Pengembangan Produk Kayu Rekayasa Skala Industri melalui Modifikasi Non-Biocide Ramah Lingkungan

Abstract

Permintaan kayu komersial di Indonesia meningkat pesat seiring pertumbuhan industri konstruksi dan furnitur, sementara pasokan kayu rotasi panjang dari hutan alam terus menurun akibat deforestasi dan konversi lahan. Kondisi ini menimbulkan kesenjangan pasokan bahan baku kayu yang signifikan. Sebagai alternatif, pemerintah mengembangkan hutan tanaman cepat tumbuh yang menghasilkan kayu rotasi pendek, seperti karet (Hevea brasiliensis), mahoni (Swietenia spp), akasia (Acacia mangium), dan jati (Tectona grandis). Namun demikian, jenis kayu ini memiliki keterbatasan dari sisi keawetan, kekuatan mekanis, dan stabilitas dimensi karena tingginya proporsi kayu juvenil. Kelemahan kayu rotasi pendek menjadikan nilai jualnya rendah dan kurang kompetitif di pasar. Untuk mengatasinya, diperlukan teknologi peningkatan mutu kayu yang ramah lingkungan, ekonomis, dan dapat diterapkan pada skala industri. Modifikasi panas telah lama digunakan untuk meningkatkan stabilitas dimensi, tetapi sering menurunkan kekuatan mekanis kayu. Modifikasi kimia konvensional dengan biosida juga memiliki kelemahan berupa penggunaan bahan beracun yang tidak ramah lingkungan. Oleh sebab itu, diperlukan pendekatan modifikasi non biosida ramah lingkungan yang dapat memperbaiki sifat kayu tanpa dampak ekologis negatif. Penelitian ini menerapkan metode modifikasi non-biosida berbasis glycerol–citric acid (GCA) 40% yang dikombinasikan dengan perlakuan panas. Sementara itu, perkembangan produk kayu rekayasa seperti finger joint laminated board (FJLB) telah membuka peluang peningkatan nilai tambah kayu kualitas rendah, dengan luaran utama berupa pengembangan bevel siding board untuk aplikasi eksterior. Tujuan penelitian ini adalah 1) Mengoptimalkan metode modifikasi panas dan kimia menggunakan GCA dalam skala industri. 2) Menganalisis dan mengkarakterisasi kayu rotasi pendek serta produk FJLB hasil modifikasi non-biosida pada skala industri. Tahapan penelitian diawali dengan pengukuran log kayu untuk menentukan dimensi dan kualitas awal bahan baku. Selanjutnya dilakukan pemotongan sampel sesuai ukuran uji dan proses pengeringan awal (kiln drying) untuk menurunkan kadar air kayu. Setelah itu, kayu yang telah kering diolah melalui impregnasi larutan GCA 40% dalam kiln industri berkapasitas 5 m³, proses impregnasi vakum sebesar -65cm/Hg selama 15 menit, dan tekanan sebesar 8-10 bar selama 6-8 jam hingga jenuh, dilanjutkan dengan pemanasan pada suhu 150?°C selama 20 jam guna memperkuat ikatan kimia di dalam sel kayu. Kayu termodifikasi kemudian diproses menjadi produk rekayasa. Papan disambung (finger joint lumber) menggunakan teknik finger joint dan dilaminasi (edge gluing lumber) menjadi FJLB dengan perekat berbasis air jenis isosianat, sehingga menghasilkan panel berukuran industri yang siap diuji lebih lanjut untuk hasil akhir produk FJLB dengan pelapisan permukaan untuk penggunaan eksterior. Pengujian dilakukan terhadap sifat fisis, stabilitas dimensi, mekanis, dan biologis (ketahanan terhadap perusak kayu). Hasil menunjukkan bahwa metode modifikasi GCA menurunkan kadar air rata-rata sebesar 81,75% (nilai akhir 1,36 3,17%) dan meningkatkan kerapatan rata-rata sebesar 27,85% (nilai akhir 713,53 kg/m³). Stabilitas dimensi membaik dengan nilai ASE (anti-swelling efficiency) rata-rata 53,26% dan penyerapan air menurun hingga 28,55%. Nilai leachability rendah (=3,41%) membuktikan keberhasilan fiksasi bahan kimia ke dalam dinding sel kayu. Sifat mekanis kayu solid termodifikasi memiliki MOE (modulus of elasticity) rata-rata 10.671,15 kgf/cm² dan MOR (modulus of rupture) 767,78 kgf/cm² (kelas kuat II–III). Untuk produk FJLB, MOE mencapai 83.841,12 kgf/cm² dan MOR 210,83 kgf/cm². Meskipun terjadi penurunan MOR akibat sambungan finger joint, kekuatan produk masih memenuhi standar industri. Uji lapang (graveyard test) menunjukkan peningkatan signifikan dalam keawetan dari 4 menjadi 10, dengan kehilangan massa rata-rata hanya 9,73% pada kayu termodifikasi solid, dan skor 3,5 dari skala 4. Analisis FTIR (fourier transform infrared) mendeteksi pita serapan baru pada 1720 cm?¹ (C=O ester), yang menunjukkan terbentuknya ikatan ester antara gliserol, asam sitrat, dan komponen dinding sel kayu. Hal ini membuktikan keberhasilan modifikasi kimia yang mendukung peningkatan stabilitas dimensi serta ketahanan biologis terhadap organisme perusak kayu. Berdasarkan analisis skor, mahoni solid termodifikasi memperoleh skor tertinggi (20), diikuti akasia solid (19), serta jati solid dan jati FJLB (18). Penelitian ini membuktikan bahwa kombinasi impregnasi GCA dan perlakuan panas pada skala industri efektif meningkatkan kualitas kayu rotasi pendek, baik dalam bentuk solid maupun komposit FJLB. Temuan ini menegaskan potensi penerapan teknologi modifikasi non-biosida ramah lingkungan sebagai strategi berkelanjutan untuk memperkuat daya saing industri kayu nasional sekaligus mendukung konservasi sumber daya hutan. Selain itu, hasil penelitian juga menunjukkan bahwa FJLB termodifikasi sangat layak direkomendasikan untuk diproduksi secara luas, dengan catatan diperlukan kajian lebih mendalam untuk menemukan jenis perekat yang paling sesuai serta pengaturan mesin jointing yang optimal, sehingga kualitas rekat dan performa produk dapat ditingkatkan secara maksimal.

