Melt-Mastication for Polyolefin Nanocomposite Dispersions

Transcription

1 Melt-Mastication for Polyolefin Nanocomposite Dispersions Brian M. Cromer, E. Bryan Coughlin, and Alan J. Lesser University of Massachusetts Amherst, Amherst MA Department of Polymer Science and Engineering ACCE

2 Outline Background Exfoliated graphene nanoplatelets (xgnp) Polyolefin-nanographite (PO-xGnP) nanocomposites Methods to fabricate PO-xGnP nanocomposites In-situ solution polymerization Melt-mixing Melt-mastication Results and Discussion Optical microscopy (OM) Differential scanning calorimetry (DSC) Wide-angle X-ray diffraction (XRD) Dynamic mechanical analysis (DMA) 2

3 Exfoliated Graphene Nanoplatelets (xgnp) Drzal Group, Michigan State University Graphite-derived nanoparticle Platelet geometry Edge functional groups Schematic of a Graphene Nanoplatelet nm μm Fukushima, H., PhD Thesis, Michigan State University, East Lansing, MI, USA, (2003). 3

4 Fabrication Techniques for PO-xGnP Nanocomposites Polyolefin Pellets xgnp Mechanical Processing Polyolefin-xGnP Nanocomposite 1 μm Mechanical Processing Techniques Solid State Processing Melt-Processing 4

5 Fabrication Techniques for PO-xGnP Nanocomposites Polyolefin Pellets xgnp Mechanical Processing Polyolefin-xGnP Nanocomposite 1 μm Mechanical Processing Techniques Solid State Processing Melt-Processing Chemical Techniques In-Situ Polymerization 5

6 Potential Benefits of PO-xGnP Nanocomposites Polyolefin Pellets Nanographite Processing PO-xGnP Nanocomposite Modulus Strength Conductivity Permeability 1 μm 6

7 PO-xGnP Nanocomposite Challenges Polyolefin Pellets Nanographite Melt-Mixing (e.g. Extrusion) PO-xGnP Nanocomposite Modulus Strength Conductivity Permeability 1 μm 100 μm 7

8 Ideal Processing Technique Polyolefin Pellets Nanographite Processing PO-xGnP Nanocomposite Modulus Strength Conductivity Permeability 1 μm Ideal Processing Technique Achieve efficient nanoparticle dispersion Continuous/high-throughput Economical 8

9 New Techniques for PO-xGnP Nanocomposites Solid State Ball Milling 1 Solid State Shear Pulverization (SSSP) 2,3 In-Situ polymerization 4 SPEX SamplePrep 8000D Dual Mixer/Mill 1 Solid state shear pulverization setup 2,3 [1] X. Jiang, L. T. Drzal, J. Appl. Polym. Sci., 124, (2012) [2] K. Wakabayashi, C. Pierre, D. A. Dikin, R. S. Ruoff, T. Ramanathan, L. C. Brinson, J. M. Torkelson, Macromolecules, 41, (2008).1 [3] K. Wakabayashi, S. Brouse M. Boches, US A (2013) [4] Cromer, B.M., Lesser, A.J., Coughlin, E.B., In-situ Polymerization of Graphene- Isotactic Polypropylene Nanocomposites, SPE-ANTEC, 2013, in press. Polypropylene polymerization catalyst 4 9

10 In-situ Polymerization of ipp-xgnp Nanocomposites 1. Combine xgnp, MAO, toluene 2. Saturate with propylene monomer 3. Add metallocene catalyst 4. Polymerize 3 hours 10

11 Equipment Mass flow controller Catalyst injection port P R O P Y L E N E echanical Stirrer Cooling Jacket Toluene + xgnp + MAO Coughlin, EB. Macromolecules 2002, 35, From University of Hamburg 9.5 L Capacity 11

12 Synthesis Product: ipp-xgnp Composites Color change with increased xgnp loading Reactor powders from in-situ synthesis of ipp-xgnp composites In-Situ Synthesized 0% In-Situ Synthesized 2% In-Situ Synthesized 4% Catalyst activity decreased with increasing xgnp TGA confirmed xgnp loading Char Yield (%) Molecular Weight (kda) ᴆ Activity (kg ipp/ [mmol Zr*bar*h])

13 Melt-Mixing Reference ipp-xgnp composites prepared by melt mixing Protocol: Combine xgnp, ipp Pellets (ExxonMobil), process stabilizers Mix in a static mixer 30 min, 190 ⁰C, 60 RPM Brabender Static Mixer, Model R.E.E. 6 Prepared 0, 2, and 4 wt% samples 13

