Relationship between morphological changes and mechanical properties in HDPE films exposed to a chlorinated environment

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Abstract

The effect of an oxidative environment on HDPE morphology and mechanical performance were studied. Extruded HDPE film samples of thickness (~70 μm) (as-extruded and heat treated) were exposed to 5 ppm chlorinated water at 70 °C for up to 1250 h. As extruded samples had an initial crystallinity of 75% and heat treated samples an initial crystallinity of 83%. The initial molecular weight for all samples was approximately 200 kg-mol−1. Changes in morphology and mechanical properties as a function of exposure time were evaluated. The most significant changes occur after 500 h exposure. Fourier-Transform Infrared Spectroscopy (FTIR) spectrum data indicate an increase in the carbonyl functional groups with increased exposure time. As the exposure time increased, the molecular weight (Mw) of the samples decreased, with Mw of the as extruded samples being consistently less than that of the heat treated samples. Crystallinity increased nearly linearly with exposure time. XRD data reveal that the interlamellar spacing decreases significantly between 500 and 750 h exposure, from 102 to 85 Å. Mechanical test data show a similar trend with tensile strength and strain at break. After exposure time of 500 h the samples become increasingly brittle. The combined morphology and mechanical data demonstrate, independent of exposure time, that there is a critical combination of molecular weight (<85 kg-mol−1) and interlamellar spacing (<85 Å) corresponding to the transition from ductile to brittle behavior.

Original languageEnglish (US)
Article number109027
JournalPolymer Degradation and Stability
Volume171
DOIs
StatePublished - Jan 2020

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Polyethylene
High density polyethylenes
Molecular weight
mechanical properties
Mechanical properties
molecular weight
crystallinity
Tensile strain
heat
Functional groups
Fourier transform infrared spectroscopy
Tensile strength
spacing
Water
tensile strength
Hot Temperature
infrared spectroscopy
trends
water

Keywords

  • Chlorine degradation
  • HDPE processing
  • Mechanical properties
  • Morphological changes

Cite this

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title = "Relationship between morphological changes and mechanical properties in HDPE films exposed to a chlorinated environment",
abstract = "The effect of an oxidative environment on HDPE morphology and mechanical performance were studied. Extruded HDPE film samples of thickness (~70 μm) (as-extruded and heat treated) were exposed to 5 ppm chlorinated water at 70 °C for up to 1250 h. As extruded samples had an initial crystallinity of 75{\%} and heat treated samples an initial crystallinity of 83{\%}. The initial molecular weight for all samples was approximately 200 kg-mol−1. Changes in morphology and mechanical properties as a function of exposure time were evaluated. The most significant changes occur after 500 h exposure. Fourier-Transform Infrared Spectroscopy (FTIR) spectrum data indicate an increase in the carbonyl functional groups with increased exposure time. As the exposure time increased, the molecular weight (Mw) of the samples decreased, with Mw of the as extruded samples being consistently less than that of the heat treated samples. Crystallinity increased nearly linearly with exposure time. XRD data reveal that the interlamellar spacing decreases significantly between 500 and 750 h exposure, from 102 to 85 {\AA}. Mechanical test data show a similar trend with tensile strength and strain at break. After exposure time of 500 h the samples become increasingly brittle. The combined morphology and mechanical data demonstrate, independent of exposure time, that there is a critical combination of molecular weight (<85 kg-mol−1) and interlamellar spacing (<85 {\AA}) corresponding to the transition from ductile to brittle behavior.",
keywords = "Chlorine degradation, HDPE processing, Mechanical properties, Morphological changes",
author = "K. Majewski and Mantell, {S. C.} and M. Bhattacharya",
year = "2020",
month = "1",
doi = "10.1016/j.polymdegradstab.2019.109027",
language = "English (US)",
volume = "171",
journal = "Polymer Degradation and Stability",
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publisher = "Elsevier Limited",

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TY - JOUR

T1 - Relationship between morphological changes and mechanical properties in HDPE films exposed to a chlorinated environment

AU - Majewski, K.

AU - Mantell, S. C.

AU - Bhattacharya, M.

PY - 2020/1

Y1 - 2020/1

N2 - The effect of an oxidative environment on HDPE morphology and mechanical performance were studied. Extruded HDPE film samples of thickness (~70 μm) (as-extruded and heat treated) were exposed to 5 ppm chlorinated water at 70 °C for up to 1250 h. As extruded samples had an initial crystallinity of 75% and heat treated samples an initial crystallinity of 83%. The initial molecular weight for all samples was approximately 200 kg-mol−1. Changes in morphology and mechanical properties as a function of exposure time were evaluated. The most significant changes occur after 500 h exposure. Fourier-Transform Infrared Spectroscopy (FTIR) spectrum data indicate an increase in the carbonyl functional groups with increased exposure time. As the exposure time increased, the molecular weight (Mw) of the samples decreased, with Mw of the as extruded samples being consistently less than that of the heat treated samples. Crystallinity increased nearly linearly with exposure time. XRD data reveal that the interlamellar spacing decreases significantly between 500 and 750 h exposure, from 102 to 85 Å. Mechanical test data show a similar trend with tensile strength and strain at break. After exposure time of 500 h the samples become increasingly brittle. The combined morphology and mechanical data demonstrate, independent of exposure time, that there is a critical combination of molecular weight (<85 kg-mol−1) and interlamellar spacing (<85 Å) corresponding to the transition from ductile to brittle behavior.

AB - The effect of an oxidative environment on HDPE morphology and mechanical performance were studied. Extruded HDPE film samples of thickness (~70 μm) (as-extruded and heat treated) were exposed to 5 ppm chlorinated water at 70 °C for up to 1250 h. As extruded samples had an initial crystallinity of 75% and heat treated samples an initial crystallinity of 83%. The initial molecular weight for all samples was approximately 200 kg-mol−1. Changes in morphology and mechanical properties as a function of exposure time were evaluated. The most significant changes occur after 500 h exposure. Fourier-Transform Infrared Spectroscopy (FTIR) spectrum data indicate an increase in the carbonyl functional groups with increased exposure time. As the exposure time increased, the molecular weight (Mw) of the samples decreased, with Mw of the as extruded samples being consistently less than that of the heat treated samples. Crystallinity increased nearly linearly with exposure time. XRD data reveal that the interlamellar spacing decreases significantly between 500 and 750 h exposure, from 102 to 85 Å. Mechanical test data show a similar trend with tensile strength and strain at break. After exposure time of 500 h the samples become increasingly brittle. The combined morphology and mechanical data demonstrate, independent of exposure time, that there is a critical combination of molecular weight (<85 kg-mol−1) and interlamellar spacing (<85 Å) corresponding to the transition from ductile to brittle behavior.

KW - Chlorine degradation

KW - HDPE processing

KW - Mechanical properties

KW - Morphological changes

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