Analisi di fenomeni di deformazione meccanica di materiali ... · The mechanical properties of...
Transcript of Analisi di fenomeni di deformazione meccanica di materiali ... · The mechanical properties of...
Analisi di fenomeni di deformazione meccanica di materiali mediante luce
di sincrotrone
Claudio De RosaDipartimento di Chimica, Università di
Napoli “Federico II” - Italy -
Elastic solidsElastic solidsThree principal ways of simple deformation: shearCompression or isotropic tension (volume deformation);Uniaxial tension
shear compression Uniaxial tension
γ σ G= ∆ σ K= ε σ E=
AF
ELLL 1 ε
0
0f=
−=
AF
GLL 1αtanγ
2
1 === A
FKV
V 1∆ ∆ ==
Shear strain Tensile strain
AF
= σ (Shear or Tensile or Compressive stress)
Volume change
γ σ G= ε σ E=∆ σ K=
Hooke’s law for ideal elasticHooke’s law for ideal elastic solidssolidsE, G, K = E, G, K = Modulus Modulus of of ElasticityElasticity; E = ; E = Young’s ModulusYoung’s Modulus
Poisson’s ratio
⎟⎠⎞
⎜⎝⎛=
dεd1-10.5 ν V
V
E = 3K(1 - 2ν) E = 2G(1 + ν)
a) Partially stabilized with 3 mol% Y2O3.
b) Source: Modern Plastics Encyclopedia ’96. Copyright 1995, The McGraw-Hill Companies.
ElasticElastic DeformationDeformationThe elastic deformation of materials is reversible.The initial dimensions are recovered upon removing the tension.The elastic deformation produces only reversible changes of bond length, bond angles and, in the case of crystalline materials, deformation of the unit cell.
ordrdFE ⎟
⎠⎞
⎜⎝⎛∝
StressStress--strain curvesstrain curves
strain
stre
ss
ε σ E=
For small values of strain the stress-strain relationship is linear(elasticity range, Hooke’s law)
Plastic Plastic DeformationDeformation
strain
stre
ss
Elastic deformation: Behavior of fragile, glassy materials, as ceramics, some polymers and thermosets.
Plastic deformation: For higher values of strains the material experiences a permanent irreversible deformation. Behavior of ductile materials as metals and thermoplastic polymers
Mechanical Properties Mechanical Properties of of MaterialsMaterialsTensile strengthTensile strength
Tensile strength: the maximum value of the stress in the stress-strain curve.It is a measure of the strength of the material, that is the resistance to the plastic deformation (50MPa for Al, 600-1000 MPa for steel)
Slip Slip SystemsSystemsThe Plastic Deformation corresponds to the slip of the more The Plastic Deformation corresponds to the slip of the more densely packed plane of atomsdensely packed plane of atoms
Plane (111) slip direction <110>
Slip system {111}<110>
11).1( 1),1(1 ),111( (111), [101] 0],1[1 ],011[
Three slip directions for each of the four equivalent planes of the family {111}. Number of slip systems: 12
Motion Motion of of DislocationDislocation
The plastic deformation is favored by motion of dislocation that produce slip of planes but only few atoms really move.
Plastic Plastic DeformationDeformation of of PolymersPolymers
1) Slip processes within the lamellae; 2) intralamellar mosaic block slips;3) at larger strain, stress-induced melting of lamellae (mechanical melting) followed by recrystallization in new oriented crystallites, whose assembly forms fibrils.
StressStress--StrainStrain CurvesCurves of of PolymersPolymers
Tensile strength or
Strain-hardening
High crystallinity
Amorphous
The physical and mechanical properties of polymers depends on the crystal structure and the microstructure of single molecules. Polymorphic transitions during deformation play an important role
The The mechanical properties mechanical properties of of polymers dependpolymers depend on on occurrenceoccurrence of of phase transitions during deformationphase transitions during deformation
Syndiotactic polypropylene samples of different crystallinity
0 100 200 300 400 500 600 700 8000
4
8
12
16 sPP, low crystallinitysPP, high crystallinity
σ (M
Pa)
ε (%)
The low crystalline sample shows tensile strength similar to that of the high crystalline sample, due to crystallization under tension or structural transformations during deformation
ElastomersElastomers1) Elastomers are high –molecular weight polymers possessing chemical and/or physical cross-linking. 2) For industrial applications the temperature at which the elastomers is used must be above the Tg (to allow for full chain mobility), and in its normal state (unextended), theelastomes should be amorphous.3) The restoring force, after elongation, is largely entropic. As the material is elongated, the random chains are forced to occupy more-ordered positions (extended conformation). On release of the application force, the chains tend to return to a more random state.4) Gross mobility of entire chains must be low. The cohesive energy forces between chains of elastomes permit rapid, easy, expansion. In its extended state, an elastomeric chain exhibits a high tensile strength, whereas at low extension it has a low modulus.
