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SUMMARY:Keynote 8 - Studying the influence of molecular conformation on ex
 tensional rheology by combining filament stretching rheometry with ex-situ
  SANS
DTSTART;VALUE=DATE-TIME:20181211T130000Z
DTEND;VALUE=DATE-TIME:20181211T134000Z
DTSTAMP;VALUE=DATE-TIME:20260523T152608Z
UID:indico-contribution-492@lindico453.srv.lu.se
DESCRIPTION:Speakers: Qian Huang (Chemical Engineering\, Technical Univers
 ity of Denmark)\nExtensional flow is a major type of deformation in many p
 olymer processing operations such as blow molding and fiber spinning. Exte
 nsional rheology of polymer melts is highly sensitive to molecular archite
 cture and conformation. In the past four decades\, people have made a grea
 t effort to study the dynamics of polymer chains in extensional flow in or
 der to predict the rheological behaviour by using constitutive equations b
 ased on molecular theories (e.g. the tube model). However\, while producin
 g pure extensional flow in a highly controlled manner (e.g. constant strai
 n rate) is already a challenge\, rheology measurements give indirect infor
 mation of molecular conformation in terms of stress-strain responses only.
  Thus combining state-of-the-art extensional rheometry with scattering tec
 hniques provides a powerful tool to understand polymer dynamics.\n\nIn thi
 s work\, we measure the extensional rheology of polystyrene (PS) melts usi
 ng a filament stretching rheometer which is able to produce a well-defined
  extensional flow. We show that the rheological behaviour of PS melts with
  different molecular architectures (linear and star shaped) is identical i
 n fast extensional flow\, indicating the same molecular conformation. The 
 hypothesis of the same molecular conformation is confirmed in small angle 
 neutron scattering (SANS). We also measure a bi-disperse PS blend containi
 ng linear chains of two molecular weights\, and a monodisperse PS melt con
 taining the short linear chains only\, in stress relaxation following a fa
 st extensional flow. By combing rheological measurements with SANS measure
 ments\, we show that there are nematic effects and strain coupling between
  the short and long chains in the blend. Furthermore\, we show that the ch
 ain stretch idea in the tube model can be critically tested through analys
 ing the SANS data at different time in stress relaxation process.\n\nhttps
 ://lindico453.srv.lu.se/event/67/contributions/492/
LOCATION:Elite Hotel Ideon Tera
URL:https://lindico453.srv.lu.se/event/67/contributions/492/
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