Efficient solid‐phase synthesis of acetylated lignin and a comparison of the properties of different modified lignins

Abstract

The chemical modification of lignin can greatly enhance its functionality and exploit its application areas. To avoid the difficulties of separation and environmental pollution in the traditional liquid-phase method, we prepared acetylated lignin by a mechanical-activation-assisted solid-phase synthesis (MASPS) technology with a customized stirring ball mill as a reactor and studied its structure and properties. Ultraviolet-visible analysis showed that the degree of esterification (DE) of the acetylated lignin produced by the MASPS technique was 77.59%, whereas the DEs of those produced by traditional liquid-phase synthesis (LPS) and thermal solid-phase synthesis (TSPS) were only 42.29 and 27.54%, respectively. Fourier transform infrared spectroscopy and NMR analyses indicated that both phenolic hydroxyls and aliphatic hydroxyls participated in the reaction, and the reactivity of the phenolic hydroxyls was higher than that of the aliphatic hydroxyl groups. The acetylation of aliphatic hydroxyl mainly happened at the g of arylglycerol-b-aryl ether (b-O-4). Scanning electron microscopy analysis showed that the acetylated lignins prepared by MASPS and TSPS were irregular blocks with coarse surfaces and loose structures, whereas the lignin prepared by LPS consisted mostly of regular balls with a smooth surface and a compact structure. Differential scanning calorimetry and thermogravimetric analyses indicated that the glass-transition temperatures and thermal stability of the acetylated lignin increased by orders with the processing techniques of MASPS, TSPS, and LPS. MASPS integrated the activation and reaction in the same equipment without the use of a solvent and showed advantages of a high efficiency, environmental protection, and easy operation. V C 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44276.

Effect of lignin esters on improving the thermal properties of poly(vinyl chloride)

“…PVC resin (SG‐5) was supplied by Guangzhou Linsheng Chemical Co., Ltd. (China). Enzymatic hydrolysis L, kindly supplied by Ji'nan Yang Hai Chemical Co., Ltd. (China), was used as raw L. The L esters were prepared according to a process reported in our previous article …”

“…Enzymatic hydrolysis L, kindly supplied by Ji'nan Yang Hai Chemical Co., Ltd. (China), was used as raw L. The L esters were prepared according to a process reported in our previous article. 22 Preparation of the L Ester-PVC Plates PVC and L ester in proportion (85:15) were put into a highspeed mixer for intensive mixing. The uniform mixture was added to a homemade mold with dimensions of 100 × 100 × 10 mm 3 and pressed with a XLB25-D vulcanizing press (Zhejiang Shuangli Huzhou Stars Rubber Machinery Manufacturing Co., Ltd., China).…”

“…We examined the preparation of activated L and L esters by a mechanical-activation-assisted solid-phase synthesis technology and their properties in our previous studies. 21,22 We found that the structure of L was affected by mechanical activation, esterification, and the preparation method, synthetic conditions, and esterifying agent. Herein, to learn about the effect of esterification on the thermal stabilization of L for PVC, the thermal stabilities and mechanical properties of different L ester-PVC plates and the action mechanism were studied.…”

“…We examined the preparation of activated L and L esters by a mechanical‐activation‐assisted solid‐phase synthesis technology and their properties in our previous studies . We found that the structure of L was affected by mechanical activation, esterification, and the preparation method, synthetic conditions, and esterifying agent.…”

Esterification mechanism of lignin with different catalysts based on lignin model compounds by mechanical activation-assisted solid-phase synthesis

“…So, some new preparation methods such as supercritical carbon dioxide as solvent, microwave, and reactive extrusion have been paid close attention. [18][19][20] In order to strengthen the activity of lignin and avoid the solvent pollution in liquid synthesis and tedious collection of the product, an environmentally friendly and effective mechanical activation-assisted solid-phase synthesis (MASPS) technology was adopted to prepare acetylated lignin in our previous work, 21 and the esterication mechanism of lignin was discussed. However, it is difficult to get comprehensive information of the mechanism due to its complicated structure, and more feasible ways are required to further investigate the esterication mechanism of lignin.…”