Synthesis and characterization of low temperature curable phthalonitrile containing propargyl- novolacs through click-chemistry approach

Sreelal, Niranjana; Sunitha, K.; Balachandran, Nisha; Vijayalekshmi, K. P.; Chandran, M. Satheesh

doi:10.1007/s10965-022-03207-y

Cited by 3 publications

(1 citation statement)

References 47 publications

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“…Though these materials are excellent shields of EM waves, these have high density, are less flexible, and are prone to corrosion. − These drawbacks lead to the quest of newer materials, especially polymeric materials owing to their desirable features including lightweight, low cost, easy shaping, tunable conductivity, and shielding mechanism by absorption instead of reflection. − For the shielding material to interact with the electromagnetic radiation and be able to capture and disperse the external signals, it should possess either magnetic or electric dipoles. , Following collision, the electromagnetic radiation is converted into heat by means of its interaction with magnetic or electric dipoles. Polymers with inherent nitrogen content can engage in dipole interactions with electromagnetic waves by forming active spots on their surface that are either electron-rich or electron-deficient which can improve the EMI shielding performance. , Phthalonitriles (PN), a high-performance class of resins, have remarkable mechanical properties and exceptional flame resistance. − The outstanding thermal properties and high nitrogen content of PN makes them potential materials for EMI shielding applications. Another significant family of high-performance polymers with superior mechanical properties, high nitrogen content, and outstanding processability is cyanate ester (CE) resins. − It is expected that the formation of nitrogen-containing network in the cured resin blend comprising polycyanurate and polyphthalonitrile can influence the EMI shielding properties significantly.…”

Section: Introductionmentioning

confidence: 99%

Phthalonitrile and Cyanate Ester-Based Carbon Foams for Effective Electromagnetic Interference Shielding Applications

Sreelal,

Saraswathy,

Thomas

et al. 2024

ACS Appl. Eng. Mater.

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Lightweight materials with high electromagnetic interference (EMI) shielding effectiveness (SE) are greatly sought to address the increasing electromagnetic menace, especially in aerospace domain. In this work, lightweight foam-based EMI shielding materials are realized from phthalonitrile (PN), cyanate ester (CE), and a blend of PN−CE resin matrices by infusing into a rigid graphitic board (RGB) template. The low-density (0.3 and 0.4 g/cm 3 ) carbon foams have achieved good electrical conductivity of 0.45−0.62 S/cm, high total EMI shielding efficiency of ∼72−78 dB, specific EMI shielding of 75−195 dB, and thickness-normalized EMI shielding of 150−390 dB, indicating the excellent shielding of incident EM waves.The heterocyclic cross-linked networks formed from the ring formation polymerization of nitrile and cyano moieties are instrumental in conferring high EMI SE to the carbon foams. The primary EMI shielding mechanism is determined to be absorption. A thermal degradation mechanism proposed further confirms the formation of a hybrid graphitic structure conducive for high EMI SE. The polarization effects brought on by the built-in nitrogen-containing cured framework also contribute to the shielding efficiency. These lightweight carbon foams are prospective EMI shielding materials expected to be useful in aerospace, aeronautical, and high-end industrial fields in the future.

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Section: Introductionmentioning

confidence: 99%

Phthalonitrile and Cyanate Ester-Based Carbon Foams for Effective Electromagnetic Interference Shielding Applications

Sreelal,

Saraswathy,

Thomas

et al. 2024

ACS Appl. Eng. Mater.

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Aromatic nitrile resins with improved processability and thermal properties prepared by collaborative design of structure and blending strategy

Yang,

Zhu,

Zhou

et al. 2024

European Polymer Journal

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Fast-Processable Non-Flammable Phthalonitrile-Modified Novolac/Carbon and Glass Fiber Composites

et al. 2022

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Phthalonitrile resins (PN) are known for their incredible heat resistance and at the same time poor processability. Common curing cycle of the PN includes dozens hours of heating at temperatures up to 375 °C. This work was aimed at reducing processing time of phthalonitrile resin, and with this purpose, a novolac oligomer with hydroxyl groups fully substituted by phthalonitrile moieties was synthesized with a quantitative yield. Formation of the reaction byproducts was investigated depending on the synthesis conditions. The product was characterized by 1H NMR and FT-IR. Curing of the resins with the addition of different amounts of novolac phenolic as curing agent (25, 50 and 75 wt.%) was studied by rheological and DSC experiments. Based on these data, a curing program was developed for the further thermosets’ investigation: hot-pressing at 220 °C and 1.7 MPa for 20 min. TGA showed the highest thermal stability of the resin with 25 wt.% of novolac (T5% = 430 °C). The post-curing program was developed by the use of DMA with different heating rates and holding for various times at 280 or 300 °C (heating rate 0.5 °C/min). Carbon and glass fiber plastic laminates were fabricated via hot-pressing of prepregs with Tg’s above 300 °C. Microcracks were formed in the CFRP, but void-free GFRP were fabricated and demonstrated superior mechanical properties (ILSS up to 86 MPa; compressive strength up to 620 MPa; flexural strength up to 946 MPa). Finally, flammability tests showed that the composite was extinguished in less than 5 s after the flame source was removed, so the material can be classified as V-0 according to the UL94 ratings. For the first time, fast-curing phthalonitrile prepregs were presented. The hot-pressing cycle of 20 min with 150 min free-standing post-curing yielded composites with the unique properties. The combination of mechanical properties, scale-up suitable fast-processing and inflammability makes the presented materials prospective for applications in the electric vehicle industries, fast train construction and the aerospace industry.

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Synthesis and characterization of low temperature curable phthalonitrile containing propargyl- novolacs through click-chemistry approach

Cited by 3 publications

References 47 publications

Phthalonitrile and Cyanate Ester-Based Carbon Foams for Effective Electromagnetic Interference Shielding Applications

Phthalonitrile and Cyanate Ester-Based Carbon Foams for Effective Electromagnetic Interference Shielding Applications

Aromatic nitrile resins with improved processability and thermal properties prepared by collaborative design of structure and blending strategy

Fast-Processable Non-Flammable Phthalonitrile-Modified Novolac/Carbon and Glass Fiber Composites

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