TOPIC - RUBBERCONSTRUCTION AND MATERIALS

BY:KUSHAGRA GOELMOHD. KADIR

Rubber

Rubber also known as elastomers are high polymers having a unique property of undergoing large deformation under load and returning to their original shape and dimension on its removal owing to lengthening and shortening of the springs of spring polymeric chains (elastomer molecule is not a straight chained but in form of coil )

The upstretched rubber molecule is amorphous in stretching the molecules in it get partially aligned to one another . On releasing the stress chain regains its original coiled state

Rubber

Rubber is very important engineering material for any nation the most one being tire industry.

India is the fifth largest natural rubber producing country in the world after Malaysia, Indonesia, Thailand and Sri Lanka.

Kerala State accounts for about 91 % of the total area under rubber industry and for Kanyakumari district in Tamil Nadu, the percentage is about 5 % .

The remaining 4% area is located in karnatka , Andman and Nicobar island, Goa , Maharashtra and north eastern states.

The total area under rubber cultivation in the country is about 522000 hectares.

The commercial use of rubber came into existence with the discovery of process known as the vulcanization in year 1836 by Good Year.

CHARACTERISTICS OF RUBBER

FLEXIBLE ELASTIC NON TRANSPARENT HARD AND STRONG INSULATE ELECTRICITY ACID & ALKALINE RESISTANT DOESN’T CONDUCT

PROPERTIES

PHYSICAL PROPERTIES• NON REACTIVE • CHEMICALLY RESISTANT TO MANY FLUIDS • NON CONDUCTIVE • POOR CONDUCTION OF HEAT AND ELECTRICITY• ELASTIC • TOUGH• ELECTRIC RESISTANT AND INSULATOR

Classification NATURAL RUBBER SYNTHETIC RUBBER

NATURAL RUBBER

Consists of basic material latex , dispersion of isoprene which polymerizes to form long coiled chain of polyisoprene . It’s made from sap occurring in cells of various parts of plants such as HAVEA BRASILIANSIS & GAUYILE .

Latex is obtained by making incisions in bark of rubber tree allowing sap to flow out . It’s collected and diluted to contain 15-20% of rubber and then stained to remove any dirt . Thereafter rubber is coagulated by adding acetic or formic acid . The coagulated rubber is then treated to produce crude rubber known as CREPE RUBBER &SMOKED RUBBER which is further processed ,milled and vulcanized to produce commercial rubber .

Natural Rubber Plantation : The rubber trees are planted. They start oozing outafter a period of about 5 to 7

years and continue to ooze out for a life to about 30 yrs. Anormal rubbertree gives about 10N to 50N of dry rubber per year.

Tapping Latex : A vertical groove about 600mm long is made in the rubber tree by means of a

pointed knife at a height of about 1m from the ground level . The vertical groove is connected of slanting grooves inclined upward. An earthenware pot is attached at the lower end of vertical groove to collect the latex

that oozes out of the tree. The latex from the pot is taken by the tapper everyday or every alternate day and at

the time ,the grooves are slightly widened. The care should taken to see that the grooves do not penetrate beyond the cambium layer of the tree.

Natural Rubber

Purification: The impurities such as leaves ,sand,debris,etc.are removed.

Coagulation : The latex then converted into a massive form by the process of coagulation. The coagulant usually adopted is weak acetic acid. The addition of coagulant converts latex into curd like form. It is then pass through rollers. The water from latex thus separated out and the natural rubber is obtained in

the form of Globules of sheets.

Natural Rubber

The process of obtaining Natural Rubber is carried out in following four stages.

1) plantation 2) Tapping Latex 3) Purification 4) Coagulation.

NATURAL RUBBER

CREPE RUBBER Produced by coagulating

rubber in presence of retarder like sodium bisulphate .

Then passed between rollers of creping machine where most of serum is squeezed out and a sheet of resembling crepe is formed

SMOKED RUBBER Produced by pouring diluted latex

into tanks having sides with vertical grooves .Diluted formic or acetic acid is added and stirred .

Partition plates are inserted and left for 16 hours . Slabs formed are removed and passed through series of rollers with decreasing clearance . The sheet are kept for 4 days in smoke house having a temperature of 40-50%

Synthetic Rubber The term synthetic or artificial rubber was conceived through research and

development as a polymer which could be used to replace the natural rubber. The real beginning of a synthetic rubber industry started in USA , Germany and

other foreign countries.

