This is one of the subjects to master in the field of rubber technology. Compounding is not really a science . It is part art, part science. In compounding one must cope with literally hundreds of variables in material and equipments. There is no infallible mathematical formulation to help the compounder, that is why compounding is so difficult a task

What is rubber compounding and Why are we doing it ?
How can we do it successfully?

Rubber compounding is the art & science of selecting and combining elastomers and additives to obtain an intimate mixture that will develop the necessary physical & chemical properties for a final finished products as per specification desired to achieve the required useable properties in all types of rubber products used in various applications.

Objectives of Rubber Compounding:

1. To secure certain properties in the finished product to satisfy service requirements

2. To attain processing characteristics necessary for efficiant utilisation of available equipments

3. To achieve the desirable properties & process ability at the lowest possible cost. In other words, the most important criteria in compounding is, to secure an acceptable balance among demands arising from the above criteria.

Equipment For Rubber Compounding

What is mixing?

Mixing is defined as a process of incorporating the compounding ingredients into the rubber, done on an open rubber mixing mill at the beginning of a mixing cycle the rubber is forced or drawn in to the working area between pair of rolls on open mixing mill . The process of incorporation, mastication, & dispersion are the most important functions of mixing which contributes to a very good product as regards a compound to meet all the desired properties as per specification of required compound.

What is a mixing mill?

Is defined as the machine with two differential speed rolls, running in opposite direction, forming a nip for mastication mixing , or warming before extrusion . The rotation of the rolls pulls the ingredients through the nip, which is the clearance between the rolls. The remaining surface of the roll is used as means of transportation for returning stock to the nip for further mixing

Internal Mixer is a machine with profiled rotors rotating in an enclosed chamber in opposite direction , it is used for rapid mixing and large throughput due to its versatility, it is tending to replace the open mixing mill, Specially as a batch mixer. The basic purpose of all internal mixers are the ability to exert high localized shear stress to the material being mixed. A lower shear rate stirring, a homogenous action, that is the effective ness of dispersive mixing results from the combination of high shear stress and large shear deformation. . An internal mixer design is a compromise based on experience to best accommodate the wide range of compounds typical of a manufacturing operation involving mixed products.

Banbury Machine:

Banbury mixer consists of a completely enclosed mixing chamber in which two sprial shaped rotors operate a hopper at the top to receive compounding ingredients for mixing and a door at the bottom for discharging the mixed batch of compound .the bulk of the shearing action takes place between the rotor and the chamber wall

A Compounder must have the following knowledge:

• An understanding of the plant, processing methods available to him in the organization,

• Moulding unit knowledge to develop compounds for compression moulding, transfer moulding and injection moulding
• In a tyre industry a compounder must have knowledge of tyre machinery, tyre moulds

• In extrusion industry he must have knowledge of the type of extrusion process in operation.

• Up to date and elaborate knowledge of both the chemical and the physical properties of elastomers is most essential

• Knowledge of vulcanizing system available, knowledge of in- process physical testing and also testing of finished products

• A good comppunder with experience must be able to convert science in to art. So that he has the capability of producing material that will be easy to process and he must be able to produce and formulate economical, practical compounds as competition in today’s world is quite severe.

Using a stable free radical Peroxide vulcanization of rubbers offers various advantages over sulphur vulcanisation. Like rapid vulcanization without reversation at higher temperatures, good compression set, excellent heat ageing properties, possibility to co-vulcanise saturated and unsaturated rubber blends etc. These are attributed to the C- C cross – links formed during peroxide vulcanization, which have the same bond strength as the C – C bonds in the polymer back bone. As per the generally accepted mechanism, peroxide vulcanization is initiated by the thermal decomposition of organic paroxides to highly reactive free radicals which then abstract hydrogen atoms from the elestomer, yielding rubber to macro radicals. These micro radicals combine to form the cross – links. One outstanding problem that restricts the wider industrial use of peroxide vulcanization is the low scorch safety. If scorch control can be significantly improved, the range of industrial application of peroxide vulcanization can be broadened. Earlier works to use radical scavengers / co – agent combination to introduce scorch control has not succeeded in bringing about scorch to a level equilant to sulphur/accelerator combination. The present paper addresses it and shows that stable nitroxyl free radical, 2, 2, 6, 6,- tetramethylpiperidine-1- oxyl [TEMPO ], used in bringing about living free radical polymerization, can control scorch in peroxide vulcanization in a way similar to the sulphur/ accelerator system.

