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IS 1508:1972 is the Indian Standard (BIS) for extenders for use in synthetic resin adhesives (urea-formaldehyde) for plywood- code of practice. This code of practice provides guidelines on the selection, requirements, and use of extenders (such as wheat flour and tapioca starch) in urea-formaldehyde synthetic resin adhesives for the manufacture of plywood. It covers the preparation of the adhesive mix and outlines precautions to maintain optimal bond strength.
Extenders for Use in Synthetic Resin Adhesives (Urea-formaldehyde) for Plywood- Code of Practice
Overview
Status
Current
Usage level
Specialized
Domain
Materials Science — Wood and Other Lignocellulosic Products
! Always ensure extenders are free from lumps, dirt, and foreign matter, as these can drastically reduce the bonding strength of the plywood.
! Higher extension ratios (amount of extender added) reduce the cost but also significantly decrease the water resistance and durability of the cured adhesive bond.
! Extenders should be mixed uniformly to prevent localized weak spots in the adhesive line.
JIS K 6802:2019JSA (Japanese Standards Association), Japan
MediumCurrent
Urea resin adhesives for wood
Specifies requirements for the UF adhesive system, including performance of mixed adhesive which contains extenders.
GB/T 14732-2017SAC (Standardization Administration of China), China
MediumCurrent
Wood adhesives -- Methods of test
Provides test methods for wood adhesives, many of which align with the performance tests required for the extended adhesive in IS 1508.
BS EN 204:2016BSI (British Standards Institution) / CEN (European Committee for Standardization), UK/Europe
LowCurrent
Classification of non-structural adhesives for joining of wood and derived timber products
Classifies the final adhesive bond durability (D1-D4), which is the performance goal for which extenders in IS 1508 are used.
ASTM D907-22ASTM International, USA
LowCurrent
Standard Terminology of Adhesives
Provides the standard definition for 'extender', but does not specify any material properties or performance requirements.
Key Differences
≠IS 1508 is a prescriptive standard for a raw material component (the extender), specifying its chemical and physical properties like ash content, pH, and fineness.
≠Most international standards (e.g., EN 204, JIS K 6802) are performance-based, focusing on the properties of the final adhesive bond or the mixed adhesive system, not the individual components.
≠International standards often include requirements for formaldehyde content/emission, a critical parameter not addressed in the 1972 version of IS 1508.
≠IS 1508 specifies exact extender types (wheat flour, tapioca flour, wood flour), whereas international standards are material-agnostic as long as performance criteria are met.
Key Similarities
≈The ultimate objective is to ensure satisfactory adhesive bond quality for interior grade plywood, where unfortified UF resins are typically used.
≈Both IS 1508 and related standards like JIS K 6802 recognize the importance of rheological properties like viscosity and pot life for the processability of the adhesive mix.
≈Performance evaluation in both IS 1508 and international standards relies on testing the glue shear strength of prepared plywood specimens in both dry and wet conditions.
≈The principle of accelerated aging through warm water immersion (e.g., 60°C for 3 hours) is a common test method to assess the durability of the bond.
Parameter Comparison
Parameter
IS Value
International
Source
Fineness of Extender (e.g., Wheat Flour)
Min 99.5% shall pass through 150-micron IS Sieve.
Not explicitly specified. Controlled by manufacturer to meet overall adhesive performance.
JIS K 6802:2019
pH of Extender (10% aqueous suspension)
5.0 to 7.0 for wheat/tapioca flour.
Not specified for extender. The pH of the base liquid resin is specified instead (e.g., 7.5 to 9.5).
JIS K 6802:2019
Pot Life of Adhesive Mix
Not less than 3 hours at 30°C.
Shall be as indicated by the manufacturer when tested according to the standard's method.
JIS K 6802:2019
Glue Shear Strength (Dry State)
Average failing load > 100 kgf (~980 N) on specified plywood specimen.
Average tensile shear strength > 6.0 MPa on specified wood specimen.
JIS K 6802:2019
Glue Shear Strength (Water Resistance Test)
Immerse in water at 60°C for 3h. Average failing load > 80 kgf (~785 N).
Immerse in water at 60°C for 3h. Average tensile shear strength > 2.0 MPa.
JIS K 6802:2019
Ash Content of Extender
Max 1.5% for wheat/tapioca flour; Max 2.5% for wood flour.
Not specified in adhesive standards; considered a property of the raw material.
JIS K 6802:2019
⚠ Verify details from original standards before use
Key Values3
Quick Reference Values
maximum moisture content of extender12%
maximum ash content in wheat flour1.5%
typical mesh size requirement100 percent passing 150-micron IS Sieve