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Elucidating Structure-Property-Processing Relationships with On-Line Raman

IP.com Disclosure Number: IPCOM000011712D
Publication Date: 2003-Mar-12

Publishing Venue

The IP.com Prior Art Database

Related People

R. Guenard: AUTHOR [+6]

Abstract

Synthetic polymer development is becoming increasingly more sophisticated with improved modeling, highly specific catalysts, enhanced processing and materials blending to name a few. These advancements in polymer design commensurately require highly selective measurements on the molecular level to obtain correlation between polymer structure, processing variables and end-use properties. Coupling the powerful fundamental attributes of Raman spectroscopy with on-line sampling flexibility is invaluable in obtaining this type of structural information. A case study showing the utility of on-line Raman in the development of nylon 6 fibers will be presented. Nylons are often extruded into fibers and used in many fiber applications. Polycaprolactam, or nylon 6, is among the largest players in these applications. Physical and molecular structural analysis of nylon 6 is difficult because of its dynamic and polymorphic nature. Furthermore, the glass transition temperature of nylon 6 decreases significantly with moisture content which compromises the ability to draw process variable conclusions based upon off-line measurements. We have found the use of on-line Raman measurements to provide the precise and dynamic information necessary to optimize both process conditions and fiber properties. In this presentation the fundamentals of measuring relative crystallinity and orientation in nylon 6 by Raman spectrometry will be discussed. Off-line Raman measurements of relative polymer crystallinity and orientation will be compared to those made on-line. Finally, we will show correlation of Raman data with processing variables and polymer structure that are important in end-use properties of synthetic fibers.

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   Elucidating Structure-Property- Processing Relationships of Polymer Fibers with On-Line Raman

Rob Guenard, Rajesh P. Paradkar, Anne Leugers, Gerry Billovits and John Warakomski

   The Dow Chemical Company Corporate Research and Development Analytical Sciences

RDG PITTCON 2003 March 13, 2003

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2Research Goals

* Study molecular structure development in fiber spinning process of a nylon 6 alloy material.

* Correlate molecular structure with processing conditions and fiber properties.
* Provide analytical knowledge to researchers for product optimization.

* Provide knowledge to modelers in evolution towards simulated R&D.

RDG PITTCON 2003 March 13, 2003

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3Structure Property Processing Relationships

   Fiber properties - tensile modulus - dyeability
- structural stability - appearance, etc.

Molecular Structure & morphology
- composition
- tacticity
- crystallinity
- orientation, etc.

     Processing - melt temperature - spinning rate
- draw ratio
- thermal history, etc.

RDG PITTCON 2003 March 13, 2003

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4On-line Raman-Advantages

*Compositionally rich information about crystalline AND amorphous phases of the polymer sample.

*Good optical sampling for single filaments with various cross sections or yarns.

*Fast algorithms for streaming data enabling process control

*Polarized Raman can be used to estimate relative orientation.

RDG PITTCON 2003 March 13, 2003

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5Polymorphism in Nylon 6

* At least two main polymorphs of PA6 have been identified and relatively well characterized using XRD
* Formation depends on the crystallization conditions

Nylon Plastics Handbook
M.I. Kohan (editor) Hanser Publishers 1995, Page 370

RDG PITTCON 2003 March 13, 2003

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6

Morphological Changes with Moisture

*Moisture disrupts inter-chain hydrogen bonding, lowers Tg
*Increased chain mobility allows the PA6 chains to adopt lower energy planar zigzag conformation

C

N H

N H

O

H

O

H

As Spun control

Autoclave

Water

H

O

H

O

C

RDG PITTCON 2003 March 13, 2003

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7Polymorphism in Nylon 6

Normalized intensity

5000

4000

3000

1635

γ-form

1080

1120

921.8

962.3

1298 12751167 1232 13661378

1440

2000

1000

1467

1126

1635

α-form

s s

1062

931.6

800 1000 1200 1400 1600 1800

12011168

13061280

1376

1444

0

Raman Shift (cm-1)

Mode α-form γ-form

δ(CH2) 1444 cm-1, 1423 cm-1, 1439 cm-1 1467 cm-1, 1481 cm-1 t(CH2) 1307 cm-1, 1280 cm-1 1298 cm-1 , 1275 cm-1 ν(CC) 1127 cm-1 1120 cm-1
ν(C-CO) 933 cm-1 922 cm-1

RDG PITTCON 2003 March 13, 2003

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8Quiescent Crystallization of Nylon 6

1305 1109 1076 1440 1649

1062 933

1440

164010761062 11...