids, is caused by dissipation by two
Mat. Res.. Publicado em: 07/06/2018
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21. Relaxational Dynamics in the PYR14-IM14 Ionic Liquid by Mechanical Spectroscopy
The anelastic spectrum of the N-butyl-N-methyl-pyrrolidinium (trifluoromethanesulfonyl) (nonafluorobutanesulfonyl)imide (PYR14-IM14) is reported for the first time. On cooling, at 4 Kmin-1 the sample undergoes a glass transition around 190 K. In the liquid phase, a thermally activated relaxation process is measured and it is analyzed by means of a modified
Mat. Res.. Publicado em: 04/06/2018
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22. Damping of the Woodwind Instrument Reed Material Arundo donax L
The viscoelastic properties (E', G', tanΦ, δ) of Arundo donax (AD) and a polypropylene-beech fiber composite (PPC) were measured from RT to 580K for various frequencies and strains. E' of AD varies between 5250-6250MPa depending on ageing at RT while E'(RT)=2250MPa of PPC is signifcantly lower. E' of the AD is higher than E' of PPC in the whole investigate
Mat. Res.. Publicado em: 04/06/2018
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23. The effect of molecular weight and hydrolysis degree of poly(vinyl alcohol)(PVA) on the thermal and mechanical properties of poly(lactic acid)/PVA blends
Abstract The effect of molecular weights and hydrolysis degrees (HD) of polyvinyl alcohol (PVA) on thermal and mechanical properties and crystallinity of polylactic acid (PLA)/PVA blends was investigated. Blends were prepared by the melt blending method using PLA/PVA ratios: 80/20, 90/10 and 97/3 wt. %. A single glass transition temperatures was observed fo
Polímeros. Publicado em: 21/05/2018
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24. Replacement of Commercial Silica by Rice Husk Ash in Epoxy Composites: A Comparative Analysis
Since epoxy resins are used as composite matrix with excellent results, and silica is one of the fillers most often employed, this study compared the performance of rice husk ash (RHA) as filler in epoxy composites, in replacement for high-purity silica. Composites were molded containing 20%, 40%, and 60% (wt) silica or RHA. Viscosity analysis, infrared spec
Mat. Res.. Publicado em: 05/04/2018