Agnelli, S.

Galimberti, MAURIZIO STEFANO

Musto, Sara

Pandini, S.

Romele, P.

Serafini, Andrea

Torricelli, F.

S. Agnelli

S. Pandini

F. Torricelli

P. Romele

M. Galimberti

S. Musto

A. Serafini

Archivio istituzionale della ricerca - Politecnico di Milano

Anisotropic properties of natural rubber nanocomposites with sp2 carbon allotropesS. Agnelli, S. Pandini, F. Torricelli, P. Romele(Università degli Studi di Brescia, Brescia, Italy)M. Galimberti, S. Musto, A. Serafini(Politecnico di Milano, Milano, Italy)XIV Convegno Nazionale AIMAT 2017XI CONVEGNO NAZIONALE INSTMIschia Porto (Na), 12-15 luglio 2017Carbon black (CB)Rubber reinforcement: carbon fillers vs nanofillersMWCNTNano-grafiteN326*Agnelli et al.,eXPRESS Polymer Letters Vol.8, No.6 (2014) 436–449TEM images of isoprene rubber + 30 phr filler*Particle geometry:GraphenenanoparticlesCarbon nanotubes3D-like 2D-like 1D-likeExamples:Surface area:Primary particlesdimension scale:dispersion:highlow~1 nmparticles singularly dispersed~10 nmparticles aggregatedNanofillersConventional fillersvsRubber reinforcement: carbon fillers vs nanofillersHigh surface area = high reinforcement efficiencyBET surface area [m2/g]:20077MWCNTCB (N326)‘’master’’ curveMWCNTCB (N326)Agnelli et al.,eXPRESS Polymer Letters Vol.8, No.6 (2014) 436–449Carbon black (CB)Rubber reinforcement: carbon fillers vs nanofillersParticle geometry:GraphenenanoparticlesCarbon nanotubes3D-like 2D-like 1D-likeNanofillersConventional fillersAspect ratio: max dimension/min dimension of the particleHigh aspect ratio  possible preferential orientation ANISOTROPIC propertiesAnisotropy in rubbers filled with CNT“The alignment of MWCNTs in the 50/50 NR/NBR blends can be controlled by milling the compounds at a tight nip gap.” (Kueseng et al., Polymer Testing 32 (2013) 1229–1236)Orientation and alignment of CNT is seeked to fully exploite their properties along specific directions,particularly for electronical applications (field emission displays and sensors, data storage, and light-emitters)Most attention is given to unidirectional alignment and longitudinal properties.Methods for the alignment of CNTs(Ponnamma et al., Mater. Chem. C, 2014, 2, 8446):- extrusion or injection molding. Alignment degree can be tuned by the shear rate as well as the pressure applied- In situ polymerization- mechanical stretching- electrospinning- filtration- plasma-enhanced chemical vapor deposition (PECVD)- template- force field-induced alignment- magnetic field-induced alignment- liquid crystalline phase-induced alignmentMD = Machine directionTD = Transverse directionMillingdirectionAim of the workDescribe anisotropic propertiesof a nanofilled homogeneous elastomeric materialalong three main spatial directionsin a very common rubber product: a rubber plate.Plate is produced by a common base production technique, at low shar rate.Other processes can allow to tuneanisotropy levels.Evaluation also of the propertiesalong transversal directions, usuallyneglected.?The plate is a typical product for quality tests and material standard characterization neglects transversaldirection.WHY?Rubber bellowsAdvanced designProper material characterizationExperimental details• Material: NR filled with different fillers (CB) and nanofillers (nanoG and CNT) • A base production process is used: compression molding• Tests along different directions, also through the thickness shear tests• Property considered: dynamic moduli and Payne effect• Matrix: peroxide cured natural rubber (NR)• Fillers and nanofillers:• nanoG:  Synthetic Graphite 8427® from Asbury Graphite Mills Inc (BET surface area=330 m2/g)• CNT: Baytubes® C150 P from Bayer Material Science (BET surface area =200 m2/g)• CB: N326 from Cabot (BET surface area =77 m2/g)• CB: Printex XE2 from Degussa(BET surface area =1000 m2/g)Ingredient Amount [phr (volume fraction)]NR 100 100 100 100Filler 0 4 (0.02) 15 (0.07) 35 (0.15)DCUP 3.5 3.5 3.5 3.5NR=SMR GP, from Lee RubberDCUP=dicumyl peroxide.Materialsphr = weight parts per hundred rubberProduction processMixing by Brabender(50 ml mixing chamber)Two roll mill(5 times,1 cm as the nip between the rolls)Compression molding3 mm thick plateExperimental details• Material: NR filled with different fillers (CB) and nanofillers (nanoG and CNT) • A base production process is used: compression molding• Tests along different directions, also through the thickness shear tests• Property considered: dynamic moduli and Payne effectExperimental details• Material: NR filled with different fillers (CB) and nanofillers (nanoG and CNT) • A base production process is used: compression molding• Tests along different directions, also through the thickness shear tests• Property considered: dynamic moduli and Payne effectExpected structuring of CBExperimental detailsExpected structuring of anisometricparticles (nanoG and CNT)• Material: NR filled with different fillers (CB) and nanofillers (nanoG and CNT) • A base production process is used: compression molding• Tests along different directions, also through the thickness shear tests• Property considered: dynamic moduli and Payne effectnanoG CNTDynamic-mechanical testsin shear modeShear sandwitch