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GENERAL PURPOSESNATURAL RUBBER (SMR GP) PRODUCTION PST 161 UNIVERSITI TEKNOLOGI MARA 1
DEFINITION• SMR GP, general purposes natural rubber is the major material for tire production.• Made from 60:40 mixture of latex-grade sheet rubber and field coagulum.• Prepared from: blend of latex rubber, unsmoked sheet rubber, field coagulum rubber and plasticizer. 2
IMPORTANCE OF SMR GPPRODUCTION• Dark colored rubber Make it suitable for tire production.• Blending of latex and sheet rubber ensure high quality of SMR GP.• Uses of plasticizer in SMR GP gives beneficial to tire manufacturers. 3
GENERAL PROPERTIES• Contains blending of latex rubber, unsmoked sheet rubber, field coagulum rubber and plasticizer.• The properties of this materials are by following proportions: – 30% weight of latex rubber – 30% weight of sheet rubber – 30% weight of coagulum rubber – 10% weight of rubber plasticizer 4
• There are two types of SMR GP which have different composition from one another: – SMR GP 1 – SMR GP 2 Weight (%) Raw materials SMR GP 1 SMR GP 2 Field latex 60 30 Rubber coagulum 40 40 Unsmoked sheet rubber - 30 5
PROCESS FLOW OF SMR GP• Production of SMR GP involves the method of blending which is involving co- coagulation of latex-oil mixture and wet crumbs.• Wet crumbs use prepared from a blend of unsmoked sheet and field coagulum.• Subsequent processing gives: – Very uniform blend – Minimum mechanical working• The process flow are presented below: 6
• The process above involving the following steps:1. Field coagulum is pre- cleaned and then formed into a blanket. – depends on the quality of raw material and should give a blanket with less than 0.12% wt. dirt.2. The unsmoked sheets are milled into a blanket.3. The unsmoked sheet and field coagulum blankets are blended 8
4. The crumbs are transferred and spread evenly into a latex coagulation tank, then manually sprayed with 10% formic acid solution.5. required amount of emulsified aromatic oil and then mixed into a pre- determined quantity of latex. – Hydroxylamine Neutral Sulphate is added to the latex as viscosity stabilizer. 9
6. The latex- oil mixture is adjusted to pH 7.0 to 7.5 and poured into the coagulation tank.7. Latex-crumb coagulum then processed and dried. 10