[8]
MDI is analytical reagent from BASF Chemical Co. Ltd, Chongqing, triethylamine and ethanol are both analytical reagents from Tianjin Kermel Chemical Reagent Co., Ltd, P. R. China. The main apparatuses are Thermo electron corporation AVATAR 330 FT-IR (USA), Perkinelmer Thermogravimetric Analyzer Pyris6 TGA (USA) and WRS-1B Digital melting point apparatus. Reagents including 10.0 g MDI (0.04 mol) and 0.1 g Catalyst triethylamine (1%wt) were added into a 250 mL three necked flask, and then 37.5 g (0.096 mol) MEMAA was added in. The reaction was progressed according to reaction temperature 75 ˚C and reacted for 2 h. Then, the reaction mixture was removed into 100 mL ethanol/ice water (1:1 by volume) to crystallize. The crystal was obtained by pump filter and washed thrice by 90 mL ice water. Finally, TOBBDHMI in light yellow was obtained after vacuum dried with melting range 186.6 ˚C ~189.3 ˚C and yield 82.4%. Thermal stability of the product was studied by Thermogravimetric Analyzer, programmed temperature rising method was applied in a dynamic nitrogen flow of 20 mL/min, at heating rate of 10˚C /min and from room temperature to 600 ˚C. The infrared spectrum of the product was obtained by KBr coating method. The melting range was tested by Digital melting point apparatus. Results and Discussion The infrared spectrum of TOBBDHMI was shown in Fig.2. The IR spectrum showed that stretching vibration characteristic absorption peaks of 3039.28 cm-1 from =CH, 2932.93 cm-1 and 2853.88 cm-1 from C-H (CH2 and CH3), 1777.20 cm-1 from C=O (ester), 1699.83 cm-1 from C=O (acid amide), 1598.75 cm-1 and 1500.00 cm-1 from C=C (benzene ring), 1309.95 cm-1 from C-N (aryl), 1053.03 cm-1 from C-N (alkyl), and bending vibration characteristic absorption peaks of 1451.74 cm-1 from CH2 appeared. The IR spectrum results confirmed that the target product TOBBDHMI was successfully synthesized from MEMAA and MDI by certain reaction. Fig.3 TG and DTG curves of TOBBDHMI Fig.2 Infrared spectrum of TOBBDHMI The TG and DTG curves of TOBBDHMI were shown in Fig.3. The initial decomposition temperature of TOBBDHMI was 270 ˚C, final decomposition temperature was 510˚C, decomposition rate was the highest at 370˚C, weight loss 15% was at 309˚C, weight loss 30% was at 360℃, weight loss 50% was at 410˚C. Thermogravimetric analysis indicated that the target product TOBBDHMI had good heat resistance. Fig.5 Effect of material ratio of MEMAA to MDI on the yield of TOBBDHMI (catalyst 1.0%, reaction temperature 75˚C, reaction time 2 h) Fig.4 Effect of the catalyst dosage on the yield of TOBBDHMI (material ratio of MEMAA to MDI 2.4:1, reaction temperature 75˚C, reaction time 2 h) Fig.4 showed the effect of the catalyst dosage on the yield of TOBBDHMI. As the dosage of catalyst triethylamine changed from 0.6% to 1.0%, the yield of TOBBDHMI increased along with the increase of catalyst dosage. However, when the catalyst dosage was higher than 1.0%, the yield decreased, suggesting that too much catalyst dosage is not suitable for TOBBDHMI synthesis. Therefore, the optimal catalyst triethylamine dosage is 1.0%. The effect of material ratio of MEMAA to MDI on the yield of TOBBDHMI was showed in Fig.5. When the material ratio of MEMAA to MDI increased from 2.0:1 to 2.4:1, the yield of TOBBDHMI increased as the material ratio increased. Whereas, when the ratio was higher than 2.4:1.0, the yield basically remained unchanged. Therefore, the optimal material ratio of MEMAA to MDI suitable for TOBBDHMI synthesis is 2.4:1. Fig.6 Effect of reaction temperature on the yield of TOBBDHMI (catalyst dosage 1.0%, material ratio of MEMAA to MDI 2.4:1, reaction time 2 h) Fig.7 Effect of reaction time on the yield of TOBBDHMI (catalyst dosage 1.0%, material ratio of MEMAA to MDI 2.4:1, reaction temperature 2 h) The effects of reaction temperature and reaction time on the yield of TOBBDHMI were also investigated (Fig.6 and Fig.7, respectively). It's obvious to draw that the optimal reaction temperature for TOBBDHMI synthesis is 75˚C and optimal reaction time for TOBBDHMI synthesis is 2 h. Conclusions Tung oil, a Chinese renewable biomass resource, was introduced into bismaleimide structure to form Tung oil-based bi-dihydrogen-maleimide (TOBBDHMI) which showed excellent heat resistance. The target product is potential to be used alone or with other bismaleimide monomers to improve polymeric materials' heat resistance and/or mechanical properties. Acknowledgement This work is supported by the grant from the Key Project of Science and Technology Development Plan of Changsha city, China (No. K1009015-11) and the grant from the Special Scientific Project for Forestry Public Industry of State Ministry of Science and Technology of China (No. 200904023). References
Google Scholar
