Developing non‐halogen and non‐phosphorous flame retardant bismaleimide resin with high thermal resistance and high toughness through building crosslinked network with Schiff base structure

Abstract

High flame retardancy has become a necessary property for heat‐resistant thermosetting resins (HRTRs) in many cutting‐edge fields. However, developing HRTRs with excellent flame retardancy through sustainable strategy (halogen‐free and phosphorus‐free) is still a great challenge. Herein, a novel halogen‐free and phosphorus‐free allyl compound with Schiff base structure (PDM) was efficiently synthesized from biobased protocatechualdehyde, and then four new flame retarding bismaleimide resins (BP1, BP2, BP3, BP4) were developed by building crosslinked network with PDM. The molar ratio of allyl to imide has a significant effect on performances of BP resins, BP2 resin (its molar ratio of allyl to imide is 0.86) shows the best integrated performances, it has not only high impact strength (14.37 ± 1.1 kJ/m2), but also the highest glass transition temperature (343.5°C) and limiting oxygen index (36.4%) among halogen‐free and phosphorus‐free flame retarding bismaleimide resins reported so far. The investigation on flame retardant mechanism of BP resins shows that the mechanism includes condensed‐phase and gas‐phase flame retarding effects.

Low dielectric constant and highly intrinsic thermal conductivity fluorine‐containing epoxy resins with ordered liquid crystal structures

“…Besides, TFSAEy/DDM has excellent flame retardance (Figure S5), and the corresponding limiting oxygen index (LOI) is 27.8%, 16.8% higher than that of E‐51/DDM (23.8%), which is also higher than that of E‐51/TFSA (26.7%), E‐51/TFGA (25.3%), and TFGAEy/DDM (27.1%). This is because the molecular structure of TFSAEy contains a large number of fluorinated groups, which can be beneficial to shielding the oxygen transport by generating the hydrogen fluoride 65 . And the π–π conjugation of biphenyl units and the formation of an ordered crystalline structure in TFSAEy/DDM can effectively prevent heat transfer during combustion, which is also beneficial to further improving flame‐retardant properties 66 .…”

“…This is because the molecular structure of TFSAEy contains a large number of fluorinated groups, which can be beneficial to shielding the oxygen transport by generating the hydrogen fluoride. 65 And the π-π conjugation of biphenyl units and the formation of an ordered crystalline structure in TFSAEy/DDM can effectively prevent heat transfer during combustion, which is also beneficial to further improving flame-retardant properties. 66 In conclusion, TFSAEy/DDM cured resins have the optimal comprehensive properties, such as a low ε value, highly intrinsic λ value, excellent mechanical properties, outstanding heat resistance, wear resistance, and flame retardancy, which would replace conventional epoxy resins in the high-heating electronic component packaging and printed circuit boards.…”

Bismaleimide resin co‐modified by allyl ether of resveratrol and allyl ether of eugenol‐grafted polysiloxane with enhanced toughness, heat resistance, and flame retardancy

“…Based on our previous studies, the curing of BAPA resin should contain the end reaction between the allyl groups of both AER and PMES-Ally and maleimide groups taking place at the early stage of curing, Claisen rearrangement of AER units, D-A reaction, and self-polymerization of maleimide. [24][25][26][27][28][29][30] The possible network structure of the cured BAPA resin is illustrated in Scheme 2.…”