Handbook on Rubber and Allied Products (with Project Profiles)


Handbook on Rubber and Allied Products (with Project Profiles)

Author: NPCS Board
Format: Hardcover
ISBN: 9789381039267
Code: NI252
Pages: 163
Price: Rs. 2,295.00   US$ 200.00

Published: 2013
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***** Limited Edition (AVAILABLE IN PHOTOSTAT VERSION ONLY) ******

Rubber products industry is an important resource based industry sector in India. Over the last decade the rubber industry has witnesses a steady and strong growth. Rubber exhibits unique physical and chemical properties. Rubber's stress-strain behavior exhibits the Mullins effect and the Payne effect, and is often modeled as hyperelastic. Rubber strain crystallizes. Owing to the presence of a double bond in each repeat unit, rubber is susceptible to vulcanisation and sensitive to ozone cracking.
    The two main solvents for rubber are turpentine and naphtha (petroleum). The former has been in use since 1764 when François Fresnau made the discovery. Giovanni Fabbroni is credited with the discovery of naphtha as a rubber solvent in 1779. Because rubber does not dissolve easily, the material is finely divided by shredding prior to its immersion.
    Rubber particles are formed in the cytoplasm of specialized latex-producing cells called laticifers within rubber plants. Rubber particles are surrounded by a single phospholipid membrane with hydrophobic tails pointed inward. The membrane allows biosynthetic proteins to be sequestered at the Surface of the growing rubber particle, which allows new monomeric units to be added from outside the biomembrane, but within the lacticifer. The rubber particle is an enzymatically active entity that contains three layers of material, the rubber particle, a biomembrane, and free monomeric units.
    The monomer adds to the pyrophosphate end of the growing polymer. The process displaces the terminal high-energy pyrophosphate. The reaction produces a cis polymer. The initiation step is catalyzed by prenyltransferase, which converts three monomers of isopentenyl pyrophosphate into farnesyl pyrophosphate. The farnesyl pyrophosphate can bind to rubber transferase to elongate a new rubber polymer.
      The major contents of this book are project profiles of projects like Processing of Crude Rubber, Latex Rubber Foam Products, Rubber Floor Mats, Latex Rubber Threads, Rubber Compounding for Automotive Industry, Rubber Gaskets, Reclaim Rubber, Rubber Powder from Waste Tyre, Carbon Black from Waste Tyre Pyrolysis, Equipments used in Rubber Industry.
        Project profile contains information like; Introduction, Uses and Applications, Properties, Manufacturing Process, Plant Economics, Rated Plant Capacity, Plant & Machinery, Fixed Capital, Raw Material, Total Working Capital, Cost of Project, Total Capital Investment, Turn Over/ Annum, Profit Sales Ratio, Rate of Return, Break Even Point (B.E.P).
      This book is very useful for new entrepreneurs, technical institutions, existing units and technocrats etc.

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***** Limited Edition (AVAILABLE IN PHOTOSTAT VERSION ONLY) ******

1. Introduction
2. Processing of Crude Rubber
3. Latex Rubber Foam Products
4. Rubber Floor Mats
5. Latex Rubber Threads
6. Rubber Compounding for Automotive Industry
7. Rubber Gaskets
8. Tyre for Truck, Lorry, Bus and Cars
9. Reclaim Rubber
10. Rubber Powder from Waste Tyre
11. Carbon Black from Waste Tyre Pyrolysis
12. Equipments used in Rubber Industry

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Sample Chapters

(Following is an extract of the content from the book)
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Latex rubber foam products


Latex is originally defined as the stable dispersion of natural rubber particles in aqueous medium as produced in the rubber tree. They are complex colloid systems containing polymer molecules as major fraction. The polymer may be a homo polymer or co-polymer .Stereo regularity and the complexity of the polymer molecules (linear / branched / cross linked) is maintained in the latex form. Lattices are rubbery or resinous in nature and the rubber molecules can be cross linked. Lattices can be plasticized or oil extended. Lattices have their own mechanical properties and temperature limits of serviceability. Latex products are subject to degradation and adequate antioxidant protection is necessary. They can be classified broadly into four main types: natural, synthetic, artificial and modified latices. In Natural lattices large number of plant species secretes lattices containing polyisoprenes, but only Hevea braziliensis latex is industrially important. In á Synthetic lattices with the rapid growth of polymer chemistry since 1940, a large number of synthetic lattices are now available commercially. Artificial lattices are the dispersions of reclaimed rubber, butyl rubber or other polydiene rubbers. They also include latices made by solution polymerization and conversion of the polymer solution into latex. Modified lattices are produced by the chemical modification of the existing types. For e.g., controlled vulcanization of the rubber in latex would produce modified latex generally known as the prevulcanized latex. Natural Rubber Latex (NR Latex) is the most widely used latex for the manufacture of latex based rubber products. Natural rubber (NR) processing sector is an industry which produces raw materials used for the manufacture of rubber industrial products (conveyor belts, rubber rollers, etc.), automotive products (fan belts, radiator hoses, etc.), latex products (rubber gloves, toys hygienic products, etc.) and many kinds of adhesives. The major users of natural rubber are tire and footwear industries.


