Karakteristik Resin Uretan Non Isosianat Berbasis Lignin Termodifikasi sebagai Perekat Kayu Lapis

Abstract

Permintaan poliuretan sebagai perekat kayu lapis mengalami peningkatan akibat meningkatnya permintaan kayu lapis. Perekat poliuretan komersial terbentuk dari reaksi gugus hidroksil (-OH) poliol dan isosianat (-NCO) Metilen Difenil Isosianat (MDI). Namun, poliol dan MDI bersifat toksik, mahal, dan berasal dari minyak bumi yang tidak terbarukan. Lignin modifikasi demetilasi-glioksalasi yang berasal dari hasil isolasi lindi hitam memiliki fungsi yang sama dengan poliol yaitu sebagai penghasil gugus -OH. Dimetil karbonat (DMC) dan Heksametilen Tetraamina (HMTA) memiliki fungsi yang sama dengan MDI yaitu sebagai agen cross linker poliuretan. Penelitian ini bertujuan untuk menganalisis pengaruh jenis formula perekat poliuretan berbasis lignin termodifikasi terhadap karakteristik formula perekat dan karakteristik kayu lapis sebagai upaya mengurangi konsentrasi isosianat dan mengganti poliol pada perekat poliuretan. Pembuatan perekat poliuretan diawali isolasi lignin dari lindi hitam kemudian dianalisis rendemen, kadar air, dan gugus fungsinya. Lignin yang dihasilkan dimodifikasi demetilasi dan glioksalasi. Perekat poliuretan disintesis dengan mencampurkan lignin modifikasi (demetilasi-glioksalasi), DMC dan HMTA. Selanjutnya campuran ditambahkan Sodium silikat sebagai filler dan MDI sebagai agen cross linker tambahan yang konsentrasinya dibuat bervariasi. Formula perekat dibedakan berdasarkan nisbah campuran perekat poliuretan non isosianat dengan MDI yaitu formula F1 (10:0), F2 (9,9:0,1), F3 (9,5:0,5), F4 (9:1,0), dan F5 (8,5:1,5). Perekat yang diperoleh dianalisis morfologi dan kenampakkan, pH, kadar padatan, sifat reologi, FTIR, mass loss perekat, dan pH larutan hidrolisat. Kayu lapis dibuat dengan kempa panas suhu 150 ? selama 4 menit selanjutnya dilakukan conditioning. Kayu lapis dikarakterisasi kerapatan, kadar air, delaminasi, keteguhan rekat, dan kerusakan kayunya. Rendemen lignin yang dihasilkan yaitu 43,09±1,57% dengan kadar air 3,47±0,13%. Perekat berwarna coklat kehitaman dan tingkat homogenitasnya meningkat seiring penambahan MDI serta pH perekat bersifat basa. Kadar padatan, viskositas, dan kekuatan kohesi meningkat sering penambahan MDI. Pada gugus fungsi perekat kondisi padat berhasil teridentifikasi gugus-gugus penanda terbentuknya ikatan uretan. Mass loss perekat berkurang seiring penambahan MDI, penurunan suhu hidrolisis, dan kondisi perekat setelah mengalami curing. Derajat keasaman larutan hidrolisat bersifat basa. Pengujian karakteristik kayu lapis mengacu pada SNI 8916.2:2023 dan JAS No. 233: 2003. Kadar air kayu lapis semua formula sudah memenuhi standar. Kerapatan kayu lapis yaitu pada rentang 0,32–0,43 g.cm-3. Delaminasi kayu lapis yang memenuhi standar <33,33% yaitu formula F2, F3, F4, dan F5. Keteguhan rekat yang memenuhi standar >0,7 MPa yaitu formula F2, F3, F4, dan F5. Kerusakan kayu yang memenuhi standar >50% yaitu formula F5. Formula F5 merupakan formula terbaik yang dapat mengurangi penggunaan 85% isosianat dan mengganti 100% poliol.

The demand for polyurethane as a plywood adhesive has increased due to the increasing demand for plywood. Commercial polyurethane adhesives are formed from the reaction of the hydroxyl group (-OH) of polyol and the isocyanate (-NCO) of Methylene Diphenyl Isocyanate (MDI). However, polyols and MDI are toxic, expensive, and come from non-renewable petroleum. Demethylation-glyoxalation-modified lignin derived from the isolation of black liquor has the same function as a polyol, namely as a producer of -OH groups. Dimethyl carbonate (DMC) and Hexamethylene Tetraamine (HMTA) have the same function as MDI, namely as polyurethane cross-linker agents. This research aims to analyze the effect of a modified lignin-based polyurethane adhesive formula on the adhesive formula characteristics and plywood characteristics as an effort to reduce isocyanate concentration and replace polyol in polyurethane adhesive. The manufacture of polyurethane adhesive begins with the isolation of lignin from black liquor, and then the yield, moisture content, and functional groups are explained. The resulting lignin is demethylated and glyoxalized. Polyurethane adhesive was synthesized by mixing modified lignin (demethylation-glyoxalation), DMC, and HMTA. Next, the mixture was added with Sodium silicate as a filler and MDI as an additional cross-linker agent whose concentrations were varied. Adhesive formulas are differentiated based on the mixture ratio of non-isocyanate polyurethane adhesive with MDI, namely formula F1 (10:0), F2 (9.9:0.1), F3 (9.5:0.5), F4 (9:1.0 ), and F5 (8.5:1.5). The adhesive obtained was analyzed for morphology and appearance, pH, solids content, rheological properties, FTIR, adhesive mass loss, and pH of the hydrolyzate solution. Plywood is made by hot pressing at a temperature of 150 ? for 4 minutes, then conditioning. Plywood is characterized by density, moisture content, delamination, tensile strength, and wood failure. The yield of lignin produced was 43.09 ± 1.57% with a moisture content of 3.47 ± 0.13%. The adhesive is blackish brown, and the level of homogeneity increases with the addition of MDI, and the pH of the adhesive is alkaline. Solids content, viscosity, and cohesive strength increase with the addition of MDI. In the solid-state adhesive functional groups, marker groups for forming urethane bonds were successfully identified. Adhesive mass loss decreases with the addition of MDI, decreasing hydrolysis temperature, and the condition of the adhesive after curing. The degree of acidity of the hydrolyzate solution is basic. Testing plywood characteristics refers to SNI 8916.2:2023 and JAS No. 233: 2003. The moisture content of all plywood formulas meets the standards. The density of plywood is in the range of 0.32–0.43 g.cm-3. Plywood delamination that meets the standard <33.33% is formula F2, F3, F4, and F5. Tensile strength that meets the standard >0.7 MPa, namely formulas F2, F3, F4, and F5. Wood failure that meets the standard >50% is formula F5. Formula F5 is the best formula that can reduce the use of 85% isocyanate and replace 100% polyol.