Update on Engineering and Structural Adhesives

198 Pages·2010·4.04 MB·English

by  Dunn

Update on
Engineering and
Structural Adhesives
David Dunn
iSmithers – A Smithers Group Company
Shawbury, Shrewsbury, Shropshire, SY4 4NR, United Kingdom
Telephone: [phone] Fax: [phone]
http://www.ismithers.net
First Published in 2010 by
iSmithers
Shawbury, Shrewsbury, Shropshire, SY4 4NR, UK
©2010, Smithers Rapra
All rights reserved. Except as permitted under current legislation no part
of this publication may be photocopied, reproduced or distributed in any
form or by any means or stored in a database or retrieval system, without
the prior permission from the copyright holder.
A catalogue record for this book is available from the British Library.
Every effort has been made to contact copyright holders of any material
reproduced within the text and the authors and publishers apologise if
any have been overlooked.
ISBN: 978-1-84735-480-8 (Hardback)
978-1-84735-481-5 (ebook)
Typeset by Argil Services
Printed and bound by Lightning Source Inc.
P
reface
Engineering and structural adhesives are distinguished from other
adhesives by being high-strength materials designed to support static
or dynamic loads (often substantial loads).
These adhesives are often subjected to cycling high and low
temperatures and aggressive fluids or the weather. In general, they
are used for the bonding of rigid structures, although some degree of
flexibility or toughness is often desirable in the adhesives to counter
the effects of movement, impact or vibration. Although traditionally
used in the metal-working industries, these adhesives are now even
more widely used with more modern materials.
This review describes the most important adhesives for engineering
applications:
• Anaerobics
• Epoxies
• Reactive acrylics
• Ultraviolet light (UV)-cured adhesives
• Polyurethanes
• Reactive hot-melt polyurethanes
• Special formulations of cyanoacrylates
It covers the basic chemistry, applications, advances in technology,
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Update on Engineering and Structural Adhesives
and durability testing of these adhesives. Important breakthrough
technologies are highlighted, such as the use of organoboranes as
initiators for the bonding of low-surface-energy plastics, and the use
of nanotechnology to improve properties. Key articles and patents are
cited: these represent some of the key developments in the subject.
David J Dunn
Ohio, USA
July 2010
iv
C
ontents
1 Introduction .........................................................................1
2 Types of Engineering and Structural Adhesives .....................5
2.1 Anaerobic Adhesives ...................................................6
2.2 Epoxy Adhesives .......................................................14
2.3 Reactive Acrylic Adhesives .......................................23
2.4 UV Adhesives ...........................................................30
2.4.1 Basic Chemistry of UV Systems .................30
2.4.1.1 Free-Radical Systems ................31
2.4.1.2 Cationic Systems ......................33
2.4.2 Benefits of UV Systems ..............................35
2.4.3 Advances in UV Technology ......................35
2.4.4 Applications of UV Adhesives ...................36
2.5 Polyurethane Adhesives ...........................................38
2.5.1 Non-reactive Adhesives .............................41
2.5.2 Reactive Adhesives ...................................42
2.6 RHMU ....................................................................45
2.7 Cyanoacrylate Adhesives .........................................47
2.7.1 Low-volatile Cyanoacrylates ....................52
2.7.2 Surface-insensitive Cyanoacrylates ............52
2.7.3 Thermally Resistant Cyanoacrylates ..........52
2.7.4 Toughened Cyanoacrylates ........................53
2.7.5 Bonding of Non-polar Plastics ...................54
Update on Engineering and Structural Adhesives
2.7.6 Preventing Skin Bonding ............................54
2.7.7 Glass Bonding and Moisture Resistance ....54
2.8 Comparison of Engineering and Structural Adhesives 55
3 Applications of Adhesives ...................................................63
3.1 Industrial Assembly ..................................................64
3.1.1 Appliances .................................................64
3.1.2 Electrical and Electronic ............................66
3.1.3 Medical Devices ........................................71
3.2 Transportation ..........................................................75
3.2.1 OEM Automotive ......................................77
3.2.1.1 Powertrain Applications ...........79
3.2.1.2 Body Applications .....................84
3.2.1.3 Electrical Applications...............88
3.2.1.4 Trim Applications .....................88
3.2.2 Aerospace ..................................................91
3.2.3 Marine ......................................................94
4 Advances in Adhesive Technology ......................................99
4.1 Bonding of Metals ....................................................99
4.1.1 Bonding of Aluminium ............................103
4.1.2 Bonding of Dissimilar Metals and
Metals to other Substrates .......................104
4.2 Bonding of Plastics and Composites .......................105
4.2.1 General Plastic and Composite Bonding ..105
4.2.2 Bonding of Specific Plastics ......................107
4.2.3 Bonding of Non-polar Plastics .................109
4.2.3.1 Flame Treatment ....................109
4.2.3.2 Chemical-surface Treatment ....109
4.2.3.3 Plasma Treatment ....................110
vi
Contents
4.2.3.4 Fluorination ............................111
4.2.3.5 Polymer Modification..............111
4.2.3.6 Surface Primers .......................112
4.2.3.7 Organoboranes ......................114
4.3 Bonding of Glass and Ceramics ..............................123
5 Durability of Adhesively Bonded Structures .....................137
5.1 Surface Treatments for Metals ................................140
5.2 Testing and Inspection of Adhesive Bonds .............145
6 Application and Curing of Adhesives ...............................155
7 Standards for Adhesives ...................................................161
7.1 ISO Standards .........................................................162
7.2 European Standards ................................................164
7.3 ASTM Standards ....................................................166
8 Health and Safety Issues ...................................................169
9 Future Trends ...................................................................171
Abbreviations ...........................................................................173
Index ........................................................................................175
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Update on Engineering and Structural Adhesives
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1
Introduction
Adhesives are materials designed to hold materials together by
surface attraction, often as alternatives to mechanical fastening
systems. Adhesives come in several forms: thin liquids, thick pastes,
films, powders, pre-applied on tapes, or solids that must be melted.
Adhesives can be designed with a wide range of strengths, all the
way from weak temporary adhesives for holding papers in place to
high-strength structural systems that bond cars and airplanes. In many
industries, adhesives compete with mechanical fastening systems such
as nuts and bolts, rivets or welding and soldering [1].
Engineering and structural adhesives are distinguished from other
adhesives by being high-strength materials that are designed to
support static or dynamic loads (often substantial loads).
These adhesives are often subjected to cycling high and low
temperatures and aggressive fluids or the weather. In general they
are used for the bonding of rigid structures, although some degree of
flexibility or toughness is often desirable in the adhesives to counter
the effects of movement, impact or vibration. Although traditionally
used in the metal-working industries, these adhesives are now even
more widely used with more modern materials. The commonest
materials bonded with structural adhesives are metals, glass, ceramics,
plastics and composites. Adhesives used for bonding wood in the
construction and furniture industry are often structural, but wood
bonding is usually treated as a subject in its own right and is not
covered in this review.
1