Karakteristik Perekat Hybrid Fenol Formaldehida- Metilen Difenil Diisosianat dan Papan Untai Berarah Kayu Sengon

Abstract

Papan untai berarah (PUB) adalah papan komposit struktural yang terbuat dari untaian panjang, tipis, dan lebar yang lapisannya disusun atau berorientasi tegak lurus dan diikat dengan perekat thermosetting tipe eksterior melalui tekanan panas. Papan untai berarah dapat menjadi pengganti kayu lapis yang lebih efisien karena dapat memanfaatkan kayu cepat tumbuh, kayu berdiameter kecil, kayu berkualitas rendah, dan kayu cacat dengan nilai ekonomis rendah. Perekat phenol- formaldehyde (PF) merupakan salah satu polimer thermosetting komersial yang banyak digunakan sebagai perekat dalam industri komposit kayu (papan partikel, kayu lapis, PUB, dan lainnya) karena berbagai keunggulan yang dimilikinya. Namun, PF komersial yang tersedia belum mampu memberikan sifat yang unggul saat diaplikasikan pada panel kayu khususnya PUB. Perekat PF diformulasikan dengan penambahan katalis yang bersifat basa yaitu NaOH dan CaCO3 20% (b/v) pada konsentrasi 1% dari kadar padatan perekat PF, kemudian ditambahkan metilen difenil diisosianat (MDI) sebagai agen pengikat silang (cross linker) sebanyak 2,5% dan 5,0% dari kadar padatan perekat PF. Perekat dengan perlakuan katalis dan agen pengikat silang ini kemudian disebut perekat hybrid PF-MDI. Karakteristik perekat hybrid PF-MDI diuji melalui beberapa instrumen pengujian seperti kadar padatan, waktu gelatinasi, viskositas, pH, analisis gugus fungsi dan senyawa yang terkandung di dalamnya, analisis termomekanis, dan derajat kristalinitas. Perekat ini kemudian diaplikasikan pada PUB kayu sengon berukuran 25 cm x 25 cm x 1,2 cm. PUB diuji sifat fisis (kerapatan, kadar air (KA), daya serap air (DSA), pengembangan tebal (PT), kehilangan berat (weight loss), dan pH papan setelah hidrolisis) dan mekanis (modulus of elasticity (MOE), modulus of rupture (MOR), dan internal bonding (IB)). Karakteristik PUB dengan perekat hybrid PF-MDI tersebut dibandingkan dengan Canadian Standards Association (CSA) 0437.0 (Grade O-1) untuk mengetahui pengaruh perlakuan perekat terhadap performa papan yang dihasilkan. Hasil penelitian menunjukkan faktor katalis dan agen pengikat silang mampu meningkatkan kadar padatan perekat, mempercepat waktu gelatinasi, dan meningkatkan viskositas untuk formulasi N-2,5 (NaOH 20% (m/v) 1% dan MDI 2,5%), tetapi menurunkan viskositas untuk formula perekat lainnya meski masih memenuhi standar. Sifat DSA PUB meningkat seiring dengan penambahan katalis dan agen pengikat silang jika dibandingkan dengan PF kontrol, tetapi perlakuan katalis CaCO3 yang diberikan bekerja optimal dalam menurunkan sifat PT pada PUB. Uji hidrolisis memberikan weight loss yang rendah dan pH mendekati netral untuk setiap papan untai berarah. Sifat mekanis rata-rata meningkat dengan perlakuan, kecuali pada sifat MOE sejajar serat. Formulasi yang disarankan untuk hasil yang paling optimal adalah C-2,5 (CaCO3 20% (m/v) 1% dan MDI 2,5%).

Oriented strand board (OSB) is a structural composite board made of long, thin, and wide untais whose layers are oriented perpendicularly and bonded with an exterior-type thermosetting adhesive via hot pressing. Oriented strand board can be a more efficient substitute for plywood because it can take advantage of fast- growing wood, small diameter wood, low quality wood, and defective wood with low economic value. Phenol-formaldehyde (PF) adhesive is one of the commercial thermosetting polymers that is widely used as an adhesive in the wood composite industry (particle board, plywood, OSB and others) due to its various advantages. However, commercially available PF has not been able to provide superior properties when applied to wood panels, especially oriented strand board. PF adhesive is formulated with the addition of an alkaline catalyst, namely NaOH and CaCO3 20% (w/v) at a concentration of 1% of the solids content of PF adhesive, then methylene diphenyl diisocyanate (MDI) is added as a cross linker agent as much as 2.5% and 5.0% of the PF adhesive solids content. This adhesive with catalyst and crosslinking agent treatment is then called PF-MDI hybrid adhesive. The characteristics of the PF-MDI hybrid adhesive were tested through several test instruments such as solids content, gelation time, viscosity, pH, analysis of functional groups and compounds contained therein, thermomechanical analysis, and degree of crystallinity. This adhesive was then applied to a sengon OSB measuring (25 x 25 x 1.2) cm3 and the physical and mechanical properties of oriented strand board were tested to determine the effect of the adhesive treatment on the performance of the resulting boards. The physical properties of oriented strand board include density, moisture content (MC), water absorption (WA), thickness swelling (TS), weight loss and acidity of oriented strand board after hydrolysis. The mechanical properties of oriented strand board are modulus of elasticity (MOE), modulus of rupture (MOR), and internal bonding (IB). The OSB characteristics with PF-MDI hybrid adhesive compared to Canadian Standards Association (CSA) 0437.0 (Grade O-1). The results showed that the catalyst factor and crosslinking agent were able to increase the solids content of the adhesive, accelerate the gelation time, increase the viscosity with the N-2.5 formulation and decrease it for the other formulations although they still met the standard. The properties of WA on oriented strand board increased with the addition of catalysts and crosslinking agents when compared to the control PF, but the CaCO3 catalyst treatment provided worked optimally in reducing the TS properties of oriented strand board. The hydrolysis test gave low weight loss and nearly neutral acidity for each oriented strand board. The average mechanical properties increased with treatment, except for the MOE parallel to grain. The recommended formulation for optimal results is C-2.5 (CaCO3 20% (m/v) 1% and MDI 2,5%).