Permanent deformation
elastomer
Different types of cross-links in elastomers
Entanglements or chemical bonds
Block copolymers
Semicrystalline polymer with low level of crystallinity
Thermoplastic elastomers:the network forms at low temperatures and melts at high temperature.
More Disorder
The Entropic Spring
Less Disorder
Decrease of Entropy
Loss of entropy during stretching implies that there is aretractive force for recovery when external stress is removed.
Stretching
Hysteresis cycle: The energy is not completelyrecovered
1,41,4--ciscis PolyisoprenePolyisoprene (Natural Rubber )(Natural Rubber )
Stretching
Release of the tension
Stretched poorly-crystalline
Stretched fiber after release of the tension - Amorphous
Positive enthalpic contribution
Amorphous Formation of small Crystals
Stretching
Release of the tension
Elasticity is merely entropic!0 40 80 120 1600
200
400
600
σ (k
Pa)
ε (%)
Natural Rubber
Relaxing
Relaxing
Stretching
Stretching
Study Study of of relationships between relationships between mechanical propertiesmechanical properties and and structurestructure
In-situ structural evolution during deformation can be studied by time-resolved X-ray diffraction with synchrotron radiationand simultaneous recording of the stress-strain curve.
0 500 1000 1500 20000
10
20
30
40
[rr] = 11.0%
Strain (%)
Stre
ss (M
Pa)
TimeTime--resolvedresolved WAXS WAXS analysis analysis Synchrotrone DaresburySynchrotrone Daresbury (UK)(UK)
Tensile apparatus with Tensile apparatus with hothot-- and and cryostagecryostage
CCDCCD
Synchrotrone Synchrotrone light light source source DaresburyDaresbury (UK)(UK)
Polypropylene from Polypropylene from Metallocene CatalystsMetallocene Catalysts
From highly isotactic to highly syndiotactic From highly isotactic to highly syndiotactic polypropylenepolypropylene and and anythinganything in in betweenbetween
iPPiPP: : TTmm = 165 = 165 -- 50 °C50 °CsPPsPP: : TTmm = 155 = 155 -- 40 °C40 °Catacticatactic PP
Different physical properties depending on stereoregularity
PP
The crystallization plays the most important roleThe physical properties depend on the crystallization behavior, which in turn depends on the microstructure.
ChainMicrostructure
Catalyst structure
Crystallizationproperties
Mechanicalproperties
s(2/1)2 helixs(2/1)2 helix transtrans--planarplanar TT66GG22TT22GG22 helixhelix
SyndiotacticSyndiotactic PolypropylenePolypropylene
SyndiotacticSyndiotactic PolypropylenePolypropylene
RR
R
RR
L
L
a
L L
bForm II
aL
L
L
L
L
b
Form I
Form III Form IV
βa s in
b
L L
LL
L
b
a
Plastic Plastic deformation deformation and and elasticelastic behaviorbehavior of of sPPsPP
E (MPa) σb (MPa) εb (%) ts (%)256 15 400 300
UNORIENTED COMPRESSIONUNORIENTED COMPRESSIONMOULDED SAMPLESMOULDED SAMPLES
0 100 200 300 4000
4
8
12
16
Stre
ss (M
Pa)
Strain (%)
Plastic deformation
E (MPa) σb (MPa) εb (%) ts (%)335 30 25 0
STRESSSTRESS--RELAXED RELAXED ORIENTED FIBERSORIENTED FIBERS
0 5 10 15 20 25 300
10
20
30
Strain (%)
St
ress
(MPa
)
Elastomeric behavior
oriented sPP fibers show good elastic properties.oriented oriented sPPsPP fibers show good elastic propertiesfibers show good elastic properties.
