history of polymers
1. rubber
- e raser, rubberized fabrics without vulc anization
- 1839 : goodyear discovered vulc anization
- 1851 : ebonite, hard rubber, was commercialized
2. cellulose
- 1838 : cellulo se nitrate discovered and commercialized in 1870 by hyatt
- 1865 : cellulo se acetate
3. synthetic polymers
- o ldest one is phenol-formaldehyde
- 1907 : phenolic resins and varnishes produced (small scale)
- 1900 ’s : first use of styrene in sy nthetic rubbers for copolymer wit hdiene
- 1930 : polystyrene in germany, 1937 in u.s.
bill p9
billmeyer, p11
definition 1
, 1. polymer : many part – a large molecule made up of smaller repeating unit
synonym: macromolecule
2. monomer : a molecule which comb ines with other molecules of t he same or
different type to form a polymer
acrylonitrile ch
=chcn
2
units, eg. hexatriacontane –oligomer of pe n-ch3. oligomer – a low-molecular-weight polymer , contains at least two monomer
3
-ch
29
)
2
-(ch
3
- polymer : have significant mechanical strength
- o ligomer : not strong enough to be practically useful
rudin p 2
bill, p4
definition 2
4. repeating unit
– a portion of the macromolecules such that the complete polymer
might be produced by linking together a sufficiently large numb er of these units though bonds between specified atoms : rp ??monomer
- comprise a single identifiable precursor – ps, pe, pvc
- also be composed of several smaller molecules : pet, n6,6
hexamethylene d ia mine
adipic a cid
terephthalic acid
or dimethyl t er ephthalate
+ ethylene glycol
rudin p 3
definition 3
-poly(vinyl alcohol), rp ??monomer
*it is prepared from vinyl acetate monomer, resulting poly(viny l a cetate),
followed by alcoholysis w ith etha nol or methanol to generate pol y(vinyl a lcohol)
5. end-group : exact nature of the end-groups is frequently not known and
end-group usually has negligible effect
- ps : cups, containers, housing s for electrical equipments. mn> 150,000
thus containing 1500 rp, but 2 end-groups.
6. deg ree of polymerizatio n (dp)
– a number of repeating units in the polymer molecules
- m olecular weight m=(dp) m
repeating unit
, where m
0
= weight of
0
rudin p 7
classification of polymers
1. thermoplastics
- a polymer softens and can be made to flow when it is heated.
-it hardens o n cooling and retains the s hape imposed at elevated temp.
- heating and cooling cycle can be repeated many times , in principle
- pe, ps, pp
2. thermosets
- a polymer undergoes a chemical change to produce a network polymer
- can be shaped with heat and pressure,
- t he number of cycle is s everely limited
-once cured, cannot be dissolved or processed
- epoxy,
3. thermoplastic-thermosets
- g enetically thermoplastic
- but has reactive terminal groups which can be cured to form th ermos et
- pi, pes, pe, pvc
rudin p23
thermoset vs. thermoplastic
linear growthstarting monomer complete cure
/branching
gellation
linear growth
/branching
thermoset vs. thermoplastic
starting monomer complete cure
gelation
ref : mcgrath handout
thermosets vs. thermoplastics
properties thermosets thermoplastics
melt viscosity low high (semi-crystalline)
processability excellent poor
chemical resistance good poor
data base large small
recylability no yes
modulus high low
creep resistance good fair
fracture toughness low high
usage of polymers
1. raw materials for goods
2. adhesives
3. matrix for composites
types of adhesi v es
1. application and setting
2. origin : natural, semisynthetic, synthetic,
3. cure solubility crosslink ing : soluble, crosslinked
4. hybrid and coupling agents
5. film adhesives
6. high temperature res istance flame res is tance
ref: skeist, p5
definitions in adhesion science
adh esio n
adherend a body which is held t o another body by an adhesive
adh esive a substance capab l e o f hol d in g mater i als tog e ther
by surface attachment
structural a b o nding ag ent used fo r transfer r ing l o ads b e tween
adhesive adher en ds, ex posed to service environments ty p ical
