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Crepe rubber

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Form of coagulated latex
Latex collection from a rubber tree

Crepe rubber is coagulated latex that is rolled out in crinkled sheets and commonly used to make soles for shoes and boots but also a raw material for further processed rubber products.

Processing

After the collection of the latex milk, sodium sulphite (Na2SO3) or ammonia is added to prevent coagulation.

When the latex arrives in the factory, sodium bisulphite (NaHSO3) or sodium metabisulphite (Na2S2O3) are added to prevent enzymatic reactions and discoloring.

Sodium para toluene thiophenate (an aromatic mercaptan) is often added as a bleaching agent.

Colloidal latex is then mixed with formic acid to cause it to coagulate. The coagulum is processed in a "creping battery", a series of machines that crush, press, and roll the coagula. The sheets are then hung in a heated drying shed and, after drying, sorted by grade and packed for shipping.

Types

There are several types and grades of rubber crepe, mainly distinguished by the grade and pre-processing of the latex used in their manufacture.

  • Pale latex crepe (PLC) is a premium grade, made from raw field latex.
  • Estate brown crepe (EBC) is made from "cup lump" (raw, naturally coagulated rubber from the collection cup) and other coagula.
  • Re-milled crepe is made from "wet slab coagulum" (cured latex, still wet from the coagulation tanks), latex sheets (unsmoked) and cup lump.
  • Smoked blanket crepe is made from thick sheets of latex that have been processed in a smoker.
  • Flat bark crepe is made from scraps and other poor quality raw product.

Gallery

  • Hand-powered latex creping machines Hand-powered latex creping machines
  • Removing coagulum from coagulating troughs Removing coagulum from coagulating troughs
  • Creping battery Creping battery
  • Milling honey-colored crepe Milling honey-colored crepe
  • Milling white crepe Milling white crepe
  • Spooling crepe from last finishing mill Spooling crepe from last finishing mill
  • Smooth crepe spooled for transfer to the drying shed Smooth crepe spooled for transfer to the drying shed
  • Wet coagulum crepe blanket Wet coagulum crepe blanket
  • Smallholder's sheet in a drying shed Smallholder's sheet in a drying shed
  • White crepe hanging in a drying shed White crepe hanging in a drying shed
  • Laminating white crepe for sole crepe Laminating white crepe for sole crepe
  • Laminating honey-coloured crepe for sole crepe Laminating honey-coloured crepe for sole crepe
  • Sole crepe inspection and packing Sole crepe inspection and packing

References

  1. ^ Manufacture of latex crepe rubber (pdf-document), Raw Rubber Process Development & Chemical Engineering Dept., Rubber Research Institute of Sri Lanka, Ratmalana, January 2016
  2. Cecil, John; Mitchell, Peter; Diemer, Per; Griffee, Peter (2013). "Processing of Natural Rubber, Manufacture of Latex-Grade Crepe Rubber". ecoport.org. FAO, Agricultural and Food Engineering Technologies Service. Retrieved March 19, 2013.
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