SyndiotacticSyndiotactic PolypropylenePolypropylene - Elastomeric Properties -
Stretched fiber sampleTrans-planar form III
Stretching
Release of the tension
Stretched fiber sampleafter the release of the tension
Helical form II
0 10 20 30 40 50 60 700
10
20
30
40
50
Strain (%)
Stre
ss (M
Pa)
b
a
aL
L
L
L
L
bEnthalpic elasticity
in sPP?
C. De Rosa, F. Auriemma, O. Ruiz de Ballesteros Macromolecules 2001, 34,4485.
Molecular SpringMolecular Spring
helix trans-planar
stretching
relaxationc=7.40Å c=5.06Å
sPP Form II. (T2G2)n Helical conformation
4 monomeric unit/period
sPP Form III. trans-planar conformation
2 monomeric unit/period
Removing the tension each crystal shrinks by 38% along the c axis i.e. 100(5.06x2 - 7.4)/7.40 = 38%
Well formed crystals
Syndiotactic Syndiotactic PolypropylenePolypropylene
Form II Form III
1,41,4--ciscis polyisoprene polyisoprene (not vulcanized )(not vulcanized )
long entangled chains
Stretching
Release of the tension
Is elasticity in s-PP partly enthalpic?
negative enthalpiccontribution to free energy
Amorphous Formation of small Crystals
Stretching
Release of the tension
Elasticity is merely entropic!
positive enthalpiccontribution to free energy
Low modulusHigh modulus
Stress-stress curve and X-ray diffraction simultaneously recorded during stretching
Monochromatic radiation λ=0.718Å and 1.4ÅConstant strain rate = 5mm/min
12 frames/min, 2 s exposure time
Dynamometer and Synchrotron radiation, ESRF Grenoble and Daresbury
( ) 00 / LLL −=ε
L
AF /=σ
L0
F
Plastic Plastic deformation deformation and and polymorphic transition polymorphic transition of of sPPsPP
0 100 200 300 4000
4
8
12
16
Stre
ss (M
Pa)
Strain (%)
The deformation behavior is controlled by critical strains rather than critical stresses:A) Onset of isolated inter-and intra-lamellar slip process.B) Yield point with collective activity of slip processes.C) Destruction of lamellar crystals and formation of fibrils.
G. Strobl J.Macromol.Sci.Phys. 2001, B40, 775, Phys. Rev. Lett. 2003, 91, 1
The phase transitions are also, probably, strain controlled rather than stress controlled.
When a critical value of the strain (εc) is achieved the stable helical form starts transforming into the trans-planar form III. The transition is complete at the strain εm. The values of critical strain εc and εm depends on the stereoregularity
s-PP unoriented film… [rrrr]=93%
ε = 0t=0 s
15.1%20 s
30.2%40 s
45.3%60 s
60.4%80 s
90.6%120 s
106%140 s
ε = 136%180 s
75.5%100 s
121%160 s
trans-planartrans-planar helical
F. Auriemma, C. De Rosa J. Am. Chem. Soc. 2003, 125, 13143F. Auriemma, C. De Rosa Macromolecules 2003, 36, 9396
Plastic deformation of sPP
During stretching irreversible morphological and structural changes occur. The elastic recovery is small (<100%, for ε≈400%).
0 50 100 150 200 25002468
10121416 sPP [rrrr]=93%
Stre
ss (M
Pa)
Strain (%)
sPP [rrrr]=78%
sPP fiber [rrrr]=93%A - Stretching trans-planarhelix
ε= 0t= 0s
9.67%40s
19.3%80s
21.8%90s
31.4%130s
41.1%170s
0340s
9.67%300s
19.3%260s
21.8%250s
31.4%210s
ε= 41.1%t =170s
B - Releasing the tension helixtrans-planar
F. Auriemma, C. De Rosa J. Am. Chem. Soc. 2003, 125, 13143
4 5 6 7 8 9 10 11
41.1%38.7%36.3%33.8%31.4%29.0%26.6%24.2%21.8%19.3%19.3%16.9%14.5%12.1%9.67%7.25%4.84%2.42%
(111)h
(110)t
(110)h
(200)h
2θ (deg)
Stre
tchi
ng D
irect
ion
(020)t
ε=0
DecreasesIncrease
No structural changes occur below a critical
strain ≈10%
sPP fiber [rrrr]=93% Equatorial layer line
The reflections of the helical form II gradually disappear, while those of the trans-planar form III gradually appear
No structural changes occur above a critical
strain ≈10%
sPP fiber [rrrr]=93% Equatorial layer line
The reflections of the trans-planar form III gradually disappear, while those of the helical form II gradually appear
During the cyclic deformation the degree of crystallinityremains constant. 4 5 6 7 8 9 10 11
41.1%38.7%36.3%33.8%31.4%29.0%26.6%24.2%21.8%19.3%16.9%14.5%12.1%9.67%7.25%4.84%2.42%
(111)h
(110)t
(110)h
(200)h
2θ (deg)
Rele
ase
of th
e te
nsio
n
(020)t
ε=0
0 10 20 30 40 500
10
20
30
40
50
60
σ (M
Pa)
ε (%)
critical stress during stretching
critical stress during tension removal
The critical stress during stretching and relaxing steps do not coincide, because the hysteresis is not zero.
