Handbook of Adhesives and Surface Preparation: Technology, Applications and Manufacturing

418 Pages·2010·17.24 MB·English

by  Sina Ebnesajjad

PLASTICS DESIGN LIBRARY(PDL)
PDL HANDBOOK SERIES
SeriesEditor:Sina Ebnesajjad,PhD
President, FluoroConsultantsGroup, LLC
ChaddsFord,PA,USA
www.FluoroConsultants.com
ThePDL Handbook Seriesisaimed at awide range ofengineersand otherprofessionals working inthe plastics
industry, andrelated sectors using plastics and adhesives.
PDL isa series of data books,referenceworks andpractical guides covering plastics engineering,applications,
processing, and manufacturing,and applied aspectsofpolymer science,elastomers andadhesives.
Recenttitles inthe series
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ISBN:9780815520276
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ISBN:9780815520214
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HANDBOOK OF ADHESIVES AND
SURFACE PREPARATION
Technology, Applications and Manufacturing
Edited by
Sina Ebnesajjad
President, FluoroConsultants Group, LLC
Amsterdam (cid:129) Boston (cid:129) Heidelberg (cid:129) London (cid:129) New York (cid:129) Oxford
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Firstpublished 2011
Newmaterial included inthis work
Copyright (cid:1) 2011.Published by Elsevier Inc. All rights reserved.
Previouslypublished materialappearing inthis work
Copyright (cid:1) 2006,2008,2011. Published by ElsevierInc. All rights reserved.
Copyright (cid:1) 2005,2006.Published by ElsevierLtd. All rights reserved.
Material inthis work originallyappeared in Adhesives TechnologyHandbook (Second Edition),edited bySina
Ebnesajjad(ElsevierInc.,2008,ISBN978-0-8155-1533-3),SurfaceTreatmentofMaterialsforAdhesionBonding,edited
bySinaEbnesajjadandCyrusF.Ebnesajjad(ElsevierInc.,2006,ISBN978-0-8155-1523-4),HandbookofAdhesivesand
Sealants,Volume1,editedbyPhilippeCognard(ElsevierLtd,2005,ISBN978-0-0804-4554-0),HandbookofAdhesives
andSealants,Volume2,editedbyPhilippeCognard(ElsevierLtd,2006,ISBN978-0-0804-4708-7)andAppliedPlastics
EngineeringHandbook,editedbyMyerKutz(ElsevierInc.,2011,ISBN978-1-4377-3514-7).
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may benotedherein).
Notices
Knowledge and best practice inthisfield are constantlychanging. As new research and experiencebroaden our
understanding, changes inresearch methods,professional practices, ormedical treatmentmay become necessary.
Practitioners and researchers mustalways rely on their own experience and knowledge inevaluating andusingany
information,methods,compounds,orexperimentsdescribedherein.Inusingsuchinformationormethodstheyshould
be mindfulof their own safety and the safety of others, including parties for whom theyhavea professional
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Acknowledgments
InthisworkIhaveselectedarangeofmaterialfrom support, knowledge, good nature, and patience. His
recent books published by Elsevier, including titles in support of this project has been essential to the mate-
the William Andrew imprint. Thus, I would like to rialization of the book.
offer my recognition to the authors of the selected I would like to thank my editorial assistant Miss
material, and editors of the books from which I have Kristin N. Dross for her work on the contents of this
sourcedthismaterial:JohnBishopp,ChristianDecker, book. She reviewed, edited and corrected the writings
Cyrus F. Ebnesajjad, Guy Rabilloud, Peter G. Pape, of the content, raised questions, and helped me find
PhilippeCognard,editoroftheHandbookofAdhesives answers to them.
and Sealants and Myer Kutz, editor of the Applied Lisa Jones was the project manager for the
Plastics Engineering Handbook. production of this book and has my heartfelt appreci-
I would like to offer my deepest appreciations to ation for her diligence and unlimited patience.