Synthetic Rubber

The synthetic rubber can be grouped in the following two categories:1) General purpose synthetic rubber: These rubbers are used freely in wide ranging applications. The most important all purpose rubber was then and still is a Styrene-butadiene

rubber . It was called earlier inn USA and Canada as GR-S and in Germany BUNA-S. It is now referred as SBR all over the world.2) Special purpose synthetic rubber These rubbers are developed with especial end use in view and They include

butyl ,nitrile ,chloroprene ,E.D.P.M. ,Acrylic , Polysulphide , silicone ,Viton etc. India is accounted for 0.5% of the total world production of synthetic rubber . First synthetic rubber plants of India , Synthetics and chemical ltd. Was setup at

Bareilly ,U.P. in 1961.

TYPES OF SYNTHETIC RUBBER

STYRENE BUTADIENE (SBR)

Originally developed as a low cost substitute for natural rubber

Good water resistance and abrasion resistance

Poor weathering resistance, but can overcome with specific raw materials

Not recommended for contact with oils and solvents

Not used with concentrated acids or alkalis

Maximum continuous operating temperature is about 225°F

BUTYL Very good resistance to most

gases including air highly resistant to ozone and

weathering Abrasion resistance close to

natural rubber and good for concentrated acids and alkalis

Not recommended for petroleum product exposure

Maximum continuous operating temperature is about 300°F

TYPES OF SYNTHETIC RUBBER

EPDM Exceptional resistance to

weathering and ozone Excellent resistance to water,

most gases, steam, and heat aging

Good for exposure to concentrated acids and alkalis, but not recommended for exposure to oils and solvents

Maximum continuous operating temperature is about 350°F

FKM(VITON) High cost, but high

performance material Outstanding resistance to most

chemicals, oils and solvents Good oxidation and ozone

resistance Maximum continuous operating

temperature is about 650°F "Viton" is a trademark of

DuPont and signifies material produced by DuPont

TYPES OF SYNTHETIC RUBBER

NITRILE (BUNA) Much better oil and solvent resistance

compared to either natural rubber or Neoprene

Recommended for most oil field applications

Can be formulated for use at low temperatures

Good compression set and abrasion resistance, but poor weathering resistance

Can be used with concentrated acids and alkalis but there are better alternatives

Maximum continuous operating temperature is about 275°F

NEOPRENE (CHLOROPRENE)

Good general purpose rubber with properties close to natural rubber, but is synthetically produced

Better resistance to oils and solvents compared to natural rubber but similar low compression set

Can be compounded for flame resistance

Good weathering resistance Poorer low temperature performance

compared to natural rubber Maximum continuous operating

temperature is about 275°F

APPLICATIONS

RUBBER FLOORING

Used To A Large Extent In Public And Industrial Building Because Of Their Good Wearing Qualities ,Resiliency And Noise Insulations .

Made Up Of Pure Rubber Mixed With Fillers, Such As Cotton Fiber ,granulated Color Asbestos Fiber And Desired Coloring Pigments

Manufactured In Form Of Sheet Or Tiles, In A Varity Of Patterns And Colors

RUBBER ADHESIVE

Most All Rubber Based Glues And Bonding Agents Are Made Of Rubber Mixed With Other Compounds

Suited As A Bonding Element Because Of Its Flexibility Some Types Of Bonding Compounds Made With Rubber Are Used As

Sealants. Not Suitable For Bonding In High Temperature Situations. Since Its Water Resistant It Is Used Where Dampness Is An Issue . Might Be Damaged By Some Solvents and not suitable for bonding

heavy pieces .

EXPANSION JOINTS

A mid structure separation which designed to relieve stress on building materials caused by building movement by :

Thermal expansion &contraction caused by temperature changed, Sway caused by winds, Seismic events

It marks a gap through all building assemblies including walls , floors, deck, planters , plazas etc. because the joint biscuits the entire section .

Used to bridge the gap and restore the building assembly functions while being able to accommodate the expected movements .

BEARING PADS

RUBBER BEARING PADS ARE USED IN : Bridge bearing masonry pads Handrail bearings pads Pads between steel beam , girders ,grates &columns Shock and vibration isolation Heavy equipment mounting pads Railway tie pad applications Pads underneath concrete vaults

THANK YOU