Use of TEMPO has led to the reduction in cross link density due to the reaction of it with the macro free radicals generated. A recent US patent described a method to over come this by modifying the TEMPO. THE PRESENT PAPER SHOWS THAT THE REDUCTION IN CROSS-LINK DENSITY CAN BE VERY WELL COMPENSATED USING APPROPRIATED CO-AGENTS.

Some standards attempt to reserve the term elastomer for a cross linked material. Elastomer’s are a class of materials which differ quite obviously from all other solid materials in that they can be stretched easily and almost completely reversibly, to high extensions. An ordinary postal rubber band illustrate this behaviour. It will generally be made from natural rubber, and can be stretched to seven times its original length, after which – before reaching its ultimate breaking elongation –it can be released and will rapidly recover to almost exactly the original length that it had before stretching.

The material is said to be elastic. Most synthetic elastomers are not as elastic as natural rubber, but all can be stretched or other vice deformed in a reversible manner to an extent which easily distinguishes them from all other solid matrials. A metal spring exhibits a high reversible elasticity, but this is a feature of its wound shape. The actual metal itself of which the spring is made only deforms slightly, by twisting locally, of any particular point, nothing like the high deformation of which elastomers are capable.

A hybrid vehicle is basically one that runs on 2 engines. One is a normal engine that runs on regular fuel like petrol or diesel, and the other is an electric engine. This means, to put it simply, that when you want to speed up, the normal engine runs the car, and charges the electric engine at the same time. But when you want to save fuel and take it easy, the electric engine takes over and does what the fuel engine normally does.

There are plenty of rubber components in these brilliant cars. Most windshields have rubber moulding that makes it fit properly on the frame. But if this is not fitted properly, it could lead to problems. For instance, in the winter, the rubber will contract, and will make a buzzing sound as the air flows over it. In the summer, the rubber will expand, and the noise will not be audible anymore.

A good rubber manufacturer will be able to provide high quality products at good prices. There are a lot of specifications that need to be taken care of.  The manufacturer should be able to provide compression, transfer and injection molding services, so that the finished product is nothing less than fantastic and reliable.

There are plenty of car parts made from moulded rubber such as pump impellers, silicone steering column seals, gas pump nozzle gaskets and gear shift boots for off road equipment. All these need to be crafted to perfection in order for maximum performance of the vehicle. Other important parts that need attention to detail are flapper valves with rubber bonded to cast aluminum, idler rollers with neoprene bonded to steel cylinder seals with Viton and many more. The list goes on and on, and if these parts are not made properly, it could be hazardous.

Various rubber gaskets have different purposes, and they come in all sorts of shapes and sizes. Some of these types are ring and full face gaskets, insulator gaskets, jacketed gaskets and flange gaskets. One can also get custom moulded gaskets.

The different types of rubber gaskets include industrial, heat resistant and high temperature rubber gaskets. There are four ways of manufacturing a rubber gasket, and they are water jet cut, rubber molding, die cut and hand cut.

There are plenty of rubber gasket manufacturers in India, but while searching for the right kind of rubber gaskets, one must take note of a few things. For one, make sure that they operate at maximum pressure and temperature and they should also have good radio frequency and electromagnetic shielding.

There are also companies that manufacture other kinds of gaskets such as die cut, oil resistant, urethane gaskets, neoprene gaskets and silicone gaskets, but the most popularly used ones are made from rubber. Usually people opt to buy rubber gaskets in bulk, as they are cheaper to acquire that way, but one can also buy them at retail prices.

The rubber industry is a large one, and in India, we all use rubber products in our day-to-day activities. The rubber industry works hard all year round to make sure that we get the necessary supply of rubber.

There are a lot of aspects to the supply of rubber, and the rubber manufacturers have to keep on thinking of ways and means to do the job right. With today’s high-end technology, manufacturers are trying various techniques such as cloning, which will definitely be beneficial in the long run for both the users as well as suppliers of rubber.