The reversible transition between forms II and III occurs above (during stretching) and below (during relaxation) a critical strain.
critical strain
During the cyclic deformation the degree of crystallinityremains constant.
The structural evolution of sPP is fast and occurs on the same time scale as the rate the material is stretched.
The reversible phase transition between the helical form II and the trans-planar form III occurs directly, without involving transformations through a third, disordered, intermediate phase
It is a cooperative process implying conformational and structural rearrangements of large bundles of close neighboring chains.
HOTCOLD
Ni/Ti alloys
Here the transition is thermally induced…
These alloys show elastic properties - the so called pseudoelasticity OR superelasticity - associated to a reversible phase transition between
austenite- and martensite-like structures.
Austenite Martensite(CsCl-like structure) (tetragonal)
… in Ni/Ti alloys this transition may be also induced by application of external stress… when the stress is removed, martensite transforms back to austenite, and the sample recovers shape and dimensions of the unstrained state.
It is due due to small and cooperative movements of groups of atoms
What about the mechanism of martensitic phase transition in sPP?
Cooperative Cooperative solid solid state state transitiontransition
F. Auriemma, C. De Rosa Macromolecules 2003, 36, 9396
High High molecular weight poorly molecular weight poorly syndiotactic polypropylenesyndiotactic polypropylene
Resconi et al. 2003 (Basell, Polyolefins)
N
N
Me2Si TiMe2
N
Me2Si
N
TiMe2
N
Me2Si TiCl2
Amorphouspolypropylene
[rrrr] = 25-26%Mw = 1.200.000
Semicrystalline “syndiotacticsyndiotactic--amorphousamorphous”polypropylene (sam-PP)
[rrrr] = 40-55%
[rrrr]=54.6%, Mw=1.308.600, Mw/Mn=2.1
5 10 15 20 25 30 35 40
the meltcooled from
e
d
c
a
b
020
192 h
48 h
6 h
24 h
Inte
nsity
2θ (deg)
200
5 10 15 20 25 30 35 40
the meltcooled from
e
d
c
b
a
192 h
48 h
6 h
24 hIn
tens
ity
2θ (deg)
200020
[rrrr]=51.6%, Mw=672.700
““SyndiotacticSyndiotactic--amorphousamorphous” ” PolypropylenePolypropylene. . TTmm = 50 °C,= 50 °C,Low stereoregularityLow stereoregularity [[rrrrrrrr] = 40] = 40--55%,55%, low crystallinity low crystallinity (15%).(15%).
N
N
Me2Si TiMe2
N
Me2Si
N
TiMe2
samPP
Mechanical properties of Mechanical properties of samsam--PP samplesPP samples
0 100 200 300 400 500 600 7000
2
4
6
ε (%)
[rrrr]=41.4%
[rrrr]=46.9%
[rrrr]=45.8%
[rrrr]=51.6%
σ (M
Pa)
[rrrr]=54.6%sam-PP: stress-strain curves of elastomers with high strength; E = 5-20 MPa, ts = 20-30%
N
Me2Si
N
TiMe2
Unoriented samples show good elastic properties
Stress-strain tests
Small crystals act as physical crosslinks
Plastic deformation
0 100 200 300 4000
4
8
12
16
St
ress
(MPa
)
Strain (%)
Highly crystalline s-PP: stress-strain curve of stiff plastics with plastic deformation,E = 200-300 MPa, ts = 300%. Unorientedfilms do not present elastic behavior because of the occurrence of plastic deformation in the first stretching.
