Karakteristik Bambu Gombong (Gigantochloa pseudoarundinacea) Termodifikasi Senyawa Boron, Minyak Mimba, dan Pemanasan

Abstract

Bambu merupakan material potensial untuk industri, konstruksi, furniture, dan kerajinan, karena pertumbuhannya yang cepat serta memiliki sifat fisis dan mekanis yang baik. Bambu juga berperan penting dalam kegiatan ekonomi dan praktik budaya masyarakat lokal. Bambu gombong merupakan salah satu jenis bambu dengan dimensi relatif besar, ketersediaannya melimpah, dan banyak digunakan oleh masyarakat. Tantangan penggunaan bambu gombong yaitu ketahanannya rendah (kelas IV) terhadap serangan organisme perusak (rayap dan jamur). Sehingga memerlukan proses pengawetan untuk memperpanjang umur layanannya. Boric acid equivalent (BAE) umum digunakan sebagai bahan pengawet, tetapi aplikasinya perlu dikombinasikan dengan perlakuan dan bahan lain untuk mengurangi ketercucian. Penelitian bertujuan mengevaluasi pengaruh efektivitas kombinasi perlakuan BAE, minyak mimba dan pemanasan, terhadap sifat fisis bambu gombong dan ketahanannya terhadap jamur pelapuk dan uji lapang (rayap dan pemaparan alami). Bambu dikeringkan dengan bantuan kipas sampai kadar air ±12%. Kemudian bambu dipotong sesuai dengan ukuran contoh uji (CU). Modifikasi bambu dilakukan tahap pertama dengan impregnasi 1 menggunakan BAE 5% (dalam tangki impregnasi berukuran panjang 5 m dan diameter 45 cm) pada tekanan 7 kg cm-2 selama 3 jam. Tahap kedua, dilakukan pemanasan pada suhu 60 ?, 150 ?, dan 180 ? selama 2 jam, dilanjutkan dengan impregnasi 2 menggunakan minyak mimba yang prosesnya sama dengan impregnasi 1. Analisis gugus fungsi dilakukan terhadap bambu termodifikasi dan pada bambu setelah uji pemaparan alami menggunakan fourier transform infrared spectroscopy (FTIR). Selain itu, dilakukan analisis kandungan minyak mimba menggunakan gas chromatography-mass spectrometry (GC-MS). Analisis data menggunakan rancangan acak lengkap faktorial dengan 3 faktor (2 × 3 × 2) terdiri dari penggunaan BAE (tanpa BAE; dengan BAE), suhu pemanasan (60 ?, 150 ?, 180 ?) serta penggunaan minyak mimba (tanpa minyak mimba; dengan minyak mimba). Jika hasil yang diperoleh dari analisis sidik ragam (ANOVA) berpengaruh nyata pada selang kepercayaan 95%, maka dilanjutkan dengan uji Duncan. Parameter keberhasilan pengawetan dapat diukur dengan banyaknya pengawet yang masuk ke dalam bahan. Retensi yang dihasilkan dari proses impregnasi BAE sebesar 21,70 ± 1,09 kg m–3. Nilai weight percent gain minyak mimba yang didapatkan lebih tinggi pada bambu tanpa perlakuan BAE dan pemanasan 60 ? (24,09%) dibandingkan bambu dengan perlakuan BAE sebelumnya pada pemanasan 60 ? (10,39%). Kombinasi perlakuan BAE, perlakuan pemanasan, dan minyak mimba secara umum berpengaruh dalam peningkatan sifat fisis dan ketahanan terhadap organisme perusak. Penambahan minyak mimba pada perlakuan BAE, terbukti mampu menurunkan ketercuciannya hingga 27% lebih rendah dibandingkan perlakuan BAE tunggal. Impregnasi minyak mimba baik secara tunggal maupun kombinasi (BAE-minyak mimba) dapat menurunkan nilai daya serap air hingga 46% dan 28% dibandingkan bambu tanpa perlakuan minyak. Perlakuan modifikasi tersebut juga mampu menurunkan nilai susut rasio tangensial-radial (T/R) dibandingkan kontrol serta meningkatkan stabilitas dimensi. Perubahan warna yang signifikan terutama terjadi pada pemanasan suhu tinggi (150–180 ?), yang mengindikasikan adanya perubahan kimia akibat modifikasi termal. Perlakuan modifikasi bambu secara umum dapat meningkatkan ketahanan bambu dari serangan organisme perusak. Perlakuan minyak mimba dengan pemanasan 180 ? menghasilkan kehilangan berat yang nyata lebih rendah 62,46% dibandingkan kontrol dalam uji terhadap jamur pelapuk putih. Penggunaan BAE dapat menurunkan kehilangan berat bambu hingga 48% dibanding kontrolnya pada pengujian terhadap rayap skala lapang. Kehilangan berat bambu yang diberi perlakuan kombinasi perlakuan (BAE-pemanasan 180 ?-minyak mimba) pada pengujian rayap skala lapang menurun hingga 44,18% daripada kontrolnya. Analisis gas chromatography-mass spectrometry menunjukkan bahwa minyak mimba didominasi oleh golongan asam lemak, alkil halida, dan alkena diduga memiliki aktivitas antirayap, repelen terhadap serangga, antijamur, dan antimikroba sehingga berkontribusi terhadap peningkatan ketahanan bambu terhadap organisme perusak. Perlakuan impregnasi BAE-pemanasan 180 ?-minyak mimba secara signifikan meningkatkan sifat fisis, menurunkan ketercucian bahan pengawet, dan daya serap air, serta meningkatkan stabilitas dimensi. Ketahanan bambu gombong terhadap jamur pelapuk putih meningkat dari kelas IV menjadi kelas II. Ketahanan terhadap rayap skala lapang dan pemaparan alami masing-masing meningkat hingga 3,45 dan 3,54 kali dibandingkan kontrol. Modifikasi kombinasi ini berpotensi meningkatkan pemakaian bambu dan aplikasinya untuk penggunaan jangka panjang.