Latex is a dispersion of rubber particles in an aqueous phase. Most types of rubber, both natural and synthetic, can be made into a latex form. Latex gets used in specialized applications such as those requiring oil, solvent or flame resistance. Different mixing techniques produce different grades of dispersions i.e. ball milling or ultrasonic’s for fine particle dispersions and simple stirring or colloid milling for coarse dispersions. Latex dipping is used to make thin articles such as gloves, balloons, catheters, bladders; hot water bottles etc and very fine particle dispersions are needed. Coarser particle sized dispersion (slurry) is acceptable for latex foam, used mainly for carpet backing. The following range of additives can be mixed with the latex dispersion or emulsion:

Stabilisers: to maintain the rubber particles in a stable state of suspension. These include sulphonates, inorganic complex phosphates and soaps.

Curing agents, usually sulphur.

Accelerators- including dithiocarbamates, thiazoles, thiurams, and xanthates.

Thickeners- including casein, glue, cellulose derivatives.

Anti degradants- including waxes, substituted phenols, amine based antioxidants.

PH adjusters- including ammonia, sodium and potassium hydroxide, and formaldehyde.

Biocides, mostly halogen derivatives, for suppression of bacterial decay and fungal infection.

Coagulants and gelling agents, include calcium, magnesium and aluminum salts, acetic and formic acid, cyclohexylamine acetate and ammonium acetate. 


This uses a porcelain or aluminum mould (or former) that is repeatedly dipped in the latex compound. Once set, the coated former is washed, air-dried and vulcanized in steam autoclaves before the product is removed. To increase the thickness of the deposit obtained per dip, the former is immersed in coagulant before and after each latex dip.

Latex casting is a similar technique to dipping but is used to make hollow seamless articles. The product forms on the inside of the mould (in contrast to dipping) giving a better surface definition. This process is uncommon.


Latex mixing plant and processing equipment such as carpet backing machines, may present a range of mechanical hazards that will require effective safe guarding by the latest available techniques..


The process of Concentration involves removal of substantial quantity of serum from the latex and increases its rubber content to about 60%. In creaming process, a creaming agent (tamarind seed powder) is added and allowed to remain undisturbed till the desired level of creaming (concentrated rubber) is obtained. In Centrifuging, the latex is subjected to centrifuge force in a bowl rotating at speed around 6,000 surrounding the axis of rotation.

Uses and Applications

       •   The rubber latex pillows, mattresses, cushions, bedding etc. are used in luxury purposes. The latex foam mattresses are used for manufacturing of sheets in automobiles, cars, tempos, buses, jeeps, aero plane, etc. In hotel some time the floor mat are also used

       •   In Bed Pillows this item has been widely accepted. They are produced by a large number of the accepted shape used for feather or down pillows, they are generally very soft, but not flabby, retain their shape without “fluffing,” and are particularly advantageous for allergy sufferers.

       •   Decorative Pillows are comparatively new application for foam, but is being received enthusiastically by the buying public.

       •   Reversible Furniture Cushions is very popular in the furniture field. A similar application is non-reversible furniture seats and backs, airplane, bus, and truck seating.

       •   Mattresses. Its application is the largest latex volume consumer. They are widely used in hospitals where they permit maximum comfort with minimum replacement where they permit maximum comfort with minimum replacement.

       •   Automotive Pads. The automobile producers are the largest users of foam rubber in view of number of pieces used. Foam rubber topper pads are now considered standard equipment in most automobiles.

       •   Composite Products. Latex foam slab is frequently combined during processing with various other materials. A layer of ungelled foam can be deposited directly to the back of a rug, sheeting, upholstery fabric, curled hair and similar types of materials for use as under carpet padding, ironing board padding, lining materials, etc. Applications in this field are limited only by one’s imagination.

