TY - JOUR
T1 - Thermoreversible DMDBS phase separation in iPP: The effects of flow on the morphology
AU - Balzano, Luigi
AU - Portale, Giuseppe
AU - Peters, Gerrit W.M.
AU - Rastogi, Sanjay
N1 - Generated from Scopus record by KAUST IRTS on 2021-02-16
PY - 2008/7/22
Y1 - 2008/7/22
N2 - The crystallization rate of isotactic polypropylene (iPP) is often enhanced with sorbitol-based nucleating agents like 1,3:2,4-bis(3,4-dimethylbenzylidene) sorbitol or DMDBS. In the concentration range from the eutectic point (∼0.1 wt %) to 1 wt %, DMDBS crystallizes before the polymer, building a network of nanofibrils. The surface of this network hosts a large number of tailored nucleation sites that promotes the epitaxial nucleation of iPP. The formation of DMDBS fibrils corresponds to a liquid-solid phase separation that occurs on cooling, at a temperature TcDMDBS. On heating, DMDBS fibrils dissolve in iPP at a temperature TmDMDBS > TcDMDBS. For DMDBS contents less than 1 wt %, both T cDMDBS and TmDMDBS depend on the composition. We show that in the temperature window Tc DMDBS < T < TmDMDBS a percolated network of DMDBS fibrils is retained. This network can be broken with a shear flow that aligns the fibrils. At these high temperatures, iPP does not crystallize. Upon cooling, in the early stages of nucleation, the orientation of the fibrils is transferred to the lamellae because of the epitaxial relation between iPP and DMDBS. With this templating mechanism, we obtained well oriented crystalline morphologies of iPP after a shear pulse (shear rate of 60 s-1 applied for 3 s) at 185°C for 0.3 wt %, at 195°C for 0.7 wt % and at 210°C for 1 wt % of DMDBS. © 2008 American Chemical Society.
AB - The crystallization rate of isotactic polypropylene (iPP) is often enhanced with sorbitol-based nucleating agents like 1,3:2,4-bis(3,4-dimethylbenzylidene) sorbitol or DMDBS. In the concentration range from the eutectic point (∼0.1 wt %) to 1 wt %, DMDBS crystallizes before the polymer, building a network of nanofibrils. The surface of this network hosts a large number of tailored nucleation sites that promotes the epitaxial nucleation of iPP. The formation of DMDBS fibrils corresponds to a liquid-solid phase separation that occurs on cooling, at a temperature TcDMDBS. On heating, DMDBS fibrils dissolve in iPP at a temperature TmDMDBS > TcDMDBS. For DMDBS contents less than 1 wt %, both T cDMDBS and TmDMDBS depend on the composition. We show that in the temperature window Tc DMDBS < T < TmDMDBS a percolated network of DMDBS fibrils is retained. This network can be broken with a shear flow that aligns the fibrils. At these high temperatures, iPP does not crystallize. Upon cooling, in the early stages of nucleation, the orientation of the fibrils is transferred to the lamellae because of the epitaxial relation between iPP and DMDBS. With this templating mechanism, we obtained well oriented crystalline morphologies of iPP after a shear pulse (shear rate of 60 s-1 applied for 3 s) at 185°C for 0.3 wt %, at 195°C for 0.7 wt % and at 210°C for 1 wt % of DMDBS. © 2008 American Chemical Society.
UR - https://pubs.acs.org/doi/10.1021/ma7024607
UR - http://www.scopus.com/inward/record.url?scp=48949103035&partnerID=8YFLogxK
U2 - 10.1021/ma7024607
DO - 10.1021/ma7024607
M3 - Article
VL - 41
SP - 5350
EP - 5355
JO - Macromolecules
JF - Macromolecules
SN - 0024-9297
IS - 14
ER -