Fishing line

Nylon 6 can be extruded and drawn into a single fine fishing filament.

Fishing line, illustrative image

Material

Monofilament line: Nylon 6

Material selection rationale

Tensile strength
A drawn filament carries tension along its length.
Toughness and flexibility
The line bends around a spool and into knots without behaving like a rigid rod.
Direction-dependent strength
Drawing improves properties along the filament, while a knot bends and concentrates stress in that same line.

How it becomes a product

  1. Extrude a filament: Molten PA6 passes through a small opening and is cooled.
  2. Draw and wind: Stretching aligns the chains; the conditioned line is wound onto a spool. Extruded monofilament is drawn to the intended diameter and cooled under controlled conditions before winding.

Preparation routes

Caprolactam route

Hydrolytic ring-opening polymerisation. Opening caprolactam rings and linking the units forms nylon 6 chains. Unlike nylon 6,6, this route does not require a separate diamine–diacid pair. Ring opening retains the monomer’s amide-derived atoms in each six-carbon repeat. It is not the same feedstock reaction as forming nylon 6,6 from two molecules.

Water participates in initiation and the reaction equilibria. Later extraction and drying remove residual small molecules and prepare the polymer for processing. Drawing line or brush filaments aligns existing chains rather than continuing the ring-opening reaction.

  1. Polyamides: nylon 6 and nylon 6,6Chemical Industry Education Centre, University of York
  2. Reference document on best available techniques in the production of polymersEuropean Commission, Joint Research Centre · 2007

From cyclohexanone through an oxime to caprolactam

  1. Cyclohexanone + Ammonia + Hydrogen peroxide → Caprolactam

    In the selected ammoximation route, cyclohexanone, ammonia and hydrogen peroxide produce cyclohexanone oxime. A separate vapour-phase Beckmann rearrangement converts that oxime into the cyclic amide caprolactam. Nitrogen enters the ring in the rearrangement; the six-carbon skeleton becomes a seven-membered lactam ring, ready for a later nylon 6 polymerisation.

  1. New technology to manufacture caprolactam: oxime formation and Beckmann rearrangementSumitomo Chemical
  2. Caprolactam process feedstocks, Investors Handbook 2012, section 5-5Sumitomo Chemical
  3. Vapour-phase Beckmann rearrangement technology transfer, November 2024Sumitomo Chemical

Sources

  1. Polyamides for monofilaments and fishing lineBASF
  2. Polyamides: nylon 6 and nylon 6,6Chemical Industry Education Centre, University of York