Karakteristik Bio-Poliuretan Non-Isosianat Berbasis Lignin sebagai Bahan Impregnasi Serat Rami

Abstract

Industri tekstil membutuhkan alternatif pengganti serat kapas karena tidak mampu memenuhi permintaan serat alami secara global yang terus meningkat. Serat rami (Boehmeria nivea (L.) Gaudich) memiliki banyak potensi sebagai bahan baku terbarukan namun memiliki beberapa kelemahan seperti rendahnya sifat ketahanan api yang dapat diperbaiki dengan impregnasi poliuretan (PU). Namun PU yang digunakan umumnya berbahan dasar sintetis yang tidak dapat diperbaharui dan berbahaya bagi lingkungan. Pengembangan PU dari sumber daya terbarukan dan ramah lingkungan melalui penggunaan biopoliol seperti lignin dan tanpa isosianat perlu dilakukan. Oleh karena itu, penelitian ini bertujuan menganalisis karakteristik lignin hasil isolasi dari lindi hitam proses kraft pulping, sifat-sifat non-isosianat-poliuretan berbasis lignin (L-NIPU), dan menganalisis serat rami baik sebelum dan setelah impregnasi dengan L-NIPU. Lignin hasil isolasi lindi hitam yang berasal dari PT Tanjungenim Lestari (PT. TEL) berbahan baku kayu mangium (Acacia mangium) dianalisis karakteristiknya. Lignin diformulasi menjadi dua formula L-NIPU yaitu F1 (Lignin-Dimetil Karbonat (DMC): heksamin (HMT) 80% (1:1)) dan F2 (Lignin-DMC:HMT 80% (1:2) yang diimpregnasi ke dalam serat rami selama 30, 60, dan 90 menit pada suhu 25±2 °C di bawah 50 kPa. Fourier Transform Infrared Spectrometer (FTIR), Rotational Rheometer, Dynamic Mechanical Analyzer (DMA), FESEM-EDX, Thermogravimetric Analysis (TGA), spektrometer massa kromatografi gas pirolisis (Py-GCMS), Universal Testing Mechine (UTM), dan uji hidrolisis digunakan untuk mengevaluasi sifat serat rami terimpregnasi. Hasil penelitian menunjukkan karakteristik lignin isolasi mirip dengan lignin standar dengan sifat termal yang lebih baik. Reaksi antara lignin-DMC dengan HMT berhasil membentuk gugus uretan (R-N-H-(C=O)-R) dari L-NIPU. Viskositas L-NIPU F2 lebih rendah dibandingkan dengan F1. Stabilitas termal dan sifat termomekanis (storage modulus, loss modulus, dan tan delta) L-NIPU formula F2 lebih baik dibanding dengan F1. Nilai WPG dan sifat mekanis serat rami termpregnasi L-NIPU lebih baik dari serat rami tanpa impregnasi L-NIPU. Ada kecenderungan semakin lama waktu impregnasi menghasilkan nilai WPG, intensitas FTIR gugus uretan yang lebih baik, sifat termomekanis, kristalinitas, dan sifat mekanik serat rami yang lebih baik. Namun, jenis formula tidak mempengaruhi nilai WPG dan sifat mekanis serat rami (kuat tarik dan MOE). Stabilitas panas rami yang diimpregnasi L-NIPU ini lebih rendah dari rami yang diimpregnasi isosianat (pMDI).

The textile industry needs an alternative to cotton fiber because it is unable to meet the increasing global demand for natural fibers. Ramie fiber (Boehmeria nivea (L.) Gaudich) has a lot of potential as a renewable raw material but has several drawbacks such as low fire resistance properties which can be improved by polyurethane (PU) impregnation. However, the PU used is generally made from synthetic materials which cannot be moved and is harmful to the environment. It is necessary to develop PU from renewable and environmentally friendly resources through the use of biopolyols such as lignin and without isocyanates. Therefore, this study aims to analyze the characteristics of lignin isolated from black liquor from the kraft pulping process, the properties of lignin-based non-isocyanate-polyurethane (L-NIPU), and to analyze ramie fiber both before and after impregnation with L-NIPU. The lignin isolated from black liquor from PT Tanjungenim Lestari (PT. TEL) made from mangium wood (Acacia mangium) was analyzed for its characteristics. Lignin was formulated into two L-NIPU formulas namely F1 (Lignin-Dimethyl Carbonate (DMC): hexamine (HMT) 80% (1:1)) and F2 (Lignin-DMC:HMT 80% (1:2) which were impregnated into ramie fiber for 30, 60, and 90 minutes at 25±2 °C under 50 kPa Fourier Transform Infrared Spectrometer (FTIR), Rotational Rheometer, Dynamic Mechanical Analyzer (DMA), FESEM-EDX, Thermogravimetric Analysis (TGA), pyrolysis gas chromatography-mass spectrometer (Py-GCMS), Universal Testing Machine (UTM), and hydrolysis test were used to evaluate the properties of impregnated ramie fibers. The results showed that the characteristics of insulating lignin were similar to standard lignin with better thermal properties. The reaction between lignin-DMC and HMT succeeded in forming a urethane group (R-N-H-(C=O)-R) from L-NIPU. The viscosity of L-NIPU F2 is lower than F1. Thermal stability and thermomechanical properties (storage modulus, loss modulus, and tan delta) of L-NIPU formula F2 are better than F1. WPG value and mechanical properties of L-NIPU impregnated ramie fiber were better than ramie fibers without L-NIPU impregnation. There is a tendency that the longer impregnation time results in better WPG values, FTIR intensity of the urethane group, better thermomechanical properties, crystallinity, and mechanical properties of ramie fiber. However, the type of formula does not affect the WPG value and the mechanical properties of ramie fiber (tensile strength and MOE). The heat stability of L-NIPU impregnated ramie was lower than isocyanate (pMDI) impregnated ramie.