2. Morphological Structure of Polymerspt.bme.hu/~vas/PhD_Polymer Materials Science/PolMatsScience_LMV... · 2 3 Polymer Materials Science Recapitulation Structure of Polymers (microscale

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Polymer Materials ScienceBMEGEPT9107, 2+0+0, 3 Credits

Lecturer: Prof. Dr. László Mihály Vas

Budapest University of Technology and EconomicsDepartment of Polymer Engineering

2016.11.10.

2. Morphological Structure of Polymers

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Polymer Materials ScienceBooks, textbooks, lecture notes, guides

� G. Bodor: Structural investigation of polymers. Akadémai Kiadó, Budapest; Ellis Horwood, Chichester, 1991.

� I.M. Ward, D.W. Hadley: An introduction to the mechanical properties of solid polymers. J. Wiley & Sons, Chichester – New York, 1993.

� T.A. Osswald, G. Menges: Materials Science of polymers for engineers. Hanser Pub., New York, 1996.

� L.M. Vas: Lecture notes, ppt slides, http://pt.bme.hu/~vas

� G. Strobl: The Physics of Polymers. Concepts of Understanding theirStructures and Behaviour. Springer Verlag, Berlin. 1996.

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Polymer Materials ScienceRecapitulation

� Structure of Polymers (microscale levels)

• Atomic structure• Molecular structure• Morphological or fine structure

� Properties of Polymers (macroscale levels)

• Mechanical properties• Effect of temperature• Effect of humidity• Other properties

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Content of Polymer Materials ScienceRecapitulation

� Polymer materials, typical material classes, molecular and

morphological structure of polymers, polymer blends and alloys

� Testing methods of polymer structures

� Mechanical behavior of polymer materials

� Behavior of polymers under changing temperature, humidity and other environmental factors

� Strength and fracture-mechanical properties of polymers

� Phenomenological modeling of the mechanical behaviors of

solid polymers

� Statistical-mechanical modeling of polymers

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Classification of PolymersRecapitulation

� Classification respect of structure

• Linear polymers (linear, chain molecular structure)

- Semi-crystalline polymers (e.g. PE, PP, PA, PAN, PET)

- Amorphous polymers (PVC, PS, PMMA, PC)

• Crosslinked polymers (network structure – amorphous polymers.)

- Elastomers (weakly cross-linked, e.g. rubbers: NR, BR, PUR)

-Duromers (strongly cross-linked; resins: e.g. UP, EP, VE)

� Classification in respect of thermal and mechanical behavior

• Thermoplastics (they can be molten reversibly ⇒ linear polymers; e.g. PE, PP, PA, PET, PVC, PS, PMMA, PC)

• Non-thermoplastics - thermosets- Linear polymers (Kevlar, PAN, cellulose, chitin, protein)- Crosslinked polymers (elastomers, duromers)- Semi-crosslinked & semi-crystalline polymers (wool fiber, XPE)

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Structural Levels of PolymersRecapitulation

Graph-point:

structural level

Graph-line:

transition between

structural levels

(along the line:

ordering and uniting

operations)

Structural graph Structural levels of PE

↑

↓ Crystallite

Crystal-cell

Fibril

Spherulite

Polymer part

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Micro- and

macrostructural

levels of

polymersRecapitulation

Properties measurable on

macro-level are the resultant

of the microscale ones.

• Density

• Mechanical properties

• Thermal properties

• Moisture take up

• Others

Structural graph

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Morphological structure 1.

� Differences between the materials of small and

large molecules

• Long term elasticity• Differences in the crystallinity

Crystalline parts – primary transition (Tcr<T

m)

Amorphous parts – secondary transition (Tg)

Crystallinity Melting Hysteresis Character of transition

Materials of small molecules

Total Sharp melting point

No Throughequilibriumstates

Materials of large molecules

Partial Meltinginterval

Exists Far from equilibrium state

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� Transitions of 1st and 2nd order

• First order transition (Tm

): the free enthalpy (G) is continuous, the volume

(V) is discontinuous

• Second order transition (Tg): G, V are continuous, the thermal expansion

coefficient (α) is discontinuous

Small molecule material Polymer material

Tg

Tm

Tm

Tg

Vas László M.2016.11.10.

