Extenders for use in synthetic resin adhesives (Urea-Formaldehyde) for plywood - Code of practice
2006 Edition

Overview of Scope

This section defines the quality and testing criteria for extenders incorporated in adhesive resin mixtures, ensuring proper bonding in veneer applications.

Highlights:

• Coverage: Addresses extenders that meet purchaser-defined tests aligned with IS 1508.
• Acidity (Clause 5.6):
  • Calculated as the milliliters of 0.1 N NaOH consumed per gram of moisture and fat-free extender.
  • Controls adhesive pH to prevent premature curing and bonding issues.
• Mixing Process (Clause 6):
  1. Combine extenders with a portion of resin to create a paste.
  2. Incorporate the remaining resin to form a uniform mixture.
  3. Apply liquid ammonia to protein-based extenders to unfold proteins.
  4. For powdered resin, use partial water to prepare extender paste before adding remaining water and resin.

Acidity Calculation:

[ \text{Acidity} = \frac{\text{ml of 0.1 N NaOH used}}{\text{1 g of moisture & fat-free extender}} ]

References:

• Quality testing according to IS 1508.
• Emphasis on correct resin-extender mixing sequence for optimal performance.

flowchart LR
    Extender --> MixWithPartResin[Mix with part resin]
    MixWithPartResin --> FormPaste[Form paste]
    FormPaste --> AddRemainingResin[Add remaining resin]
    AddRemainingResin --> SmoothMix[Obtain smooth resin mix]
    SmoothMix --> AddIngredients[Add other ingredients]

This process ensures homogenous distribution and prevents lumping, which is critical for adhesive strength.

Key References in Standard

• Standards Cited:

  • Extender quality testing per IS 1508.
  • ICS classifications: 79.060.10 (Adhesives), 83.040.30 (Wood-based panels), 83.180 (Veneers).

• Acidity Details (Clause 5.6):

  • Acidity measured as ml of 0.1 N NaOH per gram of moisture and fat-free extender.
  • Elevated acidity might cause pre-curing and reduce bonding efficacy.
  • Adjust pH of adhesive mix accordingly.

• Mixing Instructions (Clause 6):

  1. Blend extenders with a portion of resin to form paste.
  2. Add remaining resin to achieve smooth consistency.
  3. For protein extenders, include liquid ammonia to unfold proteins.
  4. In powder resin cases, use part water for extender paste, then add remaining water and resin.

• Updates and Contacts:

  • Verify latest amendments.
  • Consult BIS offices for clarifications.

Summary Table:

flowchart LR
    Extender --> MixPartResin[Mix with part resin]
    MixPartResin --> PasteFormed[Paste formed]
    PasteFormed --> AddResin[Add remaining resin]
    AddResin --> SmoothAdhesive[Obtain smooth adhesive]
    subgraph Protein_Extenders
      PasteFormed --> AddAmmonia[Add liquid ammonia]
      AddAmmonia --> AddResin
    end

Refer to IS 1508 for detailed testing procedures.

Summary of Essential Requirements

Key Points:

• Extender Quality: Must comply with purchaser's specifications and IS 1508 testing (Clause 5.0).
• Acidity (Clause 5.6):
  • Expressed as ml of 0.1 N NaOH consumed per gram of moisture and fat-free extender.
  • Excessive acidity risks premature adhesive curing and weak bonding.
  • pH adjustment of final adhesive mix is necessary.

Mixing Procedure (Clause 6):

1. Combine extenders with part resin to form a paste.
2. Avoid adding all resin simultaneously to prevent lumps.
3. Introduce a small fraction of liquid ammonia for protein extenders to unfold proteins.
4. Add remaining resin and stir to achieve a smooth mixture.
5. Incorporate other ingredients as required.
6. For powder resins, prepare extender paste with part water before adding remaining water and resin.

Acidity Formula:

[ \text{Acidity} = \frac{\text{ml of 0.1 N NaOH}}{\text{g of moisture & fat-free extender}} ]

Mixing Flowchart:

flowchart TD
    Start[Extender] --> MixPartResin[Mix with part resin]
    MixPartResin --> CheckProtein{Is extender protein-based?}
    CheckProtein -- Yes --> AddAmmonia[Add liquid ammonia]
    CheckProtein -- No --> AddRemainingResin[Add remaining resin]
    AddAmmonia --> AddRemainingResin
    AddRemainingResin --> Stir[Stir to smooth consistency]
    Stir --> AddIngredients[Add other ingredients]
    AddIngredients --> FinalMix[Final adhesive mix ready]

Check IS 1508 for updated testing protocols and standards.

Classification and Properties of Extenders

1. Extender Categories (Clause 4):

• Protein-Based Extenders: Derived from protein-rich sources.
• Amylaceous (Starch-Based) Extenders: Contain 90-95% starch, which swells and increases resin volume, enhancing adhesive performance.
  • Examples include tamarind seed powder, tapioca starch, maida, and wheat flour.

