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Self-nucleated Crystallization of a Branched PolypropyleneAlotaibi, Dhwaihi 01 January 2011 (has links) (PDF)
Long chain branched polypropylene (LCBPP) crystallizes rapidly and with high nucleation density. The origin of this fast crystallization process is not well understood. It has been attributed to its complicated molecular architecture. In this research, we explore isothermal crystallization of LCBPP, 5%LCBPP and linear polypropylene (LPP) through rheological, thermal, microscopy and optical measurements at different experimental temperatures. The time resolved mechanical spectroscopy technique was used to predict the liquid-to-solid transition (gel point) at different crystallization temperatures (supercooling rates) in order to understand the structure during the crystallization process.
The crystallization process of LCBPP was completed in time scale less than that of 5%LCBPP and LPP at different supercooling rates. This has been observed in all crystallization experiments using DSC, SALS and Rheometery. LCBPP exhibit stiff behavior at gel point compared to 5%LCBPP and LPP which imply that the small spherulites observed under polarized microscopy are stiff. Understanding of the rheological behavior during crystallization process will help to develop polymer with different processing conditions and applications.
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Rheological Properties of Protein HydrogelsScott, Shane 13 January 2012 (has links)
Certain hydrogel forming de novo proteins that utilize different crosslinking
methods are studied experimentally on a rheometer. The stress reaxation
modulus of CRC, a telechelic, triblock protein, is shown to be that of
a stretched exponential function with a value of β ≅ 0.5. The insertion of
an integrin binding domain and changes in pH within the range 6.5–8.5 are
shown not to significantly affect the resulting rheological behavior. A selective
chemical crosslinker is used on CRC hydrogel systems and is shown to
change the rheological behavior of the system to that of a combination of a
chemically and physically crosslinked system. Chemically crosslinked hydrogels
composed of W6, a wheat gluten-based protein, demonstrate a storage
modulus weakly dependent on the angular frequency that is much greater
than the loss modulus, with a modulus concentration dependence of c^9/4.
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Rheological Properties of Protein HydrogelsScott, Shane 13 January 2012 (has links)
Certain hydrogel forming de novo proteins that utilize different crosslinking
methods are studied experimentally on a rheometer. The stress reaxation
modulus of CRC, a telechelic, triblock protein, is shown to be that of
a stretched exponential function with a value of β ≅ 0.5. The insertion of
an integrin binding domain and changes in pH within the range 6.5–8.5 are
shown not to significantly affect the resulting rheological behavior. A selective
chemical crosslinker is used on CRC hydrogel systems and is shown to
change the rheological behavior of the system to that of a combination of a
chemically and physically crosslinked system. Chemically crosslinked hydrogels
composed of W6, a wheat gluten-based protein, demonstrate a storage
modulus weakly dependent on the angular frequency that is much greater
than the loss modulus, with a modulus concentration dependence of c^9/4.
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Rheological Properties of Protein HydrogelsScott, Shane 13 January 2012 (has links)
Certain hydrogel forming de novo proteins that utilize different crosslinking
methods are studied experimentally on a rheometer. The stress reaxation
modulus of CRC, a telechelic, triblock protein, is shown to be that of
a stretched exponential function with a value of β ≅ 0.5. The insertion of
an integrin binding domain and changes in pH within the range 6.5–8.5 are
shown not to significantly affect the resulting rheological behavior. A selective
chemical crosslinker is used on CRC hydrogel systems and is shown to
change the rheological behavior of the system to that of a combination of a
chemically and physically crosslinked system. Chemically crosslinked hydrogels
composed of W6, a wheat gluten-based protein, demonstrate a storage
modulus weakly dependent on the angular frequency that is much greater
than the loss modulus, with a modulus concentration dependence of c^9/4.
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Rheological Properties of Protein HydrogelsScott, Shane January 2012 (has links)
Certain hydrogel forming de novo proteins that utilize different crosslinking
methods are studied experimentally on a rheometer. The stress reaxation
modulus of CRC, a telechelic, triblock protein, is shown to be that of
a stretched exponential function with a value of β ≅ 0.5. The insertion of
an integrin binding domain and changes in pH within the range 6.5–8.5 are
shown not to significantly affect the resulting rheological behavior. A selective
chemical crosslinker is used on CRC hydrogel systems and is shown to
change the rheological behavior of the system to that of a combination of a
chemically and physically crosslinked system. Chemically crosslinked hydrogels
composed of W6, a wheat gluten-based protein, demonstrate a storage
modulus weakly dependent on the angular frequency that is much greater
than the loss modulus, with a modulus concentration dependence of c^9/4.
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