for the structuring loads between adh erends
bond th e union of mat er ials by adhesive joint : th e location
at which two adherends are held together with a layer
of adhesive
bond the unit load applied in tension, compressio n, flexure, peel,
strength impact, cleav ag e or shear, requir ed to break an adhesive assembly
with failure occurring in o r near the plane of the bond
adhesive rupture of an adhesive bond, such that the sepa ration appears to b e
failur e that the sepa ration appears to be at the ad hesive and adherend
psa a viscoelastic m aterial s which , in solvent free from, remains
permanently tacky at rt. such mat erial will adhere instantane o usly
and tenaciously to most solid su rfac es with the ap pl ication of very
slight manual pr essur e
(astm standard v15.06, 1989)
types of adhesives : appl i cati on and sett i ng
1. cooling of a thermoplastic
• thermo plastics soft en and mel t when heated , b ecoming hard again when cooled
latex followed by frying and cooling• they can be applied from hot-mel t , as a p owd er, by extrud er or from solv ent or
• eva(packaging), polyam ides(soling of shoes),polyvinyl butyral (c ar safety gl ass)
2. release of sol vent or carrier
or organic solvent to lower visc osity and thus improve wetting • solutions and latexes contain the adhesive composition in admix ture with water
• solvent has to be removed befo re bonding unless adherends are pe rmeable
• organic solv ent : cost, shortag e, flamability, toxicity, pollu tion
in situ
3. polymerization
• all thermosetting resin including solution fo r m , elastomer , vin yl type monomer
• fast production, low cost, strong bond, no solvent
• condensation type : by-product (water)-phenolic and amino resins
anaero bics, and rad iation-curabl e p o l y mers • addition type : no by-product, po lyes ter, epoxy, urethane, cyan oacrylate.
4. pr essur e sensitive adhesiv e
• do not under g o p r o g r essive increase in viscosity, b ut tacky sta ge
• they can be removed from the adherend without mark-off
ref: skeist, p5
advantages and disadvantages of adhesion
advan t ages
1. ability to join dissimilar mat erials, eg. metal to composite
2. ability to join thin sheet materials
3. improved stress distribution of bonded joints
4. convenient and cost effective
5. increased design flexibility
6. improved appearance-smooth, blemish free
7. improved corrosion resistance
dis advant ages
1. elaborate surface tre atment may be required
2. limited upper service temperature
3. mechanical strength may be limited in tension and shear
4. difficult to repair and inspect
5. health hazard (fo r solvent processing)
6. may require long process time
ref: yoon, thesis
requi ri rements for a good b ond
the basic requirements for a good adhesive bond ar e the followi ng.
??cleanliness of surfaces
??wetting
??proper choice of adhesiv e
??good joint design
cl eanl i nes s
- t o obtain a good adhesive bond it is important to start with a clean adherend surface.
- foreign materials such as dirt, oil, moisture, and weak-oxide lay ers, must be
removed, or else the adhesive wi ll bond to these weak-boundary layers rather than to
the sub strate.
- there are various sur face treatme nts that may remove of streng then the weak-
boundary layers.
- theses treatments generally inv olve physical or chemical proce sses, or a combination
of both.
we t t i n g
the result of good wetting is greater contact area between the adherends a nd the
adhesive over which the for ces of adhesion may act.
ref: landrock, p7
thermodynamics of adhesion
young ?
sv
cos???
lv
= ?sl
= ?sv
+ cos???
- ?
sl
lv
-(1)
work of adhesion - dupre - two immiscible
work of cohesion
?
wa = ?
sv
- ?
sl
+ ?
lv
wa = ?
sv
+ ?
lv
- ?
sl
-(2)
lv
wc = 2 ?
lv
-(3)
l
= 2 ?
= cos???
lv
+ ?
lv
= ?
(cos??+ 1)
lv
?
?
sv
spreading wa > wc
?
s. coefficient s
l/s
= ?
sv
s
l/s
-(?
lv
sv
)
sl
+ ?
sl
> 0 : sp ontaneous spr ead ing
??
= wa - wc = ?
- ?
sl
lv-2?
lv
+ ?