clampsof DMA Q800 – TA Instruments9 mm3 mm3 mmExperimental details• Material: NR filled with different fillers (CB) and nanofillers (nanoG and CNT) • A base production process is used: compression molding• Tests along different directions, also through the thickness shear tests• Property considered: dynamic moduli and Payne effectThrough-thickness In-planeExperimental detailsDynamic-mechanical testsin shear mode• Material: NR filled with different fillers (CB) and nanofillers (nanoG and CNT) • A base production process is used: compression molding• Tests along different directions, also through the thickness shear tests• Property considered: dynamic moduli and Payne effectThrough-thickness In-planeExperimental detailsDynamic-mechanical testsin shear mode• Material: NR filled with different fillers (CB) and nanofillers (nanoG and CNT) • A base production process is used: compression molding• Tests along different directions, also through the thickness shear tests• Property considered: dynamic moduli and Payne effectPayne effect• Provides information about the strength of filler network• Related to dissipation of energy in dynamic-mechanical applications of elastomeric materialsExperimental details• Material: NR filled with different fillers (CB) and nanofillers (nanoG and CNT) • A base production process is used: compression molding• Tests along different directions, also through the thickness shear tests• Property considered: dynamic moduli and Payne effectTest conditions:Room temperature (23÷26°C)Frequency: 1 HzShear strain amplitude range: 0.013%÷30%Dynamic-mechanical testsin shear modeResultsNR + 35 phr CNTThrough-thicknessIn-planeG31G32Through-thicknessG21 G12In-planeAgnelli et al., Macromolecules 2016, 49, 8686−8696NR + 35 phr CNTResultsG31G32Through-thicknessG21 G12In-planeAgnelli et al., Macromolecules 2016, 49, 8686−8696NR + 35 phr nanoGResultsIn-planeThrough-thicknessThrough-thicknessIn-planeG31G32G21 G12NR + 35 phr N326Through-thickness In-planeResultsG31 G32 G21 G12NR + 35 phr PrintexThrough-thicknessIn-planeG31 G32G21 G12NR + 35 phr N326Through-thickness In-planeResultsG31 G32 G21 G12NR + 35 phr PrintexThrough-thicknessIn-planeG31 G32G21 G12In-planeThrough-thicknessNRAnisotropy indexResultsThrough-thicknessIn-planeLow shear strain amplitude (0.025%)G’IPG’TTAnisotropy index:ResultsnanoGCNTLow shear strain amplitude(0.025%)Anisotropy level of storage modulusN326PrintexResultsInvestigations of filler structuringnanoG CNTAnalyses• Transmission electron microscopy (TEM) analysis• Electrical resistivity measurementsPreliminary data on:• NR + 15 phr CNT• NR + 35 phr CNT ?Transmission electron microscopy (TEM) analysisResultsTEM:Philips CM200 electron microscope200 kVField Emission Gun filamentUltrathin slice (approximately 70–100 nm thick) preparation by ultramicrotomy technique.(sample temperature: -130° C; diamond knife) Materials:• NR + 15 phr CNT• NR + 35 phr CNT Ultrathin sections obtained perpendicular  to the reference axis 1 Sketch of expected CNT structuring:ResultsNR + 35 phr CNTBright field Transmission electron microscopy (TEM-BF) analysisResultsNR + 35 phr CNTCNT preferentialorientationby SAED analysisSAED ring pattern (002) Debye-Scherrer ring  d-spacing of 0.34 nmconcentric arrangements of the nanotubes wallsabc dElectron diffraction measurementsby Selected Area Electron Diffraction (SAED) Patterns ResultsNR + 15 phr CNTBright field Transmission electron microscopy (TEM-BF) analysisResultsNR + 15 phr CNTCNT preferentialorientationby SAED analysisSAED ring pattern abcdElectron diffraction measurementsby Selected Area Electron Diffraction (SAED) Patterns (002) Debye-Scherrer ring  d-spacing of 0.34 nmconcentric arrangements of the nanotubes wallsResultsElectrical resistivity measurementsMeasurement setup:Specimens: 3x3x3 mm3KEITHLEY 2636A System SourcemeterContacts: Copper+silver pasteMaterials:• NR + 15 phr CNT• NR + 35 phr CNT Through-thicknessIn-planeII I132In-plane 1Through-thicknessIn-plane 2ResultsElectrical resistivity measurementsNR + 15 phr CNT NR + 35 phr CNTrTT/rIP = 38Anisotropy index:In-plane 1 Through-thicknessIn-plane 2 Through-thicknessIn-planeIIII IrTT/rIP = 10Conclusions• Dynamic shear characterization allowed to estimate the mechanical anisotropy level in a thin rubber plate.• In a homogeneous compression molded rubber plate, CNT and nanoG confer a transversal isotropic behavior, whose intensity depends on filler content .• This behavior could be interpreted as a consequence of a random orientation of the filler particles in the sheet plane, and of their planar piling up through the sheet thickness.• A combined microscopy approach (TEM+SAED) and electrical measurements provided confirmation of CNT structuring.IITransverse isotropy is observed in sedimentary rocks at long wavelengths.Thank you for you attention!Grand Canyon

Anisotropic properties of natural rubber nanocomposites with sp2 carbon allotropes

https://re.public.polimi.it/bitstream/11311/1035894/1/3%20-%20AIMAT17%20-%20Anisotropic%20properties.pdf

Anisotropic properties of natural rubber nanocomposites with sp2 carbon allotropes

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