TY - JOUR
T1 - Monitoring elasticity and orientation in syndiotactic polypropylene
AU - Parthasarathy, Gautam
AU - Sevegney, Michael S.
AU - Kannan, Rangaramanujam M.
N1 - Funding Information:
We thank Dr Gulay Serhatkulu in helping us with the powder diffraction measurements. We thank the Fina Oil and Chemical company LaPorte, TX for providing us with the sPP samples. Financial support from NSF DMR 9876221 and WSU (IMR) are gratefully acknowledged.
PY - 2005/7/28
Y1 - 2005/7/28
N2 - The effect of temperature on the elasticity and structure of syndiotactic polypropylene (sPP) is investigated using a combination of WAXD and rheo-optical FTIR spectroscopy. sPP has a rich crystal structure, which leads to unique mechanical behavior. Beyond yield point, it exhibits elastic response associated with deformation-induced structure-structure transformation. The structure and orientation were measured both during and after uniaxial tensile stretching of films (up to 200%) as a function of temperature (25-70 °C). Our WAXD and rheo-FTIR results suggest that as the temperature increases, there is a reduction in the extent of helical to trans-planar conformational change upon stretching. When the strain is released, there is partial transformation of trans-planar conformation back to helical. The presence and orientation of the trans-planar conformation plays a key role on the elastic behavior of sPP beyond the yield point. Rheo-optical FTIR dichroism studies provide further insights into the elasticity in syndiotactic polypropylene. Different proportions of helical and trans-planar conformations orient to different extents. The helical conformation does not orient appreciably at higher temperature though they are present beyond the yield point. In contrast, the trans-planar chains show a significant increase in dichroism beyond the yield point, suggesting that there is a difference in mobility (orientation) of the helical and trans-planar chains. This further supports the importance of trans-planar chains on the elastic behavior.
AB - The effect of temperature on the elasticity and structure of syndiotactic polypropylene (sPP) is investigated using a combination of WAXD and rheo-optical FTIR spectroscopy. sPP has a rich crystal structure, which leads to unique mechanical behavior. Beyond yield point, it exhibits elastic response associated with deformation-induced structure-structure transformation. The structure and orientation were measured both during and after uniaxial tensile stretching of films (up to 200%) as a function of temperature (25-70 °C). Our WAXD and rheo-FTIR results suggest that as the temperature increases, there is a reduction in the extent of helical to trans-planar conformational change upon stretching. When the strain is released, there is partial transformation of trans-planar conformation back to helical. The presence and orientation of the trans-planar conformation plays a key role on the elastic behavior of sPP beyond the yield point. Rheo-optical FTIR dichroism studies provide further insights into the elasticity in syndiotactic polypropylene. Different proportions of helical and trans-planar conformations orient to different extents. The helical conformation does not orient appreciably at higher temperature though they are present beyond the yield point. In contrast, the trans-planar chains show a significant increase in dichroism beyond the yield point, suggesting that there is a difference in mobility (orientation) of the helical and trans-planar chains. This further supports the importance of trans-planar chains on the elastic behavior.
KW - Elasticity
KW - Rheo-optical FTIR dichroism
KW - Syndiotactic polypropylene
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U2 - 10.1016/j.polymer.2005.05.144
DO - 10.1016/j.polymer.2005.05.144
M3 - Article
AN - SCOPUS:33748938348
VL - 46
SP - 6335
EP - 6346
JO - Polymer
JF - Polymer
SN - 0032-3861
IS - 17
ER -