Abstract:Here, composite based on quartz fibre-reinforced fluoro-polyimide was fabricated using a hot press process, which was reported having well thermal and dielectric properties. The polyimide exhibited extremely high glass transition temperature (T g ) up to 471°C, and 5% weight loss temperature (T 5 ) about 560°C both in nitrogen and air. Also, optimisation of processing parameters of composite was investigated. Moreover, the quartz fibre/polyimide composite possessed excellent high-temperature mechanical propert… Show more
“…It was found that the values of transmittance efficiency were found to decrease first and then increase with the increase of the frequency at each incident angle, which was in fluctuation condition. A similar result was previously reported for the other waving transmitting plates, 31,32 implying that there would always be one or more frequency bands with higher transmission efficiency at wide frequency range in case of a certain thickness.Figure 11.(a) The transmittance efficiency of the resulting composite at different incident angles; (b) Dielectric constant and dielectric loss of quartz fabric-reinforced phthalonitrile PN-SF composite at the incident angle θ = 0°.…”
Section: Resultssupporting
confidence: 82%
“…It was found that the values of transmittance efficiency were found to decrease first and then increase with the increase of the frequency at each incident angle, which was in fluctuation condition. A similar result was previously reported for the other waving transmitting plates, 31,32 implying that there would always be one or more frequency bands with higher transmission efficiency at wide frequency range in case of a certain thickness.…”
Section: Processability Of the Phthalonitrile Resinsupporting
This study reports the fabrication of quartz fabric reinforced phthalonitrile composite possessing good thermal and wave-transmitting properties. Phthalonitrile-terminated oligomer PN-SF curing behavior was investigated using differential scanning calorimetry (DSC) and dynamic rheological analysis (DRA), revealing a good processability pre-curing temperature of only 175°C. The thermoset exhibited the 5% loss temperature about 462°C, and after the temperature rising to 400°C and 400°C/2 h aging, the weight loss was only 10%, indicating that the resulting thermoset possessed outstanding thermal property. Moreover, the resulting thermosets possessed extremely high glass transition temperature (Tg) about 420°C. Besides, the quartz fabric/phthalonitrile composite possessed extremely excellent mechaical properties. Importantly, the transmission efficiencies can reach 87% at a certain frequency at the incident angle of 0°∼35°, indicating its well waving-transmitting performance. Meanwhile, the composite exhibited stable and relatively low dielectric constant and dielectric loss at the range of 12∼18 GHz. This study can serve as a basis for rapid evaluation of the high heat resistance and waving-transmitting phthalonitrile resin-based composite in various application environments.
“…It was found that the values of transmittance efficiency were found to decrease first and then increase with the increase of the frequency at each incident angle, which was in fluctuation condition. A similar result was previously reported for the other waving transmitting plates, 31,32 implying that there would always be one or more frequency bands with higher transmission efficiency at wide frequency range in case of a certain thickness.Figure 11.(a) The transmittance efficiency of the resulting composite at different incident angles; (b) Dielectric constant and dielectric loss of quartz fabric-reinforced phthalonitrile PN-SF composite at the incident angle θ = 0°.…”
Section: Resultssupporting
confidence: 82%
“…It was found that the values of transmittance efficiency were found to decrease first and then increase with the increase of the frequency at each incident angle, which was in fluctuation condition. A similar result was previously reported for the other waving transmitting plates, 31,32 implying that there would always be one or more frequency bands with higher transmission efficiency at wide frequency range in case of a certain thickness.…”
Section: Processability Of the Phthalonitrile Resinsupporting
This study reports the fabrication of quartz fabric reinforced phthalonitrile composite possessing good thermal and wave-transmitting properties. Phthalonitrile-terminated oligomer PN-SF curing behavior was investigated using differential scanning calorimetry (DSC) and dynamic rheological analysis (DRA), revealing a good processability pre-curing temperature of only 175°C. The thermoset exhibited the 5% loss temperature about 462°C, and after the temperature rising to 400°C and 400°C/2 h aging, the weight loss was only 10%, indicating that the resulting thermoset possessed outstanding thermal property. Moreover, the resulting thermosets possessed extremely high glass transition temperature (Tg) about 420°C. Besides, the quartz fabric/phthalonitrile composite possessed extremely excellent mechaical properties. Importantly, the transmission efficiencies can reach 87% at a certain frequency at the incident angle of 0°∼35°, indicating its well waving-transmitting performance. Meanwhile, the composite exhibited stable and relatively low dielectric constant and dielectric loss at the range of 12∼18 GHz. This study can serve as a basis for rapid evaluation of the high heat resistance and waving-transmitting phthalonitrile resin-based composite in various application environments.
Polyimide (PI) films with simultaneously low dielectric
loss (Df) values at high frequencies and excellent general
properties
are urgently needed with the rapid development of high frequency communication
technology. Herein, we proposed that dielectric loss can be decreased
by reducing intermolecular friction work. Inspired by liquid crystals
with low intermolecular frictions, novel liquid-crystal-like PI films
were designed by simultaneously introducing mesogen units and promoting
groups (−CF3) and then being thermally imidized
via a unique solvent-assisted continuous ramping process without any
stretching or shearing process. The liquid-crystal-like PI films exhibited
ultralow Df values such as 0.00365 at 1 MHz, 0.00184 at
10 GHz, and 0.0027 at 0.75THz, which were 28.7%, 45.4%, and 97.0%
lower, respectively, than those of PI films without liquid-crystal-like
structures. The results of molecule simulations further demonstrated
that liquid-crystal-like structures can reduce intermolecular friction
work by slowing dipole rotation, leading to ultralow Df values of PI films. The liquid-crystal-like PI films also exhibited
thermal expansion coefficients of 11.4 ppm/K, tensile strengths of
228.7 MPa, Young’s moduli of 6.15 GPa, and elongations at break
of 16.4%.
“…The fiber-resin adhesion is responsible for weak or strong interfaces which play an important role in the functionality of reinforced composites [28]. Due to their excellent dielectric, mechanical, and thermal properties, quartz fibers are recognized as the best fibers among the glass fiber family [29]. Moreover, they have good adhesion compatibility with polymeric resins [30].…”
Polymer matrix wave transparent composites are used in a variety of high-speed communication applications. One of the applications of these involves making protective enclosures for antennas of microwave towers, air vehicles, weather radars, and underwater communication devices. Material performance, structural, thermal, and mechanical degradation are matters of concern as advanced wireless communication needs robust materials for radomes that can withstand mechanical and thermal stresses. These polymer composite radomes are installed externally on antennas and are exposed directly to ambient as well as severe conditions. In this research, epoxy resin was reinforced with a small amount of quartz fibers to yield an improved composite radome material compared to a pure epoxy composite with better thermal and mechanical properties. FTIR spectra, SEM morphology, dielectric constant (Ɛr) and dielectric loss (δ), thermal degradation (weight loss), and mechanical properties were determined. Compared to pure epoxy, the lowest values of Ɛr and δ were 3.26 and 0.021 with 30 wt.% quartz fibers in the composite, while 40% less weight loss was observed which shows its better thermal stability. The mechanical characteristics encompassing tensile and bending strength were improved by 42.8% and 48.3%. In high-speed communication applications, compared to a pure epoxy composite, adding only a small quantity of quartz fiber can improve the composite material’s dielectric performance, durability, and thermal and mechanical strength.
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