Ahmad, Naveed
(2013)
Relationship between Rheology and Molecular Structure of Innovative Crystalline Elastomers.
[Tesi di dottorato]
Item Type: |
Tesi di dottorato
|
Lingua: |
English |
Title: |
Relationship between Rheology and Molecular Structure of Innovative Crystalline Elastomers |
Creators: |
Creators | Email |
---|
Ahmad, Naveed | naveed.ahmad@unina.it |
|
Date: |
29 March 2013 |
Number of Pages: |
192 |
Institution: |
Università degli Studi di Napoli Federico II |
Department: |
Ingegneria Chimica, dei Materiali e della Produzione Industriale |
Scuola di dottorato: |
Ingegneria industriale |
Dottorato: |
Ingegneria chimica |
Ciclo di dottorato: |
25 |
Coordinatore del Corso di dottorato: |
nome | email |
---|
D'Anna, Andrea | anddanna@unina.it |
|
Tutor: |
nome | email |
---|
Grizzuti, Nino | nino.grizzuti@unina.it | Talarico, Giovanni | talarico@unina.it | Ianniruberto, Giovanni | iannirub@unina.it |
|
Date: |
29 March 2013 |
Number of Pages: |
192 |
Uncontrolled Keywords: |
Rheology,Syndiotactic polypropylene,Poly-1Butene,Crystallization behavior and Extensional Flow |
Settori scientifico-disciplinari del MIUR: |
Area 03 - Scienze chimiche > CHIM/05 - Scienza e tecnologia dei materiali polimerici |
Aree tematiche (7° programma Quadro): |
NANOSCIENZE, NANOTECNOLOGIE, MATERIALE E PRODUZIONE > Materiali |
[error in script]
[error in script]
Date Deposited: |
05 Apr 2013 10:03 |
Last Modified: |
17 Jun 2014 06:04 |
URI: |
http://www.fedoa.unina.it/id/eprint/9248 |

Abstract
The study of the rheology of polyolefins based on homogenous metallocenic catalyst has been mainly devoted to the understanding of material process ability. When used at a more advanced and sophisticated level, however, rheology is a useful tool to highlight the details of the polymer microstructure, such as the chemical stereo-regularity or the degree of chain branching. Rheology is also used to study the crystallization kinetics of the polymers and it gives more precise analysis than the conventional techniques
like differential scanning calorimetry (DSC) when the crystallization kinetics are slow. When cooled below thermodynamic melting temperature, crystalline polymers undergo crystallization. The early stages of this process
are characterized by the gradual change in the mechanical response of the material from the liquid to the solid, which is due to the microstructure evolution of the system. This is one of the great features of the rheological
technique, which distinguishes it from the traditional DSC technique.
In the present research work relationships between rheological parameters
and molecular structure of syndiotactic polypropylenes (sPP) and poly-1butenes of different stereoregularity are explored by performing oscillatory shear experiments using ARES rheometer. The rheological response is found
very sensitive to the degree of syndiotacticity of syndiotactic polypropylene, while in the case of poly-1butenes, it is also found dependent on the
stereoregularity.
Crystallization behavior of a series of syndiotactic polypropylenes of different degrees of syndiotacticity is investigated by performing both isothermal and non-isothermal crystallization tests using rheological and differential scanning calorimetric techniques. The aim is to investigate the
effect of degree of syndiotacticity on the crystallization behavior of the syndiotactic polypropylene and to couple the rheological methods to more conventional techniques (such as Differential Scanning Calorimetry). Crystallization behavior is found strongly dependent on the degree of syndiotacticity of syndiotactic polypropylene. Good agreement is found
between the results obtained by both the rheological and differential scanning calorimetric (DSC) methods.
The effect of extensional flow on the crystallization kinetics of sPB is examined both in the melt and crystal phase by applying different extensional rates using sentmanat extensional rheometer (SER). Extensional
flow is found to enhance the rate of crystallization in the crystal phase, which is further proved by the small angle X-Ray scattering experiment (SAX).
Downloads per month over past year
Actions (login required)
 |
View Item |