Hot Melt Adhesives for Todays Applications

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Hot Melt Adhesives for Todays Applications
Real-World Tutorials
Hot Melt Adhesives
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Outline

• I. Introduction
• II. Typical Adhesive Properties
• III. Raw Materials

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Introduction

• Hot Melt Adhesive n. A thermoplastic, polymer
  based adhesive which is applied in the molten
  state at temperatures typically above 250F and
  which functions primarily by mechanical
  anchorage.

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Introduction

• Benefits of Hot Melt Adhesives Compared to
  traditional adhesives, Hot Melts are versatile
  and well-suited to a wide range of manufacturing
  applications
• Fast processing
• Environmentally friendly
• Bond-impervious surfaces
• Gap-filling
• Safe
• Efficient shipment and storage

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Comparison to Other Technologies
Hot Melt adhesives provide superior performance
to water- and solvent-based options, most notably
in the areas of speed and cost.
Solvent-Based
Water-Based
Hot Melts
Speed
Low VOC
Cost Effectiveness
Adhesion
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Some Hot Melt Forms
Hot Melts come in a variety of forms, making them
versatile and well-suited for a range of
industrial applications. Various forms are needed
to ensure compatibility with different
applications equipment systems.

• Bags
• Slats

• Cakes
• Bricks

• Pellets
• Pillow

• Bulk (drum, pail, molten rail car)

Bag
Cake/Brick
Pillow
Pellet
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Industries Served

• H.B. Fuller Hot Melt Adhesives are used every day
  around the globe in many industries, including

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Equipment

• Highly versatile, Hot Melts can be applied using
  numerous methods, depending upon the application
  requirements
• Nozzle
• Slot Die
• Extrusion
• Wheel
• Screen Printing
• Melt Blown
• Spiral Spray

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Equipment

• Dispensing of Hot Melts can be accomplished using
  any of the following
• Drum unloaders
• Pail unloaders
• Melt reservoirs
• Pre-melters
• Vacuum conveyance

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Typical Adhesive Properties
This tutorial will now discuss, in detail, Hot
Melt Adhesive properties including
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• Viscosity
• Color and Color Change
• Peel Adhesion Failure Temperature - Kraft paper
  (PAFT)
• Softening Point (Mettler)
• 180 Peel Adhesion (PSA)
• Shear Adhesion Failure Temperature - PSA (SAFT)
• Loop Tack

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Typical Adhesive Properties

• Substrate Specific Adhesion
• ambient
• sub-ambient
• accelerated aging at elevated temperature
• Thermal Stability
• Mechanical Properties

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Typical Adhesive Properties

• 1. VISCOSITY
• Resistance to flow
• Measured at relevant application temperature
  (250-350F)
• Knowledge of application conditions typical
• temperature
• shear rate
• Brookfield Thermosel (low shear)
• Dynamic Mechanical Analysis (low to high shear)
• Capillary Rheometer (high to very high shear)

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1. Viscosity

• Brookfield Thermosel measures the resistance to
  flow

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Typical Adhesive Properties

• 2. COLOR AND COLOR CHANGE
• Indicative of chemical purity, oxidation or
  oxidative tendencies
• Subjective and quantitative
• Measured before and after heat aging
• Several quantitative methods
• Gardner
• Saybolt
• Hunter

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Typical Adhesive Properties

• 3. Peel Adhesion Failure Temperature (PAFT)
• Non-PSA Hot Melts
• Measures the resistance to deformation in a peel
  adhesion mode at elevated temperatures
• Temperature ramped from 70 F at 1 F/min
• 100 gm weight, 1 x 1 specimen, Kraft paper
• Run in triplicate

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Typical Adhesive Properties

• 4. Shear Adhesion Failure Temperature for
  Packaging (SAFT)
• Measures the resistance to deformation in a shear
  mode at an elevated temperature
• Temperature ramped from 70 F at 1 F/min
• 500 gm weight, 1 x 1 specimen, Kraft paper
• Run in triplicate

