Thermal and Dielectric Properties of Cyanate Ester Cured Main Chain Rigid-Rod Epoxy Resin

Thermal and dielectric properties of rigid-rod bifunctional epoxy resin 4,4-bis(2,3-epoxypropoxy) biphenyl epoxy (BP) and commercial epoxy resin diglycidyl ether of bisphenol A (DGEBA) were studied using differential scanning calorimeter (DSC), thermogravimetric analyzer (TGA), dynamic mechanical analyzer (DMA), thermal mechanical analyzer (TMA) and dielectric analyzer (DEA). These two epoxies were cured with cyanate ester hardener 2,2’-bis(4-cyanatophenyl) propane (AroCy B10). The BP/B10 system consisting of a rigid-rod structure exhibited better thermal properties than the DGEBA/B10 system with a flexible structure. Anisotropic BP/B10 (2:1) had the highest 5% weight loss temperature, the highest amount of residue and a smaller thermal expansion coefficient than the commercial DGEBA/B10 system. The BP/B10 system, which cured at the LC phase temperature, had higher Tg than the commercial DGEBA/B10 system, as found from dynamic mechanical analysis. The BP/B10 system also demonstrated better dielectric properties than the commercial DGEBA/B10 system when enough curing agent was provided.

Investigation of frequency dependent mechanical properties of porous materials using dynamic mechanical analyzer and frequency-temperature superposition theory

In acoustic design of engineering applications - such as in the acoustic analysis of passenger vehicles - poroelastic materials are of great importance. One of the most influencing properties in determining their noise-reduction potential is the storage modulus. The purpose of this study is to examine the frequency dependence of storage modulus of selected porous acoustic materials at least up to 1000 Hz. This is executed by using the combined use of dynamic mechanical analyzer and frequency-temperature superposition theory. All other methods for measuring the storage modulus fall short in determining frequency-dependence above 100 Hz: quasi-static mechanical analyzer is mostly used for determining an averaged constant value deduced from low-frequency measurements, while the usage of an electromagnetic shaker capable for high-frequency excitation may include effects of fluid motion inside the pores, thus significantly modifying the results. Frequency-temperature superposition enables to determine the storage modulus values in a wide frequency range, based on low-frequency measurements, where fluid-structure interaction is negligible. It was found that the modulus varied significantly up to and beyond 1000 Hz, and thus, acoustical characterization of these materials can be significantly improved using the proposed method. The work concludes with recommendations to improve the accuracy of the results.

Tensile Strength of PMMA/n-ZrSiO4 Composites Using Dynamic Mechanical Analyzer (DMA)

This study aimed to determine the tensile strength and strain properties of poly(methyl methacrylate) (PMMA)/nano-zircon (n-ZrSiO4) composites with various nano-zircon sizes. Wet milling method for 5 and 15 h without annealing treatment was used to obtain the nano-zircon powders. Results showed that milling for 15 hours can reduce zircon size up to 93 nm. Meanwhile, the composites were synthesized with zircon compositions of 1, 2.5, and 5 wt.%. Dynamic Mechanical Analyzer (DMA) measurement were carried out to characterize the tensile-strain dependence on filler compositions of the PMMA/n-ZrSiO4 composites. The PMMA/n-ZrSiO4 composite with 5 wt.% and 15h milling zircon exhibited the highest tensile strength, ca. 10.02 MPa or 2 times of the pure PMMA. The tensile strength of the composites can be explained from the mean size and size distribution of the filler.

Multiscale Characterization of E-Glass/Epoxy Composite Exposed to Extreme Environmental Conditions

Fiber-reinforced polymer matrix composites continue to attract scientific and industrial interest since they offer superior strength-, stiffness-, and toughness-to-weight ratios. The research herein characterizes two sets of E-Glass/Epoxy composite skins: stressed and unstressed. The stressed samples were previously installed in an underground power distribution vault and were exposed to fire while the unstressed composite skins were newly fabricated and never-deployed samples. The mechanical, morphological, and elemental composition of the samples were methodically studied using a dynamic mechanical analyzer, a scanning electron microscope (SEM), and an x-ray diffractometer, respectively. Sandwich composite panels consisting of E-glass/Epoxy skin and balsa wood core were originally received, and the balsa wood was removed before any further investigations. Skin-only specimens with dimensions of ~12.5 mm wide, ~70 mm long, and ~6 mm thick were tested in a Dynamic Mechanical Analyzer in a dual-cantilever beam configuration at 5 Hz and 10 Hz from room temperature to 210 °C. Micrographic analysis using the SEM indicated a slight change in morphology due to the fire event but confirmed the effectiveness of the fire-retardant agents in quickly suppressing the fire. Accompanying Fourier transform infrared and energy dispersive X-ray spectroscopy studies corroborated the mechanical and morphological results. Finally, X-ray diffraction showed that the fire event consumed the surface level fire-retardant and the structural attributes of the E-Glass/Epoxy remained mainly intact. The results suggest the panels can continue field deployment, even after short fire incident.