2. Quality Parameters (Clause 5.6):

• Acidity Measurement: Conduct titration with 0.1 N NaOH.
  • Acidity = volume of 0.1 N NaOH (ml) per gram of moisture and fat-free extender.
  • High acidity can trigger premature curing, reducing bond quality.

3. Mixing Guidelines (Clause 6):

• Combine extenders with part of resin to avoid lumps.
• For protein extenders, add a small percentage of liquid ammonia to unfold proteins.
• Add remaining resin and stir to form a uniform adhesive.
• For powdered resin, use part water for extender paste preparation, then add remaining water and resin.

Acidity Calculation:

[ \text{Acidity} = \frac{\text{ml 0.1 N NaOH}}{\text{weight of extender (g)}} ]

Summary Table of Extender Types:

flowchart LR
    Extenders --> ProteinBased[Protein-based]
    Extenders --> StarchBased[Amylaceous (Starch-based)]
    StarchBased --> Tamarind[Tamarind seed powder]
    StarchBased --> Tapioca[Tapioca starch]
    StarchBased --> Flour[Maida, Wheat flour]
    ProteinBased --> AmmoniaTreatment[Require ammonia treatment]

Note: Extenders must be free from insects, mold, and fungi (Clause 3.3) to maintain quality.

Quality Criteria for Extenders

1. Testing Requirements (Clause 5.0):

   • Extenders must meet purchaser's specifications.
   • Testing conducted according to IS 1508.

2. Acidity Control (Clause 5.6):

   • Acidity is determined by titrating 1 gram of moisture and fat-free extender with 0.1 N NaOH.
   • High acidity may cause premature curing and poor bonding.
   • Adjustments to adhesive pH are necessary when acidity is elevated.

3. Mixing Procedure (Clause 6):

   • Begin by mixing extenders with part of the resin to form a paste.
   • Gradually add remaining resin to ensure smooth consistency.
   • For protein extenders, liquid ammonia is added to unfold protein molecules.
   • For powder resins, use part of water to prepare the extender paste before adding remaining water and resin.

Acidity Calculation:

[ \text{Acidity} = \frac{\text{ml of 0.1 N NaOH}}{\text{mass of sample (g)}} ]

Quality Testing Summary:

flowchart TD
    Sample[Extender Sample] --> Testing[Test as per IS 1508]
    Testing --> PassCheck{Pass quality tests?}
    PassCheck -- Yes --> AcidityMeasure[Measure acidity]
    PassCheck -- No --> Reject[Reject extender]
    AcidityMeasure --> HighAcidity{Is acidity high?}
    HighAcidity -- Yes --> AdjustPH[Adjust adhesive pH]
    HighAcidity -- No --> ProceedMix[Proceed to mixing]
    ProceedMix --> MixExtender[Mix extender with part resin]
    MixExtender --> AddRemainingResin[Add remaining resin gradually]
    AddRemainingResin --> AddIngredients[Add other ingredients]
    AddIngredients --> FinalAdhesive[Final adhesive mix ready]

Always consult the most recent versions of IS 15684 and IS 1508 for updates.

Mixing Extenders into Resin (Clause 6)

Process Overview:

• Initial Step: Blend extenders with a portion of the resin to produce a paste-like consistency.
  • Avoid incorporating all resin at once to prevent powder flotation and lump formation.
• Protein Extenders:
  • Add a small amount of liquid ammonia to unfold proteins, improving dispersion.
• Next Steps:
  • Introduce the remaining resin and stir thoroughly to achieve a smooth, uniform adhesive.
• Additional Ingredients: Add as necessary to complete the adhesive formulation.

For Powdered Resin:

• Use part of the water to prepare the extender paste.
• Then add the remaining water and resin to finalize the mix.

Important Notes:

• Protein extraction mixing time is approximately 15 to 20 minutes.
• Extender particles should pass IS sieve No. 100 to ensure adequate fineness.
• Proper mixing ensures even adhesive distribution, prevents premature curing, and avoids defects such as blisters.

Mixing Summary Table:

flowchart TD
    Extender --> MixPartResin[Mix with part resin]
    MixPartResin --> ProteinCheck{Is protein extender?}
    ProteinCheck -- Yes --> AddAmmonia[Add liquid ammonia, mix 15-20 min]
    ProteinCheck -- No --> AddRemainingResin[Add remaining resin]
    AddAmmonia --> AddRemainingResin
    AddRemainingResin --> Stir[Stir thoroughly]
    Stir --> AddIngredients[Add other ingredients]
    AddIngredients --> FinalMix[Final adhesive mix]

This method ensures consistent dispersion, proper viscosity, and optimal bonding as per the code.

Testing and Inspection Guidelines

• Reference Testing Standard: Follow IS 1508 for extender testing (Clause 5.0).

• Acidity Test (Clause 5.6):

  • Acidity measured by titrating 1 gram of moisture-free, fat-free extender with 0.1 N NaOH.
  • High acidity can lower adhesive pH, causing premature curing and poor bonding.

