Investigation of adhesion occurring between polyurethane substrates and polyurethane surface ...

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Loughborough University
Institutional Repository
Investigation of adhesion
occurring between
polyurethane substrates and
polyurethane surface
coatings
ThisitemwassubmittedtoLoughboroughUniversity’sInstitutionalRepository
by the/an author.
Additional Information:
• A Doctoral Thesis. Submitted in partial fulfilment of the requirements
for the award of Doctor of Philosophy of Loughborough University.
Metadata Record: https://dspace.lboro.ac.uk/2134/10447
Publisher: (cid:13)c Khosrow Bidari
Please cite the published version.
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LOUGHBOROUGH
UNIVERSITY OF TECHNOLOGY
LIBRARY
AUTHOR/FILING TITLE
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- 2 JUL 1993
16 .1 tHl 1995
30 JUN 1995
28 JUN 1996
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INVESTIGATION OF ADHESION OCCURRING BETWEEN
POLYURETHANE SUBSTRATES AND POLYURETHANE SURFACE COATINGS
by
KHOSROW BIDARI
A Doctoral Thesis submitted in partial fulfilment
of the requirements for the award of
Doctor of Philosophy
of the
Loughborough University of Technology
1991
Supervisor: R J. Heath, PhD
Institute of Polymer Technology and
Materials Engineering
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This thesis is dedicated to my dear parents and my
darling wife, Parvaneh.
* * * * *
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ERRATA
Page No Line No
3 5 'will ranain' for 'remains'
4 Table 1.1 add 'foam' after 'rigid'
6 10 insert full stop after ' involved' - insert
'these'before 'can'
7 15 insert 'are' after 'thinners'
25 12 'neutralisation of' for 'neutralising'
27 15
27 16 insert 'it' after 'using' - delete 'it'
after 'alone'
40 8 'made' for 'being' - delete 'the'
50 17 , swelling' for 'intumencing'
80 10 'observed' for 'real'
82 2 , adsorption' for 'adhesion'
83 16 'the' for 'both'
98 25 'confined' for 'combined'
99 9 'rrolecular layer' for 'lattice'
NB: All line numbers refer to text only; headings, diagrams and
equations not being counted.
ACKNOWLEDGEMENTS
I am deeply indebted to my supervisor, Dr R J Heath, for
his invaluable assistance, advice and unceasing
encouragement throughout the preparation of this thesis.
I wish to thank all who have helped in this work. In
particular, Baxenden for materials and time on RIM
equipment, Macpherson Coatings Ltd, Compounding
Ingredients Ltd and Gusmer Corporation (USA) for
materials and considerable advice.
I am especially grateful to my wife, Parvaneh, for her
assistance, patience and moral encouragement.
Finally, my thanks go to all the IPTME staff and
colleagues and to Mrs Janet Smith for her patient
efforts in typing this thesis.
i
ABSTRACl'
In the last ~ decades a substantial 8lID\IDt of research has been
carried out on the physi=-chemical aspects of adhesion. However,
this phenomenon when related to organic coatings on polymeric
substrates has undergone only limited study.
This research primarily studies the adhesion properties of
polyurethane (PU) paint materials applied to a range of different PU
substrate materials. Sane PU coated polyester substrates are also used
to provide a IIOre ocmplete understanding of interfaces produced. The
coating of substrates has been by the tramt ional technique of post
nouJ.d coating (FM::) and a relatively new technique of in-nouJ.d coating
(IK:) .
This thesis gives a review of the chemistry of polyurethane and
related materials, the surface coating of plastics with special
emphasis on the need for protection of PU products, the theories of
adhesion and the concepts of wetting and surface thenrodynamics. The
materials, equipnent and techniques used for the preparation of IK:
and FM:: nouJ.dings are also described.
A number of physical and chemical surface analysis techniques are
carried out on original and coated substrates to determine the
thermodynamic properties of solid surfaces.
ii
Various mechanical tests are employed to measure the strength of
adhesion in coated substrates and to evaluate the m:Jdes of failure,
including tensile adhesion pull-off, instrumented falling weight
impact and hardness. The feasibility of thermal analysis techniques is
examined and the results of differential scanning calorimetry (DSC)
and dynamic mechanical thermal analysis (JlIIII'A) reported. The nature of
surface topography is examined using electron microscopy and X-ray
microanalysis.
It is concluded that mechanisms praroting interfacial bonding of IM:
and PlVC systems are based on a ccrnbination of adhesion theories. For
IM: systems scme potential for chemisorptive bonding may be expected
if free isocyanate and hydroxyl are present on both surfaces. For PlVC
systems considerable potential for dispersive and polar forces may
exist.
It is argued that interfacial interaction between PU or a polyester
substrate and a PU based coating depend on processing conditions.
However, to optimise adhesive bonding the physical and chemical
activity of surfaces must be maximised during processing. The overall
results indicate that IM: mouldings are generally superior in terms of
their interfacial and adhesion properties to PlVCs.
iii