Copolymerization modification: improving the processability and thermal properties of phthalonitrile resins with novel comonomers

Abstract

Two novel tetrahydrophthalic anhydride end‐capped imide compounds (THAN and THBN) with high thermal stability were synthesized to promote the curing reaction of 1,3‐bis(3,4‐dicyanophenoxy)benzene (3BOCN), and to study the effects of comonomer structure on the curing behavior and thermal performance of phthalonitrile resins. The curing behaviors of THAN/3BOCN and THBN/3BOCN blends with various molar ratios were investigated using rheological analysis and differential scanning calorimetry, suggesting a wide processing window. Dynamic mechanical analysis and thermogravimetric analysis showed that the cured resins possessed high glass transition temperatures (> 500 °C), and superior thermal and long‐term thermo‐oxidative stabilities with weight retention of 95% ranging from about 544 to 558 °C in both nitrogen and air. All these results indicated that the processability and thermal properties of phthalonitrile resins could be improved further by modifying the structure of comonomer in this kind of curing system. © 2018 Society of Chemical Industry

New model phthalonitrile resin system based on self‐promoted curing reaction for exploring the mechanism of radical promoted‐polymerization effect

“…The thermal and thermal‐oxidative properties of Resins 1–4 were compared with the previously reported PN resins, as shown in Table . Among them, both A‐37 and Resins 1–4 are cured by radical promoted‐polymerization mechanism . It can be seen from the table that the Resins 1–4 and A‐37 have similar thermal properties.…”

“…Our recent work has indicated that the alicyclic mono‐imide moiety (MAIM) could promote the polymerization and simplify the reaction path of PN [1,3‐bis(3,4‐dicyanophenoxy)benzene (3BOCN)] by the radical process . The product structures of radical promoted‐polymerization effect were mainly composed of isoindoline, minor phthalocyanine, which was different with traditional curing systems, since there was no triazine formed, and almost no nitrile left .…”

“…In order to explore the problems left in the previous work, it is necessary to design a new model system for continuous research work. Previously, the mechanism study on radical promoted‐polymerization effect was based on the blending system (MAIN/CN1) of the alicyclic imide compounds and the PN compounds . There are some interfering factors in the system, such as diffusion control during the reaction process and volatility‐causing variations of components.…”

Polymerization mechanism of 4-APN and a new catalyst for phthalonitrile resin polymerization

“…At present, researchers basically believe that CN polymerization mainly produces triazine, isoindole and phthalocyanine rings, [31][32][33][34][35][36][37][38][39][40][41][42] does not produce small molecules, and gives the polymerization mechanism of forming the three heterocycles. However, this does not explain the experimental results in this paper very well.…”

Enhanced properties of phthalonitrile resins under lower curing temperature via complex curing agent

“…So far, several methods have been developed to improve the above problems, including design of new phthalonitrile resin precursors and curing agents . For example, Yang et al prepared two novel tetrahydrophthalic anhydride end‐capped imide compounds to promote the curing reaction of 1,3‐bis(3,4‐dicyanophenoxy)benzene and also studied the effects of comonomer structure on the curing behavior and thermal performance of phthalonitrile resins. Wang et al prepared a novel high temperature vinylpyridine‐based phthalonitrile polymer; the monomer exhibited a lower melting point (92°C), which allowed for a longer processing window (146°C) and enhanced the processability without compromising the thermal and oxidative stabilities.…”