Plywood Tea Chests: Part-2 Plywood
1996 الطبعة

The standard permits the use of any timber species for tea-chest plywood, with Annex B providing guidance on preferred species typically used. These species are generally non-durable hardwoods or softwoods, necessitating preservative treatment due to the impracticality of sapwood removal. Commonly utilized species include Poplar, Eucalyptus, Rubberwood, Mangium, Sal, and occasionally Teak. Preservative treatment is essential to enhance durability and protect against fungal and insect damage during storage and transit.

IS 10 Part 2 specifies mandatory preservative treatments because most timber used is non-durable and contains sapwood. Veneers should be soaked for 10 to 20 minutes in a 1.5-3% solution of boric acid or a boric acid-borax mixture, with temperature adjustments depending on veneer moisture content. Hot-pressed plywood panels undergo dipping in a 4% boric acid or borax solution for 30 to 60 minutes while still warm, ensuring a minimum dry salt retention of 3.0 kg/m³. Qualitative and quantitative verification methods are also outlined to confirm adequate treatment levels.

The plywood's moisture content must not exceed 15% after pressing and conditioning, as stipulated in Clauses 5.5 and 9.3. Moisture is measured according to the method described in IS 1734 (Part 1): 1983, with individual testing of each panel within the selected sample. Maintaining this limit ensures the plywood's dimensional stability and resistance to deterioration during service.

Glue shear strength is tested using six specimens cut into three strips each, 25 mm in width, following IS 1734 (Part 4): 1983. The minimum average failing load for the specimens is 686 N (70 kgf), and no single specimen should fall below 540 N (55 kgf). For the strips, average glue shear strength must be at least 540 N, with individual strips not less than 440 N. These criteria ensure adequate bonding strength in the plywood panels.

Random sampling is performed on each lot according to the lot size, with sample sizes and permissible defective counts specified in Table 1 of the standard. Visual and dimensional inspections are carried out on the selected panels, with acceptance granted if defectives do not exceed allowable limits. Sub-samples from the primary sample undergo laboratory testing for water resistance, adhesive strength, moisture content, and veneer treatment. Moisture content is assessed individually for all sampled panels. This comprehensive sampling and testing framework ensures that plywood products conform reliably to the standard's quality requirements.