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Matteo Traina , Alessandro Pegoretti and Amabile Penati

Università degli Studi di Trento Dipartimento di Ingegneria dei Materiali e Tecnologie Industriali (DIMTI). INSTM Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali.

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Matteo Traina , Alessandro Pegoretti and Amabile Penati

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  1. Università degli Studi di TrentoDipartimento di Ingegneria dei Materialie Tecnologie Industriali (DIMTI) INSTMConsorzio Interuniversitario Nazionaleper la Scienza e Tecnologia dei Materiali POLYETHYLENE-CARBON BLACK NANOCOMPOSITES: MECHANICAL RESPONSE UNDER CREEP AND DYNAMIC LOADING CONDITIONS Matteo Traina, Alessandro Pegoretti and Amabile Penati University of Trento (DIMTI) and INSTM; Via Mesiano 77, 38050 Trento – Italy E-mail: matteo.traina@ing.unitn.it; On web: www.unitn.it VI CONVEGNO NAZIONALE SULLA SCIENZA E TECNOLOGIA DEI MATERIALI (June 12th-15th, 2007; Perugia)

  2. INTRODUCTION aggregate structure SSA (m2/g) particle diameter primaryparticle aggregate agglomerates OAN (cm3/g) Carbon black (CB)Carbon (graphene layers) Combustion or decomposition (CXHY) 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 (…)

  3. INTRODUCTION Carbon black (CB)

  4. INTRODUCTION SSA / OAN SSA / OAN SSA / OAN SSA / OAN 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) CB FILLED COMPOSITES

  5. EXPERIMENTAL MATERIAL (polymeric matrix) HDPE-CB composites VISCOELASTIC BEHAVIOR Creep tests  DMTA tests COMPOSITE MORPHOLOGYconstant filler content (1 vol%)

  6. EXPERIMENTAL CB1353 CB226 HDPE-CB composites VISCOELASTIC BEHAVIOR Creep tests  DMTA tests COMPOSITE MORPHOLOGYconstant filler content (1 vol%) Effect of the SSA of CBmatrix HDPEcomposite HDPE-CB226composite HDPE-CB1353

  7. EXPERIMENTAL PROCESSING Melt compounding (Extrusion)Twin screw extruder(ThermoHaake PTW16)T = 130-200-210-220-220°Cn = 12 rpm HDPE-CB composites VISCOELASTIC BEHAVIOR Creep tests  DMTA tests COMPOSITE MORPHOLOGYconstant filler content (1 vol%) Effect of the SSA of CBmatrix HDPEcomposite HDPE-CB226composite HDPE-CB1353 Effect of the degreeof filler dispersionMultiple extrusions(up to 3 times)

  8. FILLER DISPERSION HDPE-CB composites>>> thin section (microtome) >>> optical microscope Extrusions 1x 2x 3x HDPE-CB226 500 µm As the SSA decreases, as the degree of dispersion is better. HDPE-CB1353 As the number of extrusions increases,as the degree of the filler dispersion is better.

  9. FILLER DISPERSION HDPE-CB composites>>> ultra-thin section (cryo-ultramicrotome) >>> transmission electron microscope >>> PRELIMINARY RESULTS HDPE-CB226, 2x HDPE-CB226, 1x CB226 As the number of extrusions increases,as the degree of the filler dispersion is better.

  10. MOLECULAR WEIGTH DISTRIBUTION HDPESize Exclusion Chromatography (SEC)1,2,4 trichlorobenzene (TCB) at 140°C MW The HDPE undergoes a progressive thermo-mechanical degradation during the extrusion processes. HDPEHDPE-CB IP

  11. CREEP: GENERAL COMPARISON Creep tests: 30°C, 10 MPa EFFECT OF MULTIPLE EXTRUSIONS: 3x > 2x > 1x HDPE > HDPE-CB226 > HDPE-CB1353 EFFECT OF THE FILLER: HDPE > HDPE-CB226 > HDPE-CB1353 3x > 2x > 1x extruded 1x extruded 2x extruded 3x