Dr.KayvonModjarrad(MD,PhD),InfectiousDisease I wish to thank all the companies that have gener-
Specialist and Dr. Peter E. Dross, neuroradiologist for ously contributed to this book by allowing the author
the review and revision of Chapter 14. Their patience useoftheirdata,information,illustrations,photographs
in explaining medical topics to me was beyond andproductandprocess. Ihavedonemybesttoensure
generous. My thanks go to Dr. Norman Rocheleau, thenameofeachcompanyiscitedforeachuse.
DDM for the review of the sections on dental appli-
cations of adhesives.
My sincere appreciation goes to my colleague, Sina Ebnesajjad
managerandfriendMr.MatthewDeansforhistireless Chadds Ford, Pennsylvania
xvii
Dedicated to the memories of my dear friend
William Andrew Woishnis
Who left the world too early, too young.
Preface
A basic industrial process is the bonding of similar itisusefulforallinvolvedintheproductvaluechains,
and dissimilar materials to each other. Bonding using and it offers information helpful to engineers, chem-
an adhesive has proven to be an effective means of ists, students, and all others involved in material
attaching materials together. adhesion and processing.
Therearenumerousbooksaboutadhesives.Several Every attempt has been made to enhance the
excellentbooksareavailablethatdealwiththesubject accessibility of the information to create a reader-
of adhesives from various viewpoints. Some have friendlytext.Inthebalanceofpracticalandtheoretical
looked at adhesives from the perspective of synthesis, subjects, practical has been given definite precedence.
chemistry, or bonding techniques. Others have treated This is a trade-off that the author readily acknowl-
thesubjectfromapracticalstandpoint.Ofthese,most edges.Therearenumerousgoodbooksandsourcesfor
are attempts to describe adhesion in relation to the study of the theory and science of adhesion and
avarietyofmaterials,includingplastics,metals,wood, adhesives.
and so on. A few books regarding applications of The references listed at the end of each chapter
adhesives are highly specialized in particular indus- serve as both bibliography and additional reading
tries, such as metals and construction. sources. Most of the basic practical technology of
Whatisdifferentaboutthisbook?Thepresentbook adhesives was developed decades ago. Older refer-
is focused on practitioners of adhesion technology ences have been retained wherever they represent the
from an end-user’s perspective, thus covering most preferred source of information for a specific topic.
substrates, such as plastics, metals, elastomers, and Readers can find a wealth of information and reports
ceramics.Theinformationisaimedatallowingreaders that have been declassified by the Defense Technical
to select the right adhesive and successfully bond Information Center (www.dtic.mil), most of which
materials together. Other than the choice of the date to the 1960s.
appropriate adhesive, surfaces must be pretreated The book consists offour parts. Part I contains two
according to specific methods and prior to the appli- introductory chapters that describe the fundamental
cation of adhesives. By including generous selections concepts of surface treatment and adhesion. Part II is
from the recent back catalog of both Elsevier and comprised of chapters that describe surface tension
William Andrew publishing (now part of Elsevier), I (energy)concepts,surfacecharacterizationtechniques,
aim to provide to an audience of engineers and other and surface preparation methods for metals and ther-
professionals working with adhesives, a wide-ranging moplastics, thermosets, and elastomers.
and practical handbook. Part III describes the characteristics of adhesives
Thisbookdescribestreatmentmethodsthatmustbe from the standpoints of chemical structure and
applied to a material surface before successful adhe- application. Heat-resistant and UV-cure adhesives are
sive bonding is possible. There are numerous exam- discussed in separate chapters because of their
ples, ranging from wallpaper in a house and paint on importance to the adhesive industry.
surfaces to parts used in the construction of aircraft. Part IV of the book describes the applications of
The aim of the contents is to explain, in an accessible adhesives with respect to special adherends. Applica-
yet complete manner, all that is required to achieve tions of adhesives in aerospace, electronic, and
successful adhesion bonding of different materials. medical/dental have been described in separate chap-
Fundamental material considerations have been tersbecauseoftheimportanceandbreadthofadhesion
givenprioritytofacilitatetheuseofthecontentsofthis useintheseindustries.Therearefew,ifany,adhesives
book in different industries. The book is both a refer- thatarenotusedbytheseindustries,thusrenderingthe
enceandasourceforlearningthebasics.Additionally, information in the chapters useful to nearly any other
xix
xx PREFACE
industry. After all, the aerospace industry has been informationpresentedinthisbookreflecttheopinions
a pioneer in the use of structural adhesive bonding in of any of the companies or individuals that have
critical applications. contributed to the book. If there are errors, they are
Appendix A discusses Safety, Environmental, an inadvertent oversight on the part of the author.
