PRODUCTION OF MATERIALS IV (CONTD)

PLASTICS AND RUBBER
CONTENT :
PRODUCTION OF RUBBER
INTRODUCTION
Rubber is world-wide used material. Two types are in use Natural and Synthetic Rubber.
Natural rubber is made from Latex, a milky juice tapped from rubber tree. Synthetic rubber is manufactured from petroleum, coal tar, natural gas, water, etc.
The main chemicals used are styrene, butadiene, hydrocarbons, etc.
Rubber tree is called HeveaBrasiliensis.
STAGES OF RUBBER PRODUCTION
The stages involved in rubber production are: (a) Latex Preparation: Tapping, which is the processof cutting grooves at the bark of rubber trees to drain and collect the milky juice in a cup, is carried out first. After tapping, coagulationtakes place by dissolving the latex in a tank of water and sieved to remove dirts from it. Formic acid is added to the latex to form solid particles that rise to the surface to form crude rubber. Drying is carried out by feeding it through a rolling machine. (b) Plasticization: This is the process of softening dried rubber for easy moulding. This is carried out in a milling machine by adding material called softeners or plasticizers. This process is necessary for only coagulated and dried crude rubber. (c) Compounding And Mixing: This is a process of adding measured quantities of ingredients to latex or plasticized rubber. Ingredients added are fillers, used to increase the volume and strength of rubber. Accelerators are used to speed up vulcanization while anti-oxidants are used to slow down the rate at which rubber wears and sulphur is used for vulcanization. (d) Shaping: the process of formimg rubber into various shapes. Shaping takes place in special moulds prepared for it. The methods used are injection moulding, calendaring and dipping. (e) Vulcanisation: is the process of treating rubber products with sulphur, heat and other vulcanizing agents. The heating process causes the sulphur to mix with the rubber and cure(preserve) it. Vulcanisation makes rubber very elastic, stronger more durable.