This standard outlines the performance criteria for adhesives employed in structural laminated wood products designed for outdoor exposure. It guides manufacturers, engineers, and quality assurance professionals to ensure adhesives deliver strong bonding, environmental durability, and meet mechanical requirements under exterior conditions.
Overview
This standard outlines the performance criteria for adhesives employed in structural laminated wood products designed for outdoor exposure. It guides manufacturers, engineers, and quality assurance professionals to ensure adhesives deliver strong bonding, environmental durability, and meet mechanical requirements under exterior conditions.
Audience
Contents
Structure
This section defines the extent and main specifications of adhesives suitable for structural laminated woodwork, referencing IS 707-1976 for terminology and emphasizing practical field application requirements. Key parameters include wood moisture levels (8-12%), surface cleanliness, adhesive spread rates (150-250 g/m² per surface), assembly timings (open: 5-15 mins, closed: 15-30 mins), pressure range (0.1 - 0.7 N/mm²), and curing durations (minimum 24 hours at ambient temperatures). Rounding of test results follows IS 2-1960 guidelines.
Definitions are primarily aligned with IS 707-1976, covering steel types and other referenced materials. Rounding off procedures for test data adhere to IS 2-1960, ensuring consistent significant figures. No specific formulas or tables reside within this clause, but cross-references provide clarity on terms.
Adhesives covered are mainly reaction products formed from phenol and/or resorcinol with aldehydes such as formaldehyde, resulting in phenol-based, resorcinol-based, or combined phenol-resorcinol adhesives. Preparation requires adherence to manufacturers' instructions using distilled water if needed. Manufacturers must supply detailed instructions regarding chemical nature, storage, mixing, and application relevant to laminated wood.
This clause categorizes adhesives by type as phenol-based, resorcinol-based, or phenol-resorcinol-based. Composition requirements stipulate reaction products of phenol and/or resorcinol with aldehydes. Test results must be rounded per IS 2:1960, maintaining specified significant digits. Classification aids in selecting adhesives for specific durability and resistance needs.
Performance demands include resistance to delamination under outdoor conditions, verified by cyclic wet-dry testing specified in Appendix D. Delamination must not exceed 5% of the glued area. Bond strength must comply with IS 7189. The section outlines test specimen preparation, cyclic exposure, delamination measurement, and pass/fail criteria to assure long-term structural integrity.
Sampling is performed per lot size with container numbers determined by lot volume, selecting containers randomly via IS 4905-1968. Composite samples are created by mixing representative portions from selected containers totaling at least 0.5 kg. Testing of composite samples ensures conformity to all standard requirements, with data rounded according to IS 2-1960.
Adhesive packaging must bear clear, permanent markings indicating manufacturer identity, material description, batch and manufacturing dates, expiry date, and reference to usage instructions. Labels should include the phrase 'To be stored in a cool dry place.' Optional ISI certification marks may be applied per regulations. Manufacturer-provided instructions must cover moisture content, surface prep, adhesive spread, assembly times, pressure, and curing conditions.
Wood should have moisture content between 8-12% and be clean and free from contaminants. Adhesive may be applied as a single or double spread with typical amounts of 150-200 g/m². Open assembly time ranges from 5 to 10 minutes, closed assembly time from 10 to 30 minutes. Pressure applied is generally between 0.7 to 1.5 N/mm². Curing requires 4-6 hours at ambient temperatures or shorter durations at elevated temperatures. Adherence to manufacturer instructions is essential.
Adhesive is stirred and spread as a 0.5 mm thick film over a 15 x 15 cm glass surface, cured per instructions, then ground to pass a 40-micron sieve. A 2 g sample is mixed with 10 ml of freshly boiled and cooled distilled water, stirred, and stored sealed for 72 hours at room temperature. pH is recorded every 24 hours until consecutive readings differ by no more than 0.05 units. The final pH must be at least 4.0.
Laminated wood beams are conditioned and planed to a uniform width of 50 mm, then cut into 80 mm lengths for testing. These specimens undergo shear and delamination tests as specified, ensuring standardized sample dimensions and conditioning for reproducible results.
Specimens prepared per standards are tested using a self-aligning shearing tool applying load at a maximum rate of 1.25 cm/min. Shear strength is calculated as load at failure divided by shearing area. Minimum required shear strength is 20 N/mm² when dry and 12 N/mm² after boiling. Controlled moisture conditions are maintained during testing.
After cyclic wet-dry exposure, specimens are dried and delamination length measured using a 0.125 mm thick feeler gauge, ignoring isolated delaminations under 2.5 mm or those more than 5 mm apart. The total delamination length at both ends is summed and expressed as a percentage of specimen length, which must not exceed 5% to pass.
Frequently Asked
IS 9188 (1979) pertains to adhesives utilized in structural laminated wood products for outdoor use, focusing on those that provide waterproof and durable bonds. It includes phenolic and aminoplastic adhesives commonly used for exterior plywood, cold setting casein glues suited for interior applications, and polyvinyl acetate (PVA) based adhesives primarily intended for indoor joinery. The standard emphasizes performance criteria ensuring resistance to delamination and environmental degradation.
Prior to bonding, each wood lamination should be freshly surfaced to guarantee clean, smooth contact areas. Machining tolerances of ±0.25 mm are required to maintain uniform thickness and fit. Adhesive should be spread evenly across all surfaces following manufacturer guidelines. After assembly, appropriate pressure and temperature must be applied and maintained to achieve a robust bond.
Curing conditions depend on the adhesive type and manufacturer's instructions, typically including maintaining specified temperature during pressure application for a minimum curing period. Post-curing, laminates are conditioned at approximately 27 ± 2°C with 50–70% relative humidity for the recommended duration. For example, phenolic adhesives often cure at 60–70°C for 2–4 hours under pressure. Uniform adhesive spread and correct wood moisture content are critical for effective curing.
Resistance to shear by compression is tested using specimens prepared as specified, placed in a testing machine equipped with a self-aligning shearing tool to apply uniform load. The load is applied continuously at a rate not exceeding 1.25 cm/min until failure. Shear strength is calculated as the load at failure divided by the shearing area. Minimum acceptable values are 20 N/mm² when dry and 12 N/mm² after boiling.
Containers must be clearly and permanently marked with the manufacturer's name or mark, material description, batch number, manufacturing date, expiry date, and a reference to the manufacturer's usage instructions. The label should also include the statement 'To be stored in a cool dry place.' Optional ISI certification marks may be included per applicable regulations. These requirements ensure product traceability and proper handling.
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