Relationship between the dielectric and mechanical properties and the ratio of epoxy resin to hardener of the hybrid thermosetting polymers

Abstract

Foi investigada a relação entre as propriedades dielétricas (constante dielétrica, ε'; fator de perda, ε"; energia de ativação, E a ) e a proporção de resina epóxi (OG) para endurecedor em polímeros termorrígidos de resina epóxi (OG). A amplitude do pico de ε" decresce com o aumento da porcentagem em massa de OG até aproximadamente 73% e aumenta levemente para maiores % OG. A temperatura da posição do pico de ε" aumenta com o aumento da % OG, alcançando valores máximos para formulações no intervalo de 67 a 73%, e então, decresce acentuadamente para maiores % OG. A energia de ativação obtida por relaxação dielétrica aumentou com a % OG até aproximadamente 70%. Um aumento adicional na % OG até 83% reduz a E a . As curvas das propriedades mecânicas de módulo de tensão e resistência à fratura como função da % em massa de OG apresentaram um comportamento similar.The relationship between the dielectric properties (dielectric constant, ε', and loss factor, ε"; activation energy, E a ) and the ratio of epoxy resin (OG) to hardener of the epoxy resin thermosetting polymers was investigated. The amplitude of the ε" peak decreases with increasing OG content until about 73 wt.% and slightly increases at higher OG content. The temperature of the position of the ε" peak increases with the increasing of OG content, reaching maximum values for compositions in the range of 67 and 73 wt.%, and then it decreases sharply at higher OG content. The activation energy obtained from dielectric relaxation increased with increasing wt.% OG up to around 70 wt.%. Further increase in concentration of OG up to 83 wt.% reduced E a . The curves of tensile modulus and fracture toughness mechanical properties as a function of OG content presented a similar behavior.

Chlorine‐Free Catalytic Formation of Silsesquioxanes with Si‐OH and Si‐OR Functional Groups

“…Materials and Methods: The chemicals were purchased from the following sources: Hybrid Plastics for tetrasilanolPOSS (C 48 H 44 O 14 Si 8 ) (DDSQ‐4OH) disilanolPOSS (C 32 H 74 O 13 Si 8 ) ( i Bu 8 POSS‐2OH) and trisilanolPOSS (C 28 H 66 O 12 Si 7 ) ( i Bu 7 POSS‐3OH); POCH for methanol, 2‐propanol, ethyl acetate and copper acetate hydrate; Merck for dichloromethane (DCM), tetrahydrofuran (THF), diethyl ether, n ‐pentane, benzene, chloroform, [D]chloroform, sodium metal, benzophenone, 1,5‐cyclooctadiene, sodium trimethylsilanolate, chlorosilanes, palladium catalysts [Pd(PPh 3 ) 4 ] and Pd/C (Pd on activated carbon), Pt/C (Pt on activated carbon, Degussa type), [Pt 2 (dvds) 3 ] (Karstedt's catalyst) 2 % xylene solution, platinum and rhodium acetylacetonates, rhodium chloride, calcium hydride, molecular sieves and anhydrous magnesium sulfate, triethylamine and silica gel 60. Silsesquioxane substrates were prepared according to the literature procedures, so too were Pt/SDB, Rh/SDB, Rh/SiO 2 and [RhCl(cod)] 2 . All solvents and alcohols were dried with sodium or CaH 2 prior to use and stored under argon over type 3A molecular sieves.…”

Hydrophobic Materials Based on Fluorocarbofunctional Spherosilicates

“…The rhodium siloxide complex [{Rh(-OSiMe 3 (cod)} 2 ] was synthesized according to the original procedure described by Marciniec et al [31,32]. 1,1,2,2,3,3,4,4-Octafluoropentyl allyl ether was synthesized by the Williamson reaction [33] and octakis (hydridodimethylsiloxy) octasilsesquioxane was prepared according to the procedure described by Caetano et al [29]. Glass plates were purchased from Thermo Scientific.…”

“…1 H NMR(300 MHz), 13 C NMR(75 MHz), and 29 Si NMR(59 MHz) spectra were recorded on a Varian XL 300 spectrometer at room temperature using C 6 D 6 as a solvent. Water contact angle was measured using Kruss DSA 100E Drop Shape Analyzer equipped with software-controlled (DAS4 2.0): x, y, z-axis table, quadruple dosing unit, zoom and focus adjustment, illumination, camera with 780 580 px resolution.…”

“…Moreover, the developed method is very attractive from the economic viewpoint because it is characterized both by simple technology and the use of considerably cheaper starting materials than those employed to date. The main reagents are octakis(hydridodimethylsiloxy)octasilsesquioxane (that is obtained in a simple and fast way based on the method described in the literature [29]) and fluoroalkyl allyl ether. The preparation of the latter reagent is based on the Williamson reaction by using fluorinated alcohols (that are considerably cheaper than commonly used fluoroalkyl iodides) and allyl chloride [30].…”

Analysis of the dielectric spectra of composite sealing coatings in a wide frequency range

“…Interest in studies of the relative dielectric permittivity ε and the loss tangent tanδ of polymers is due not only to the importance of these parameters for definite applica tions, but also to the possibility of their usage in studying the features of the molecular mobility of polymer chains. The relaxation processes in poly mers, kinetics of polymerization and linkage, changes of the viscosity and ionic conductivity, and processes at the structure interfaces and phase boundaries in composites were studied in [7][8][9] by applying the DS method.…”