Multiscale characterisation of single synthetic fibres: Surface morphology and nanomechanical properties

Dajana M Gubala, Robert L Harniman, Jean-Charles Eloi, Patryk Wasik, Didier Wermeille, Lili Sun, Eric Robles, Meng Chen, Wuge H Briscoe

Research output: Contribution to journalArticle (Academic Journal)

Abstract

Hypothesis:: Thermal through-air bonding process and slip additive treatment affect fibre surface structure and
nanomechanical properties, which is extremely difficult to characterise on a single-fibre level.
Experiments:: Optical microscopy (OM) was applied to study the effect of air-through bonding, spunbonding, and
crimping on fibre geometry and general appearance. A “spray-on” method developed here using a custom-designed
fibre holder allowed a direct measurement of static contact angles of water droplets on single fibres. Scanning
electron microscopy (SEM) showed different morphological features on the fibre due to the nonwoven fabric-
making process and additive treatment. Synchrotron X-ray diffraction (XRD) was applied to study the effect
of erucamide presence on polypropylene (PP) fibre crystal structure. Atomic force microscopy (AFM) imaging
provided complementary characterization of fibre topographic features such as average surface roughness, along
with adhesion force mapping by quantitative nanomechanical (QNM) AFM imaging.
Findings: Our results show the effect of nonwoven making process and surfactant additive treatment on the fibre
surface structure and nanomechanical properties. Wettability experiment on the single fibre revealed the hydrophobic
nature of all the synthetic fibres. For polyethylene/polyethylene terephthalate (PE/PET) bicomponent
single fibres, the polyethylene sheath was found to possess fibrillar microstructure - typical for drawn fibres,
whereas the fibres entangled in nonwoven fabrics exhibited a uniform, porous surface morphology attributed to
the through-air process. Adhesion force mapping allowed us to correlate fibre nanomechanical properties with its
topography, with surface pore interiors showing higher adhesion than the flat polyethylene region. Furthermore,
on the polypropylene (PP) fibre surface treated with erucamide (13-cis-docosenamide; a common slip additive
used in polyolefin film processing), we observed overlapping multilayers consisting of 4 nm erucamide bilayers,
attributed to the slip additive migration onto the fibre surface. X-ray diffraction (XRD) measurements of the fibres
did not detect the presence of erucamide; however, AFM imaging provided evidence for its migration to the fibre
surface, imparting influence on the surface structure and adhesive properties of the fibre. Single-fibre AFM imaging
also allowed a detailed analysis of different surface roughness parameters, revealing that both through-air
bonding in the nonwoven making process and the slip additive (erucamide) treatment reduced the surface roughness,
an effect more pronounced for the PE/PET than the PP fibres. The wettability, surface morphology, and
adhesion properties from this study, obtained with unprecedented resolution and details on single fibres, are
valuable to informing rational design of fibre processing for fibre optimal properties, critically important in many
industrial applications.
Original languageEnglish
Pages (from-to)398-411
JournalJournal of Colloid and Interface Science
Volume571
Early online date14 Mar 2020
DOIs
Publication statusE-pub ahead of print - 14 Mar 2020

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Keywords

  • Polymer fibres
  • Nonwovens
  • Softness
  • Surface characterisation
  • Erucamide
  • Single fibres
  • Blooming
  • Fibre crimping

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