Economic Aspects, and Future Trends. Appendix B A note indicating suggestions or specific errors to the
providesanexactcopyoftheFDAGuidanceforTissue publisher,forthepurposeofcorrectingfutureeditions,
Adhesive for the Topical Approximation of Skin would be much appreciated.
issued in May2008. A glossary section roundsoff the
book.
I hope this book is useful to thosewho practice the Sina Ebnesajjad
art of adhesion as a profession. None of the views or Chadds Ford, Pennsylvania
1 Introduction and Adhesion Theories
Sina Ebnesajjad
1.1 Definition of Adhesives The distinction between structural and nonstruc-
turalbondsisnotalwaysclear.Forexample,isahot
and Adhesive Bonding
melt adhesive used in retaining a fabric’s plies
An adhesive is a material that is applied to the structuralornonstructural?Onemayarguethatsuch
surfaces of articles to join them permanently by an an adhesive can be placed in either classification.
adhesivebondingprocess.Anadhesiveisasubstance However, the superglues (cyanoacrylates) are clas-
capable of forming bonds to each of the two parts sified as structural adhesives even though they have
whenthefinalobjectconsistsoftwosectionsthatare poor resistance to moisture and heat.
bonded together.1 A feature of adhesives is the rela-
tively small quantities that are required compared to 1.2 Functions of Adhesives
the weight of the final objects.
Adhesion is difficult to define, and an entirely The primary function of adhesives is to join parts
satisfactory definition has not been found. The together. Adhesives accomplish this goal by trans-
following definition has been proposed by Wu.2 mitting stresses from one member to another in
“Adhesionrefers to the state in which two dissimilar a manner that distributes the stresses much more
bodies are held together by intimate interfacial uniformly than can be achieved with mechanical
contact such that mechanical force or work can be fasteners. Adhesive bonding often provides struc-
transferredacrosstheinterface.Theinterfacialforces tures that are mechanically equivalent to or stronger
holding the two phases together may arise from van than conventional assemblies at lower cost and
der Waals forces, chemical bonding, or electrostatic weight. In mechanical fastening, the strength of the
attraction. Mechanical strength of the system is structureislimitedtothatoftheareasofthemembers
determinednotonlybytheinterfacialforces,butalso in contact with the fasteners.4 Obtaining adhesive
by the mechanical properties of the interfacial zone bonds that are stronger than those of the strength of
and the two bulk phases.” adherends is not unusual.
There are two principal types of adhesive Smooth surfaces are an inherent advantage of
bonding: structural and nonstructural. Structural adhesively joined structures and products. Exposed
adhesive bonding is bonding for applications in surfaces are not defaced and contours are not
whichtheadherends(theobjectsbeingbonded)may disturbed, as happens with mechanical fastening
experience large stresses up to their yield point. systems. This feature is important in function and
Structural adhesive bonds must be capable of appearance. Aerospace structures, including heli-
transmitting stress without losing of integrity within copter rotor blades, require smooth exteriors to
design limits.3 Bonds must also be durable minimize drag and to keep temperatures as low as
throughout the useful service life of a part, which possible.Lighterweightmaterialsthanareusedwith
may be years. In addition to possessing significant conventional fastening can often be used with
resistance to aging, a structural bond is defined as adhesive bonding because the uniform stress distri-
having a shear strength greater than 7 MPa. bution in the joint permits full utilization of the
Nonstructural adhesives are not required to support strength and rigidity of the adherends.4 Adhesive
substantial loads but merely hold lightweight mate- bondingprovidesmuchlargerareasforstresstransfer
rials in place. This type of adhesive is sometimes throughout the part, thereby decreasing stress
called a “holding adhesive.” Pressure-sensitive tapes concentration in small areas.
and packaging adhesives are examples of nonstruc- Dissimilar materials, including plastics, are
tural adhesives. readily joined by many adhesives, provided that
HandbookofAdhesivesandSurfacePreparation,ed.SinaEbnesajjad.DOI:10.1016/B978-1-4377-4461-3.10001-X
(cid:1)2011ElsevierInc.Allrightsreserved.
