Diffusion of sulfuric acid solutions in nylon 6,6 monitored by neutron activation analysis

L. Brown, V. T. Bui, H. W. Bonin

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2 Citations (Scopus)

Abstract

Nylon 6,6 is an excellent material for the study of the diffusion mechanism and associated mechanical performance of polymers saturated with aqueous solutions of varying pH at different temperatures. The diffusion profile was studied for samples saturated at temperatures ranging from 20 to 90°C in solutions decreasing in pH from distilled water to 1.0M sulfuric acid. The presence of sulfuric acid molecules within the diffusing solutions acts to promote hydrolysis of the polyamide molecules. The degree of hydrolysis is dependent on saturation temperature and solution pH. The extent of degradation was evaluated via changes to mechanical performance and inherent viscosity and often results in a reduction of the stress at yield, flexural modulus, and inherent viscosity on increasing temperature and decreasing pH. The use of neutron activation analysis allowed for an evaluation of the sulfur content within the samples as a function of diffusing time. This demonstrated that although the mechanical performance decreases rapidly on initial exposure to the aqueous medium, this is likely due to plasticization. As diffusion time progresses, the sulfur content within the sample continues to rise to a level where the acid/water molar ratio is much higher in the sample than that of the bulk. This results in an enhancement of the degradation process as time progresses.

Original languageEnglish
Pages (from-to)2476-2487
Number of pages12
JournalJournal of Applied Polymer Science
Volume97
Issue number6
DOIs
Publication statusPublished - 15 Sep 2005
Externally publishedYes

Keywords

  • Diffusion
  • Neutron activation analysis
  • Polyamide (Nylon)
  • Sulfuric acid
  • Viscosity

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