Co-reporter:Chao Li, Qichao Ran, Rongqi Zhu and Yi Gu
RSC Advances 2015 vol. 5(Issue 29) pp:22593-22600
Publication Date(Web):18 Feb 2015
DOI:10.1039/C5RA00350D
A cured product of aldehyde-functional benzoxazine has good heat-resistant performance. The thermal degradation process of this polybenzoxazine was actively studied by TGA-FTIR and Py-GC/MS. The temperature range of pyrolysis and the major products were determined by TGA-FTIR. A stepwise-temperature testing method based on Py-GC/MS was employed to identify the structures and contents of the pyrolysis products at different temperature stages. Transformation and chemical structures of the polymer bulk during the pyrolysis process were speculated. The results showed that the reactions of the aldehyde groups can form special crosslinking structures which effectively prevent the release of phenols during the pyrolysis process. Additionally, benzophenone compounds and carbon monoxide were detected.
Co-reporter:Xiaodan Li, Xiaoyong Luo, Ming Liu, Qichao Ran, Yi Gu
Materials Chemistry and Physics 2014 Volume 148(1–2) pp:328-334
Publication Date(Web):14 November 2014
DOI:10.1016/j.matchemphys.2014.07.051
•Two model compounds, PA and s-PA, were successfully synthesized and purificated.•There is no phenolic hydroxyl in the final ring-opened structures of s-PA.•Compared with PA, s-PA also can catalyze the polymerization of BADCy.•The main catalytic process is caused by the oxygen anion.•The catalytic effect from the phenolic hydroxyl is a secondary factor.Two model compounds, 3-Phenyl-3,4-dihydro-2H-1,3-benzoxazine (PA) and 6,8-dimethyl-3-(2,4,6-trimethyl-phenyl)-3,4-dihydro-2H-1,3-benzoxazine (s-PA), were successfully synthesized and purificated. Compared with PA, s-PA also catalyzed the polymerization of BADCy even though there was no phenolic hydroxyl in its final ring-opened structures. It was confirmed that the real mechanism of benzoxazine catalyzing the polymerization of cyanate ester is the nucleophilic addition reaction of the oxygen anion on ring-opened benzoxazine to the positively charged carbon atom on cyano group. The catalytic effect also contains the contribution from the phenolic hydroxyl, but it is a secondary factor.
Co-reporter:Huachuan Zhang;Min Li;Yuyuan Deng;Chengxi Zhang;Qichao Ran;Yi Gu
Journal of Applied Polymer Science 2014 Volume 131( Issue 19) pp:
Publication Date(Web):
DOI:10.1002/app.40823
ABSTRACT
In this article, a kind of styrylpyridine-containing polybenzoxazine was obtained via the Knoevenagel reaction between benzaldehyde and methylpyridine groups. The benzoxazine monomer (MPBC) containing the benzaldehyde and methylpyridine groups was synthesized firstly and its structure was characterized by Fourier transform infrared (FTIR) spectra, 1H NMR and 13C NMR. With the aid of differential scanning calorimetry, FTIR, and photoluminescent tests, the interesting curing behaviors were probed. The results showed that the ring-opening polymerization occurred at lower temperature, and the Knoevenagel reaction further took place at elevated temperature. The amine and phenol moieties were bonded together to form the styrylpyridine structure. Due to these special crosslinking structures, the corresponding polybenzoxazine exhibited excellent thermal stability, and had a special high char yield of 74.5%. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40823.