Bamboo is a potential material for industrial, construction, furniture, and handicraft applications due to its rapid growth and favorable physical and mechanical properties. Bamboo also plays an important role in local economies and cultural practices. Gombong bamboo is one of the bamboo species with relatively large dimensions, wide availability, and extensive use by local communities. However, its main limitation is its low natural durability (class IV) against biodeteriorating organisms, such as termites and fungi, which necessitates preservation treatments to extend its service life. Boric acid equivalent (BAE) is commonly used as a preservative, but its application needs to be combined with other treatments to reduce leaching. This study aimed to evaluate the effectiveness of combined BAE treatment, neem oil impregnation, and heat treatment on the physical properties of gombong bamboo and its resistance to decay fungi, termites, and natural weathering. Bamboo samples were air-dried using a fan until reaching a moisture content of approximately 12%, then cut into test specimens. The modification process consisted of two main stages. First, bamboo was impregnated with 5% BAE using an impregnation tank (5 m in length and 45 cm in diameter) at a pressure of 7 kg cm-2 for 3 hours. This was followed by heat treatment at 60, 150, and 180 °C for 2 hours, and then a second impregnation using neem oil under the same conditions as the first impregnation. Additional characterization included functional group analysis using fourier transform infrared spectroscopy (FTIR) on modified bamboo and bamboo after non ground contact natural weathering, as well as gas chromatography-mass spectrometry (GC-MS) analysis to identify the chemical composition of neem oil. Data were analyzed using a completely randomized factorial design with three factors (2 × 3 × 2), BAE treatment (without and with BAE), heat treatment temperatures (60 ?, 150 ?, 180 ?), and neem oil application (without and with neem oil). When significant effects were detected by analysis of variance (ANOVA) at a 95% confidence level, Duncan’s multiple range test was applied. Preservation performance was evaluated based on the amount of preservative retained in the material. The average retention obtained from BAE impregnation was 21,70 ± 1,09 kg m-3. The weight percent gain of neem oil was higher in bamboo without prior BAE treatment and heated at 60 °C (24,09%) compared to bamboo that had received BAE treatment before heating at 60 °C (10,39%). Overall, the combination of BAE, heat treatment, and neem oil improved physical properties and enhanced resistance to biodeterioration. The addition of neem oil to BAE treatment reduced preservative leaching by up to 27% compared with BAE alone. Neem oil impregnation, either as a single treatment or in combination with BAE, reduced water absorption by up to 46% and 28%, respectively, compared with untreated bamboo. The modification treatments also lowered the tangential-radial shrinkage ratio tangential-radial (T/R) relative to the control, indicating improved dimensional stability. Pronounced color changes were observed at higher heat treatment temperatures (150–180 °C), suggesting chemical alterations due to thermal modification. In general, the modification treatments enhanced bamboo resistance to biodeteriorating organisms. Neem oil treatment combined with heating at 180 °C resulted in a significantly lower weight loss by 62,46%, compared to the control in the white rot fungal decay test. BAE application decreased weight loss by up to 48% in ground-contact biodeterioration tests, while the combined treatment (BAE-heat at 180 °C-neem oil) further reduced weight loss by up to 44,18%. Gas chromatography-mass spectrometry analysis showed that neem oil was dominated by fatty acids, alkyl halides, and alkenes, which are believed to exhibit antitermitic, insect repellent, antifungal, and antimicrobial activities, thereby contributing to improved bamboo durability. The combination treatment of BAE, heat treatment at 180 °C, and neem oil significantly improved physical properties, reduced preservative leaching and water absorption, and enhanced dimensional stability. The durability of gombong bamboo against white rot fungi increased from class IV to class II. Resistance to field termites and natural exposure increased by 3,45 and 3,54 times, respectively, compared to the control. This combined modification approach shows strong potential for extending the service life and broadening the long term applications of gombong bamboo.