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Nonlinear rheology and strain recove...

Patham, Bhaskar.

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Nonlinear rheology and strain recovery of short chain branched polyolefin elastomers and thermoplastic olefin blends.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Nonlinear rheology and strain recovery of short chain branched polyolefin elastomers and thermoplastic olefin blends./
Author:	Patham, Bhaskar.
Description:	242 p.
Notes:	Adviser: K. Jayaraman.
Contained By:	Dissertation Abstracts International66-04B.
Subject:	Engineering, Chemical. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3171511
ISBN:	9780542082672

Nonlinear rheology and strain recovery of short chain branched polyolefin elastomers and thermoplastic olefin blends.
Patham, Bhaskar.

Nonlinear rheology and strain recovery of short chain branched polyolefin elastomers and thermoplastic olefin blends. - 242 p.

Adviser: K. Jayaraman.

Thesis (Ph.D.)--Michigan State University, 2005.

Polyolefin elastomers are random copolymers having a polyethylene backbone with the higher olefinic comonomer incorporated as short-chain branches. These random copolymers are widely used as polymer modifiers for thermoplastic materials such as polypropylenes, resulting in thermoplastic olefin (TPO) blends. This thesis addresses the nonlinear rheological behavior of the elastomers and then of the TPO blends.

ISBN: 9780542082672Subjects--Topical Terms:

1018531
Engineering, Chemical.

Nonlinear rheology and strain recovery of short chain branched polyolefin elastomers and thermoplastic olefin blends.
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020 $a 9780542082672
035 $a (UMI)AAI3171511
035 $a AAI3171511
040 $a UMI $c UMI
100 1 $a Patham, Bhaskar. $3 1270270
245 1 0 $a Nonlinear rheology and strain recovery of short chain branched polyolefin elastomers and thermoplastic olefin blends.
300 $a 242 p.
500 $a Adviser: K. Jayaraman.
500 $a Source: Dissertation Abstracts International, Volume: 66-04, Section: B, page: 2197.
502 $a Thesis (Ph.D.)--Michigan State University, 2005.
520 $a Polyolefin elastomers are random copolymers having a polyethylene backbone with the higher olefinic comonomer incorporated as short-chain branches. These random copolymers are widely used as polymer modifiers for thermoplastic materials such as polypropylenes, resulting in thermoplastic olefin (TPO) blends. This thesis addresses the nonlinear rheological behavior of the elastomers and then of the TPO blends.
520 $a The effects of varying short chain branch density (SCB) on the melt rheology of three ethylene-octene random copolymers have been investigated. In particular, the strain-hardening behavior in extensional flow and strain recovery following nonlinear shear creep has been evaluated. The zero-shear viscosity followed trends in the backbone molecular weight closely. While the three copolymers were indistinguishable in linear viscoelastic creep and recovery, recovery following nonlinear shear creep decreased progressively with increasing SCB density. This reveals that the extent of rapid chain equilibration that occurs over Rouse time scales at higher strains was progressively lower with increasing SCB density. Strain hardening in uniaxial extensional flow was observed for all three copolymers. At strain rates below the primitive chain equilibration rates, strain hardening increases progressively with increasing SCB density. At higher rates, upon onset of primitive chain stretch, the strain hardening behavior for the three melts merges.
520 $a Two thermoplastic olefin (TPO) blends were characterized in the context of injection molding; the surface morphology of injection molded tensile bars with these materials showed surface defects or flow marks to different extents. The flow marks were traced to different degrees of strain recovery in the dispersed phases of the two blends. This recovery occurred over injection molding timescales of the order of a few seconds. Strain recovery after shear creep was higher in the blend that displayed more severe flow marks in injection molding; the corresponding elastomer by itself also showed a greater extent of creep recovery. The quick strain recovery in the elastomer must be associated with elastic stresses rather than interfacial tension.
520 $a A new experimental apparatus was assembled to study strain recovery after elongation of a model elastomer suspended in a less viscoelastic medium at room temperature. Small drops of well-characterized elastomers suspended in a matrix fluid of lower viscosity and elasticity, are stretched rapidly without wall effects in this setup; the stretch ratio of the drops is then recorded over time. Preliminary results confirm significant recovery over a few seconds. Exploration of the full range of parameters with this setup is left for future work.
590 $a School code: 0128.
650 4 $a Engineering, Chemical. $3 1018531
650 4 $a Engineering, Materials Science. $3 1017759
650 4 $a Plastics Technology. $3 1023683
690 $a 0542
690 $a 0794
690 $a 0795
710 2 $a Michigan State University. $3 676168
773 0 $t Dissertation Abstracts International $g 66-04B.
790 $a 0128
790 1 0 $a Jayaraman, K., $e advisor
791 $a Ph.D.
792 $a 2005
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3171511