Microstructure evolution of ammonia‐catalyzed phenolic resin during thermooxidative aging

Abstract

The thermooxidative aging of ammoniacatalyzed phenolic resin for 30 days at 60-170 C was investigated in this article. The aging mechanism and thermal properties of the phenolic resin during thermooxidative aging were described by thermogravimetry (TG)-Fourier transform infrared (FTIR) spectroscopy, attenuated total reflectance (ATR)-FTIR spectroscopy, and dynamic mechanical thermal analysis. The results show that the CAN bond decomposed into ammonia and the dehydration condensation between the residual hydroxyl groups occurred during the thermooxidative aging. Because of the presence of oxygen, the methylene bridges were oxidized into carbonyl groups. After aging for 30 days, the mass loss ratio reached 4.50%. The results of weight change at high temperatures coincided with the results of TG-FTIR spectroscopy and ATR-FTIR spectroscopy. The glass-transition temperature (T g ) increased from 240 to 312 C after thermooxidative aging for 30 days, which revealed the postcuring of phenolic resins. In addition, an empirical equation between the weight change ratio and T g was obtained.

Yolk–Shell Fe3O4@Void@N‐Carbon Nanostructures Based on One‐Step Deposition of SiO2 and Resorcinol‐3‐Aminophenol‐Formaldehyde (R‐APF) Cocondensed Resin Dual Layers onto Fe3O4 Nanoclusters

“…[ 42,43 ] In addition, compared with the infrared spectra of Fe 3 O 4 @SiO 2 @R‐APF nanospheres and Fe 3 O 4 @SiO 2 @N‐Carbon nanospheres, that of the Fe 3 O 4 @Void@N‐Carbon nanospheres (Figure S2c, Supporting Information) preserves a vibrational absorption peak of the substituted benzene ring skeleton at 1620 and 1458 cm −1 . [ 44 ] However, the characteristic peaks [ 45–47 ] of SiO 2 at 800, 954, and 1100 cm −1 substantially disappeared, consistent with TEM results of the removal of the SiO 2 layer (Figure 1g).…”

Nitrogen‐Enriched Fe3O4@Carbon Nanospheres Derived from Fe3O4@3‐Aminophenol/Formaldehyde Resin Nanospheres Based on a Facile Hydrothermal Strategy: Towards a Robust Catalyst Scaffold for Platinum Nanocrystals

“…Ammonia hydroxide plays two significant roles in this synthesis step. On the one hand, 3-aminophenolm onomers and formaldehyde react to form numerous intermediates of benzoxazine, phenolic, and other oligomers [19] with ammonium hydroxide as ac atalyst. On the other hand, witht he strong interaction between NH 4 + ions and À COO À on the surface of Fe 3 O 4 /PAA nanoclusters, the NH 4 + ions are absorbedo utside the nanoclusters, and thus the negatively chargedm agnetic nanospheres turn out to be positive.…”

Microstructure evolution of SW/EPN composites during hot air aging

“…Methylene in EPN may be oxidized to carbonyl after thermal air aging . Here, the band near 1650 cm −1 refers to the CO in diphenylketone and quinone.…”

“…The phenomenon implies that the decomposition of diphenylketone occurs at higher aging temperatures. Diphenylketone decomposes and then be oxidized to quinone, acids, or esters . The possible reaction in soft segment of EPN is shown in Scheme A.…”