Study On Lignin And Its Composites In The Application Of Epoxy Resin Adhesive

With the fossil resource shortage and serious environment pollution, replacing chemical raw materials with renewable resources is an important topic to keep sustainable development. Lignin as biodegradable materials and biological base material has received more and more people’s attention all over the world. Lignin contains various functional groups, but it could hardly participate in each reaction with the lower reactivity. In this thesis, depolymerized lignin by using industrial lignin as the raw material reduced the relative molecular mass and increased the activity of lignin. The silica/lignin composites and depolymerized lignin/silicate composites were obtained by using rice husk as raw materials. The performances of epoxy resin with above materials to replace bisphenol A were investigated, which good results had been achieved.1. The depolymerized lignin instead of bisphenol A directly participated in the synthesis of epoxy resin with Na OH as catalyst. The best depolymerized condition was 15 wt% Na OH for 1.5 h at 250 o C, and the phenol hydroxyl content of lignin was0.5% to 2.11% by the undepolymerization and depolymerization. The epoxy value of epoxy resin replacing 20 wt % bisphenol A was 0.37(undepolymerization) and 0.82(depolymerization), respectively. Comparing with the epoxy value of neat epoxy resin(0.73), the change was obvious. The tensile strengths of lignin based epoxy resin were1.16 MPa(undepolymerization) and 2.66 MPa(depolymerization), respectively. The biggest tensile strength was 2.18 MPa, which was greater than that of the neat epoxy resin. At the same time, the thermal decomposition temperature is higher than that of neat epoxy resin for 18 o C.2. Different ratios of lignin/silica composites were obtained using H2SO4 to adjust p H of lignin/silicate solution. When p H = 3.5, the ratio of lignin and silicaclosed to 1:1, and the phenol hydroxyl content of lignin in the composites was 3.36%,the epoxy value and tensile strength of epoxy resin instead of 20 wt % bisphenol A were 0.831 and 2.68 MPa, which were 114% and 123% of neat epoxy resin.3. We in situ synthesized epoxy resin by Na OH as catalyst to depolymerize lignin/silicate extracted from rice husk. When the ratio of epichlorohydrin and bisphenol A was 9:1, and the content of lignin/silicate solution was 35 wt%, the epoxy value for the synthesis of epoxy resin was 1.42, and the tensile strength of that was3.98 MPa, respectively, which was 194% and 183% of the neat epoxy resin. At the same time, the epoxy value and tensile strength of without depolymerized lignin/silica based epoxy resin were 0.64 and 1.92 MPa, respectively.Our country is an agricultural country, and rice husk contains abundant resources including 40 wt % of lignin and silica. Studying its development as a substitute instead of bisphenol A for synthesis of epoxy resin had important research value and industrialization development prospects.