UV Curable Adhesives – Achieving Success through Formulation

2017 Adhesives and Sealant ConventionApril 4, 2017Atlanta, GA

Neil Cramer, Mike Idacavage, Ashten Vogelsberg, Tara Scott and Amelia Davenport

Colorado Photopolymer Solutions

Mechanical Bonding Increase roughness by abrading surface Chemically etch the surface Swell substrate to promote penetration of

coating (Plastics)

Chemical Bonding Surface Modification Residual Functional Groups

Diffusive Polymer Entanglement

Dispersive Van Der Waals

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Adhesion promoters are materials that are added to a formulation to enhance adhesion

Typically added in relatively small amounts There are a wide range of different types of

adhesion promoters for different substrates and applications

• Acrylic acrylates• Carbonyls• Chlorinated• Phosphates

• Carboxylic Acid Groups

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ASTM Tape Test Procedure Glass, Steel, ABS, PC –

substrate

125 um drawdown bar

Irradiate with broadband or LED

Cross hatch with razor blade

Peel with scotch tape

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Formulations contain 4 wt% photoinitiator HCPK Broadband UV light source 125 µm drawdown bar Adhesion tested using a cross hatch adhesion tape test

TMP(EO)3TA Exhibits good adhesion to PC & ABS w/o adhesion promoters Exhibits poor adhesion to glass & structural steel

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Formulations contain 10 wt% added adhesion promoter

TMP(EO)3TA Exhibits poor adhesion to glass & structural steel w/CEA Exhibits good adhesion to glass & structural steel w/Phosphate

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Aliphatic Urethane Acrylate Exhibits good adhesion to PC & ABS w/o adhesion promoters Exhibits poor adhesion to glass & structural steel

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Formulations contain 10 wt% added adhesion promoter

Aliphatic Urethane Acrylate Exhibits good adhesion to glass & structural steel w/CEA Exhibits good adhesion to glass & structural steel w/Phosphate

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Thiol-Ene Exhibits good adhesion to PC & ABS w/o adhesion promoters Exhibits poor adhesion to glass & structural steel

SH

SH

HS

= =

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Formulations contain 10 wt% added adhesion promoter

Thiol-Ene Exhibits poor adhesion to glass & structural steel w/CEA Exhibits good adhesion to glass & structural steel w/Phosphate

SH

SH

HS

= =

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Good adhesion to PC & ABS – across all systems Adhesion to Glass & Structural Steel varies w/CEA – Formulation

Dependent Adhesion to Glass & Structural Steel good w/Phosphate –

Formulation Independent

Three different formulation chemistries Four different common substrates Two different common adhesion promoters

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No significant differences in adhesion

HCPK vs TPO as photoinitiator Formulations with HCPK were cured with a broadband mercury

source Formulations with TPO were cured with a 385 nm LED

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Photoinitiator does not affect adhesion Irradiation source does not affect adhesion

TMP(EO)3TA CEA/Phosphate –HCPK/TPO

Aliphatic Urethane Diacrylate CEA/Phosphate –HCPK/TPO

Thiol-Ene CEA/Phosphate –HCPK/TPO

Broadband vs 385 nm vs 405 nm

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ViscosityWetting/Diffusive

Modulus, Shrinkage & StressFilm Integrity/Surface Interaction

Polymerization MechanismShrinkage, Stress, Surface Interaction

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Film Integrity: Film Thickness & Modulus

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Adhesion is better for rubbery materials18

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CEA is a relatively poor adhesion promoter for glass with TMP(EO)3TA & Thiol-Ene

~ 30 wt% CEA is required for adhesion to steel Results are formulation dependent

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~ 8 – 20 wt% Phosphate is required for adhesion to glass ~ 5 - 20 wt% Phosphate is required for adhesion to steel Results are formulation dependent

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OLIGOMER

ADDITIVES

MONOMERS

PHOTOINITIATORS

Fully Formulated Industrial Metal Coating

Component PropertiesBase Acrylate Monomer (50-80%) Base Properties & Viscosity

Oligomer (10-25%) ToughThiol Monomer (5-25%) Reduce Oxygen Inhibition

Adhesion Promoter (5-15%) Adhere to MetalsPhotoinitiator (1-6%) Achieve Rapid Curing

Inhibitor (< 1%) Stabilize Formulation[Optional] White Pigment (1-5%) Colored Resin

[Optional] Glass Filler (1-5%) Increase Viscosity/Scratch Resistance

Formulation Tested on metal for Adhesion using cross-hatch testing

Adhesion properties are independent of photoinitiator type and irradiation source

Phosphate is a good all-purpose adhesion promoterFormulations may be hazy

Thicker formulations (~250 um) exhibit better adhesion than thinner formulations (~ 50 um)

Rubbery materials exhibit better adhesion than glassy materials

Optimized adhesion promoter concentrations are formulation and thickness dependent

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IGM Resins Donation of materials

Miwon North America Inc Donation of materials

Dymax Oligomers & Coatings BlueWave® 405 nm LED Flood System

Sartomer Donation of materials

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Thank You!

Contact information:Dr. Mike J. IdacavageVP Business DevelopmentColorado Photopolymer Solutions1880 S. Flatiron Ct, Suite JBoulder, CO 80301303-551-3213mike.idacavage@cpspolymers.comwww.cpspolymers.com

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