Thischapterhasbeenadaptedfrom‘IntroductionandAdhesionTheories’inAdhesivesTechnologyHandbook(2nded.),
Ebnesajjad(cid:1)2008ElsevierInc. 3
4 HANDBOOK OF ADHESIVES AND SURFACE PREPARATION
propersurfacetreatmentsareused.Adhesivescanbe will cover both advantages and disadvantages of
used to join metals, plastics, ceramics, cork, rubber, adhesive bonding, and some points are reiterated.
andcombinationsofmaterials.Adhesivescanalsobe
formulated to be conductive. The focus of this book
1.4.1 Advantages
is on adhesives for bonding plastics, thermosets,
elastomers, and metals. (cid:1) Uniform distribution of stress and larger stress-
Where temperature variations are encountered in bearing area5,6
theserviceofanitemcontainingdissimilarmaterials,
(cid:1) Joins thin or thick materials of any shape
adhesives perform another useful function. Flexible
adhesivesareabletoaccommodatedifferencesinthe (cid:1) Joins similar or dissimilar materials
thermal expansioncoefficients of theadherends, and (cid:1) Minimizesorpreventelectrochemical(galvanic)
therefore prevent damage that might occur if stiff
corrosion between dissimilar materials
fastening systems were used.
(cid:1) Resists fatigue and cyclic loads
Sealing is another important function of adhesive
joining.Thecontinuousbondsealsoutliquidsorgases (cid:1) Provides joints with smooth contours
thatdonotattacktheadhesive(orsealant).Adhesives/ (cid:1) Seals joints against a variety of environments
sealants are often used in place of solid or cellular
(cid:1) Insulates against heat transfer and electrical
gaskets. Mechanical damping can be imparted to
conductance (in some cases adhesives are
astructurethroughtheuseofadhesivesformulatedfor
designed to provide such conductance)
that purpose. A related characteristic, fatigue resis-
tance,canbeimprovedbytheabilityofsuchadhesives (cid:1) The heat required to set the joint is usually too
to withstand cyclic strains and shock loads without low to reduce the strength of the metal parts
cracking. In a properly designed joint, the adherends (cid:1) Dampens vibration and absorb shock
generallyfailinfatiguebeforetheadhesivefails.Thin
(cid:1) Provides an attractive strength/weight ratio
orfragile partscan alsobe adhesivelybonded.Adhe-
sive joints do not usually impose heavy loads on the (cid:1) Quickerand/orcheapertoformthanmechanical
adherends, as in riveting, or localized heating, as in fastening
welding. The adherends are also relatively free from
heat-induceddistortion.4
1.4.2 Disadvantages
(cid:1) The bond does not permit visual examination
1.3 Classification of Adhesives
of the bond area (unless the adherends are
transparent)5e7
Adhesivesasmaterialscanbeclassifiedinanumber
(cid:1) Careful surface preparation is required to
of ways, such as chemical structure or functionality.
obtain durable bonds, often with corrosive
Adhesivesarecategorizedintotwoclasses:naturaland
chemicals
synthetic. The natural group includes animal glue,
casein- and protein-based adhesives, and natural (cid:1) Long cure times may be needed, particularly
rubberadhesives.Thesyntheticgrouphasbeenfurther where high cure temperatures are not used
divided into two subcategories industrial and special (cid:1) Holdingfixtures,presses,ovens,andautoclaves,
compounds. Industrial compounds include acrylics,
notusuallyrequiredforotherfasteningmethods,
epoxies, silicones, etc. An example of the specialty
are necessities for adhesive bonding
groupispressure-sensitiveadhesives.
