This paper investigated the upcycling process of thermoplastic waste polystyrene (WPS) into thermosetting particleboard adhesive using two cross-linkers, namely methylene diphenyl diisocyanate (MDI) and maleic anhydride (MA). The WPS was dissolved in an organic co-solvent. The weight ratio of WPS/co-solvent was 1:9, and 10% of cross-linkers based on the WPS solids content were added subsequently at 60 °C under continuous stirring for 30 min. The adhesive properties, cohesion strength, and thermo-mechanical properties of WPS-based adhesives were examined to investigate the change of thermoplastic WPS to thermosetting adhesives. The bonding strength of WPS-based adhesives was evaluated in particleboard made of sengon (Falcataria moluccana (Miq.) Barneby & J.W. Grimes) wood and rice straw particles at different weight ratios according to the Japanese Industrial Standard (JIS) A 5908:2003. Rheology and Dynamic Mechanical Analysis revealed that modification with MDI and MA resulted in thermosetting properties in WPS-based adhesives by increasing the viscosity at a temperature above 72.7 °C and reaching the maximum storage modulus above 90.8 °C. WPS modified with MDI had a lower activation energy (Ea) value (83.4 kJ/mole) compared to the WPS modified with MA (150.8 kJ/mole), indicating the cross-linking with MDI was much faster compared with MA. Particleboard fabricated from 100% sengon wood particles bonded with WPS modified with MDI fulfilled the minimum requirement of JIS A 5908:2003 for interior applications.

The properties of laminated wood prepared from sengon wood (Falcataria moluccana Miq. Barneby & Grimes) bonded with a modified gutta-percha (MGP) adhesive at various laminae surface roughness profiles were investigated. The wood laminae were sanded using sand papers of KAG grit designation of 80, 100, 150, 220, 300, and 400. A lower value of KAG grit designation with a lager particle size of sand resulted in a rougher surface of the bonded laminae; a rougher laminae surface profile resulted in a greater shear strength of the laminated wood. The shear strength was highest for laminated wood treated with sand paper of KAG 80 and smallest for laminated wood treated with KAG 400. In general, the bonding strength was enhanced with decreasing KAG grit designation. The adhesion performance, in terms of spread and adhesive penetration, improved after sanding, which widened the contact area on the wood surface.

The reaction between polyols and diisocyanates forms polyurethane (PU) adhesives. However, these materials are derived from petroleum-based chemicals, whose availability is declining. As an environmentally friendly, renewable, and formaldehyde-free alternative, tannins offer a promising solution. This study aimed to characterize tannin-based polyurethane (TPU) adhesives modified with bio-polyol, analyze their performance, and determine optimal tannin extract formulation for use as a plywood adhesive, as the first step toward developing eco-friendly TPU adhesives. TPU adhesives were made using modified polyvinyl alcohol (PVOH) and tannins at concentration levels of 0%, 10%, 20%, 30%, 40%, and 50%. The analysis is carried out on raw materials, adhesives, and plywood. The results showed that adding tannin extracts had a significant effect on viscosity, tannin solids content, density, delamination, and dry and wet adhesion strength, but not for moisture content. Functional group analysis (FTIR) confirmed that both liquid and solid TPU adhesives contained urethane, hydroxyl, and isocyanate functional groups. The lowest DMA loss modulus was observed in TPU with tannin 20%. Additionally, the highest adhesion strength was achieved with 20% TPU, which correlated with increased wood failure. Based on these findings, PVOH/tannin 20% was considered an effective formula for TPU adhesives.

Pemberdayaan Masyarakat Melalui Pengolahan Sampah Plastik Styrofoam Menjadi Perekat Bernilai Guna dan Bernilai Ekonomi di Desa Cibeusi Jatinangor Sumedang

Developing cold-setting adhesives derived from waste styrofoam (WS) of expanded polystyrene foam for laminated gmelina wood involves innovative recycling of WS into functional adhesives. As a type of thermoplastic polymer, WS can be used as an adhesive at room temperature. In this study, WS was functionalized into cold-setting adhesives through dissolution and cross-linking reaction with methylene diphenyl diisocyanate (MDI) at a concentration of 40% w/v at 60°C. The mixture was then stirred at 200 rpm for 30 minutes. The adhesive is characterized by its ability to be set at room temperature, offering environmental benefits and practical applications in wood lamination. Solids content, gelation time, viscosity, cohesion strength, functional group analysis, morphological features, and curing temperature analysis were performed to characterize the cold-setting adhesives. The WS-MDI-40% had 62.4% solids content, 906.8 mPa.s viscosity, 182.3 Pa cohesion strength, and 197.8 minutes of gelation time at room temperature. The adhesion performance was evaluated in laminated wood using gmelina wood at glue spread rates of 250 and 300 g/m2 and cold-pressed at various durations. The block shear strength value of laminated wood bonded with WS-MDI-40% at 300 g/m2 and cold-pressed for 24 hours was higher than that of other samples, reaching 8.2 MPa, which met the Japanese Agricultural Standard (JAS No. 234) for glued laminated timber, exceeding the minimum requirement of 5.4 MPa. Fourier transform infrared (FTIR) spectroscopy revealed that the cold-setting WS-MDI-40% were cross-linked via urethane linkages (R–NH–COO–R). The free –N=C=O groups could react with the –OH groups of gmelina wood to produce laminated wood during cold-pressing. This study suggested a recycling alternative of WS into a cold-setting wood adhesive for laminated wood, which can be utilized in interior applications. Keywords: adhesive, block shear strength, cohesion strength, cold-setting, gmelina wood