The demand for commercial timber in Indonesia has increased rapidly along with the growth of the construction and furniture industries, while the supply of long-rotation timber from natural forests has continued to decline due to deforestation and land conversion. This situation has created a significant gap in the availability of raw wood materials. As an alternative, the government has developed fast-growing plantation forests that produce short-rotation timber, such as rubber (Hevea brasiliensis), mahogany (Swietenia spp.), acacia (Acacia mangium), and teak (Tectona grandis). However, these species have limitations in durability, mechanical strength, and dimensional stability due to the high proportion of juvenile wood. The weaknesses of short-rotation timber reduce its market value and competitiveness. To overcome this, environmentally friendly, economical, and industrially applicable wood modification technologies are required. Heat modification has long been used to improve dimensional stability but often reduces mechanical strength. Conventional chemical modification using biocides also has drawbacks, particularly the use of toxic substances that are harmful to the environment. Therefore, an environmentally friendly non-biocidal modification approach is needed to improve wood properties without causing negative ecological impacts. This study employed a non-biocidal modification method based on 40% glycerol–citric acid (GCA) combined with heat treatment. At the same time, the development of engineered wood products such as finger-joint laminated board (FJLB) has created opportunities to enhance the added value of low-quality timber, with the primary output being the development of bevel siding boards for exterior applications. The objectives of this research were: (1) to optimize thermal and chemical modification methods using GCA at an industrial scale; and (2) to analyze and characterize short-rotation timber and FJLB products resulting from non biocidal modification at an industrial scale. The research began with log measurements to determine the dimensions and initial quality of the raw material. The samples were then cut according to testing standards and pre-dried (kiln drying) to reduce moisture content. Subsequently, the dried timber was processed through impregnation with a 40% GCA solution in an industrial kiln with a 5 m³ capacity, followed by vacuum impregnation at –65 cm/Hg for 15 minutes and pressure treatment at 8–10 bar for 6–8 hours until saturation. This was followed by heating at 150 °C for 20 hours to strengthen chemical bonding within the wood cell walls. The modified timber was then processed into engineered products. Finger-jointed lumber was produced and further laminated (edge-glued lumber) into FJLB using water-based isocyanate adhesive, yielding industrial-sized panels that were subsequently tested, with surface finishing applied for exterior use. Testing was conducted on physical properties, dimensional stability, mechanical properties, and biological resistance (decay resistance). The results demonstrated that GCA modification reduced the average moisture content by 81.75% (final values 1.36–3.17%) and increased the average density by 27.85% (final value 713.53 kg/m³). Dimensional stability improved, with an average anti swelling efficiency (ASE) of 53.26%, while water absorption decreased by 28.55%. Low leachability (=3.41%) confirmed the successful fixation of chemicals within the wood cell walls. The mechanical properties of modified solid wood showed an average modulus of elasticity (MOE) of 10,671.15 kgf/cm² and modulus of rupture (MOR) of 767.78 kgf/cm² (strength class II–III). For FJLB products, MOE reached 83,841.12 kgf/cm² and MOR 210.83 kgf/cm². Although MOR decreased due to finger-jointing, the product’s strength still met industrial standards. Field testing (graveyard test) showed a significant increase in durability from 4 to 10, with an average mass loss of only 9.73% in modified solid wood, and a rating of 3.5 out of 4. Fourier-transform infrared (FTIR) analysis detected a new absorption band at 1720 cm?¹ (C=O ester), indicating the formation of ester bonds between glycerol, citric acid, and wood cell wall components. This confirmed the success of the chemical modification in enhancing dimensional stability and biological resistance against wood-degrading organisms. Based on scoring analysis, modified solid mahogany achieved the highest score (20), followed by solid acacia (19), as well as solid teak and teak FJLB (18). This study demonstrated that the combination of GCA impregnation and heat treatment at an industrial scale effectively enhanced the quality of short-rotation timber, both in solid form and as FJLB composites. These findings highlight the potential of environmentally friendly non-biocidal modification technologies as a sustainable strategy to strengthen the competitiveness of the national wood industry while supporting forest resource conservation. Moreover, the results indicate that modified FJLB is highly feasible for large-scale production, although further research is required to determine the most suitable adhesive type and optimize jointing machinery settings to maximize bonding quality and overall product performance.