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
editAfter the collection of the latex milk, sodium sulphite (Na2SO3) or ammonia is added to prevent coagulation.[1]
When the latex arrives in the factory, sodium bisulphite (NaHSO3) or sodium metabisulphite (Na2S2O3) are added to prevent enzymatic reactions and discoloring.[1]
Sodium para toluene thiophenate (an aromatic mercaptan) is often added as a bleaching agent.[1]
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.[1]
Types
editThere are several types and grades of rubber crepe, mainly distinguished by the grade and pre-processing of the latex used in their manufacture.[2]
- 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
edit-
Hand-powered latex creping machines -
Removing coagulum from coagulating troughs -
Creping battery -
Milling honey-colored crepe -
Milling white crepe -
Spooling crepe from last finishing mill -
Smooth crepe spooled for transfer to the drying shed -
Wet coagulum crepe blanket -
Smallholder's sheet in a drying shed -
White crepe hanging in a drying shed -
Laminating white crepe for sole crepe -
Laminating honey-coloured crepe for sole crepe -
Sole crepe inspection and packing
References
edit- ^ a b c d Manufacture of latex crepe rubber (pdf-document), Raw Rubber Process Development & Chemical Engineering Dept., Rubber Research Institute of Sri Lanka, Ratmalana, January 2016
- ^ 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.