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Shear-induced crystallization of polyethylene

Shear-induced crystallization of polyethylene. (see Heeley, Morgovan, Bras, Dolbnya, Gleeson, & Ryan, Phys. Chem. Comm. (2002) 5 , 158-160. Shear-induced crystallization of polyethylene studied by small- and wide-angle X-ray scattering (SAXS/WAXS) techniques )

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Shear-induced crystallization of polyethylene

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  1. Shear-induced crystallization of polyethylene (see Heeley, Morgovan, Bras, Dolbnya, Gleeson, & Ryan, Phys. Chem. Comm. (2002) 5, 158-160. Shear-induced crystallization of polyethylene studied by small- and wide-angle X-ray scattering (SAXS/WAXS) techniques) In situ study of development of shear-induced macrostructure of PE injection molding ––> shear flow in polymer changes crystallization kinetics & morphology chain alignment ––> 'shish kebab' structure

  2. Shear-induced crystallization of polyethylene (see Heeley, Morgovan, Bras, Dolbnya, Gleeson, & Ryan, Phys. Chem. Comm. (2002) 5, 158-160. Shear-induced crystallization of polyethylene studied by small- and wide-angle X-ray scattering (SAXS/WAXS) techniques) In situ study of development of shear-induced macrostructure of PE synchrotron radiation using shear cell & heating stage 5 sec/frame – after shear (100 pulses/sec for 5 & 10 sec) crystallization temperature

  3. Shear-induced crystallization of polyethylene Results stacking of lamellae along shear direction shear direction lower MW - less orientation

  4. Shear-induced crystallization of polyethylene More results invariant vs crystallization time lower MW - less orientation

  5. Pores in polymers & carbons (see Olivier, Lagasse, Schaeffer, Barnes, & long, Macromolecules (1996) 29, 8515-8621. SA small-angle-scattering study of the pore-orientation periodicity in porous polymer and carbon materials) Banded spherulites ––> carbon foams crystallized blend of maleic anhydride (MA) & polyacrylonitrile (PAN) bands are ~ 3.5 mm in width in this system (can use SAXS) sublimate MA & pyrolyze ––> carbon foams (98% void volume)

  6. Pores in polymers & carbons (see Olivier, Lagasse, Schaeffer, Barnes, & long, Macromolecules (1996) 29, 8515-8621. SA small-angle-scattering study of the pore-orientation periodicity in porous polymer and carbon materials)

  7. Pores in polymers & carbons (see Olivier, Lagasse, Schaeffer, Barnes, & long, Macromolecules (1996) 29, 8515-8621. SA small-angle-scattering study of the pore-orientation periodicity in porous polymer and carbon materials) q–4 averages of intensity data around azimuth - not on absolute scale

  8. Pores in polymers & carbons (see Olivier, Lagasse, Schaeffer, Barnes, & long, Macromolecules (1996) 29, 8515-8621. SA small-angle-scattering study of the pore-orientation periodicity in porous polymer and carbon materials) q–4 sharp polymer/void interface averages of intensity data around azimuth - not on absolute scale

  9. Pores in polymers & carbons

  10. Pores in polymers & carbons Plots of intensity differences from intensity averages over 22 positions

  11. Pores in polymers & carbons Plots of intensity differences from intensity averages over 22 positions Plots repeat at 3 – 4 mm translation interval

  12. Pores in polymers & carbons Plots of sector averages of intensity vs translation position

  13. Pores in polymers & carbons Before pyrolysis After pyrolysis

  14. Pores in polymers & carbons Observation in as-crystallized blend: bands move when sample is rotated around growth direction indicates rotation of crystal orientations substantiated by high-angle x-ray studies orthorhombic MA cells

  15. Pores in polymers & carbons Observation in as-crystallized blend: bands move when sample is rotated around growth direction indicates rotation of crystal orientations substantiated by high-angle x-ray studies band motion observed in pyrolyzed mat'l ––> anisotropic pore rotation orthorhombic MA cells

  16. Pores in polymers & carbons band motion observed in pyrolyzed mat'l ––> anisotropic pore rotation pore shape assumed ellipsoidal

  17. Pores in polymers & carbons band motion observed in pyrolyzed mat'l ––> anisotropic pore rotation substantiated by oscillation in Porod data plots pore shape assumed ellipsoidal

  18. Pores in polymers & carbons Porod constant, KP, for isotropic case For anisotropic case Also, for average chord length, <LV>, inside pore vol. fact.

  19. Pores in polymers & carbons Porod constant, KP, for isotropic case For anisotropic case

  20. Pores in polymers & carbons Porod constant, KP, for isotropic case For anisotropic case

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