Synthesis and characterization of isocyanate-functionalized hyperbranched polyurethane and its cocuring with benzoxazine

Abstract

In the study, isocyanate‐functionalized hyperbranched polyurethane (HPUNCO) with a degree of branch of 35.2% was synthesized via an A2 + B3 method. This novel HPUNCO was used to fabricate a blend system with hydroxyl groups bearing benzoxazine precursor (BZOH) to investigate its effective on the thermal properties of BZOH. The structure of HPUNCO is confirmed by Fourier transform infrared (FTIR) and nuclear magnetic resonance spectroscopy. The curing behavior of the reactive HPUNCO/BZOH blend is investigated via differential scanning calorimetry and FTIR analyses. HPUNCO/BZOH blend indicates two successively broad exotherm peaks centered at 132 and 204°C, respectively, which is obviously different from that of BZOH with one broad peak centered at 206°C. Thermogravimetric analysis results confirmed that the thermal stability was enhanced and the char yield of BZOH was increased from 34.3 to 43.2% by cocuring with 10 wt% HPUNCO. POLYM. ENG. SCI., 55:604–613, 2015. © 2014 Society of Plastics Engineers

Development and characterization of 1,1-bis(3-methyl-4-hydroxyphenyl) cyclohexane-based benzoxazine and cyanate ester hybrid polymer matrices: Thermal and morphological properties

“…Although so many investigations are being continued on benzoxazine–cyanate ester blends, 27 –30 we attempted on 1,1-bis(3-methyl-4-hydroxyphenyl)cyclohexane-based benzoxazine and cyanate ester hybrid polymer matrices by the way how its compatibility influences thermal and morphological properties of these hybrid polymer matrices. The benzoxazine–cyanate ester hybrid polymer matrices were prepared via in situ polymerization and their molecular structure, cure behavior, T g , thermal stability, char yield, flame resistance, and morphological properties were studied by appropriate analytical techniques.…”

Synthesis and Thermal Curing of Benzoxazine Functionalized Polyurethanes

“…Hence, a different approach using blocked isocyanates was described. The isocyanate functionality was converted to thermally labile urethanes by use of bisphenol A, nitrophenol, or butanone oxime . This approach renders the BOX/PU blend more stable, and depending on the actual thermal stability of these urethanes and the applied polymerization temperature the urethane bonds can dissociate to regenerate free isocyanates.…”

“…The isocyanate functionality was converted to thermally labile urethanes by use of bisphenol A, 16 nitrophenol, 17 or butanone oxime. 18 This approach renders the BOX/PU blend more stable, and depending on the actual thermal stability of these urethanes and the applied polymer- ization temperature the urethane bonds can dissociate to regenerate free isocyanates. Unfortunately, the blocking agents, which are often volatile organic compound (VOC), may be released from the material.…”