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Foam-controlledentanglementofyarns,fibresandfilamentsinnonwovenfabrics Jukka Ketoja, Atsushi Tanaka, Jani Lehmonen,
Pirjo Heikkilä, Ali Harlin VTT Technical Research Centre of Finland Ltd
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Nonwoven fabrics
• Sheet or web structures bonded together by entangling fibres or filaments mechanically, thermally or chemically
• Numerous applications: medical products, filters, geotextiles, composites,…
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Outline
• Challenge to forming process
• Materials and methods
• Homogeneity and layering
• Micro-scale entanglement vs. mechanical properties
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CHALLENGE
Nonwovenwithcontrolled• homogeneity• layering• bonding
Yarns,fibresandfilamentswithvaried• dimensions• s>ffnesses• surfaces
Strength,s2ffness,mouldability,drape,smoothness,func2onality
FORM
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STUDIED MATERIALS
• Yarn • DES: 20-40mm, 17-25 tex • Fuesers Garne (FG): 40-80 mm, 20 tex
• Bleached kraft pulp (birch, 87°SR), 1 mm
• Viscose fibre: 6 mm, 1.7 dtex (Kelheim)
• Surfactants: • polyvinyl alcohol PVA (12 g/l) • sodium dodecyl sulphate SDS (0.2 g/l)
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Structural homogeneity easily lost with long fibres
• Conventional foam forming process
Viscose fibre, 1.7 dtex
6mm 12mm 24mm
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Factors affecting floc size
Partial least squares regression for floc size
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MIXING AND FOAM FORMING
• Two foams (5L for yarn & 3L for shorter fibres) mixed together • entanglement in foam! • large foam volume (1L foam/g fibre) • high air content ≥ 60%
• Reduced mixing speed (1600 RPM) • large bubble size and foam viscosity
• NO TURBULENCE REQUIRED
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2.
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4. Homogeneous structure with 60 mm FG yarn (+ 50% kraft)
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Flow-induced material layering
Top side Wire side
DES (20 g/m2) + kraft (40 g/m2)
1mm1mm
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Scale separation essential
DES+kraB FGyarn+viscose+kraBbridgegapsbetweenyarns
capturedbyviscosenet
KraBfibresformasmoothsurfaceagainsttheformingfabric
NOCLEARLAYERING200µm 200µm
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Micro-scale entanglement
DES + kraft DES + viscose + kraft 20 g/m2 40 g/m2
20 g/m2 20 g/m2 10 g/m2
TIGHT LOOSE
Stiff, hard nonwoven Flexible, softer nonwoven
200µm 200µm
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Further observations
• Similar binding achieved with both SDS and PVA
• Birch fibres alone sufficient to bind the fibre yarns – yarn width 60-200 µm, birch kraft fibre c.a. 1 mm long
• Viscose fibres make the binding looser and give softness
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Tensile testing • Structure: yarn (20/40 g/m2), viscose (20 g/m2), kraft (10 g/m2) • Higher strength and breaking strain with DES than with FG • Yarn amount has different effects for DES and FG
– Lower density and binding with DES
roughly linear decay due to pull out of yarns from the structure
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Conclusions • Homogeneous nonwovens with foam forming from
versatile fibre materials
• Layering with fibres/yarns of distinct dimensions
• Micro-entanglement: strength without chemical bonding + other macroscopic quality properties (flexibility, softness,…)
• DES yarn gives higher strength and strain than a commercial yarn of similar linear density
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POSTER: Foam-formed multi-layer textile structures
• DES fibres (top) • Kraft-fibre layer (bottom)
Topside
BoOomside
• Kraft fibres binding DES fibres
AtsushiTanaka,JaniLehmonen,PirjoHeikkilä,AliHarlin,JukkaKetoja(VTTLtd)
ONE FORMINGOPERATION ONLY
