Peningkatan Kualitas Kayu Sengon (Falcataria falcata (L.) Greuter & R. Rankin) Melalui Modifikasi Kombinasi Impregnasi-Densifikasi

Abstract

Kayu sengon merupakan salah satu jenis kayu cepat tumbuh dengan kualitas kayu yang relatif lebih rendah jika dibandingkan dengan kayu komersial dari hutan alam. Kerapatan, berat jenis, stabilitas dimensi, kekerasan, keawetan, dan stabilitas termal yang rendah menyebabkan penggunaan kayu sengon terbatas. Oleh karena itu, modifikasi kayu menjadi alternatif untuk meningkatkan kualitas kayu cepat tumbuh. Metode modifikasi yang dapat digunakan adalah metode impregnasi dan densifikasi. Kombinasi kedua metode tersebut dapat meningkatkan sifat-sifat kayu secara signifikan. Penggunaan bahan impregnasi ramah lingkungan seperti asam sitrat-gliserol dengan penambahan nanosilika sintesis maupun komersial sangat berpotensi meningkatkan kualitas kayu sengon. Penelitian ini bertujuan untuk menganalisis efektivitas kombinasi impregnasi menggunakan asam sitrat-gliserol dan nanosilika, kemudian dilanjutkan dengan densifikasi dalam meningkatkan kualitas kayu sengon khususnya sifat fisis, mekanis, stabilitas termal, dan ketahanan kayu sengon terhadap jamur. Kayu sengon yang digunakan berumur 5 tahun dan dipotong berukuran 2 cm × 2 cm × 2 cm. Nanosilika yang digunakan dalam penelitian ini disintesis dari daun bambu betung menggunakan metode sol-gel. Proses impregnasi dilakukan menggunakan metode vakum-tekan dengan larutan impregnasi yang terdiri dari asam sitrat-gliserol (CAG), asam sitrat-gliserol dan nano-silika sintesis (CAG-SiS), dan asam sitrat-gliserol dan nano-silika komersial (CAG-SiC). Kemudian dilanjutkan dengan densifikasi selama 5 jam pada suhu kempa 160 °C dengan variasi compression ratio (CR) 0% (undensified), 15%, dan 35%. Hasil penelitian menunjukkan bahwa modifikasi yang telah dilakukan efektif meningkatkan sifat-sifat kayu. Nilai Weight Percent Gain (WPG) pada semua perlakuan menunjukkan peningkatan hingga 80% mengindikasikan bahwa impregnan berpenetrasi dengan sangat baik ke dalam struktur kayu. Perlakuan CAG dengan penambahan nanosilika pada CR 35% berhasil meningkatkan kerapatan dan kekerasan. Seiring peningkatan CR secara konsisten meningkatkan nilai kerapatan, Anti-Swelling Efficiency (ASE), dan kekerasan kayu, yang disebabkan oleh pemadatan struktur sel yang memperkecil rongga kayu dan meningkatkan ketahanan kayu terhadap penetrasi air maupun beban mekanis. Sebaliknya, nilai WPG menurun seiring peningkatan CR akibat sebagian impregnan yang dimasukkan ke dalam kayu ikut terdorong keluar saat kayu dikempa dengan tekanan tinggi. Nilai Compression-Set Recovery (CSR) dan leachability yang rendah membuktikan bahwa modifikasi yang dilakukan mampu memfiksasi deformasi kompresi secara permanen dan sebagian besar larutan impregnasi telah terikat di dalam dinding sel melalui ikatan ester yang dikonfirmasi melalui analisis Fourier Transform Infrared Spectroscopy (FTIR). Seluruh perlakuan terbukti mampu meningkatkan ketahanan kayu sengon dari serangan jamur pelapuk putih Pycnoporus sanguineus. Thermogravimetric Analysis (TGA) dan Derivative Thermogravimetric (DTG) mengonfirmasi bahwa dengan penambahan nanosilika baik sintesis maupun komersial, stabilitas termal kayu sengon lebih baik dibandingkan dengan kayu sengon tanpa perlakuan dan CAG. Dengan demikian modifikasi kayu dengan impregnasi asam sitrat-gliserol dan nanosilika yang kemudian dilanjutkan dengan densifikasi terbukti efektif meningkatkan sifat fisis, mekanis, stabilitas termal, dan ketahanan kayu sengon terhadap pelapukan jamur putih.

Sengon wood is a fast-growing timber species with relatively lower quality compared to commercial wood from natural forests. Its low density, specific gravity, dimensional stability, hardness, durability, and thermal stability limit its use. Therefore, wood modification offers an alternative for improving the quality of fast-growing timber. The modification methods that can be used are impregnation and densification. The combination of these two methods can significantly improve the properties of the wood. The use of environmentally friendly impregnation agents such as citric acid-glycerol with the addition of synthetic or commercial nano-silica has great potential to improve the quality of sengon wood. This study aims to analyze the effectiveness of combining impregnation with citric acid-glycerol and nano-silica, followed by densification, in improving the quality of sengon wood, particularly its physical and mechanical properties, thermal stability, and resistance to fungal decay. Five-year-old sengon wood was cut into 2 cm × 2 cm × 2 cm specimens. The nano-silica used in this study was synthesized from betung bamboo leaves using the sol-gel method. The impregnation process was carried out using a vacuum-press method with impregnation solutions based on citric acid-glycerol (CAG), citric acid-glycerol and synthetic nano-silica (CAG-SiS), and citric acid-glycerol and commercial nano-silica (CAG-SiC). The impregnated wood was then densified for 5 hours at 160 °C with varying compression ratios (CR) of 0% (undensified), 15%, and 35%. The results showed that the modifications performed effectively improved the properties of the wood. The Weight Percent Gain (WPG) values across all treatments increased by up to 80%, indicating that the impregnants penetrated the wood structure very well. The CAG treatment with the addition of nano-silica at 35% CR successfully increased both density and hardness. As CR increased, the density, Anti-Swelling Efficiency (ASE), and hardness of the wood consistently increased, which was attributed to the compaction of the cell structure that reduced the wood's void spaces and enhanced its resistance to both water penetration and mechanical loading. Conversely, the WPG value decreased with increasing CR, as part of the impregnant that had been introduced into the wood was forced out during the high-pressure pressing process. The low values of Compression-Set Recovery (CSR) and leachability demonstrated that the modifications were able to permanently fix the compression deformation, with most of the impregnation solution bonded within the cell walls through ester linkages, as confirmed by Fourier Transform Infrared Spectroscopy (FTIR) analysis. All treatments were shown to improve the resistance of sengon wood against attack by the white-rot fungus Pycnoporus sanguineus. Thermogravimetric Analysis (TGA) and Derivative Thermogravimetric (DTG) analysis confirmed that, with the addition of either synthesized or commercial nano-silica, the thermal stability of sengon wood was better than that of untreated wood and wood treated with CAG alone. Thus, wood modification through impregnation with citric acid-glycerol and nano-silica, followed by densification, proved effective in improving the physical and mechanical properties, thermal stability, and resistance of sengon wood to white-rot fungal decay.