       •   Latex foam rubber recovered as manufacturing scrap or recovered from post consumer use can be chopped and utilized when mixed with polyurethane scrap, as bonded carpet cushion.


       •   Latex foam is suitable for disposal via municipal landfill or incineration in most states and municipalities.

       •   Latex foam rubber derives its physical performance properties from the vulcanization process that creates long molecular chains with strong cross linked bonds.

       •   Latex foam rubber generally has a relatively high density and is soft, thus latex foam rubber can only be used in limited amounts in the production of bonded carpet cushion.

       •   Latex Foam Producers has a high level of grip, some others are designed to offer maximum durability.

       •   Latex mattresses are naturally therapeutic and provide extraordinary orthopedic support.

       •   Superior Thermal Qualities Latex’s thermal properties are truly outstanding. Its superior cell structure gives it maximum breath-ability.

Various Products of Latex

     1.   Foamed latex products: Mattresses, Pillows, Upholstery, Carpet Backings, Packaging materials etc.

     2.   Dipped latex products: Surgical gloves, House hold gloves, Industrial gloves, Contraceptives, Feeding Bottle teats, Toy balloons etc.

     3.   Latex extrusions: Latex thread.

     4.   Latex spreading: Carpet backing, Textile treatment, Paper Coatings.

     5.   Latex castings: Toys, Bulbs.

     6.   Miscellaneous: Rubberized coir /fiber products, Battery Separators, Adhesives and PV-latex.

The two modern routes to latex foam products concern the way in which the foam is made

     (i)   Chemical foaming

    (ii)   Mechanical foaming

The mechanical foaming processes used today on such a large scale for the production of latex foam goods, uses for most of the part, a concentrated natural rubber latex which is prepared by one of the processes involving partial removal of the non-rubber substances as well as concentration of the rubber (e.g. processes such as centrifugation or creaming). Successful operation of latex foam processes normally demands a concentrated latex one containing a minimum content of the latex, during compounding, to a Valve between 0.1% and 0.25%. This facilitates gelatin and to control the process which is usually done by stirring and blowing a current of air over the surface of the compounded latex as part of the “Maturing process”.

Chemical Foaming agents are used in a wide range of applications in plastics and rubber processing. By choosing the right foaming agent system following properties could be achieved.

       •   Weight Reduction

       •   Raw Material and Cost Saving

       •   Dimensional Stability

       •   Heat Insulation

       •   Noise Absorption

       •   Special Surface Effects.

Chemical foaming agents decompose during processing in a chemical reaction which is induced by heat. The decomposition can be exothermic or endothermic.

As Latex foam products are cellular (open cell, closed cell or a combination of open cell and close cell structures) products directly produced from liquid latex compounds. The skin is a smooth surface formed by contact with the mould surface. Since Latex foam has an open cell structure because of this interconnect cell it is spongy in nature.

Natural rubber (NR) latex is a natural commodity that has tremendous economic and strategic importance. Among the applications of NR latex is the production of dipped goods, extruded threads, and adhesives, carpet-backing and moulded foams. This is primarily because of the unique characteristics of NR latex, such as high strength, flexibility and elasticity. Most NR latex products are derived via a sulphur vulcanization system, which achieves the desired physical properties for the product application.

Synthetic latex foam rubber is not flexible polyurethane foam. Synthetic latex foam rubber represents a group of materials manufactured using methods similar to natural latex foam rubber on the same processing equipment.

Synthetic latex foam rubber can be the product of natural rubber suspension and rubber substitute blends, or it can be produced using a totally synthetic process such as used to produce styrene-butadiene rubber (SBR) and polymerized chloroprene, known as neoprene.

Manufacturing Process of Latex (Rubber) Foam Products

Basic Raw Material

       •   NR Latex (deammoniated).

       •   Potassium olaste soap solution.