Co-reporter:Pei Zhao;Xiaomin Liang;Jie Chen;Qichao Ran;Yi Gu
Journal of Applied Polymer Science 2013 Volume 128( Issue 5) pp:2865-2874
Publication Date(Web):
DOI:10.1002/app.38459
Abstract
Polymer blends of polybenzoxazine (PBZ)/poly(ether imide) (PEI) were prepared by the in situ curing reaction of benzoxazine (BZ) resin in the presence of PEI. Phase separation induced by the polymerization of BZ resin was observed. The rheological behaviors, morphologies, and their evolution process of BZ/PEI blends were investigated by rheometer and scanning electron microscope. Phase separation that took place at the early stage of the curing reaction effectively reduced the dilution effect of PEI. Fourier transform infrared (FTIR) results suggested that hydrogen bonds between PBZ and PEI existed during the whole curing process, although weakened with phase separation. The decrease of isoconversion activation energy indicated that the polymerization of BZ resin was facilitated in the presence of such kind of hydrogen-bonding interactions. By changing the weight fraction of PEI, extensive phase separation was obtained in PBZ blends with 5 and 20 wt % of PEI, in which systems, the crosslinking density and glass transition temperature (Tg) of PBZ-rich phase were greatly improved compared to this single PBZ system. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Co-reporter:Hongyuan Wang;Pei Zhao;Hong Ling;Qichao Ran;Yi Gu
Journal of Applied Polymer Science 2013 Volume 127( Issue 3) pp:2169-2175
Publication Date(Web):
DOI:10.1002/app.37778
Abstract
A ternary blend (BEM) of benzoxazine (BA-a), epoxy resin (E44), and imidazole (M) was prepared to study the effect of different curing cycles on curing reactions and properties of cured resins. Reactivity of two binary blends, E44 and BA-a, with the catalyst M, was first investigated based on the curing kinetics. Results suggest that E44/M has lower reaction activation energy than BA-a/M meaning the reaction of E44/M easily proceeds. To further figure out the sequences of the curing reactions of E44, BA-a, and M in BEM, the curing behaviors of three BEM gels at 80, 140, and 180°C (defined as BEM-80g, BEM-140g, and BEM-180g) were studied by DSC and FTIR techniques. For BEM-80g, E44/M cured before BA-a/M. For BEM-180g, both curing reactions occurred simultaneously and the copolymerization of BA-a and E44 was promoted. The crosslinked structures of cured BEM with different initial curing temperatures were strongly influenced by the reaction sequences. The Tgs, flexural properties and thermal stability of the copolymers with different curing cycles were compared. Good performance of this ternary system can be obtained by choosing suitable curing cycles. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Co-reporter:Zhi Wang;Qichao Ran;Rongqi Zhu ;Yi Gu
Journal of Applied Polymer Science 2013 Volume 129( Issue 3) pp:1124-1130
Publication Date(Web):
DOI:10.1002/app.38790
Abstract
A blend of bisphenol-A based benzoxazine (BA-a)/N, N′-(2, 2, 4-Trimethylhexane-1, 6-diyl) dimaleimide (TBMI) with the ratio of 1:1 was prepared and its curing behaviors were studied by differential scanning calorimetry (DSC), Fourier Transform Infrared (FTIR). The curing mechanism was proposed based on the semiquantitative analysis from FTIR spectra. The model compound was used to study the catalysis effect of BA-a on the curing reaction of TBMI. It was found the curing reactions of BA-a and TBMI not only proceeded simultaneously, but their coreactions also occurred. The research further indicated that negative oxygen ions from ring opening of benzoxazine mainly promoted the polymerization of maleimide groups, even though the amine group of benzoxazine had a positive effect on the reaction of maleimide groups. Besides, BA-a and TBMI blends showed improved thermal properties based on the results from DMA and TGA. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Co-reporter:Pei Zhao;Qian Zhou;Xin Liu;Rongqi Zhu;Qichao Ran;Yi Gu
Polymer Journal 2013 45(6) pp:637-644
Publication Date(Web):2012-10-17
DOI:10.1038/pj.2012.179
Enlarging dynamic asymmetry in situ by controlling the polymerization sequence is known to be a good way to obtain phase separation structures in benzoxazine (BZ)/epoxy resin (ER) blending systems. In this paper, the possible reactions in BZ/ER blends were studied using model components. The results indicated that once phenolic hydroxyl groups (OH) were produced by the polymerization of BZ resin, the copolymerization between BZ and ER resin was unavoidable, which was unfavorable for the phase separation of the BZ/ER system. If ER could polymerize before BZ, the copolymerization between BZ and ER is expected to be suppressed by the lack of phenolic OH, and the dynamic asymmetry between ER and BZ could thus be enlarged, both of which are favorable for phase separation. In the following studies, a series of ER resins having different molecular weights (Mn) were used to study the possibility of phase separation in the BZ/ER systems. The turbidity observation, dynamic mechanical analysis and scanning election microscope experiments indicated that if the Mn of ER 4370 g mol−1, phase separation could take place with the polymerization of BZ resin and different morphologies could be observed by varying the ER content.
Co-reporter:Zhi Wang, Jiacheng Zhao, Qichao Ran, Rongqi Zhu, Yi Gu
Reactive and Functional Polymers 2013 73(4) pp: 668-673
Publication Date(Web):April 2013
DOI:10.1016/j.reactfunctpolym.2013.01.015
Co-reporter:Qi-Chao Ran, Nian Gao, Yi Gu
Polymer Degradation and Stability 2011 Volume 96(Issue 9) pp:1610-1615
Publication Date(Web):September 2011
DOI:10.1016/j.polymdegradstab.2011.06.002
Lanthanum chloride (LaCl3) was incorporated into five kinds of benzoxazines by different preparation methods. The thermal stability and the structures of polybenzoxazines were characterized by thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. The evolved gases from the degradation process of polybenzoxazines were analyzed by FTIR. The results showed that the thermal stability and char yields of three kinds of polybenzoxazines containing LaCl3 can be improved obviously. LaCl3 has an important effect on the polymerization reactions of benzoxazines. More stable arylamine Mannich bridges were observed in the chemical structures of the polybenzoxazines. It is these structures that can effectively retard the volatilization of aniline derivatives and result in the improvement of the thermal stability of the polybenzoxazines.
