The Next Generation of Epoxy Adhesives Technology for ...media.mycrowdwisdom.com.s3.amazonaws.com/asc/2016... · Full cure shear strength at 14 –17 MPa (2,000 –2,500 psi) Issues

The Next Generation of Epoxy Adhesives

Technology for Transportation Assembly:

Low Bake One-Component Epoxies

Daniel R. Daley

Senior Consultant

The ChemQuest Group, Inc.

2© Copyright 2016, The ChemQuest Group, Inc. All Rights Reserved

Introduction

• With over 30 years of experience at Navistar International, a

truck and engine OEM, Dan Daley has held various senior

polymeric materials engineering and lab management

positions.

• Daley’s technical leadership included solving problems in

material compatibility and chemical interactions, and

improving material performance/cost ratios and strategic

sourcing.

• The range of materials managed included soft trim such as

textiles, foams, composites, seating, upholstery and acoustic

materials and energy management solutions; fluid connectors;

lubricants and fluid systems; elastomers; automotive paint

and coatings; adhesives, sealants and joining systems.


What is the Unmet Need in Assembly?

• Automotive and truck body manufacturing plants have predominantly used 1K epoxy structural adhesives due to their superior bonding performance and manufacturing-friendly properties.

• Adhesives are co-cured in an electro-coat (e-coat) epoxy prime system at high temperatures (175ºC).

• Commercial vehicle body manufacturers that are unable to justify the capital equipment expense of a full immersion e-coat system cannot take advantage of the processing and performance benefits of a 1K Epoxy System.

• A school bus body assembled with mechanical fasteners and 2K epoxy or methyl methacrylate (MMA) adhesives is one such example.


A Significant Development is Currently Underway

• The emerging low bake 1K epoxy technology is a significant development.

• It promises to deliver all the advantages of 1K epoxy adhesives: Efficient assembly operations

High strength with toughness

Weld-thru property

• It provides assembly operations lacking the capital and infrastructure to invest in high bake systems with an ability to leverage the key advantages of technology commonly used in automotive and aircraft assembly.

• Finally, it will allow automotive manufacturers and others to use lighter weight materials that would not survive high bake conditions.


Vehicle Body Construction



• The body is constructed predominantly of metal in spite of a

wider range of available materials that offer key advantages

• Low Capitalized Body Systems mix arc welding (MIG, TIG)

and fasteners



• High Capitalized Body

Systems utilize resistance

spot welding

• Aluminum systems mix

welding (resistance and arc)

with fastening for reliability

• Prime systems are based on

capital and final market

requirements

• High-end Adhesives users

use analytical tools to

optimized performance


Construction Materials and Joining Methods

Body Construction

• Stamped Steel

Assembly Method

• Spot Weld

Commercial Auto Body

Prime

• E-coat

Bonding Technologies

• 1K epoxy structural

adhesive

Body Construction

• Steel and Aluminum

Assembly Method

• Spot Weld and SPR

Light Truck

Prime

• E-coat


• 1K epoxy structural

adhesive

Body Construction

• Aluminum and Steel

Assembly Method

• SPR, Rivets,

Fasteners & Welding

Heavy Truck

Prime

• E-coat, Precoat


• 1K & 2K Epoxies,

PUR, methyl

methacrylate (MMA)

Body Construction

• Fabricated Steel

Assembly Method

• Rivets, SPR,

Welding

School Bus

Prime

• Precoat


• 2K Epoxy, 2K methyl

methacrylate (MMA)

SPR = self piercing rivets


Future Construction Materials and Unmet Needs

Future Construction

• Steel, Aluminum & Composite

Unmet Needs

• Low bake 1K epoxy structural

adhesive and primer

• Composite Fastening

Commercial Auto Body

Future Construction

• Aluminum & Composite

Unmet Needs

• Low bake 1K epoxy structural adhesive

and primer

Light Truck / Heavy Truck

Future Construction

• Improved joining methods, paint

systems

Unmet Needs

• Low-bake cure 1K epoxy

structural adhesive

School Bus


School Bus Manufacturing

• School bus joints must be in compliance with federal

regulation, “49 CFR 571.221 - Standard No. 221; School bus

body joint strength”

Requirement “shall hold the body panel to the member to

which it is joined when subjected to a force of 60 percent of

the tensile strength of the weakest joined body panel”

• Test sections are cut into “dog bones” necked down to 8”

through the joint.


