NATURAL RUBBER COMPOSITES
NATURAL RUBBER AND ITS COMPOSITES
Published on: Mar 3, 2016
Transcripts - NATURAL RUBBER COMPOSITES
ROLL NO:17 1
•Rubber is a type of polyisoprene made up of 5 carbon isoprene
• The 5 carbon units could be linked in the cis or trans
conformations resulting in polymers with very different physical
• Rubber is composed of all cis-linked isoprene units, forms an
amorphous structure that is highly elastic.
• Gutta percha is a polyisoprene compound made of all trans-
linked isoprene units, forms linear strands but are not elastic.
•NR is a high molecular weight polymeric substance with
viscoelastic properties. it shows all the reactions of an
•Vulcanization converts the viscous nature of raw rubber into
•Vulcanized rubber will have very high tensile strength and
comparatively low elongation.
•Its hardness and abrasion resistance also high when compared
to raw rubber.
•The main use of natural rubber is in automobiles. 3
STRUCTURE OF NR
• Structurally it is cis 1,4-polyisoprene.
•Isoprene is a diene and 1, 4 addition leaves a double
bond in each of the isoprene unit in the polymer. 4
• The commercial source of natural rubber latex is the Para
rubber tree (Hevea brasiliensis).
• Other plants containing latex include:
• Rubber fig
• Panama rubber tree (Castilla elastica)
• Common dandelion
• Parthenium argentatum (Guayule).
• Russian dandelion
SOURCES OF NR
Specific gravity : 0.92
Refractive index : 1.52
Coefficient of cubical expansion : 0.00062/°C
Cohesive energy density : 63.7 Cal/cc.
Heat of combustion : 10547.084 Cal/g
Thermal conductivity : 0.00032 Cal/sec/cm/°C
Dielectric constant : 2.37
Power factor (at 1000 cycles) : 0.15-0.2
Volume resistivity : 1015 ohm.cm
Dielectric strength : 3937 V/mm 7
• Crude rubber is a tough and an elastic solid,becomes soft and
sticky as the temperature rises.
• Its specific gravity is 0.915.
• Raw natural rubber has elasticity over a narrow range of
temperature from 10 to 60.
• Raw natural rubber has low tensile strength and abrasion
• NR absorbs large quantities of water.
• It is insoluble in water, alcohol, acetone, dilute acids and
• It is soluble in ether, carbon disulphide, carbon tetrachloride,
petrol and turpentine.
• Pure rubber is a transparent, amorphous solid, which on
stretching or prolonged cooling becomes crystalline
•The latex will coagulate in the cups if kept for long. The latex
has to be collected before coagulation.
•The collected latex, "field latex", is transferred into coagulation
tanks for the preparation of dry rubber or transferred into air-
tight containers with sieving for ammoniation.
•Ammoniation is necessary to preserve the latex in a colloidal
state for longer periods of time.
•Latex is generally processed into either latex concentrate for
manufacture of dipped goods or it can be coagulated under
controlled, clean conditions using formic acid.
PROCESSING OF NR
•The coagulated latex can then be processed into the higher-
grade, technically specified block rubbers such as SVR 3L or
SVR CV or used to produce Ribbed Smoke Sheet grades.
•Naturally coagulated rubber (cup lump) is used in the
manufacture of TSR10 and TSR20 grade rubbers.
•The processing of the rubber for these grades is a size
reduction and cleaning process to remove contamination and
prepare the material for the final stage of drying.
•The dried material is then baled and palletized for storage and
shipment in various methods of transportation.
• Rubber is always compounded with additives to satisfy the
given application in terms of properties, cost, and
• Compounding adds chemicals for vulcanization.
• Mainly used reinforcing filler used in NR is carbon black.
• Other additives include antioxidants , antiozonants coloring
pigments, plasticizers and softening oils, blowing agents in
the production of foamed rubber and mold-release
COMPOUNDING OF NR
•Low Temperature Usage:-20° to -60° F | -29° to -51°C
•High Temperature Usage: Up to 175° F | Up to 80°C.
Properties Affected by Compounds:
•Low Compression Set
•Cross Link Density 14
• NR Composites and Nano composites based on
i. Reinforced with Carbon Black
ii. Reinforced with Silica
iii. Based on Carbon Nanotubes
iv. Based on Graphene
• NR Composites and Nano composites Based on Natural
iii. Reinforced with Natural Mineral Fillers
• NR Composites and Nano composites Based on Metal
or Metallic Compound Fillers
i. Metal nanoparticles and metallic compound powders are used to
strengthen the polymers, and improve their thermal stability and
gas barrier properties.
ii. NR is often reinforced with various kinds of metal nanoparticles and
metallic compound powder.
• NR Composites and Nano composites Based on Hybrid
i. NR composites filled with hybrid fillers possess outstanding
mechanical properties that are not caused by only one filler. 16
NR COMPOSITES AND ITS PROPERTIES
GLASS FIBERS BASED NR:
•Glass fibers have high tensile strength, low cost, high chemical
resistance and excellent insulating properties.
•The disadvantages are relatively low tensile modulus and high
density, high hardness, sensitivity to abrasion during handling
which tends to decrease its tensile strength, relatively low fatigue
•Fiber-reinforced NR composites are manufactured by various
processes, the most common being extrusion, injection molding
and compression molding. 17
• E-glass fiber has better tensile properties than A-glass fiber.
• E-glass/NR composites will show better tensile properties than
• Increase in fiber content leads to an increase in the strength
and modulus of a fiber reinforced polymer matrix composite.
•Uses of NR in hoses.
•NR used in soil stabilization, in vibration absorption and in road
•Catheters and surgical gloves
•Consumer products (like golf or football balls and other
recreational and sports goods, erasers, footwear).
•Non-tyre rubber items include industrial products transmission
and elevator belts, hoses and tubes, industrial lining, and bridge
•Heavy Equipment Industry(like Shock mounts,Vibration
isolators,Gaskets,Seals,Rolls,Hose and tubing).
APPLICATION OF NR COMPOSITES