Mastication, the process by which the viscosity of natural rubber is reduced to a suitable level, is an important step in the mixing process. Rubber polymers such as Natural Rubber (NR) require mastication to reduce their viscosity/elasticity and to even out variations between different polymer lots.

What is compounding of rubber?

Rubber compounding involves the science and engineering of rubbers and rubber additives, such as processing aids, fillers, and curing agents, in definite proportions to obtain a uniform mixture that will have desirable physical and chemical properties to meet processing at low cost and end use performance.

What is processing of rubber?

Rubber processing consists of four basic steps: (1) mastication, when the elastomer is sheared and the molecules are broken down to give easier flow, (2) mixing, usually carried out immediately after mastication, when additives are incorporated, (3) shaping of the viscous mass, for example, by extrusion or molding, and ...

Why do synthetic rubbers not need mastication?

Shortening the polyisoprene molecules makes the rubber softer and more malleable. Most synthetic rubbers do not need the mastication step because they are made of shorter molecules. Mixing and blending are still required, however, to combine all ingredients used in the rubber compound.

What are the factors affect on rubber mastication?

The mastication of natural rubber results in the shortening of the long molecular chains, which affects the viscosity of the material. Mechanical and thermo-oxidative breakdowns are the two major factors that interfere during mastication and processing of natural rubber.

Rubber mastication process

What is Mooney viscosity in rubber?

Mooney viscosity is defined as the shearing torque resisting rotation of a cylindrical metal disk (or rotor) embedded in rubber within a cylindrical cavity. The dimensions of the shearing disk viscometer, test temperatures, and procedures for determining Mooney viscosity are defined in these test methods.

What will happen to the rubber if prolong mastication is taking place?

These rubbers were masticated at 50°C and at 200 rpm for various mastication times to reduce their molecular weights. A too-long mastication time was found to adversely affect the impact strength and tensile toughness due to the fast agglomeration of rubber particles.

What is mastication process?

Mastication (chewing), in which food is crushed and mixed with saliva to form a bolus for swallowing, is a complex mechanism involving opening and closing of the jaw, secretion of saliva, and mixing of food with the tongue.

Which acid is used in synthetic rubber?

Neoprene rubbers are based on polychloroprene; a polymer composed of chloroprene, acetylene, and hydrochloric acid.

Why is natural rubber better than synthetic?

Both natural rubber and synthetic rubber (IR) have high tear resistance, good low temperature flexibility, and high tensile strength. An advantage natural rubber has over synthetic rubber is that natural rubber has higher tensile strength, higher tear resistance, and low odor compared to IR.

What is rubber milling?

The two roll rubber mill is a machine used to process natural rubber into various compounds. Two horizontally opposed stainless steel rolls rotate in opposite directions towards each other at different speeds to mix the rubber and ingredients used to create the rubber compounds.

What are the methods of producing rubber?

Some of the most common rubber manufacturing processes are extrusion, latex dipping, molding, and calendering. Extrusion begins with an unvulcanized compound being fed into an extruder. Once it's inside the extruder, it gets carried forward to a dye, which is a specialized manufacturing tool used to shape the rubber.

What is used in making rubber?

Natural rubber is obtained from latex, a milky liquid present in either the latex vessels (ducts) or in the cells of rubber-producing plants. Around 20,000 species of plants produce latex, but only 2,500 species have been found to contain rubber in their latex.

What is PHR in rubber compounding?

Parts per Hundred Rubber, a measure used by rubber chemists to depict what amount of certain ingredients are needed, especially pre-vulcanization.

What chemicals are added to rubber?

Both carbon black and silica, when added to a mix compound at a concentration of about 30 percent by volume, raise the elastic modulus of the rubber by a factor of two to three. They also confer remarkable toughness, especially resistance to abrasion, on otherwise weak materials such as SBR.

What chemicals are in rubber?

The main chemical constituents of rubber are elastomers, or “elastic polymers,” large chainlike molecules that can be stretched to great lengths and yet recover their original shape. The first common elastomer was polyisoprene, from which natural rubber is made.

What is rubber acid?

Formic is the acid used as a coagulating agent for coagulating latex and getting a high – quality natural rubber product. Formic acid satisfies all the requirements for a good coagulating agent.

How many types of rubber are there?

There are 2 types of rubber Natural and Synthetic. Natural rubber is an elastic hydrocarbon polymer known as an elastomer that was originally derived from latex which is a milky colloidal suspension, found in the sap of some plants.

What is formic acid used for rubber?

Formic Acid is the preferred choice for coagulating latex: it is cost-efficient, and guarantees a consistent high-quality natural rubber product – making it one of the best coagulants for natural rubber latex coagulation in dry rubber production.

What are the functions of mastication?

Mastication is the technical word for chewing. It is the first step in digestion, in which food is broken into smaller pieces using the teeth. Grinding food increases its surface area. This allows for more efficient digestion and optimal nutrient extraction.

What is mastication class 7th?

The process of chewing the food and conversion of the food to bolus is known as mastication. The process takes place in the mouth. The teeth are mainly responsible for the process of mastication. The teeth are involved in the chewing, crushing and conversion of the particles of the food.

What is mastication in biology class 10?

chewing of food and mixing of saliva with the help of tongue and teeth.

Why vulcanization is done?

vulcanization, chemical process by which the physical properties of natural or synthetic rubber are improved; finished rubber has higher tensile strength and resistance to swelling and abrasion, and is elastic over a greater range of temperatures.

What is vulcanisation of rubber?

Vulcanization is a chemical process in which the rubber is heated with sulphur, accelerator and activator at 140–160°C. The process involves the formation of cross-links between long rubber molecules so as to achieve improved elasticity, resilience, tensile strength, viscosity, hardness and weather resistance.

Why is vulcanization of rubber so important Explain with examples?

The vulcanization process is necessary to produce most useful rubber articles, like tires and mechanical goods. Unvulcanized rubber is generally not strong, does not retract essentially to its original shape after a large deformation, and it can be very sticky.