ZrCl2
C. De Rosa et al. J. Am. Chem. Soc. 2003, 125, 10913
DeformationDeformation [rrrr]=54.6%, Mw=1.308.600
high deformation
trans-planarhelical
ε = 500%
5 10 15 20 25 30
16.7°
Inte
nsity
200
2θ (deg)
trans-planar mesomorphic form
5 10 15 20 25 30
020
Inte
nsity
2θ (deg)
200
16.3°
ε = 200%
helical
low deformation
form I
5 10 15 20 25 30
020
Inte
nsity
2θ (deg)
200
16.3°
5 10 15 20 25 30
020
Inte
nsity
2θ (deg)
200
16.2°
5 10 15 20 25 30
16.5°
Inte
nsity
2θ (deg)
200
5 10 15 20 25 30
16.7°
Inte
nsity
2θ (deg)
200
[rrrr]=54.6%, Mw=1.308.600, Mw/Mn=2.1ε = 200%
ε = 300%
ε = 400%
ε = 500%
draw ratio
helical form I
trans-planar mesomorphic form
1/2 0
1/2 0
1/2 0
1/2 0
1/2 0
1/2 0
a=ah
b=a√3
a
b
R L/ R L/R L/
R L/ R L/R L/
HysteresisHysteresis cyclescyclesStress-relaxed fibers
0 50 100 150 200 250 30001234567
σ (M
Pa)
σ (M
Pa)
ε (%)
first cyclesuccessive cycle
fibers relaxed from ε = 400%
0 50 100 1500
1
2
3
4
5
first cyclesuccessive cycles
fiber relaxed from ε = 200%
0 50 100 150 200 250 3000
2
4
6
8 first cyclesuccessive cycles
σ (M
Pa)
σ (M
Pa)
ε (%)
fibers relaxed from ε = 400%
0 50 100 1500
1
2
3
4
5 first cyclesuccessive cycles
fibers relaxed from ε = 200%
[rrrr]=54.6%, Mw=1.308.600 [rrrr]=51.6%, Mw=672.700
Fibers of samPP samples show good elastic properties
Polymorphic transition Polymorphic transition and and elastic propertieselastic properties
stretching
release of the tension
[rrrr]=54.6%,Mw=1.308.600
trans-planar mesomorphic form
Reversible transition: mesomorphic form helical form I
5 10 15 20 25 30
020
Inte
nsity
2θ (deg)
200
helical form I
helix
a
b
R L/ R L/R L/
R L/ R L/R L/
trans-planarhelix
ε = 500%
5 10 15 20 25 30
16.7°
Inte
nsity
200
2θ (deg)
1/2 0
1/2 0
1/2 0
1/2 0
1/2 0
1/2 0
ElasticityElasticity in in different different ss--PPsPPs
helix trans-planar
stretching
relaxation
20 30 40 50 60 70 80 90 1000
20406080
100120
140160
T m (°
C)
[rrrr] (%)
ZrCl2
N
Me2Si
N
TiMe2
N
Me2Si TiCl2
N
Me2Si TiCl2Entro
pic elas
ticity
Enthalpic e
lastici
ty
C. De Rosa, F. Auriemma, O. Ruiz de Ballesteros Chem. Mater. 2006 in pressC. De Rosa, F. Auriemma Prog. Polym Sci. 2006, 31, 145
Phase diagramPhase diagram of of sPPsPP
RR
R
RR
L
L
a
L L
b
b
a
100 90 80 70 60 50 4050
100
200
300400500
1000
2000
form I + mesophase
mesophaseform III
defo
rmat
ion
(%)
concentration of rrrr pentads (%)
form I
form III + form I
trans-planartrans-planar
2/1 helix
εm
εc
C. De Rosa, F. Auriemma, O. Ruiz Phys. Rev. Lett. 2006, 96, 167801
The interplay between the state of the entangled amorphous and the stability of crystal blocks determines the position of the critical strain. (G. Strobl Phys.Rev.Lett. 2003, 91, 1). The two factors, the modulus of the entangled amorphous and the stability of crystal blocks, probably, depend on stereoregularity.
The The polymorphic transition is strongly polymorphic transition is strongly influenced by influenced by the the presence presence of of comonomer unitscomonomer units
helix trans-planar
stretching
relaxation
• Ethylene units stabilize the trans-planar conformation• Butene units stabilize the helical conformation.
