New Technology InsightsAl-Plastic direct-bonding

Recently, “multi-material” has become a key factor in the field of materials development. Bonding resin and metallic materials with different properties will lead to weight-reduction, high-strength materials.
Greater attention is being focused on technologies for directly bonding different types of materials: they are expected to reduce the production process time and downsize the products.
Making use of our material design know-how for aluminum and resin, we have developed a technology to directly bond aluminum to polycarbonate (PC) and many other resins that previously did not have sufficient bond strength to metal.

What is Al-Plastic direct-bonding technology?

Apply our special surface treatment to aluminum parts, perform insert molding, and directly bond aluminum to resin.

Al surface treatment Inserted into the mold Injection molding Al-Resin molding part Al surface treatment Inserted into the mold Injection molding Al-Resin molding part

Basic properties

SDK direct-bonding method _ Advantages

“Covalent bonding”+”Molecular bonding”+”Mechanical bonding “ SDK bonding technology is one consolidated these three bondings Molecular Van-der Waals/Hydrogen bond Existing adhesive technology Van-der Waals Hydrogen bond Mechanical Anchor-effect Traditional direct bonding technology Resin Aluminum Chemical covalent Covalent bond SDK direct-bonding technology “Covalent bonding”+”Molecular bonding”+”Mechanical bonding “ Resin Primer/ Undercoat Aluminum “Covalent bonding”+”Molecular bonding”+”Mechanical bonding “ SDK bonding technology is one consolidated these three bondings Molecular Van-der Waals/Hydrogen bond Existing adhesive technology Van-der Waals Hydrogen bond Mechanical Anchor-effect Traditional direct bonding technology Resin Aluminum Chemical covalent Covalent bond SDK direct-bonding technology “Covalent bonding”+”Molecular bonding”+”Mechanical bonding “ Resin Primer/ Undercoat Aluminum

*SDK bonding technology has non-anchor approach as well.

SDK direct-bonding method _ Process

  1. Etching

    • Remove oxidized scales
    • Dimple surface
      (Anchor effect)
    Aluminum
  2. Oxidation

    • Create hydroxyl group
    • Whisker-forming(Anchor effect)
    Aluminum Oxidation
  3. Functionality

    • Functional group provided for each under-coatings
    Functional layer Oxidation
  4. Dedicated for resin typeUndercoating

    • Linear or cross-linked structure
    • Robust bonding with thermoplastic resins through molecular diffusion
    • Protection of aluminum surface
    Undercoating Functional layer Oxidized layer
  5. Injection molding

    Inserted- Injection Molding

SDK Direct-Bonding with thermoplastic resins

Tensile-Shear strength

Measuring
method
ISO19095
Test piece

wrap-joint

Aluminum part
18x45x1.5mmT

Molding part
10x45x3mmT

Bonding area
5 x10mm(0.5cm2

Testing
condition

Load cell 10kN

Tensile speed 10mm/min

Temperature 23℃, 50%RH

Wrap-joint
Al-PC resin composite
Tensile-Shear strength of Aluminum (6061Alloy)-thermoplastics resins
ResinNon-crystalline
Engineering plastics
Non-crystalline
Super engineering plastics
Crystalline
Engineering plastics
Crystalline
Super engineering plastics
PC
(Non-GF)*
mPPE
(Non-GF)
PEI
(Non-GF)
PBT
(GF30%)
PP
(GF40%)
PP
(CF40%)

Tensile-
Shear
strength

25MPa 20MPa 25MPa 28MPa 13MPa 18MPa
Molding method Inserted- Injection Molding

Data represents experimental results and does not guarantee specific performance levels under actual usage.

 

*Tensile-Shear strength of Aluminum (6063Alloy)- polycarbonate resins

It helps you make a strong boding with various polycarbonate copolymer grades like impact-strength or anti-weather ability, glass-reinforced ones.

ResinVarious polycarbonate
PC(Non-GF) LEXANTMEXL1414Resin LEXANTMSLX2271TResin

ThermocompTM

DX10313Resin

Tensile-
Shear
strength
25MPa 23MPa 26MPa 22MPa
Molding Method Inserted- Injection Molding

Data represents experimental results and does not guarantee specific performance levels under actual usage.

Injection molding conditions
Measuring method ISO19095

Resin
temperature

285 ℃

Mold
temperature

90 ℃

Injection
speed

50 mm/sec

SDK bonding technology enables to make great bonding performance with general injection molding process/ temperatures by non-anchor bonding approach.
(Anchor-bonding approach results a narrow process condition with higher processing temperature.)

SDK Direct-Bonding with thermosetting resins

Tensile-Shear strength

Measuring
method
ISO19095
Test piece

wrap-joint

Aluminum part
18x45x1.5mmT

Molding part
10x45x3mmT

Bonding area
5 x10mm(0.5cm2

Testing
condition

Load cell 10kN

Tensile speed 10mm/min

Temperature 23℃, 50%RH

Tensile-Shear strength of Aluminum (6061Alloy)-thermosetting resins
ResinCF-SMC
(CF 50wt%)
BMC
Tensile-Shear
strength
23MPa 15MPa
Molding method Press-molding
Gauge 5MPa
Transfer molding
30MPa

Data represents experimental results and does not guarantee specific performance levels under actual usage.

Durability of bond strength (Aluminum-PC resin bonding)

Heat Aging Test

Measuring
method
ISO19095
Test piece

wrap-joint

Aging
condition

80℃ ~500hrs

Testing
condition

Load cell 10kN

Tensile speed 10mm/min

Temperature 23℃, 50%RH

Retention of bond strength (80°C)
Data represents experimental results and does not guarantee specific performance levels under actual usage.

Relation between bond strength and injection pressure

Sufficient bond strength is achieved with variable injection pressure

Changed gate position Normal gate position
Sectional view Normal gate position Pressure delivered to the bonding surface: large Changed gate position Pressure delivered to the bonding surface: small Bonding surface Aluminum

Variation of bond strength depending on resin injection position

Stable bond strength is achieved with variable gate position.

Bond strength Normal gate position Changed gate position
Data represents experimental results and does not guarantee specific performance levels under actual usage.

Adhesion evaluation for SDK direct-bonding

Cross-cut adhesion test

Measuring method
JIS K 5600
Criteria
Top grade: Any grids with sharp lines. No peeling.
Al test piece Area of primer coating
Water dipping test (60℃)
Initial No peeling
24hrs No peeling
12weeks No peeling

Data represents experimental results and does not guarantee specific performance levels under actual usage.

Heat-ageing test (85℃, 85%RH)
Initial No peeling
142hrs No peeling
809hrs No peeling
1204hrs No peeling

Data represents experimental results and does not guarantee specific performance levels under actual usage.