Method of test for wood particle boards and boards from other lignocellulosic materials, Part 22: Determination of surface glue ability test
1981 Edition

The test specimens must be square, measuring 50 mm by 50 mm, with thickness matching the finished board. Steel or aluminum alloy loading blocks of 50 mm square are bonded onto both specimen faces using a polyvinyl acetate dispersion adhesive conforming to IS: 4835-1979. The specimen's cross-sectional dimensions should be measured with an accuracy of ±0.3%. The bonding involves assembling the blocks and specimen in a jig, applying sufficient pressure without damaging or altering specimen thickness, and curing under ambient conditions for at least 8 hours. Specimens are conditioned as per IS 2380 Part I clauses 2.2 or 2.2.1, and moisture content is determined separately according to IS 2380 Part III.

The recommended adhesive is a polyvinyl acetate dispersion-based glue compliant with IS: 4835-1979. It must provide a bond strong enough so that failure does not occur along the adhesive interface between the loading block and specimen. The loading blocks, made of steel or aluminum alloy and measuring 50 mm square, are bonded using this adhesive. The bonding process involves assembling the blocks and specimen in a jig, applying adequate pressure to ensure good contact without damaging the specimen, and curing the assembly for a minimum of 8 hours in ambient conditions.

Surface glueability strength is computed from the maximum torque recorded during the shear failure of the bonded surface. The test involves securing the bottom metal block in a vice, applying slight vertical pressure on the top loading block to prevent displacement, and gradually turning a torque wrench until shear failure occurs. The peak torque (T) in cm·kg is noted. The surface strength (S) is then calculated as the torque divided by the glued surface area (A), expressed as S = T / A, where A is in cm². This formula converts the torque measurement into shear stress representing the adhesive bond strength.

The test setup requires specimens conditioned according to IS 2380 Part I, with controlled moisture and temperature. A standardized test specimen prepared from the material surface is needed, along with tools to apply adhesive uniformly. A press or clamping device ensures consistent bonding pressure during curing. The testing apparatus includes a device capable of applying and measuring torque or bond strength, such as a torque wrench or tensile testing machine. This setup ensures consistent, reproducible glueability test results as per IS 2380 Part 22.

Moisture content significantly affects the mechanical and physical properties of wood particle boards; increased moisture generally reduces strength and causes swelling. Accurate moisture measurement is critical for reliable test results. Moisture content is determined by oven-drying a representative sample at 105 ± 5°C until a constant weight is achieved, following IS 2380 Part III (1977). The moisture content percentage is calculated as ((Wet weight - Dry weight) / Dry weight) × 100. Moisture is measured on a separate but identical sample and reported alongside mechanical test data to ensure clarity.