Chemistry:Crepe rubber
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.[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 hung in a heated drying shed and then sorted by grade and packed for shipping.[1]
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.[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
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
- ↑ 1.0 1.1 1.2 1.3 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. http://ecoport.org/ep?SearchType=earticleView&earticleId=644&page=4363. Retrieved March 19, 2013.
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