Doc Brown's Chemistry Revision Notes - Smart Materials and Materials Science

Part 6 GORE-TEX, THINSULATE and TEFLON-PTFE


ALPHABETICAL LIST of materials, effects etc. mentioned on these pages: Smart Materials Science INDEX * CARBON FIBRES * CHROMOGENIC MATERIALS * ELECTROCHROMIC MATERIALS * GORETEX * HALOCHROMIC MATERIALS  * HIGH PERFORMANCE POLYMERS * KEVLAR * LYCRA * MAGNETIC SHAPE MEMORY ALLOYS * MAGNETOSTRICTIVE MATERIALS * NITINOL * pH SENSITIVE POLYMERS * PHOTOCHROMIC MATERIALS * PHOTOMECHANICAL MATERIALS * PIEZO ELECTRIC EFFECT-MATERIALS * PTFE * SELF-HEALING MATERIALS * SHAPE MEMORY ALLOYS * SHAPE MEMORY POLYMERS * SPANDEX * TEFLON * TEMPERATURE-RESPONSIVE POLYMERS * THERMOCHROMIC MATERIALS * THINSULATE *


Part 6. GORE-TEX (GoreTex), THINSULATE and TEFLON-PTFE


Part 6a. GORE-TEX

  • Nylon is a synthetic polymer used to make fabrics for the clothing industry, but on its own it is not very waterproof.
  • If the nylon is coated with polyurethane it becomes a much tougher durable waterproofed material for outdoor clothing.
  • Unfortunately the polyurethane coating doesn't allow water vapour through so you get too hot, sweaty and uncomfortable, because the sweat can't evaporate to keep you cool.
  • Gore-Tex is the registered trade name often applied to a particular design of (usually outdoor) clothing fabric that is designed to keep you dry in the rain without getting sweaty.
    • Strictly speaking it is the patented name a porous form of the polymer PTFE made by stretching the polymer fibres in a controlled way to create fine pores.
    • So the GoreTex itself is actually one layer in the fabric design for a particular clothing application e.g. anorak or wetsuit.
  • GoreTex fabric is made up of a layer of a plastic based on expanded PTFE and this is laminated onto a layer of another fabric.
    • The layer contains very many tiny holes called pores.
    • There are apparently around 14 million pores per square millimetre!
    • It is the tiny holes in the PTFE layer that let the water vapour molecules through, i.e. it is breathable.
    • BUT layer is waterproof because liquid water droplets cannot pass through in the opposite direction, in fact the fabric surface repels water - hydrophobic.
  • Each pore is too small for water droplets to pass through, but big enough to let water vapour molecules from sweat to go through (transpiration or 'breathability').
    • This illustrated in the diagram above, the fabric material is multi-layered (a sort of 'sandwich' composite).
    • So, if you sweat in this 'breathable' material, the water vapour can escape keeping you cooler, and you don't get the discomfort from sweat condensate,
      • AND, because water droplets can't pass through the outer tough protective layer, you should keep dry in wet weather.
    • Also note, that without the outer tough protective layer e.g. nylon or polyester, the GoreTex membrane would be easily damaged and it wouldn't be waterproof and windproof.
    • Gore-Tex products have all the useful properties of nylon-polyurethane fabrics but breathable materials!
  • Therefore you have a 'breathable' fabric which can be combined with insulation materials such as Thinsulate to make outdoor clothing that keeps you both dry (waterproof) and warm (insulating).
  • -


Part 6c. THINSULATE

  • THINSULATE is the trademark of a specially designed commercial synthetic fibre material that can be used for insulation in clothing e.g. gloves or winter jackets.

  • Thinsulate fibres are much thinner than most other artificial fibres like nylon an polyester used in clothing.

  • Human hair is 0.1 mm (100 μm), thinsulate fibs 0.010 - 0.015 mm, 10-15x thinner!

  • molecule same as Lycra?

  • They are produced as a dense tangled web of fibres that trap lots of air between the thin fibres and reflect heat too.

  • Polyesters like polyethylene terephthalate (PET), poly(propene) and poly(ethene) are used to make Thinsulate.

  • This considerably reduces heat loss, i.e. from your body and so clothes containing layers of this material keep you very warm.

    • They are supposed to be at least as good as duck down for insulation, but less water-absorbent and resistant to crushing than duck down.

    • The good thermal insulation effect is due to the high density of fibres produced by utilising very fine fibres which increases the efficiency of the air gaps to reduce heat flow.

    • Thinsulate is supposed to allow moisture to escape e.g. from sweat, which is supposed to evaporate, so Thinsulate is credited in being a 'breathable' material like Gore-Tex.

  • A further advantage is that thinsulate fibres absorb very little water, so they retain their insulating properties and still keep you warm even if your clothes get wet.

  • House insulation


Part 6c. TEFLON - poly(tetrafluoroethene)

TEFLON need ref in oil-polymer pages

  • The formation of the polymer of poly(tetrafluoroethene) by the polymerization of the monomer tetrafluoroethene (n is a very large number and can be several thousand!)

  • TEFLON is the trade name the polymer called poly(tetrafluoroethene) or polytetrafluoroethene, known by its acronym of PTFE.

  • PTFE is noted for its marked chemical inertness and high thermal stability - very heat resistant, only softens at 320oC.

    • The excellent chemical resistance is characteristic of all highly fluorinated polymers.

    • It is also an excellent electrical insulator and so is used in hard wearing insulating material electrical products.

  • It is unusually slippery for a polymer and is used in kitchen equipment e.g. to make non-stick coatings for pans - food adhesion is reduced by the particular molecular properties of PTFE.

    • PTFE's low coefficient of resistance enables it to be used for moving engineering parts in machines and even humble zips etc.

  • It is used in the clothing industry to make clothes fabrics that dirt finds difficult to stick to.

  • Because PTFE is strong and chemically unreactive it can be used to make pipes to carry potentially corroding fluid and containers for storing and transporting chemicals.

  • Its properties also make it useful as a component in the production of Gore-Tex.


WHERE NEXT?

INDEX of SMART MATERIALS PAGES

PART 1 CHROMOGENIC MATERIALS - Thermochromic, Photochromic & Electrochromic Materials

PART 2 SHAPE MEMORY ALLOYS e.g. Nitinol & Magnetic Shape Memory Alloys

PART 3 SHAPE MEMORY POLYMERS, pH and temperature sensitive-responsive polymers, Self-healing materials

Part 4 LYCRA-SPANDEX

PART 5 High performance polymers like KEVLAR

PART 6 GORETEX, THINSULATE and TEFLON-PTFE

PART 7 PIEZOELECTRIC EFFECT (PIEZOELECTRIC MATERIALS) and PHOTOMECHANICAL MATERIALS

PART 8 CARBON FIBRES

See also INDEX NANOSCIENCE-NANOCHEMISTRY pages

Nanomaterials including carbon nanotubes, carbon fibres and silver nanoparticles are on a separate page

More on chemistry applications: Uses of 220+ chemical elements, compounds, mixtures & Formulation chemistry


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