       •   Sulphur Dispersion

       •   Zinc diethyl dithiocarbamate Dispersion

       •   Zinc salt of mercapto benzothizole Dispersion

       •   Anti oxidant dispersion

       •   Filler Dispersion

       •   Zinc Oxide Dispersion

       •   Secondary Gelling Agent

       •   Sodium Silico Fluoride Dispersion

       •   Cure Open Steam

Basic Formula

Parts                                                                                                                    by wt

60% NR Latex (deammoniated)                                                                          167.0

20% Potassium olaste soap solution                                                                       5.0

50% Sulphur Dispersion                                                                                          4.0

50% Zinc diethyl dithiocarbamate Dispersion                                                         2.0

50% Zinc salt of mercapto benzothizole Dispersion                                                2.0

50% of anti oxidant dispersion                                                                           2.0-3.0

Filler Dispersion                                                                                          up to 40.00

50% Zinc Oxide Dispersion                                                                                     8.0

Secondary Gelling Agent                                                                           As required

20% Sodium Silico Fluoride Dispersion                                                            5.0-7.5

Cure Open Steam                                                                                        30-45 min


     a.   Compounding of Latex

     b.   Expanding (Foaming) to a desired volume.

     c.   Setting (Gelling) the rubber particles and

     d.   Vulcanizing

There are mainly two methods of making Latex Foam, namely

     1.   Dunlop process, and

     2.   Talalay Process.


The typical Formulations for the Dunlop process for making Foam is listed below.

 Parts                                                                                                                         by wt.

60% NR Latex (Deammoniated)                                                                               167.0

20% Potassium Olaste Soap Solution                                                                           5.0

50% Sulphur Dispersion                                                                                                4.0

50% Zinc Diethyl Dithiocarbamate Dispersion                                                              2.0

50% Zinc Salt of Mercapto Benzothizole Dispersion                                                    2.0

50% of Anti Oxidant Dispersion                                                                              2.0-3.0

Filler Dispersion                                                                                                up to 40.00

50% Zinc Oxide Dispersion                                                                                           8.0

Secondary Gelling Agent                                                                                 As required

20% Sodium Silico Fluoride Dispersion                                                                  5.0-7.5

Cure Open Steam                                                                                              30-45 min

Compounding of Latex

Latex is deammonniated and then Sulphur, Accelerator, Antioxidants and fillers (in the form of dispersion) are added to it in a mixing tank, fitted with a slow speed stirrer. The compound is then allowed to mature by keeping it slowly stirred for several hours.

Foaming and Gelling

Mechanism of Gelling Sodium Silico Fluoride is sparingly soluble in water but hydrolyses in it into hydrofluoric acid and silicic acid.

 Na2SiF6   ----------------à 2Na++SiF6–

 SiF6— + 4H2O  ----------------à Si(OH)4 + 4H+ + 6F-

Liberation of hydrofluoric acid alone is not the cause of gelling as gelling is found to occur at alkaline Ph. The silicic acid formed also plays a vital role in gelling.   

In the batch process a planetary mixer is used for foaming. The mixer is provided with a wire cage which rotates in a planetary motion at about 200 rpm. The Latex compound is weighed out into the mixer bowl; soap is then added and whipped into foam by rotating cage beater. Beating time normally varies 15 to 20 min when volume of mix increases from four to six times. The Zinc oxide and the secondary gelling agent are added, followed by Sodium Silico Fluoride. The foamed compound is then poured into the mould.

In the Continuous Process, a frothing machine known as Oakes Frother is normally used. In the machine air is injected into a stream of latex forming coarse foam which is forced between a toothed rotor and stator plate to refine foam. The Gellant is injected late in the Frothing stage. Foam is conducted through a hold to the mould. The rotar speed is adjustable for optimum foaming.

      For manufacture of large blocks of Foam Rubber moulds are fitted with metal pins for better heat transfer and easy removal of the products.

Some thickening agents are gelling agents (gellants), forming a gel, dissolving in the liquid phase as a colloid mixture that forms a weakly cohesive internal structure. Others act as mechanical thixotropic additives with discrete particles adhering or interlocking to resist strain.

Thickening agents can also be used when medical condition such as Dysphagia causes individuals difficulty when swallowing.

Vulcanization: Moulded foam products are normally cured by open steam (at 100°C (like carpet under lays) can be cured by hot air.

Working: Vulcanized foam is stripped off from the mould and worked in water by passing the product between the rollers under the surface of water bath. Excess water is then removed by passing through squeeze rollers.

Drying: The worked products are dried in the hot ovens at 60-80°C temperature. Heavier foam grades need longer drying but shorter curing, then the lighter slabs.


The original Talalay Process utilized hydrogen peroxide to generate oxygen for expansion. A later development uses Oakes type Mixer. Partially Foamed Latex compound is taken into the mould where foaming is completed by vaccum. The foamed latex is then chilled and gelled by passing carbon dioxide gas. Curing is done by hot air impingement or suction dryers. But this type of plant requires very high capital investment.

