Link points to Internet Archive / others. Not hosted by InfraLens. Details
IS 9188:1979 is the Indian Standard (BIS) for performance requirements for adhesive for structural laminated wood products for use under exterior exposure conditions. This standard specifies the performance requirements and testing methods for adhesives used in manufacturing structural laminated wood products intended for exterior use. It covers bond quality, working properties, and resistance to environmental factors like moisture and temperature cycling through delamination and shear tests.
Performance requirements for adhesive for structural laminated wood products for use under exterior exposure conditions
Overview
Status
Current
Usage level
Specialized
Domain
Materials Science — Wood and Other Lignocellulosic Products
! This standard is critical for ensuring the long-term durability of glued laminated timber (glulam) in exposed conditions, preventing bond failure due to moisture ingress.
! Adhesives meeting this standard are typically high-performance thermosetting resins like phenol-resorcinol formaldehyde (PRF).
! The tests prescribed, especially the cyclic delamination and boiling tests, are accelerated weathering tests to simulate harsh exterior conditions.
Standard Specification for Adhesives for Structural Laminated Wood Products for Use Under Exterior (Wet Use) Exposure Conditions
Specifies performance requirements for adhesives for structural glulam for exterior (wet-use) conditions.
EN 301:2018CEN (European Committee for Standardization), Europe
HighCurrent
Adhesives, phenolic and aminoplastic, for load-bearing timber structures - Classification and performance requirements
Classifies and specifies requirements for adhesives (PRF, MF) for load-bearing timber, with Type I being for exterior use.
AS/NZS 4364:2010Standards Australia / Standards New Zealand, Australia/New Zealand
HighCurrent
Timber - Bond performance of structural adhesives
Specifies test methods and bond performance requirements for adhesives used in structural timber applications, including exterior use.
JAS 234:2022Ministry of Agriculture, Forestry and Fisheries (MAFF), Japan
MediumCurrent
Glued Laminated Timber
A product standard for glulam which contains stringent performance requirements for adhesives used in its manufacture for exterior use.
Key Differences
≠IS 9188:1979 is significantly older and has not been updated, while international standards like ASTM D2559 and EN 301 are regularly reviewed to incorporate modern adhesive technologies and testing refinements.
≠The accelerated aging cycles for shear testing differ in severity. For instance, EN 301's 'A4' test involves a double boil-cool cycle (6h boil + 2h boil), which is more aggressive than the single 4-hour boil test in IS 9188.
≠IS 9188 includes a specific requirement for the pH of the mixed adhesive (e.g., ≥ 7.0 for PRF), a prescriptive property that is generally absent in modern performance-based standards like ASTM D2559, which focus solely on final bond performance.
≠While IS 9188 specifies one set of minimum shear strength values, ASTM D2559 provides different minimum shear strength requirements depending on the wood species being laminated, acknowledging the varying strength properties of different woods.
Key Similarities
≈All standards are performance-based, defining requirements through test results (strength, delamination) rather than by dictating specific adhesive chemical formulas.
≈The core test methodologies are analogous, utilizing block shear tests to measure bond strength and delamination tests (typically vacuum-pressure cycles) to assess bond durability under moisture stress.
≈A key performance indicator across all standards is the percentage of wood failure in a shear test, ensuring the adhesive bond is stronger than the wood substrate itself for a true structural bond.
≈All standards utilize severe conditioning cycles involving water saturation, boiling, and/or pressure to simulate the most challenging exterior exposure conditions the laminated wood product might face.
Parameter Comparison
Parameter
IS Value
International
Source
Delamination (Max Allowed)
≤ 5% on any single end-grain glue line (Type I)
≤ 5% for species like Southern Pine and Douglas-fir
ASTM D2559-19
Wet Block Shear Strength (Post-Boil)
≥ 55 kgf/cm² (approx. 5.4 MPa)
≥ 6.0 N/mm² (6.0 MPa) after A4 boil-cool-boil cycle
EN 301:2018
Wood Failure (Post-Boil Shear Test)
≥ 80% (Average)
Requirements vary by wood species and strength, but are typically high (e.g., ≥ 80% for Douglas Fir).
ASTM D2559-19
Shear Test Boil Duration
Boil for 4 hours, then cool for 1 hour.
Two cycles: Boil for 6 hours, cool for 2 hours, then boil for 2 hours.
EN 301:2018
Delamination Test Pressure
5.0 to 5.5 kgf/cm² (approx. 490-540 kPa) for 2 hours
75 to 80 psi (approx. 517-552 kPa) for 2 hours
ASTM D2559-19
Adhesive Working Life Test
Required; bond quality tested at the end of stated working life.
Required; specifies testing at the minimum and maximum allowable assembly times.
ASTM D2559-19
⚠ Verify details from original standards before use
Key Values5
Quick Reference Values
Min dry block shear strength (Group 1 timber)110 kgf/cm²
Min wet block shear strength (Group 1 timber)80 kgf/cm²
Max allowable delamination in cyclic test10%
Max allowable delamination in boiling test5%
Min failing load for plywood shear test (dry)120 kgf
Tables & Referenced Sections
Key Tables
Table 1 - Block Shear Strength Requirements
Key Clauses
Clause 3 - Requirements
Clause 4.3 - Test for Resistance to Delamination (Cyclic Test)
Clause 4.4 - Test for Resistance to Delamination (Boiling Test)
What type of adhesive does this standard apply to?+
It applies to adhesives for structural laminated wood products for use in exterior or weather-exposed conditions.
What is the main test for weather resistance?+
The primary tests are the 'resistance to delamination' tests (cyclic test in Clause 4.3 and boiling test in Clause 4.4), which assess the bond's durability against moisture.
What is the minimum shear strength required for Group 1 timber?+
The minimum block shear strength is 110 kgf/cm² in dry conditions and 80 kgf/cm² after a wet cyclic test, as per Table 1.
What is the maximum allowable delamination?+
Maximum delamination should not exceed 10% in the cyclic test (Clause 4.3) or 5% in the boiling test (Clause 4.4).