?
sv
- ?
lv
- ?
sl
>0 ?
sv
> ?
lv
+ ?
sl
work of adhesion : work requir ed to separate two particles
strength since the bond strength also contains the energy of di ssipat ive p r ocesses
such as viscoel astic d efo r mation, p l astic defo rmation, l ocal mic ro-cracking, etc.
sol i dif i cat i on
the liquid adhesive, once ap pl ie d, must b e capab l e o f b eing c on verted into a solid in
any one of three ways. the method by which solidification occur s d ep ends o n the
choice of adhesive. the ways in which liquid adhesives are conv erted to solids are :
??chemical r eaction by any combination of heat, p r essure and curi ng agents
??cooling from a molten liquid to a solvent
??drying as a result of solvent evaporation
ref: landrock, p7
• however, the work of adhesion, w
a
, should not be equated to the adhesive bond
factors influencing adhesive selection
??capability of bonding specific adherends
??service r e quir ements
- stress : t ension, shear, imp act, p eel, cleavage, fatigue
- c hemical factors
- e xternal : chemical ag ents, including so l vents, acids, alkalie s, etc.
- internal : plasticizers in ce rtain plastics and rubbers
??environmental factors
- w eathering , - oxidation, - light(impo rtant only with translucent adher en ds)
- m oistur e, - s alt spr ay, - t emp erat ur e extr emes (including ther mal cycling)
- b iol o gical factors(b acter ia, fungi, v e rmin, r o d ents)
??specialized functional r e quir emen ts(thermal or electrical condu ctance, etc.)
??production requirements
- a pplication method, - b onding range,
- c uring condition(time versus temperatur e), - storag e stability, - working life
- coverage
??cost
??health and safety hazards
ref: landrock, p7
types of stress in a ahesive joints
ref: landrock, p32
types of adhesive joints
plain butt – unsati sfactory
single lap (plain lap)- g ood practical
b ev elled lap – good, usually practical, difficult to mate
scarf butt – very good, usually practical, require mating
joggle lap – good practical
single strap – fair, sometimes desirable
double strap – good, sometimes desirable
recessed dou ble strap – good, expensiv e machining
b ev elled double strap – very good, difficult produ ction
step lap (half lap) – good, requ ire machining
double lap – good, when applicable
double but lap – good, requires machining
tongue and groove – excell ent, requir e machining
ref: landrock, p34
theories of adhesion
1) mechanical interlocking - adhe sive is k eyed into substrate r o ughness
supporting example : microroughess effects (?)
2) electrostatic theory - electrical double lay er (deryaguin)
a) deryaguin -only exist be tween dissimilar materials
b) fowkes - electron donor-acceptor
supporting example : tape on glass produces sp arks
3) diffusion theory- inter d iffusion o f p o l ymer chains
supporting example - autohesion, effect of solubility parameter.
4) adsorption theory (secondary bonds)
a) dip ol e –dipole, b) dipole-induced dipole
c) dipole ??london dispersion ??van der w aal ’sforces
(instantaneously induced dipoles)
supporting example : steel gage blocks, most widely held adhesi on theory.
note : dispersion forces always exist.