Moulded foam rubber can carry loads depending on the density of the foam. It can absorb energy and damp vibrations, also acting as a sound insulator. In mattresses and pillows, it does not require dusting or mechanical rearrangement: natural rubber latex foam is also known to have bactericidal properties.

Compared with natural rubber latex, SBR latex yields foam of lower tensile, strength and elongation at break. The hot tear is also poor, making the removal of the cured foam from the mould difficult. Therefore, SBR latex is rarely used alone but is usually blended with NR Latex.


Rated Plant capacity       =      1.00 MT/day

                                         =      300.00 MT/annum



No. of working days         =      25 days/month

                                         =      300 days/annum

No. of shifts                      =      1 per day

One shift                          =      8 hours

LAND & BUILDING COST                                                      TOTAL       Rs.            92,40,000.00


     1.   Planetary Mixing Machine Made by SS for slow mixing & compounding of Latex with complete accessories.

     2.   Mounds for Setting of Latex Foam

     3.   Vulcanization Chamber with automatic temp. Control and all accessories.

     4.   Conveyor Belt

     5.   Demonizing Tank SS with Complete accessories

     6.   Pot Mill (SS)

     7.   High Speed Mixture

     8.   Washing Tank (SS)

     9.   Squeezing Machine with Rubber Rolls

   10.   Boiler

   11.   Dryer Turnnel Type with automatic heating and air blowing system

   12.   Miscellaneous Machines like Valves, Motors, pipes & Fittings etc.

   13.   Erection & Installation                                                     TOTAL       Rs.            79,70,000.00


     1.   LAND & BUILDING                                                                           Rs.            92,40,000.00

     2.   PLANT & MACHINERY                                                                    Rs.            79,70,000.00

     3.   OTHER FIXED ASSETS                                                                  Rs.            64,50,000.00

                                                                                                   TOTAL       Rs.         2,36,60,000.00



     1.   Latex (60%)

     2.   Castor Oil

     3.   Potassium Hydroxide

     4.   Darvan

     5.   Valcastab T.M.

     6.   10% Casein Solution

     7.   Piperidine-Pentamethylene Dithio carbamate

     8.   Sulphur

     9.   Notax L.M.

   10.   Z M B T

   11.   10% Silicate Solution

   12.   Zinc Oxide

   13.   Bentonite

   14.   Sodium Silicofluoride

   15.   Ammonium Oleate

   16.   Printed Packing Materials

   17.   Laboratory & ETP Chemicals

   18.   Consumable Stores                                                        TOTAL       Rs.            28,28,407.00


     1.   RAW MATERIAL                                                                               Rs.            28,28,407.00

     2.   SALARY & WAGES                                                                          Rs.              2,79,600.00

     3.   UTILITIES & OVERHEADS                                                              Rs.              4,51,000.00

                                                                                                   TOTAL       Rs.            35,59,007.00


           TOTAL FIXED CAPITAL                                                                     Rs.  2,36,60,000.00

           MARGIN MONEY                                                                               Rs.     26,69,255.25

                                                                                                     TOTAL       Rs.  2,63,29,255.25


           TOTAL FIXED CAPITAL                                                                     Rs.  2,36,60,000.00

           TOTAL WORKING CAPITAL FOR 3 MONTHS                                Rs.  1,06,77,021.00

                                                                                                     TOTAL       Rs.  3,43,37,021.00


           By Sale of Latex (Rubber)

           Foam Product                                                                   TOTAL       Rs.  6,30,00,000.00

           PROFIT SALES RATIO                     =       23.32%

           RATE OF RETURN                           =       42.78%

BREAK EVEN POINT (B.E.P)         =          38.27%

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NIIR PROJECT CONSULTANCY SERVICES (NPCS) is a reliable name in the industrial world for offering integrated technical consultancy services. Its various services are: Pre-feasibility study, New Project Identification, Project Feasibility and Market Study, Identification of Profitable Industrial Project Opportunities, Preparation of Project Profiles and Pre-Investment and Pre-Feasibility Studies, Market Surveys and Studies, Preparation of Techno-Economic Feasibility Reports, Identification and Selection of Plant and Machinery, Manufacturing Process and or Equipment required, General Guidance, Technical and Commercial Counseling for setting up new industrial projects and industry.

NPCS also publishes varies technology books, directory, databases, detailed project reports, market survey reports on various industries and profit making business. Besides being used by manufacturers, industrialists and entrepreneurs, our publications are also used by Indian and overseas professionals including project engineers, information services bureau, consultants and consultancy firms as one of the input in their research.

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