• Mixing Method (Clause 6):

  1. Combine extenders with part resin to form a paste, avoiding lumps.
  2. For protein extenders, add liquid ammonia to unfold proteins.
  3. Add remaining resin and stir to achieve smooth viscosity.
  4. Add other components as needed.
  5. For powdered resin, prepare extender paste with part water before adding resin and remaining water.

Acidity Calculation:

[ \text{Acidity} = \frac{\text{ml of 0.1 N NaOH}}{\text{weight of sample (g)}} ]

Acidity Test Summary:

flowchart TD
    Sample[Extender Sample] --> DryDefat[Remove moisture & fat]
    DryDefat --> Titrate[Titrate with 0.1 N NaOH]
    Titrate --> Volume[Measure volume used]
    Volume --> Calculate[Calculate acidity (ml/g)]
    Calculate --> HighAcidity{Is acidity high?}
    HighAcidity -- Yes --> AdjustPH[Adjust adhesive pH]
    HighAcidity -- No --> ContinueMix[Proceed with mixing]

Always ensure to use the current editions of IS 1508 and IS 15684.

Packaging and Storage Requirements

1. Acidity (Clause 5.6):

• Defined as volume in ml of 0.1 N NaOH consumed per gram of moisture and fat-free extender.
• Elevated acidity lowers pH, increasing risk of premature curing and poor bond quality.
• Correct acidity levels to maintain adhesive pH.

2. Moisture Content (Clause 5.2):

• Recommended moisture content ranges between 12% and 14%.
• Excess moisture may lead to fungal or mold growth, deteriorating extender quality.

3. Mixing Method (Clause 6):

• Combine extenders with part resin to prepare a paste.
• Avoid adding entire resin quantity at once to prevent lumps.
• For protein extenders, add liquid ammonia to unfold proteins.
• Add remaining resin and stir to uniformity.
• For powdered resin, prepare extender paste with part water, then add remaining water and resin.

Quality Parameter Summary:

flowchart LR
    Extender --> MixPartResin[Mix with part resin]
    MixPartResin --> PasteFormed[Form paste-like mix]
    PasteFormed --> AddRemainingResin[Add remaining resin]
    AddRemainingResin --> AddAdditives[Add additives]
    AddAdditives --> FinalAdhesive[Final adhesive mixture]

Storage Advice: Keep extenders in a cool, dry environment to preserve moisture and acidity levels.

Safety and Handling Recommendations

1. Acidity (Clause 5.6):

• Acidity is the volume in ml of 0.1 N NaOH consumed per gram of moisture-free, fat-free extender.
• Elevated acidity can lead to premature adhesive curing, resulting in poor bond strength.
• Adjust adhesive pH accordingly to prevent these issues.

2. Mixing Procedure (Clause 6):

• Begin by mixing extenders with part of the resin to form a paste-like consistency.
• Avoid adding all resin at once to prevent lumps.
• For protein extenders, add a small percentage of liquid ammonia to unfold the proteins.
• Add the remaining resin and stir until desired viscosity is reached.
• For powder resin, prepare extender paste with part water first, then add remaining water and resin.

Acidity Measurement Summary:

Handling Best Practices:

• Strictly follow the mixing sequence for optimal adhesive properties.
• Monitor acidity and pH to avoid premature curing.
• Use ammonia carefully with protein extenders.

flowchart TD
    Extender --> MixPartResin[Mix with part resin]
    MixPartResin --> FormPaste[Form paste-like mix]
    FormPaste --> AddRemainingResin[Add remaining resin and stir]
    AddRemainingResin --> AddIngredients[Add other ingredients]
    AddIngredients --> FinalAdhesive[Final adhesive preparation]

Refer to IS 15684 for comprehensive chemical handling and safety instructions.

Notes on Annexes and Appendices

The available content does not explicitly list annexes or appendices containing formulas or tables. However, key relevant data within IS 15684 includes:

Important Specifications (Clause 5.6):

• Acidity of Extender:
  • Determined by titration with 0.1 N NaOH (ml per gram of moisture and fat-free material).
  • Higher acidity may cause premature adhesive curing and reduced bond strength.

Mixing Method (Clause 6):

• Extenders are mixed with a portion of resin to form a paste before adding the remaining resin to ensure a smooth mixture.
• Protein extenders require a small addition of liquid ammonia to unfold proteins.
• Powder resin necessitates partial water use for extender paste preparation before adding remaining water and resin.

Sample Acidity Table:

Mixing Process Diagram:

flowchart TD
    ExtenderPowder --> MixPartResin[Mix with part resin]
    MixPartResin --> FormPaste[Form paste]
    FormPaste --> AddRemainingResin[Add remaining resin]
    AddRemainingResin --> StirSmooth[Stir to smooth mix]
    StirSmooth --> AddOtherIngredients[Add other ingredients]

For comprehensive annexes, tables, and formulas, consult the full IS 15684 standard or related BIS documentation, which references additional IS codes for testing and specifications.