The Effect of Molecular Mass Distribution on Time-Dependent Behavior of Polyamides

[+] Author and Article Information
I. Emri

Center for Experimental Mechanics, University of Ljubljana, Cesta na Brdo 49, Ljubljana, Sloveniaie@fs.uni-lj.si

B. S. von Bernstorff

 BASF Aktiengesellschaft, Ludwigshafen, Germanybernd-steffen.bernstorff-von@basf-ag.de

Artificial diamonds have been researched since the early 1950s. The first man involved was American physicist Percy Williams Bridgman. His research included extensive studies of materials subjected to high pressure. He won a Nobel Prize in physics in 1946 for his achievements but never actually created synthetic diamonds. However, on December 8, 1954, a scientist from General Electric subjected black carbon powder to pressures of 50,000 atmosphere for 16h and made two small synthetic diamonds.

J. Appl. Mech 73(5), 752-757 (Jan 04, 2006) (6 pages) doi:10.1115/1.2173008 History: Received February 11, 2005; Revised January 04, 2006

In this paper we show that the time-dependent properties of polyamides may be significantly modified by altering the “initial kinetics” of the material through the modification of the molecular mass distribution. In our investigations we have used polyamide 6 (PA6) as a testing material. We have shown that the molecular weight distribution determines the time scale of material structure formation and, hence, its time-dependent properties. The melting temperature of the bimodal molecular mass distribution of polyamide 6 material is shifted for about 30°C towards higher temperatures in comparison to the conventional monomodal molecular mass distribution of PA6. Modification of the molecular mass distribution also improves the time and temperature dependence of the mechanical properties of PA6. It seems that understanding the effect of the molecular weight distribution on the process of material structure formation may well become a new approach in development of new generation polymeric materials.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 1

Different phases of polymer structure formation

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Figure 2

Changing the initial kinetics of PA6 by modifying its molecular mass distribution, measured with ultraviolet detector, for monomodal BS400N and bimodal PA6

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Figure 3

Schematics of the specimen preparation

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Figure 4

Comparison of the morphology of the two materials, using polarized microscopy: (a) BS400N and (b) bimodal PA6

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Figure 5

Comparison of the melting temperature of BS400N, and bimodal PA6 material

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Figure 6

Schematic of the CEM measuring system

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Figure 7

Schematic of the relaxometer inserts

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Figure 8

Temperature and pressure history of G(t)

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Figure 9

G(t) segments of BS400N measured at various temperatures

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Figure 10

G(t) segments of bimodal PA material measured at various temperatures

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Figure 11

Shear relaxation modulus of monomodal PA6 as a function of temperature, G(T), at a selected times

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Figure 12

Shear relaxation modulus of bimodal PA6 as a function of temperature, G(T), at a selected times

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Figure 13

Shear relaxation modulus, G(T), of mono- and bimodal PA6 as a function of temperature, at t=10s

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Figure 14

Shear relaxation properties of mono- and bimodal PA

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Figure 15

Comparison of the mechanical spectra of the mono- and bimodal PA6



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