Matteo Traina , Alessandro Pegoretti and Amabile Penati

POLYETHYLENE-CARBON BLACK NANOCOMPOSITES: MECHANICAL RESPONSE UNDER CREEP AND DYNAMIC LOADING

CONDITIONS

Matteo Traina, Alessandro Pegoretti and Amabile PenatiUniversity of Trento (DIMTI) and INSTM; Via Mesiano 77, 38050 Trento – Italy

E-mail: [email protected]; On web: www.unitn.it

INSTMConsorzio Interuniversitario Nazionaleper la Scienza e Tecnologia dei Materiali

Università degli Studi di TrentoDipartimento di Ingegneria dei Materiali

e Tecnologie Industriali (DIMTI)

VI CONVEGNO NAZIONALE SULLA SCIENZA E TECNOLOGIA DEI MATERIALI

(June 12th-15th, 2007; Perugia)

mailto:[email protected]

http://www.unitn.it/

INTRODUCTION

agglomerates

primaryparticle aggregate

Carbon black (CB)

Carbon (graphene layers)Combustion or decomposition (CXHY)

OAN (cm3/g)

aggregate structure

SS

A (

m2 /

g)

particle diameter

Microstructure:

primary particles (diameter) specific surface area (SSA) measured by the BET (Brunauer– Emmett–Teller) method (ASTM D 6556-03) TEM analysis

aggregates (structure) oil adsorption number (OAN) measured with the dibuthyl phtalate (ASTM D 2414-04) TEM analysis

Other properties (…)

INTRODUCTION

Grade (Supplier)OAN

[cm3/g]SSA

[m2/g]

CB105 Raven P-FE/B(Columbian Chemicals)

0.98 105

CB226 Conductex 975u(Columbian Chemicals)

1.69 226

CB231 Cabot XC72(Cabot Corporation)

1.78 231

CB802 Ketjenblack EC300J(Akzo Nobel)

3.22 802

CB1353 Ketjenblack EC600JD(Akzo Nobel)

4.95 1,353

Carbon black (CB)

SSA / OAN

SSA / OAN

SSA / OAN

SSA / OAN

INTRODUCTION

CB FILLED COMPOSITES

Matteo Traina, Alessandro Pegoretti and Amabile Penati , Time-temperature dependence of the electrical resistivity of high density polyethylene - carbon black composites. Journal of Applied Polymer Science, in press.

Matteo Traina, Alessandro Pegoretti and Amabile Penati , Processing and Electrical Conductivity of

High Density Polyethylene – Carbon Black Composites. XVII Convegno Nazionale AIM

(Napoli, September 11th – 15st, 2005)

EXPERIMENTAL

HDPE-CB composites

VISCOELASTIC BEHAVIOR Creep tests DMTA tests

COMPOSITE MORPHOLOGYconstant filler content (1 vol%)

Grade (Supplier) Properties

HDPE Eltex A4009(BP Solvay)

MFI = 0.8 g/10min (190°C; 2.16kg)Density = 0.958 g/cm3 (23°C)

MATERIAL (polymeric matrix)

EXPERIMENTAL

HDPE-CB composites



Effect of the SSA of CBmatrix HDPEcomposite HDPE-CB226composite HDPE-CB1353

Grade (Supplier)OAN

[cm3/g]SSA

[m2/g]

CB105 Raven P-FE/B(Columbian Chemicals)

0.98 105

CB226 Conductex 975u(Columbian Chemicals)

1.69 226

CB231 Cabot XC72(Cabot Corporation)

1.78 231

CB802 Ketjenblack EC300J(Akzo Nobel)

3.22 802

CB1353 Ketjenblack EC600JD(Akzo Nobel)

4.95 1,353

CB226 CB1353

EXPERIMENTAL

HDPE-CB composites




PROCESSING

Melt compounding (Extrusion)Twin screw extruder(ThermoHaake PTW16)T = 130-200-210-220-220°Cn = 12 rpm

Effect of the degreeof filler dispersionMultiple extrusions(up to 3 times)

FILLER DISPERSION

Extrusions 3x

HDPE-CB1353

500 µm

HDPE-CB226

2x1x

HDPE-CB composites >>> thin section (microtome) >>> optical microscope

As the number of extrusions increases,as the degree of the filler dispersion is better.

As the S

SA

decreases, as the degree of dispersion is better.

HDPE-CB226, 1x

HDPE-CB composites>>> ultra-thin section (cryo-ultramicrotome) >>> transmission electron microscope

>>> PRELIMINARY RESULTS

HDPE-CB226, 2x

CB226

FILLER DISPERSION

As the number of extrusions increases,as the degree of the filler dispersion is better.

MOLECULAR WEIGTH DISTRIBUTION

HDPESize Exclusion Chromatography (SEC)1,2,4 trichlorobenzene (TCB) at 140°C

IP

MW

HDPEHDPE-CB

The HDPE undergoes a progressive thermo-mechanical degradation during the extrusion processes.