5) chemical bonds (primary bonds, covalent)
supporting evidence : silane
1) mechanical interlocking
- adhesive is keyed into rough sub strate, having ink-bottle type holes
- b ut ink-bottle type roughness is not possible to have : only i deal case
- s urface r oughness increases surfac e ar ea and possibly make som e d e ep hol es
which may incr ease adhesion
- even if there are ink-bottle ty pe holes, it may not be possibl e to fill them
completely
ref: hull 42
2) electrostatic theory - electrical double layer (deryaguin)
interactionpositiv e charge and the other surface a net negative chargen – acid-base - force of attraction occur between two sur faces when one sur fac e c arries a net
a) deryaguin - only exist between dissimilar materials
b) fowkes - electron donor-acceptor
- s trength of ad h esion wil l d ep end on the charg e d ensity
important factor on others – glass/polymer (disposable bandage)- u nlikely a majo r contribution to adhesion in fib er/p ol ymer com posite, but
ref: hull 40
3) diffusion theory
- o nly possible for polymer chain s which can give interdiffusion
- bond strength depends on the mo lecular entanglement and a numb er
of molecules involved
- i nterdiffusion may be promoted by the presence of solvents and
plasticising agents
- t he amount of diffusion will depend on the molecular conformat ion and
constituent, and easy of molecular motion
example – autohesion : acrylate with chloroform
ref: hull 40
4) adsorption theory (secondary bonds)
- when two electrically neutral surfaces are brought sufficientl yclose
together there is a physical attr action which is bet understood by
considering the wetting of solid surface by liquid
a) dipole-dipole
b) dipole - i nduced dipole
c) dispersio n = london d ispers ion = van der wa a l ’sforces
example : steel gage blocks, most widely held adhes ion theory
note : dispersion forces alway s exis t, but relatively weak
ref: hull 38
5) chemical bonds (primary bonds, covalent)
- t he most favorable bonds if we can get, but seldom achieved
- o btained from glass/silane c oupling agent
- t he bond strength depends on the number and type of bond forme d
ref: hull 40
interphase theory
• the theory of reinforcement/ matrix interactio ns currently invo lves the recognition
of a flexible, three-dimensional interphase which polymer networ k fo rmed by the
coupling compound or the size and into which the resin or matri x c an pen etrate.
• the network may have occasional chemical attachments (bonds) to the fiber
surface, but the chief purpose of the network is to provide a l attice which the
matrix molecules can penetrate a nd can be held in close proximi ty to the fibers.
therefore, the interphase is a re gion where size (finish) and ma trix have diffused
into each others ’ domain.
• although the interphase p robably has lower modulus and lower str ength than either
the fiber or the matrix, true co hesive failure in tension (i.e. , failure between similar
substances) is pr obabl y quit e r ar e within the main part o f the interphase zone.
ref:strong 72, 74
k-jist
interface vs interphase
5? to
5000?
coh
co
matrix
oh
- matrix morphology
- unreacted species
- impurities
- voids
- surface chemistry
- topography
- fiber morphology
o
c
nh
c
fiber
- very different from fiber and resin
- a critical factor on composites properties
?
can be designed by coating or modification
ref. v. rao and l. t. drzal, polym. compos., 12, 48 (1991).
polymer composites lab.
???? ???
k-jist
acid - base interaction
1. exothermic reaction
2. no need to change backbone structure
3. car eful sel ec tion of surface t reatment method , adhesiv e and solvent
4. acidity and basicity can be me asured by igc, ftir, xps, calor imetry
bond type bond energy (kj/mole)
primary bonds ionic 600 - 1 100
covalent 60 - 7 0 0
metallic 110 -350
donor - acceptor bonds
bronsted acid - base interaction s up to 1000
lewis acid - base interaction up to 80
secondary bonds
hydrogen bonds involving fluorine up to 40
excluding fluorine 10 - 2 5
van der waals bonds
permanent dipole - dipole interactions 4 - 2 0
dipole - induced dipole i nteractions < 2
dispersion(london) forces 0.08 - 4 0
ref : adhesion and adhesives, a. j.kinloch,champman & hall, new y or k,1987
