| In the research,the polyurethane adhesive was modified by lignin blended, and the thermal oxidative aging and light aging, water resistance of lignin blended polyurethane adhesive were studied; The thermal degradation, light degradation and water degradation mechanisms of lignin blended polyurethane adhesive were studied.The lignin based polyester polyols were synthesized with corn straw lignin, and a series of lignin based polyurethane adhesives were prepared by a series of lignin based polyester polyols, and the thermal oxygen aging and light aging, water resistance performan of the lignin based polyurethane adhesives were studied. The main research contents are as follows:(1) The performance of corn straw lignin was analyzed. The results showed that the lignin was GSH type lignin, the number average molecular weight was 2733, the glass-transition temperature was 181℃, and the content of alcohol hydroxyl was 7.62%, and the content of phenolic hydroxyl was 3.64%.The lignin decomposition has two distinct phases of rapid decomposition, the first phase peak appears at 370℃～400℃, the sec-ond phase peak is 670℃～750℃.w/w0 from 10% to 50%, the activation energy was 56. 91kJ/mol～95.74kJ/mol by distributed activation energy model, and the thermal decompo-sition activation energy of lignin was 62.31kJ/mol ～101.76kJ/mol by Flynn-Wall-Ozawa equation.(2) The lignin blended polyurethane adhesives were prepared with different blending ratio of lignin, and the performance of lignin blended polyurethane adhesives were studied, the results showed that:lignin blended polyurethane adhesive with dibutyl tin dilaurate and triethylenediamine mixed catalyst, curing conditions for curing of 110℃ 3 hours was appropriate. In the series of lignin blended polyurethane adhesive, the room temperature shear strength of BLN-10 polyurethane adhesive reached the highest forl9.13MPa. The high temperature strength decline rate of BLN-5 polyurethane adhesive was the lowest. In 150℃ hot oxygen aging process of lignin blended polyurethane adhesives, the strength decline rate of BLN-20 lignin blend modified polyurethane adhesive was minimum. In 70℃ hot water aging process of lignin blended polyurethane adhesives, the strength decline rate of BLN-20 lignin blend modified polyurethane adhesive was the smallest. The lignin blend modified polyurethane adhesives thermal decomposition process was divided into two stages, the first stage decomposition temperature increased with the increase of lignin content,the second stage maximum decomposition temperature decreased with the increase of lignin content.The cross-linking degree of BLN-5 polyurethane adhesive was maximum for 5.3489×10-3mol/cm3.From the different temperature infrared spectrum and 150℃ hot oxygen aging infrared spectrum,the remnants of isocyanate were found.BLN-0 and BLN-20 two kinds of polyurethane adhesives in the first stage maximum decomposition temperature, the main gas component is C02,in the second stage maximum decomposition temperature, the main gas component is CH4. The isocyanate conversion rate of BLN-0 and BLN-5 polyurethane adhesive reaction was 16.5% and 9.5% respectively.The lignin blended polyurethane adhesive for thermal decomposition activation energy, the first phase thermal decomposition activation energy of BLN-20 polyurethane adhesive was the highest for 139.57 kJ/mol and the second phase thermal decomposition activation energy of BLN-15 polyurethane adhesive was the highest for 250.74 kJ/mol.(3) The lignin based polyester polyol synthesis highest temperature was 160℃. The maximum amount of lignin as the replacement of glycerol was 15%, the hydroxyl value and acid value of lignin based polyester polyol increases with lignin amount increase, crystallinity is decreased with lignin amount increase.(4) The series of lignin based polyurethane adhesives were prepared by lignin based polyester polyol and its performance were investigated.The results show that:BS-10 lignin based polyurethane adhesive shear strength at room temperature reached the highest for 22.62MPa. The 100℃ and 120℃ shear strength of lignin based polyurethane adhesive was more higher than the non lignin polyurethane adhesive. In 150℃ hot oxygen aging process of lignin based polyurethane adhesives, the shear strength decline rate of lignin based polyurethane adhesives were lower than that decline rate of non lignin polyurethane adhesive. In 70℃ hot water aging process of lignin based polyurethane adhesives, The strength decline rate of BS-5 and BS-10 polyurethane adhesive was less than that decline rate of lignin BS-0 polyurethane adhesive and BS-15 polyurethane adhesive surface C relative content of C=O groups from 8.03% dropped to7.69%.The lignin based polyurethane adhesive film after thermal aging, BS-15 polyurethane adhesive surface C elements relative content from 75.84% dropped to 73.17%,BS-0 polyurethane adhesive produced CO2 concentration in 277℃ and 424℃ two temperature greater, CH4 concentration was greater at 473℃,BS-15polyurethane adhesive produced CO2 concentration in 301℃ and 428℃ two temperature greater, CH4 concentration was larger at 470℃. The highest isocyanate conversion rate of BS-10 polyurethane adhesive reaction was 43.13%. The lignin based polyurethane adhesive for thermal decomposition activation energy, the first phase thermal decomposition activation energy of BS-15 polyurethane adhesive is the highest for 137.44 kJ/mol and the second phase thermal decomposition activation energy of BS-10 polyurethane adhesive is the highest for 244.50 kJ/mol. |
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