Studies on the transformation process of PVDF film from α to β phase by uniaxial stretch

Stretching process is an effective method to prepare high β- phase PVDF. PVDF film was prepared by extrusion casting in this paper, then stretched by means of uniaxial-stretching using a DMA(Dynamic mechanical analyzer), the effects of stretching conditions on the transformation from α to β phase of PVDF were studied, also with the changes regularity of mechanical properties during stretching. The phase composition was characterized by XRD, FTIR, DSC, the results show that, the optimum drawing temperature is 80°C, the optimum stretch ratio is related to the length-width ratio of the film, the increase of stretching rate is beneficial to the formation of β-phase, the β-phase can reach 80% under the optimum drawing conditions.

Analisis Sifat Mekanik Karet Silikon sebagai Kandidat Prepusium Sintetik pada Alat Peraga Khitan

Khitan atau sunat (sirkumsisi) merupakan proses tindakan medis berupa pembuangan sebagian dari kulit luar penis (prepusium) yang membungkus kepala penis (glans). Di Indonesia, khitan banyak dilakukan pada anak laki-laki ketika mencapai masa usia 7 sampai 12 tahun. Tindakan khitan dapat dilakukan oleh berbagai profesi tenaga kesehatan, seperti dokter, perawat, dan mantri sunat. Untuk melatih keterampilan tindakan khitan, salah satu metode yang dapat digunakan adalah dengan menggunakan alat peraga khitan sebagai sarana latihan memotong dan menjahit kulit penis. Tetapi, alat peraga khitan masih minim ditemukan di Indonesia. Salah satu poin penting dari alat peraga khitan adalah adanya kulit sintetis yang sifat mekaniknya mirip kulit asli agar ketika latihan memotong dan menjahit mempunyai <em>feeling</em> yang sama. Penelitian ini bertujuan untuk membuat dan menganalisis sifat mekanik karet jenis silikon sebagai material pengganti prepusium pada alat peraga khitan. Pengujian sifat mekanik dari prepusium dan karet silikon menggunakan <em>Dynamic Mechanical Analyzer</em> (DMA). Hasil penelitian menunjukkan modulus elastisitas prepusium dan silikon mempunyai tren yang sama, tetapi mempunyai nilai eksak yang berbeda. Berdasarkan hasil survei yang dilakukan terhadap beberapa praktisi khitan di Yogyakarta, kulit sintetis mudah dipotong dan dijahit serta mempunyai <em>feeling</em> yang mendekati sebenarnya.

Magnetic Ionic Liquid Nanocatalyst to Improve Mechanical and Thermal Properties of Epoxy Nanocomposites

New magnetic imidazolium ionic liquid (IIL) was synthesized to improve the curing, mechanical, and thermal characteristics of the epoxy/polyamine system. In this respect, 2-(4-minophenyl)-1.3-bis(triethoxysilyl)-1H-imidazol-3-ium acetate as IIL was synthesized and characterized by different spectroscopy tools. The IIL was used as capping to prepare Fe3O4 nanoparticles (NPs) as new Fe3O4-IIL NPs. The thermal stability, morphology, crystal lattice structures, and magnetic properties were evaluated to confirm the formation of uniform, thermal, stable, and superparamagnetic Fe3O4-IIL NPs. The prepared Fe3O4-IIL NPs were mixed with an epoxy/polyamine system to improve the curing, thermal, and mechanical properties of epoxy through chemical reactions. The dynamic mechanical analyzer and differential scanning calorimeter were used to investigate the flexibility and storage modulus of the cured epoxy/polyamine system in the absence and presence of Fe3O4-IIL NPs. The atomic force microscope and scanning electron microscope were used to evaluate the dispersion and embedding of Fe3O4-IIL NPs into epoxy matrix. The thermal, mechanical, and surface morphologies data confirmed that the incorporation of Fe3O4-IIL NPs using 3 wt. % during the curing of an epoxy/polyamine system produces superior epoxy films without cracks, holes, and NPs agglomeration.