(cid:1) Upper service temperatures are limited to
(cid:3)
approximately177 Cinmostcases,butspecial
adhesives,usuallymoreexpensive,areavailable
1.4 Advantages and
(cid:3)
for limited use up to 371 C
Disadvantages of Joining
(cid:1) Rigid process control, including emphasis on
Using Adhesives
cleanliness, is required for most adhesives
The previous discussion highlighted a number (cid:1) The useful life of the adhesive joint depends on
of advantages of adhesive bonding. This section the environment to which it is exposed
1: INTRODUCTION AND ADHESION THEORIES 5
(cid:1) Naturalorvegetable-originadhesivesaresubject between the adherends and the adhesive over which
toattackbybacteria,mold,rodents,orvermin the forces of adhesion may act.10
(cid:1) Exposuretosolventsusedincleaningorsolvent
1.5.5 Adhesive Bonding Process
cementing may present health problems
Successful bonding of parts requires an appro-
priate process. The adhesive must not only be
1.5 Requirements of a Good Bond
applied to the surfaces of the adherends; the bond
should also be subjected to the proper temperature,
The basic requirements for a good adhesive bond
are:6 pressure,andholdtime.Theliquidorfilmadhesive,
once applied, must be capable of being converted
(cid:1) Proper choice of adhesive into a solid in one of three ways. The method by
whichsolidificationoccursdependsonthechoiceof
(cid:1) Good joint design
adhesive. The ways in which liquid adhesives are
(cid:1) Cleanliness of surfaces converted to solids are:6
(cid:1) Wetting of surfaces that are to be bonded
(cid:1) Chemical reaction by any combination of heat,
together
pressure, and curing agents
(cid:1) Proper adhesive bonding process (solidification
(cid:1) Cooling from a molten liquid
and cure)
(cid:1) Drying as a result of solvent evaporation
1.5.1 Proper Choice of Adhesive
There are numerous adhesives available for Requirements to form a good adhesive bond, as
bondingmaterials.Selectionoftheadhesivetypeand well as processes for bonding, analytic techniques,
form depends on the nature of adherends, perfor- and quality control procedures, are discussed in this
mancerequirementsoftheenduse,andtheadhesive book.
bonding process.
1.5.2 Good Joint Design 1.6 Introduction to Theories
Impartingstrengthtoajointbydesignispossible.8 of Adhesion
Acarefullydesignedjointyieldsastrongerbondthan
Historically, mechanical interlocking, electro-
one not carefully designed when advantages of the
static, diffusion, and adsorption/surface reaction
mechanicaldesignarecombinedwithadhesivebond
theories have been postulated to describe mecha-
strength to meet the end use requirements of the
nisms of adhesion. Theories have recently been
bonded part.
postulatedforadhesivebondingmechanisms(Table
1.5.3 Cleanliness 1.1). It is often difficult to fully ascribe adhesive
bonding to an individual mechanism is often diffi-
To obtain a good adhesive bond, starting with
cult. A combination of different mechanisms is
a clean adherend surface is essential. Foreign mate-
most probably responsible for bonding. The extent
rialssuchasdirt,oil,moisture,andweakoxidelayers
of the role of each mechanism may vary for
must be removed, lest the adhesive be bonded to
different adhesive bonding systems. An under-
weak boundary layers rather than to the substrate.
standing of these theories is helpful to those who
Various surface treatments exist that remove or
work with adhesives.
strengthen the weak boundary layers. Such treat-
An important facet of adhesion bonds is the locus
ments typically involve physical or chemical pro-
of the proposed action or the scale to which the
cesses, or a combination.9
adhesive and adherend interact. Table 1.1 shows
a scale of action for each mechanism, which is
1.5.4 Wetting
intended to aid in the understanding of these mech-
Wettingisthedisplacementofair(orothergases) anisms. Of course, adhesiveeadherend interactions
presentonthesurfaceofadherendsbyaliquidphase. always take place at the molecular level, discussed
The result of good wetting is greater contact area later in the chapter.