Another aspect that the rubber industry needs to keep in mind at all times is how to reduce costs. In today’s times of financial crisis, everyone is doing the same. Conservation of soil and water are two of these aspects that they constantly need to control. Also, a lot of money goes into R & D of the material itself, in order to make it a better and more economically viable.

With all these steps, the ever-growing natural and man made rubber industries are making it a lot easier for the country to get its due share of rubber.

Silicon Keypads: What would the couch potato or the cellular phone addicts do without these? From calculators and digital diaries to cell phones and remote control buttons, many of these are made from silicon. Take this away, and we’ll have a nation full of whiny people who wouldn’t know what to do with their time.

Rubber mats and sheets: They prevent our car floors from getting filth on them, allow us to wipe our muddy footwear after trudging through muck all day, and basically lie on the floor waiting for someone to dirty them. What would we do without them!

Gaskets: These fill irregularities in machine parts, saving money, as well as stop leakages and between two parts of a mechanical device or machine.

Diaphragms: Without these, our population would be a lot larger than what it is today. Diaphragms prevent pregnancy, and have quite a high success rate, as long as they are used properly.

Vibration isolators: Like the name suggests, these isolate an object from the source of vibration.

These are only some of the many products that are made out of rubber. To sum it all up, with rubber, our lives would be incomplete, so we must thank the rubber and silicon rubber manufacturers.

Manufacturing rubber commercially in India started way back in the 19th century. Back then, it was used more industrially than anything else, but today, rubber has exceeded all expectations, and has moved far away from being only an industrial item. Rubber has found a place in various other industries such as fashion, lifestyle and many more. Today’s fashionistas praise rubber to no end, as it is such an easy material to work with.

The moral of this story is, that we should not take this lovely material for granted. It is all around us, and we should be grateful to all the rubber manufacturers for providing us with so much of it. Next time when we see the wheels of a public bus or when a hot meal of daal and rice is served to us piping hot straight from the pressure cooker, we should stop for a minute and thank the people who invented molded rubber.

Rubber Products India

François Fresneau produced the first scientific paper on rubber in the year 1751. Since then, this versatile material has come a long way. The para rubber tree initially grew only in South America, and when the first European returned to Portugal from Brazil with water repellent cloth samples, he was taken to court and charged with witchcraft. When rubber initially came to England, Joseph Priestley observed that the material could be used to easily wipe out pencil marks on paper, which is how it got its name.

Although South America was the main source of rubber throughout the 19th century, thousands of seeds were gathered from Brazil and sent to Sri Lanka, Indonesia, Singapore and Malaysia. The British Planters initiated the first commercial cultivation of natural rubber in India, although there were trial runs performed as early as 1873 at the botanical gardens in Kolkata.

Industrial rubber, as we know it today has indeed come long way from what it was when it was first discovered. The rubber industry in Asia is the largest, and is responsible for over 90% of the world’s rubber. Indonesia, Thailand and Malaysia are the top three rubber industries, accounting for approximately 72% of all natural rubber production in the world.

According to a few sources rubber was supposedly discovered way before 1600 B.C. Some believe that Mayans discovered rubber and made the best use of it. Apparently they used latex to make rubber balls, human figures and many other uses. It is said that they even.

They combined rubber sap from the tree and morning glory (a famed hallucinogen) to creat big rubber balls which were used for a ritual game called Tlachtlic which was a cross between basketball and football. Natives continue to use the age old process to create rubber till date.

Well this surely sounds like a fascinating theory. But rubber surely has evolved from its Mayan utility to an unavoidable material. Every industry makes the best use of rubber. In fact the growth of the Indian auto industry has led to increase in rubber production. Today rubber exists in every aspect of our mundane lives. From your basic pencil to the pharmaceutical industry; rubber is an integral part of our lives.

There are many manufacturers of rubber gaskets, rubber seals, silicon rubber products, food grade rubber etc. The list does not end here and so does the innovation. Toady India boasts of a successful rubber industry with manufacturing plants spanning all across the country.