EFFECT OF MULTIPLE EXTRUSIONS: 3x > 2x > 1x HDPE > HDPE-CB226 > HDPE-CB1353

EFFECT OF THE FILLER: HDPE > HDPE-CB226 > HDPE-CB1353 3x > 2x > 1x

CREEP: GENERAL COMPARISON

Creep tests: 30°C, 10 MPa

extruded 1x

extruded 2x extruded 3x

HDPE-CB composites




Effect of the degreeof filler dispersionMultiple extrusions(up to 3 times)

HDPE 1xHDPE 2xHDPE 3x

HDPE-CB226, 1xHDPE-CB226 2xHDPE-CB226 3x

HDPE-CB1353 1xHDPE-CB1353 2xHDPE-CB1353 3x

DEGRADATION PHENOMENAHDPE, 1xHDPE, 3x

HDPE 1xHDPE 3xHDPE-CB226 3xHDPE-CB1353 3x

FILLER EFFECTHDPE, 3xHDPE-CB226, 3xHDPE-CB1353, 3x

CREEP RESISTANCE

DEGRADATION:HDPE 3x < HDPE 1x

FILLER EFFECT:HDPE < HDPE-CB226 < HDPE-CB1353

These effects are evident at long time,while at short time the curves are almost superimposed.

CREEP: MASTER CURVES

HDPE-CB @ 30°C

HDPE @ 30°CCreep test:temperature = 3090°Cstress = 3 MPa (linear viscoelasticity)

ANALYSIS OF THE DATA:Time-Temperature Superposition Principle(temperature spectrum master curve)

LOG-linear

IN GENERAL: linear decreasing in bi-logarithmic scale the most differences is present at short time (<105 s) at long time (>105 s) the curves are superimposed

CREEP: CREEP RATE

Master curves linear viscoelasticityCreep tests constant load/stress LOG-LOG

LOG-LOG

dt

dt

strain rate:dt

dDD

Creep rate

AT SHORT TIME:

DEGRADATION: HDPE 3x > HDPE 1x

FILLER EFFECT: HDPE > HDPE-CB226 > HDPE-CB1353)

CREEP: RETARDATION SPECTRA

HDPE-CB @ 30°C

HDPE @ 30°C

ttd

tDdDL

log

log

The retardation spectrum translates:



Linear viscoelasticity:es. Maxwell generalized modelretardation time distribution

Retardation spectrum (first-order approximation)

The elastic components don’t change in a meaningful way.

CREEP: ISCOCHRONOUS COMPLIANCE

Comparison of the isochrone compliance (@ 2000s) as a function of the temperature

The compliance is divided in: elastic component (instantaneous), DE

viscoelastic component (time dependent), DV

HDPE @ 2000s, DV

HDPE-CB @ 2000s, DV

D(t=2000) = DE + DV

DE = D(t=0s)DV = D(t=2000s) – D(t=0s)

The viscoelatic components:

DEGRADATION:HDPE 3x > HDPE 1x (<70°C)

FILLER EFFECT:HDPE > HDPE-CB226 > HDPE-CB1353

Glass transition temperature:

DEGRADATION:HDPE 3x < HDPE 1x (-10°C)

FILLER EFFECT:HDPE < HDPE-CB (+4°C)

DMTA: GENERAL COMPARISON

Material Tg=T [°C]

HDPE, 1x -98.8

HDPE, 3x -108.9

HDPE-CB226, 3x -104.3

HDPE-CB1353, 3x -103.8

DMTA tests:temperature = -130 130°Cfrequency = 1 Hz

Relaxation phenomena (, )

DMTA: MASTER CURVES

HDPE-CB @ 30°C

HDPE @ 30°CDMTA test:temperature = -20130°C ( relaxation)frequencies = 0.330 Hz

ANALYSIS OF THE DATA:Time-Temperature Superposition Principle(temperature spectrum master curve)

The DMTA results are analogous to the CREEP results.

Storage modulus:



The relaxation spectra (DMTA) are consistent with the retardation spectra (CREEP) and very similar to the MWD data for the HDPE.

DMTA: RELAXATION SPECTRA

HDPE-CB @ 30°C

HDPE @ 30°C

Linear viscoelasticity:

Relaxation spectrum (first-order approximation)

1

log

log

d

EdEH

DEGRADATION:HDPE 3x >narrow> HDPE 1x

FILLER EFFECT:longer relaxation times for HDPE-CB

ACTIVATION ENERGY

ACTIVATION ENERGY of “” relaxation [kJ/mol] various method of calculation

250 255 260 265 270 275

HDPE, 1x

HDPE, 3x

HDPE-CB226, 3x

HDPE-CB1353, 3x

\

0 50 100 150 200 250

HDPE, 1x

HDPE, 3x

HDPE-CB226, 3x

HDPE-CB1353, 3x

\

CREEPshift factor

(Arrhenius equation)

DMTAshift factor

at high temperature(50100°C)

(Arrhenius equation)


FILLER EFFECT:HDPE < HDPE-CB

CONCLUSIONS

The creep resistance (in general the viscoelastic behaviour) of the HDPE-CB composites is strictly dependent:

● on the CB type as the SSA increases as the creep resistance increases >>> The filler-matrix interaction hamper the chain motions

elastic/viscoelastic components of complianceactivation energy, retardation/relaxation spectracreep rate.

● on the level of dispersion of the filler in the polymer matrix as the filler dispersion is improved as the creep resistance increases >>> The improved dispersion enhances the filler-matrix interaction, i.e. the effective surface area.

● on the degradation of the polymer matrix as the matrix degrades as the creep resistance decreases

Documents

Matteo Traina , Alessandro Pegoretti and Amabile Penati