Production of Epoxy Resin Thermoset Composite Reinforced With Epoxidized Kraft Lignin From Acacia Mangium Black Liquor

Author : Ong, Vynce Gracielyn Quebrado
Major Adviser : Manalo, Ronniel D.
Committee Members : Sanchez, Denise Ester S.; Migo-Sumagang, Maria Victoria P.; Daracan, Vivian C.
Year : 2019
Month : June
Type : Thesis
Degree: BS
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Abstract

This study aimed to produce epoxy resin thermoset composite reinforced with epoxidized lignin. Kraft lignin from Acacia mangium black liquor was extracted by addition of 4% H2SO4.until the pH was ~2. Extraction was done at 30 °C and 75 °C. The lignin was epoxidized using poly(ethylene glyol) diglycidyl (PEGDE) at various lignin:PEGDE ratios. Conditions which resulted to either the highest yield or epoxy index was used for mass production. Chemical changes were determined using Fourier Transform Infrared Spectroscopy (FTIR). The thermal transitions of the raw and modified lignin were monitored using Differential Scanning Calorimetry (DSC). Epoxidized lignin was added to the epoxy resin at different amounts. The flexural strength and water absorption were then determined. Higher yield of 91.22% when lignin is allowed to precipitate at 30 °C was observed. The yield increased with increasing lignin:PEGDE ratio. On the other hand, the highest epoxy indexed at 0.41 was obtained with the lowest ratio. A prominent peak at 1038 cm-1 and numerous peaks between 1630 cm-1 to 1900 cm-1 on wood chip FTIR spectra indicates high amount of hemicellulose and cellulose, respectively, compared to raw and epoxidized lignin. On the other hand, the epoxidation process was successfully done through presence of peaks at 865 cm-1 and 1092 cm-1 representing epoxy group and PEGDE structure, respectively. More exothermic peaks (at 335.31 °C and 443.49 °C) were seen with epoxidized lignin. The addition of epoxidized lignin below 20% w/w increased the flexural strength of the epoxy resin. The modification of lignin is less effective compared to its raw counterpart. The water absorption increased with the addition of epoxidized lignin. However, the weight gain is lower compared with the unmodified lignin.

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