Natural and Synthetic Rubber :

1. Introduction

1.3 Thermoset Elastomer

1.4 Thermoplastic Elastomer

1.2 Rubber

  1. Do not required cross-linking

1.1 Elastomer

  1. Derived from elastic polymer
  1. Displays elestic properties
  1. Rubbery materials
  1. The original name given to latex
  1. Rubber is originated from 'rub away'
  1. Crosslinked Rubber
  1. Hard & non-sticky Undergo vulcanization to become permanently insoluble and infisble

2, Rubbery materials that combine the chractheristics of rubber with the recycleability and processing advantages of plastics

2. Natural rubber and latex

Natural rubber is an elastic hydrocarbon polymer that naturally occurs as milky colloidol suspension (latex) in the sap of the rubber tree (hevea brasilensis)

2.1 Natural Rubber (NR) Latex

  1. Located in latex vessels to be founded in various parts of the tree
  1. Colloid system having the rubber particles dispersed in water
  1. Contains small amounts of proteins, resinous matters (ins, lipids), hydrocarbos and materials substances

2,2 NR Latex

  1. The latex modified for these reasons to have higher dry rubber content, DRC Values (60-65% of rubber)
  1. Modification methods: centrifugation, sedimentation, water evaporation thickening and electrodecantation
  1. Example: foam rubber, gloves, condoms, glues (produced directly from latex)

2.3 Recovering rubber from latex

  1. Involves coagulation, coagulation takes about 12 hours
  1. The coagulum (soft solid slabs) then squeezed through a series of rolls which drive out most of water and thickness to about days
  1. the sheets are then draped over wooden frames and dried in smokehouses for several days

3. Natural Rubber Harvesting And Processing (Vulcanisation Process)

3.1 Definition

  1. Aprocess of coverting natural rubber to more strong and elastic form
  1. it was discovered by Charles Goodyear,a U.S. inventor in the 19th century, which is in 1839
  1. The process involves chemical procedure wherein rubber is blended with activators, accelerator and sulphur (S) at 250 F -400F

3.2 Steps in vulcanisation process

Heating

Preparation

Cross linking

Optimum state of curve

Shaping