Resin Treated Compressed Wood Laminates (Compregs) - Specification, Part 3: For General Purposes
1989 Edition

IS 3513 Part 3 categorizes compregs into two main density grades: High Density (Grade GH) with specific gravity ranging from 1.25 to 1.35, and Medium Density (Grade GM) with specific gravity between 0.95 and 1.25. The standard recognizes four lamination types relevant for general use: Type II (majority grain aligned with principal stress), Type III (grain uniformly oriented in all radial directions), Type V (grain aligned with loading axis), and Type VI (grain arranged at right angles for enhanced compressive strength). These classifications assist in selecting compregs suitable for specific mechanical stress conditions and applications.

According to IS 3513 Part 3, compreg sheets have length tolerances of +6 mm / -0 mm, width tolerances of +3 mm / -0 mm, and thickness tolerances of ±10% for thicknesses below 6 mm and ±5% for thicknesses equal to or above 6 mm. Edge straightness and squareness are limited to 2 mm per 1000 mm (0.2%). Compreg rods come in lengths between 600 mm and 1500 mm and diameters ranging from 3 mm to 80 mm, with diameter tolerances varying with size. These dimensional standards ensure components meet engineering and industrial requirements.

Compregs under IS 3513 Part 3 must meet defined mechanical criteria including minimum tensile strength, static bending strength, compressive strength (both parallel and perpendicular to laminae), shear strength, hardness, and impact resistance. Manufacturing parameters specify resin content between 10% and 40%, curing temperatures from 135°C to 150°C, and bonding pressures ranging from 4.2 MPa to 15.5 MPa depending on density grade. The grain orientation types (II, III, V, VI) influence the mechanical performance, ensuring suitability for various structural and industrial uses.

The standard recommends utilizing any non-resinous timber species for veneer preparation, preferably using a single species per veneer pack. When multiple species are combined, their compatibility in density, modulus of elasticity, and shrinkage characteristics must be ensured. The resin utilized should be an alkali catalyzed thermosetting phenol or cresol formaldehyde resin. Impregnation methods include coating veneers with resin or interleaving resin-impregnated paper films, with resin content maintained between 10% and 40% on an oven-dry basis. Curing is carried out at temperatures between 135°C and 150°C under specified bonding pressures.

Finished compreg components should receive protective varnish coatings compliant with IS 524:1983 and IS 525:1968 standards to ensure durability. Each board, component, or package must be clearly and permanently marked with details including the type and finish, manufacturer’s name, initials or recognized trademark, year of manufacture, and batch number. Additional markings as requested by the purchaser may also be applied. This marking system guarantees traceability and adherence to quality control requirements.