examples of a/b interactions
1. pmma(basic) on window glass(basic)
- d isp e rsion fo rce only
2. cpvc(acidic) on window glass(basic)
- d isp e rsion + acid - base interaction
3. cpvc(acidic) on hci was hed window glass(acidic)
- d isp e rsion fo rce only
ref : fowkes, ency. polym. sci.& eng., supplement, john wiley & son, new york, 19 89
examples of a- b interactions
bbbaacpvc-a pmma-ba
a
a
aa
bb
bb
b
a
ba
a
b
caco3
b
a
b
a
a
b
a
2
sio
a
a
b
b
b
a
b
b
aa
b
aa
bb
bbb
bbb
b
aa
a
aaa
a
b
bb
b
a
aa
a
caco
3
a
2
sio
b
b
b
b
a
a
a
a
b
bbb
b
bbb
b
a
a
aa
a
aa
a
a
ref : fowkes & mostafa, ind. eng. chem. prod. res. dev., 17(1), 3 (1978)
ref : fowkes and mostafa, ind. en g. chem. prod. res. dev., 17 (1) , 3 (1978)
testing methods
lap sh e a r test s astm d-1002 -72 singl e la p sh e ar in te nsion
d-3163 singl e lap sh e a r, ri g i d su b strate
d-2295-72 singl e l ap sh e a r , high t emp er atur e
d-905 singl e lap sh e a r in compressi o n
d-3164-73 doubl e l a p sh e ar
pe e l te sts astm d-3 167-76 floati ng r o ll er tes t
d-903-49 180 pe el te st
d-1876-72 t-pe e l te st
d-1781-76 climbing drum pe el te st
d-2918-71 t-pe e l , durabil ity test
impact te st astm d-950-82
cree p te st astm d-1780 -72 singl e la p sh e ar in tension
d-2293- 69 shear by compression loadin
fati gu e te st astm d-31 166-73 sin g l e lap sh e a r in t ension
cleava g e test astm d-1062-78
durabi lity test astm d- 896-84 ch emical r e s i stan c e(any astm samples)
- wedge test - cantilever beam
tension
d-904-57 light( natural and artificial)
d-1183-70 cyclic loa d i ng
d-1820-70 natural outdo or aging
d-1879-70 high en ergy radiat i o n
d-2918-71 high stre ss, moi stu re&t emp(p e el on l y)
d-2919-71 high stre ss, moi stu re&t emp(sin gl e lap in
d-3762-79 we d g e te s t
b-117 salt spray test
single lap shear test
peel tests
a. 180-degree peel , b. 90-degr ee peel
c. drum peel d. t-peel
durability tests
do uble can tilever beam test
dcb i s al s o used t o measur e t h e f r ac t u r e t o ughness of adhesive bond
film/coating adhesion test
standard
bl ister tes t
cons t r ai ned
bl ister tes t
island
bl ister tes t
peni nsul a
bl ister tes t
fiber-matrix adhesion test
micro-dropinglet t es t single f i ber pull-out test
single fiber fragmentation tes t micro/meso i ndent a tion t est
me chanism of bond f ailure
- a dhesive fail ur e : interfacial bond failur e b etween the adhesi ve and adherend
??“ideal type ”- cohesive fail ur e : failur e wit h in the adhesive o r o ne o f the a dherend ??max st rength
- b ut cohesive failure does not mean all ways max.
s
trength
- u ltimate str e ngth of a joint is a more important criterion th an the mode of failure
- w eak boundary lay er and improper surface preparation have to b e c arefully eliminated
or corr e cted to have co h esive failur e m o d e
cause of premature adhesive failure
1) not enough wetting
2) i nter nal stress - ad h esive shri nkage, tec mismatch : us e fill er, el astic adhesive
adhesiv e f ai l u re
cohesive failure
surface modification
to remove weak boundary layer
to introduce functional groups for acid-base interaction, chemi cal bond
1. mechanical :
• rubbing (cloth, sand paper)
• sand blasting
2. chemical
• etching – acid, base
• solution washing
• polymer coating/silane c oating
• plasma etching, corona discharge, e-beam, radiation
• plasma polymerization
• electrochemical
tie-coat
silane coupling agent
silane coupling agents
organofunctional group chemical structure
k-jist
vinyl
h
2
c chsi(oh
???? ???
k-jist
)
3
3
epoxy
3
)
3
si(och
2
ch
2
ch
2
och
2
ch
o
amine
h
2
nch
2
ch
)
5
3
h
si(oc
2
ch
2
2
mercapto
chhs
2
ch
3
)
3
si(och
ch
2
2
methacrylate
ch
3
h
c
2
2chc cooch
ch
2
si(och
2
)
3
3
polymer composites lab
glass/pp composites
no silane silane coated
k-jist
plasma etching
process gas inlet
reaction chamber
???? ???
k-jist
-
•atom
-
excited gas species
•molecules
electrode
-
-
photons/glow discharge
(vacuum uv)
-
-
-
substrate
process gas
vacuum outlet
• ions
• electrons
• free radicals
• metastables
rf power source
chemically
modified sites
-
polymer composites lab
k-jist
plasma polymerization
gas, liquid, solid
plasma polymerization
???? ???