High High concentrationsconcentrations of of ethylene ethylene or or butene units butene units prevent occurrenceprevent occurrence of of polymorphic transitionpolymorphic transition
Melting temperatures Melting temperatures of of sPP sPP copolymerscopolymers
0 10 20 30 40 50 60 70 80 90 10040
60
80
100
120
140
160 T m
(°C)
mol% comonomer
sPP propylene-etilene copolymers propylene-butene copolymers propylene-hexene copolymers propylene-octene copolymers
C3/C4C3/C2
5 10 15 20 25 30
111
111
111
111
200
200
200
110
110
110
110
110
020 110
020
PPET(7)
PPET(6)
PPET(5)
PPET(4)
PPET(3)
PPET(2)
PPET(1)
1.5 mol%ET
0.4 mol%ET
8.0 mol%ET
9.1 mol%ET
8.5 mol%ET
2.6 mol%ET
6.3 mol%ETInte
nsity
2θ (deg)5 10 15 20 25 30
200
110
PPET(8)9.8 mol%ET
PPET(10)14.3 mol%ET
PPET(11)15.9 mol%ET
PPET(9)13.2 mol%ET
PPET(13)17.5 mol%ET
PPET(12)16.2 mol%ET
111
111
111
111
200
200
200
110
200
110
200 110
020 110
020 110
Inte
nsity
2θ (deg)
SyndiotacticSyndiotactic propylenepropylene--ethylene copolymersethylene copolymers
Ethylene units are included in crystals of sPP and induce crystallization in the kink-bands disordered modifications of form II.
ZrCl2
0 1000 2000 3000 4000 5000 60000
5
10
15
20
25
30
17.5%
15.9%16.2%
8.0%
9.1%
8.5%13.2%
14.3%6.3%
2.6%
ε (%)
σ (M
Pa)
Stress-strain tests
Thermoplastic elastomers with high modulus and high deformation. High ductility and toughness
Mechanical Properties of Mechanical Properties of syndiotacticsyndiotacticpropylenepropylene--ethylene copolymersethylene copolymers
Elastic properties and Elastic properties and polymorphicpolymorphic behavior of behavior of syndiotacticsyndiotactic propylenepropylene--ethylene copolymersethylene copolymers
<7 mol% ET
form II + mesophase trans-planar form IIIhelical
trans-planar
Stretching
Release of the tension
trans-planar
helical
trans-planar trans-planar10-18 mol% ET
Stretching
Release of the tension
trans-planarmesophase
trans-planarmesophase
0 20 40 60 80 10005
1015202530
2.3%
9.1%8.5%
8.0%6.3%
ε (%)
σ (M
Pa) Hysteresis cycles
0 50 100 150 200 2500
2
4
6
8
10
17.5%16.2%15.9%
14.3%
13.2%
ε (%) σ
(MPa
)
Elasticity in Elasticity in syndiotactic syndiotactic propylenepropylene--ethylene copolymersethylene copolymers
0 5 10 15 2040
60
80
100
120
140
T m (°
C)
ethylene content (mol%)
enthalpic elasticity
entropic elasticity
From entropic to enthalpic elasticity
0 5 10 15 200,2
0,3
0,4
0,5
cr
ysta
llini
ty
ethylene content (mol%)
helix trans-planar
stretching
relaxation
crystallinity melting temperature
C. De Rosa, F. Auriemma Adv. Mater. 2005, 17, 1503
SAXS SAXS -- CrystallizationCrystallization under under flow flow --
SAXS Synchrotrone Daresbury (UK)
λ = 1.4 Å
.r
shear
T1
time
Temperature
Tc
Tm
T2
time
shear rate = V/d =20 s-1
V = 2π rAd = sample thicknessA = number of turns in 1 sshear time = 25 s
SAXS and SHEAR FLOWSAXS and SHEAR FLOW
TimeTime--resolvedresolved simultaneoussimultaneousWAXS and SAXS WAXS and SAXS analyses analyses
Synchrotrone DaresburySynchrotrone Daresbury (UK)(UK)
time
Temperature
Tc
Tm
T1
T2
time t = 0
T = 124.4 °C t = 0 T = 122.7 °C t = 10 s T = 121.0 °C t = 20 s T = 119.4 °C t = 30 s
T = 117.8 °C t = 40 s T = 116.1 °C t = 50 s T = 112.7 °C t = 70 sT = 114.4 °C t = 60 s
flow direction
SAXSSAXS iPP, [rr] = 0.48%, Tm = 162°C