  12. HDPE-CB composites VISCOELASTIC BEHAVIOR Creep tests  DMTA tests HDPE 1xHDPE 3xHDPE-CB226 3xHDPE-CB1353 3x HDPE 1xHDPE 2xHDPE 3xHDPE-CB226, 1xHDPE-CB226 2xHDPE-CB226 3xHDPE-CB1353 1xHDPE-CB1353 2xHDPE-CB1353 3x COMPOSITE MORPHOLOGYconstant filler content (1 vol%) Effect of the SSA of CBmatrix HDPEcomposite HDPE-CB226composite HDPE-CB1353 DEGRADATION PHENOMENAHDPE, 1xHDPE, 3x Effect of the degreeof filler dispersionMultiple extrusions(up to 3 times) FILLER EFFECTHDPE, 3xHDPE-CB226, 3xHDPE-CB1353, 3x

  13. CREEP: MASTER CURVES Creep test:temperature = 3090°Cstress = 3 MPa (linear viscoelasticity) ANALYSIS OF THE DATA:Time-Temperature Superposition Principle(temperature spectrum  master curve) HDPE @ 30°C 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. HDPE-CB @ 30°C

  14. CREEP: CREEP RATE Master curves  linear viscoelasticityCreep tests  constant load/stress LOG-LOG Creep rate strain rate: 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 LOG-LOG LOG-linear AT SHORT TIME: DEGRADATION: HDPE 3x > HDPE 1x FILLER EFFECT: HDPE > HDPE-CB226 > HDPE-CB1353)

  15. CREEP: RETARDATION SPECTRA Linear viscoelasticity:es. Maxwell generalized modelretardation time distribution HDPE @ 30°C Retardation spectrum(first-order approximation) HDPE-CB @ 30°C The retardation spectrum translates: DEGRADATION:HDPE 3x < HDPE 1x FILLER EFFECT:HDPE < HDPE-CB226 < HDPE-CB1353

  16. CREEP: ISCOCHRONOUS COMPLIANCE Comparison of theisochrone compliance(@ 2000s) as a function of thetemperature The compliance is divided in: elastic component (instantaneous), DE viscoelastic component (time dependent), DV HDPE @ 2000s, DV D(t=2000) = DE + DV DE = D(t=0s)DV = D(t=2000s) – D(t=0s) The elastic components don’t change in a meaningful way. HDPE-CB @ 2000s, DV The viscoelatic components: DEGRADATION:HDPE 3x > HDPE 1x (<70°C) FILLER EFFECT:HDPE > HDPE-CB226 > HDPE-CB1353

  17. DMTA: GENERAL COMPARISON DMTA tests:temperature = -130  130°Cfrequency = 1 Hz   Relaxation phenomena (, ) Glass transition temperature: DEGRADATION:HDPE 3x < HDPE 1x (-10°C) FILLER EFFECT:HDPE < HDPE-CB (+4°C)  

  18. DMTA: MASTER CURVES DMTA test:temperature = -20130°C (a relaxation)frequencies = 0.330 Hz ANALYSIS OF THE DATA:Time-Temperature Superposition Principle(temperature spectrum  master curve) HDPE @ 30°C Storage modulus: DEGRADATION:HDPE 3x < HDPE 1x FILLER EFFECT:HDPE < HDPE-CB226 < HDPE-CB1353 HDPE-CB @ 30°C The DMTA results are analogous to the CREEP results.

  19. DMTA: RELAXATION SPECTRA Linear viscoelasticity: Relaxation spectrum(first-order approximation) HDPE @ 30°C DEGRADATION:HDPE 3x >narrow> HDPE 1x FILLER EFFECT:longer relaxation times for HDPE-CB The relaxation spectra (DMTA) are consistent with the retardation spectra (CREEP) and very similar to the MWD data for the HDPE. HDPE-CB @ 30°C

  20. ACTIVATION ENERGY ACTIVATION ENERGY of “a” relaxation [kJ/mol] various method of calculation DEGRADATION:HDPE 3x < HDPE 1x FILLER EFFECT:HDPE < HDPE-CB DMTAshift factorat high temperature(50100°C)(Arrhenius equation) CREEPshift factor(Arrhenius equation)

  21. 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 compliance activation energy, retardation/relaxation spectra creep 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

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