Volu

me

Volu

me

Temperature Temperature

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� Revelation of crystallinity by X-ray diffraction

Small molecule crystalline material

Salt (NaCl)

Amorphous polymer (PS)

Semicrystalline polymer (PET)

Diffractograms of small and

large molecule materials

Basic condition of crystallinity:

stereoregular molecule chainsVas László M.2016.11.10.

Inte

nsi

tyIn

tensi

ty

Inte

nsi

ty

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� Polymer crystal cells (extended, spiral chain forms)

PE crystal cellChain form: extended

a = 0,736 nm b = 0,492 nmc = 0,254 nm

← PP crystalChain form: spiral

↓

PA6.6 crystal cell

Chain form: extended

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� Crystallization process of polymers

= Nucleus-formation and growing Avrami equation

T=110oC: n=2

T=236oC: n=4

T=240oC: n=4

mL, m

S, m

o– mass of

liquid-, solid, polymer

Z = speed constant

N[1/sm3]= nucleus

formation constant

G[m/s]= growth

constant

n= Avrami exponent

(1≤n≤4)

Free enthalpy

of nucleus

formation (G)


PETP

Nucleus-size

Time

PET Crystallization isotherms

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� Crystallization process of polymers – Nucleus-formation and

growingNucleation and the types of nuclei

Pre-arrangements in

the melt


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� Morphological units – ordered parts

Crystallite: The smallest ordered part in the polymer

Its internal order: 3DNot a single crystal! Because it is not bounded by planes.

Names on the basis of size ratios of the envelope/hull brick:

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Morphological structure 7.a.

� Polymers and morphological structure types

� Unoriented homopolymers• Fringed micellar structure• Paracrytalline structure• Spherulite structure• Other special structures

� Oriented homopolymers• Transcrystalline structure (local)• Shish-kebab structure• Fibrillar structure (global)

� Core-sheath structure of injection molded homopolymer

� Co-polymers, polymer blends

� Filled polymers, fiber reinforced composites


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� Fringed micellar structure

• Molecular chains pass through several crystalline

and amorphous zones.

• In case of small crystallinity

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� Paracrystalline structure (Large crystallinity is possible.)

Ideal lattice and light-diffraction image 1st order lattice distortion and light-diff. image

2nd order lattice distortion and light-diff. image

Hosemann (1950)


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� Paracrystalline structure (Large crystallinity is possible.)

Ideal lattice Paracrystal-lattice (Paracr.)

Ideal Paracr. Real Paracr.

Amorphous Cluster

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Morphological structure 7.� Spherulite structure

Spherulite:

Spherical, birefringent

formation

HDPE fast crystallization, 100x

PEO – Ø0,2 mm HDPE spherulites embedded into granular structure, 100x

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PP spherulite

Stages of formation by Bernauer

� Spherulite structure

- Spherulite

+ Spherulite

Fibril

Chain

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Polymer chain: n⊥<n

n⊥< nr<nt <n

n⊥< nt<nr <n

Refractive index: n

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� Schematic summary of the spherulite structure

Ordered (crystalline) and amorphous parts in the spherulite

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In general spherulites are formed if there is/are no strong flow gradient or/and

shearing effect.

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� Oriented, fibrillar structures - Shish-kebab structures

PE

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In general, instead of spherulites, oriented structures are formed in presence of

strong flow gradient or/and shearing effect.

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� Transformation

of spherulite

into fibrillar

structure

during uniaxial

drawing of

PA6.6 foil

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� Ordered structures and amorphous parts in oriented polymers

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Fibril

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� Strongly oriented, fibrillar structures

PA6.10 – 15000x

Cellulose – 15000x

Transcrystalline structure

Around

carbon fiber

in PP

Fibrils

Many crystal nuclei

– Hindered

spherulite growth

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� Strongly oriented, fibrillar structures - Fibers

100% paracrystalline HPPE (SK60)Liquid crystalline Kevlar

(100% paracrystalline)

Oriented polyester

(PET) fiber

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PA6 single crystal

Lamellae and chain folding

PE single crystal

11/10/2016

Thickening of PE single crystal

by heat treating

� Other structural formations - Single crystals

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Hedrite (PE) Dendrite (PE)

Extended

chain lamellae

(crystallized

under high

pressure)

PTFCE

PE

� Other structural formations

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� Complex structure of extruded and injection moulded

polymer parts

2016.11.10. Woodward A.E.: Atlas of Polymer Morphology. Hanser

Pub. Munich, 1989.