14 Melt Mastication Temperature 1. Melt-Mix above T melting Melt-Mastication Heating Protocol 2. Cool to T mast 3. Isothermal Mastication T melt 10 min T mast Melt state Transition 10 min T cryst Quasi- Solid state M w Sample (kg/mol) Ð Virgin ipp Melt-Masticated ipp Melt-Masticated+Stabilizers* Time T melt > T mast > T cryst *0.1 wt% Irganox wt% Irgafos

15 Temperature Optical Microscopy 2 wt% Nanographite in ipp 100 μm 100 μm 10 min T melt Melt state T mast T cryst Transition 10 min Quasi Solid state Time 15

16 Original Image Image Analysis Method Binary Image Define Particle Perimeter 1. Convert original image to binary image 2. Use software to define particle Perimeter 3. Calculate # of particles and area of each particle 16

17 Optical Microscopy- 2 wt% Nanographite in ipp 100 μm Normalized Frequency Volume fraction within each size bin 100 μm μm Cross-sectional area (μm 2 )

18 PE-xGnP Nanocomposites Normalized frequency Volume fraction within each size bin μm Cross-sectional area (μm 2 ) Normalized Frequency Volume fraction within each size bin μm Cross-sectional area (μm 2 )

19 Heat Flow (J/g) DSC-Heating Heat Flow (J/g) wt% xgnp 4 wt% xgnp wt% xgnp-mmix 2 wt% xgnp-insitu 2 wt% xgnp-mast Temperature (C) Sample Tm ( C) Tc ( C) ΔHm (J/g) ΔHc (J/g) Virgin ipp wt% NG-InSitu wt% NG-InSitu wt% NG-Mmix wt% NG-Mmix wt% NG-Mast wt% NG-Mast wt% xgnp-mmix 4 wt% xgnp-insitu 4 wt% xgnp-mast Temperature (C) 19

20 Heat Flow (J/g) DSC-Cooling Heat Flow (J/g) 2 wt% xgnp 4 wt% xgnp wt% xgnp MMix 2 wt% xgnp InSitu 2 wt% xgnp Mast 2 4 wt% xgnp MMix 4 wt% xgnp InSitu 4 wt% xgnp Mast Temperature (C) Temperature (C) Sample Tm ( C) Tc ( C) ΔHm (J/g) ΔHc (J/g) Virgin ipp wt% NG-InSitu wt% NG-InSitu wt% NG-Mmix wt% NG-Mmix wt% NG-Mast wt% NG-Mast

21 Normalized Intensity Wide-Angle X-ray Diffraction Studies Melt-Mastication favors α-crystal Melt-Mixing favors α + Mesomorphic wt% xgnp MMix 2 wt% xgnp Mast Antonia Addeo, Nello Pasquini (ed) et al., Polypropylene Handbook. 2 ed.; Carl Hanser Verlag: Munich,

22 Storage Modulus (MPa) DMA Storage Modulus (MPa) Melt-Mastication Improves E by RT Virgin ipp 2 wt% NG-MMix 2 wt% NG-Mast Virgin ipp 4 wt% NG-MMix 4 wt% NG-Mast Temperature (C) Temperature (C) Sample ID wt% xgnp Processing Method Storage 20⁰C (MPa) Exxon ipp 0 Virgin wt% NG-MMix 2 Mixed wt% NG-Mast 2 Masticated wt% NG-MMix 4 Mixed wt% NG-Mast 4 Masticated

23 Summary New processing technique: Melt Mastication Superior dispersion quality Melt-mastication > Melt-mixing > In-Situ Polymerization Semi-crystalline resins Compatible with standard mixing equipment Characteristics of Melt-mastication Favors agglomerate sizes of 5-10 μm 2 Favors α-form crystal Increases T crystallization Increases E by 4-7% 23

24 Acknowledgements Department of Defense (DoD) through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program Professer L. T. Drzal Supplying materials Professor Luinstra and Saskia Scheel University of Hamburg Facility use and thoughtful conversations 24

25 Temperature Questions Storage Modulus (MPa) Heat Flow (J/g) 4 Melt-Mastication Heating Protocol 10 min wt% NG-MMix 4 wt% NG-InSitu 4 wt% NG-Mast T melt T mast T cryst Melt state Transition 10 min Quasi- Solid state Temperature (C) Virgin ipp 4 wt% NG-MMix 4 wt% NG-Mast Time Temperature (C) 25