Current Process

Assembly Steps

Coil coated (primed) steel is fabricated into sheets and forms

Assemblies – adhesive applied, fixture, drilled (unless SPR) then riveted

Major structures are Arc welded

Final structures – fixture, bonded, drilled and fastened

Prime and seal with cure bake

Top-coat paint – usually yellow with black rails and white roofs

Pitfalls

Mostly arc welding, little

spot welding

Metal debris from drilling

may contaminate the

joint

Riveting may cause

excessive equipment

wear (and worker

fatigue/repetitive use

injuries)


Current School Bus Joining Methods

Semi Tubular Rivet

Mono Bolt Rivet

Self Piercing Rivet

Source: American Society of Mechanical Engineers (ASME)


Comparison of Adhesive Technologies that Meet Required

Joint Strength

• 2K Epoxies

Long open time systems

Often pre mixed and used at application

Ultimate strength may require bake

Full cure shear strength at 14 – 17 MPa (2,000 – 2,500 psi)

Issues – Open assembly time, waste, clean up, post bake bonding

• 2K Methyl Methacrylate (MMA)

Short open times

Mix at application

Ultimate strength independent of bake

Ultimate shear strength 17 – 21 Mpa (2500 –3000 psi)

Issues – sociability - odor, open assembly time, cannot weld thru, flammable, repair


Contrasted to a Low Bake (120ºC) 1K Epoxy Adhesive

• Compatible with any current fastener type

• Can be resistance spot welded

• Can co-cure with sealant and prime bakes

• Does not cure until bake (pre-bake clean up is easy)

• Bulk dispense, bulk purchase

• No mix

• High strength – shear 24 – 27.5 Mpa (3,500 – 4,000 psi)

• Higher strength is greater tolerance on regulation or opportunity to reduce fastening

• No open time limits - No line stripping for partially assembled joints.

• Low bake is practical with large bodies


Required Testing Methods

FMVSS 221 Joint Test

Joint A B C D E F G H I

2k Epoxy 220F Heat Cure 6597 10131 14040 8683 8679 6314 11475 7264 9283

1k Heat Cure Estimate 12976 13048 30721 13884 13866 5232 13633 23819 31239

Min. req. 5962 5995 14115 6379 6371 2404 6264 10944 14353

FMVSS Factor 3.51 3.53 8.30 3.75 3.75 1.41 3.68 6.44 8.44

Substrate 1"x4" Plate Steel (1.6mm)

Cure Schedule 30' @ 250°F

Closed Joint Open Joint

Lap Shear (psi) Lap Shear (psi)

Initial 3,877 3,877

CF CF

1 week 4,021 3,978

CF CF

CF = Cohesive Failure


Benefits for School Bus Manufacturers

• Lower Manufacturing Costs

Replace fasteners for spot welds

Reduce fastener usage

Reduce drilling

Less waste

Better Assembly Line Management

Better energy management opportunity

Co cure in existing process

• Improved Joint Performance (e.g., side intrusion, roll over, roof strength)

• Improved Quality

Better corrosion control

Reduced repetitive injuries to workers

Less paint damage


Additional Savings and Opportunities

• Paves the way for a greater freedom in body design and improved efficiency in vehicle body assembly operations

Opportunity to incorporate lower temperature resistant materials into assemblies.

Compatible primer technologies

Low bake E-coat is under development

Lower energy usage (bake ovens estimated to be 60% of an assembly plant’s energy consumption)

Opportunity for non-automotive assembly operations to take advantage of the process improvements


Conclusions

• While 1K Epoxies offer superior processing and performance advantages, the direct (and indirect) costs of conventional high temperature curing created barriers to use.

• Those barriers are removed with a low bake 1K Epoxy System – a significant advantage to non-automotive industries.

• When an OEM switches from a 2K to 1K system:

Waste is greatly reduced

Quality is improved

Superior joining methods become available

Greater freedom in body design is realized.


Conclusions

• Moreover, a low bake system coupled with low bake immersion primer systems (120ºC or lower cure) will reduce energy costs and broaden the range of materials that can be used to meeting lightweighting requirements and further reduce costs.

• The 1K Epoxy technology will facilitate new methods and materials in the process, assembly and paint operations for other vehicle assembly operations (including School Bus assembly) for improved efficiency, performance and safety.


Headquarters

The ChemQuest Group, Inc.

8150 Corporate Park Drive

Suite 250

Cincinnati, Ohio 45242

Phone: (513) 469-7555

Fax: (513) 469-7779

www.chemquest.com

Contacts

Dan Murad

President and CEO

[email protected]

Dan Daley

Senior Consultant

[email protected]

A Special Thanks to Frank Billotto at Dow Automotive

(248) 391-6578 [email protected].

http://www.chemquest.com/

mailto:[email protected]




TM

ChemQuest Group. . . .

The Obvious Choice

Thank You

Documents

The Next Generation of Epoxy Adhesives Technology for ...media.mycrowdwisdom.com.s3.amazonaws.com/asc/2016... · Full cure shear strength at 14 –17 MPa (2,000 –2,500 psi) Issues