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