k-jist
electrode
polymerizationplasma-induced
plasma-state
polymerization
rf power source
plasma polymer intermediates
polymer film
ablation, non-polymer-forming gas
polymer composites lab
surface characterization
• sem
• afm
• contact angl e measurement
• xps(esca ), aes, si ms
• fr-i r, r aman
afm
stm
ps-pmma copolymer
domains : 14nm pmma cylinder
c&en, jan 1, 2001
infromation f rom xps
1.absolute binding energies, signal intensities: quantitative a nalysis
2.valance level : molecular information
3.shift in binding energy : chemical information
4.variable depth information : hv, ion sputtering, take-off ang le
5.auger parameter : identification of compounds
* secondary process : x-ray fluorescence & aes
wide scan
narrow scan
o, aes
533, o1s
121, al2s
257, c1s
75, al2p
poly-isopropyl acrylate
angular effect – depth profiling
= 95% signal
??= 90 ??, d=3?
??= 5 ??, d=0.3?
??= 90??= 15?
non-destructive, surface must be flat
peek-graphite composites
information from aes
1. true secondary electrons have no useful information
2. same aes process take place in xps
3. instead of kll auger electron, fluorescent x-ray an be emitte d (ka line) b o th in aes
and xps (which is principles of edx)
4. fine structure in klm spectra : chemical state information
5. chemical shift like in xps, but more complex
6. variable depth information by ion sputtering, v ariation of ta ke off angle and
combination with edx
7. mean free paths of auger electrons and photoelectrons in matt er are very si milar
8. aes is more sensitive to l ight el ements
aes spectra
aes depth profiling
titanium oxide
3-30 kv primary beam (+, -, neutal) of particles
information from sims
secondary particles, fragments, light
99% neutral : snms
0.5% positive : +sims
0.5% negative : - sims
recoil mixing, breaking +
reformation of bonds
, laser
+
, n2
-
, o2
+
, o2
+
, ga
+
, cs
+
1.sources : ar
o
, ar
2.mass analysers : quadruple, time of flight, double-focusing magnetic sector analyzer3.mass of secondary particles is analyzed (not their energy)
4.mass spectrum may be fingerprint of compounds
5.static sims : low energy, low current beam provided analysis of first atomic layer only6.dynamic sims : mass filtered, high intensity beam removes surface layers during analysis
– depth profiling
contact angle measurement
capillary rise wilhelmy plate ring method
pendent droping droping weight pendent (sessile) droping
static contact angle measurement - goniometer
dynamic contact angle measurement
sample
test liquid
microbalance
motor driven
platform
tare weight
f = ??x p x cos?
cos??= f/ ??x p
f = measure force
p = perimeter ??= surface tension
??= contact angle
applications of contact angle
measurements
?? application
1. ??? ???? ? ?? ???
2. ?? (coating) ???? ? ?? ??? ? ??? ???? .
4. ???? ?? ??? ??? ???? ? ? ??? ??
3. ???
?? ???? ?????? ???? ? ? ??? ??
6. ?? (textile) ?? ???? wettability ? ??? ?? ????? ??
7. contact lenses ??? ?? ??? ?? ? ?? ??
8. ??? ??? ?? ?? ??
5. fiber composites
fiber / ????? ??? ??? ??
ft-ir and raman
• molecules rotate and vibrate wit h characteristic frequencies, which
absorb ir radiation
• vibrational s pectroscopy provides information on bond lengths, b ond
strengths and molecular geometry
• in addition, it has been a valuable tool for chemical analysis,
identification of char acteristic groups in molecules and monito ring
intermolecular interactions
• induced moments depends on bond length and molecular orientatio n,
polarizability of the molecules varies with time
• the induced dipole oscillates at the frequencies ?
(rayleigh s cattering),
o
( ?
o
- ?
m
) and ( ?
o
+ ?
) . as a consequence, the molecules scatter
m
radiation at these frequencies. the inelastic scattering at the sum and
difference frequencies is known as raman effect .
acetylene
c–h
ft-ir spectra of plasma polymer
bu ta d i e n e
c=o
c=c
ch
3
1000150020002500300035004000
• bomem ft-ir, 128 times of scan with kbr
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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