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Typical Adhesive Properties

• 5. SOFTENING POINT
• Measure of the temperature at which the adhesive
  begins to flow
• Primarily influenced by melt point of wax or
  endblock Tg of Styrenic Block Copolymer
• Mettler, Ring and Ball methods most popular

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METTLER SOFTENING POINT

• Measures the temperature at which the hot melt
  begins to flow

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Typical Adhesive Properties

• 6. 180 PEEL ADHESION (PSAs)
• Measures adhesion strength of PSA to Stainless
  Steel
• PSA is coated on film (1x 10strips)
• aged 24 hrs
• mated to SS with 4.5 lb roller
• bond separated at constant rate in a 180 peel
  mode
• data reported in Lbs./in

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Adhesion Testing
Shear adhesion testing in progress
Peel adhesion testing in progress
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Typical Adhesive Properties

• 7. LOOP TACK
• Measures tack level of PSA to Stainless Steel
• PSA coated on film, cut into strips
• Aged
• Bent into loop, 1x 6
• Mated to SS at constant rate (no pressure) 1x 1
• Removed at constant rate
• Resistance to de-bonding is measured

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Typical Adhesive Properties

• Substrate Specific Adhesion
• Unique to the application of interest
• Use actual substrates
• Bonds prepared in method to simulate actual
  production
• Test at several different temperatures
• Ambient
• Sub-ambient
• Elevated
• Test for bond strength, substrate destruction

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Typical Adhesive Properties

• Thermal Stability
• Used to simulate pot stability of adhesive in
  melt
• Age molten adhesive at typical pot temperature
• Covered
• Uncovered
• Determine
• viscosity change
• Color change
• Formation of char, edge ring
• Skin, gels

Tests are conducted at various time intervals
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Typical Adhesive Properties

• Mechanical Properties
• Ultimate Tensile - This is the maximum force
  needed to break a dogbone specimen
• Yield Point - This is the maximum stress a hot
  melt can withstand before undergoing permanent
  deformation

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Typical Adhesive Properties

• Mechanical Properties
• Elongation at Break- This is the distance a given
  length of sample will stretch before breaking
• Youngs Modulus - This is the ratio of stress
  over strain at very small stress values

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Typical Adhesive Properties

• Mechanical Properties
• Toughness- A combination of high tensile strength
  and high elongation
• Flexibility- A combination of low yield point,
  high elongation and low youngs modulus

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Raw Materials
Typical hot melt raw materialsthe building
blocks include the following
Polymer Tackifying Resins Diluents/Plasticizer Wax
Antioxidants
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Raw Materials

• Role of Polymer
• Controls strength and flexibility
• Heat resistance, shear, impact resistance
• Dictated primarily by polymer type, molecular
  weight and amount

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Raw Materials- Polymer Content
VISCOSITY
Decreasing
Increasing
Lower Viscosity

• Higher Viscosity
• Increased Flexibility
• Increased Toughness
• Better Low Temperature Flexibility

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Raw Materials

• Role of Tackifying Resin
• Controls wetting
• Adhesion and tack
• Dictated by softening point (Tg) and
  compatibility with polymer

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Raw Materials-Tackifying Resin Content
VISCOSITY
Decreasing
Increasing

• Faster Speed
• Reduced Tack

• More Aggressive
• Increased Toughness

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Raw Materials

• Role of Diluent/Plasticizer
• Controls wetting and flow
• Viscosity reduction, modulus and open time
  adjustment
• Dictated by MW and compatibility with polymer

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Raw Materials

• Role of Wax
• Controls set speed and open time
• Heat resistance and subambient adhesion
• Dictated primarily by crystallinity, melt
  point, and Mw/Mn

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Raw Materials-Wax Content
VISCOSITY
Decreasing
Increasing

• Higher Viscosity
• Increased Flexibility
• More Aggressive Bonding

• Lower Viscosity
• Faster Rate of Set
• Less Aggressive Bonding

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