Content

• History

• Introduction of raw rubber

• What is vulcanization?

• Effect of vulcanization

• Types of additives

• Types of vulcanization

• Reference

History

• Natural rubber is obtained from latex.

• And latex is obtained from rubber tree (hevea brasilinesis).

• This is a polymer of isoprene (2-methyl-l,3-butadiene), with molecular weights in the range of 300,000.

Properties Of Raw Rubber• Properties of natural rubber

- Soft

- Sensitive to heat

- Elasticity decreases over time

- Easily oxidized by air

Polyisoprene (2-methyl-l,3-butadiene)

History Of Vulcanization

• Vulcanization Of Rubber Was Discovered In 1839 by the U.S. inventor Charles Goodyear.

• Thomas Hancock (1786–1865), a scientist and engineer, was the first to patent vulcanization of rubber .

• Hancock was awarded a British patent on May 21, 1844.

• Three weeks later on June 15, 1844 Goodyear was awarded a patent in the United States.

What is Vulcanization?

• The physical properties of the rubber can be improved by heating it with vulcanizing Agent Such As Sulphur Powder , peroxide(Benzoylperoxide , dicumyl peroxide zinc peroxide).

• It Is a Process Of Increasing Elasticity while decreasing the plasticity of material .

Effect of vulcanization

Types Of Additives

There is different kind of additives is used in rubber while vulcanization.

• Accelerators

• Activators

Accelerators

• These are the chemical substance used in a vulcanization process to reduce the curing time, oxidative degradation of elastomers during vulcanization and it has improved the property of vulcanisates.Type of Accelerators:on the basis of vulcanization rate

• Slow • Medium• Fast• Ultrafast

Slow Accelerators• Di-o-tolyl guanidine (DOTG)

Medium Accelerators• N-Cyclohexylbenzothiazyl-2-sulfenamide (CBS)

Fast accelerators• 2-Mercaptobenzothiazole (MBT)

Ultrafast Accelerators• Tetramethyl thiuram monosulfide (TMTM)• Tetramethyl thiuram disulfide (TMTD)

Activators

• Activators are compounds able to increase the efficiency of the accelerators.

Type of Activators

• zinc oxide (ZnO) - is the most known vulcanizing activator and it can be used along with the majority of known accelerators

• magnesium oxide (MgO) - is mainly use to the vulcanization of the neoprene-type elastomers.

Type of Vulcanization

Sulphur Vulcanization:

• It is usually used for the curing of unsaturated elastomers.

• It uses a sulphur powder as a vulcanizing agent.

Peroxide Vulcanization

• In peroxide vulcanization organic peroxide such as dicumyl peroxide, benzoylperoxide, zinc peroxide are used as a curing agent .

• These peroxide does not enter into a polymer but generate a free radicals which formed C-C linkage with adjacent polymer chain.

• It is applicable to both saturated and unsaturated rubbers.

Benefits of peroxide vulcanization

• It is applicable to both saturated and saturated rubber.

• Transparent product obtained due to absence of sulphur.

• Product is more stable than sulphur vulcanized product, because C-C bond is more stable than sulphur bond.

• No cross linked reversion.

Reference

• Google images

• Martin and Smith book

SUBMITED BY: PANKAJ KUMAR DAS

ROLL NO : 1308023