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� Anisotropic liquid –

liquid crystalline or

mesophase

structures

• Nematic• Smectic• Cholesteric

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� Multiphase combined structures - Copolymers

Amorphous copolymer structure composed of incompatible polymer components

Woodward A.E.: Atlas of Polymer Morphology. Hanser Pub. Munich, 1989.


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� Multiphase, combined structures

High impact PS – rubbery additive

High impact PVC – chlorinated PE

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� Multiphase, combined structures – Copolymer, blend

Woodward A.E.: Atlas of Polymer Morphology. Hanser Pub. Munich, 1989.


Two phase structure of 5% PS/95%

large molecule mass PMMA blend

Lamellar crystal structure in

PS/PEO diblock-copolymer

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� Multiphase, combined structures – TPE, TPR

Thermoplastic elastomer (TPE): linear block-copolymer, physical crosslinked

structure (meltable binding segments)

Hard segment at ambient temperature:

• Amorphous glassy state• Crystalline state (crystallite)

Bartha Z.: Gumiipari kézikönyv I. Taurus-OMIKK, Bp. 1988.


Structure of TPE

Soft segment

Hard segment

Plastomers

Place of TPR between traditional elastomers

(cauchoucs) and plastomers

Cauchoucs

PF resins

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� Multiphase, combined structures - TPE

TPE rangePhase morphology types of

two component systems



Mole

cula

r m

ass

of the

pla

stic

blo

ck

Plastic

behavior

Low processability

Small

strength

Rubberlike behavior,

large strength, good

processability

Molar mass of the elastomer blocks

Sphere Cylinder Plate/Sheet Cylinder Sphere

→ Increasing A content

→ Decreasing B content

Mass ratios of the soft and hard

segments

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� Comparison of main polymer material classes



Tg – Glassy temperature, Tm – Melting temperature, Td – Decomposition temperature

temp. – temperature, Am. – amorphous, Crys. - crystalline

PlastomersRubbers Thermoplastic elastomers

Thermoplastic (TP) Not TP

Chemical structureLinear or branched

macromolecules

Dense

network

Rare

network

Segments (blocks) of different

properties

Physical structure Am. Crys. Am. Am.

Soft

segment

am.

Hard segment

Am. Crys.

Transition temperature Tg>>25oC Tm>>25oC -- Tg<-25oC Tg<-25oC Tg>>25oC Tm>>25oC

Charac-

teristic

behavior

At ambient

temp.

Hard, tough or hard,

rigidHard, rigid

Soft,

elasticSoft, elastic

At high

temp.Viscous flow

Solid up to

Td

Elastic up

to Td

Viscous flow

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� Fiber reinforced polymer composites

Short glass fiber

reinforced unsaturated

polyester (UP)

Filament carbon/epoxy

Filament glass/UP

Filament/continuous

fiber composite

Chopped/short

fiber composite


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� Multiphase,

combined

structures

Short glass fiber

reinforced liquid

crystal polyester

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Properties of morphological structures 1.

� CrystallinityMeasurement: DSC, WAXS, Density measurement

� Crystal particle sizeMeasurement : WAXS, DSC

� Orientation – characterized by chain segments

• Crystalline – Measurement: WAXS• Amorphous – Measurement: WAXS, by calculation• Average – Measurement: Birefringence, sonic speed measurement

(ultra-sound)

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� Chain orientation and its significance

Properties of morphological structures 2.

Isotropic Uniaxial Biaxial (planar) Cold drawing and neck formation (+20-30oC)

Orientation during neckingDrawing cellulose fibers

Production of fibers, oriented foils

2016.11.10.

2. Morphological Structure of Polymerspt.bme.hu/~vas/PhD_Polymer Materials Science/PolMatsScience_LMV... · 2 3 Polymer Materials Science Recapitulation Structure of Polymers (microscale

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