I. Introduction

Rubber is a specific type of polymer called elastomer: a large molecule that can be stretched to at least twice its original length and returned to its original shape. Early forms of rubber had many glue-like properties, especially in hotweather. In cold temperatures, rubber became hard and brittle. Polymers have distinct additives which classified into four: the filler, added primarily to provide reinforcement and secondly to reduce cost; plasticizer, reduce hardness with a given level of filler, and can help with filler incorporation and dispersion; colorants, is similar as to a dyes but this colorant is dissolves in the polymer and the last is the flame retardant, To improve their flame resistance a number of products may be added to the compound, either inorganic or organic.

Every machine plays a major role in occupying each processes of a given product which makes the product precisely in the exact length, width, or any other specification that required by the costumers and lessen the productivity errors because machine are run by its program according to its command.

Rubber has become an important natural polymer in society. We make rubber from rubber trees (natural latex) and from oil (synthetic rubber). We use both types of rubber in many products. Like the Mesoamericans (Aztecs and Mayans) before them, athletes and children today play with rubber balls. Of course, the most common use for rubber is in automotive tires. But pencil erasers, shoes, gloves, dental dams and condoms contain the ubiquitous substance, too. In many products, rubber is added as a protective coating for either weatherproofing or shockproofing.

II. Definition of Terms

Accelerator

A chemical which speeds up the vulcanization reaction. This allows the rubber to cure in a shorter timeframe, at a lower temperature or both.

Autoclave A vessel that vulcanizes rubber products in a pressurized steam environment.

Backrinding

Tearing or distortion of a moulded rubber product at the line of separation of the mould pieces. Factors which can have an influence on backrinding are blank weight, blank shape, temperature, moulding pressure and breathe cycles.

Carbon black

A black pigment and reinforcement filler used in rubbers. Carbon black is a form of amorphous carbon that has a high surface-area-to-volume ratio. The degree of reinforcement increases with decreasing particle size.

Compound A term applied to a mixture of polymers, reinforcements, curatives and other ingredients to produce a rubber material. The compound is prepared according to a prescribed formula and mixing process.

Copolymer

A polymer composed from two different monomers, for example an NBR composed of polybutadiene and acrylonitrile.

Cure time

The required amount of time needed to complete the curing process to a pre-determined level. The time taken to cure is dependent on the temperature, material type and section of the rubber profile.

Curing temperature

The temperature at which vulcanization takes place.

Elastomer (also known as rubber)

A general term used to describeboth natural and synthetic polymers possessing the ability to return to their original shape after the deforming force is removed.Microwave curing

Vulcanization of rubbers by heat produced by high frequency radiation.

Mill

A machine with two counter-rotating rolls used for rubber mastication, mixing or sheeting.

Mould shrinkage

Dimensional loss in a moulded rubber product that occurs during cooling after it has been removed from the mould.

Plasticizer

A substance, usually a heavy liquid or oil, which is added to an elastomer to decrease stiffness, improve low temperature properties, reduce cost and/or improve processing.

Polymer

Literally means many units and is a large molecule constructed from many smaller monomers.

Shrinkage

The reduction in size upon cooling of a moulded rubber part.

III. Polymers

The polymer, or blend of polymers, is the fundamental component in determining the properties of the compound. It is selected to optimize service performance and processing requirements while also taking cost into account. Very high molecular weight polymers can for example produce extremely tough materials. They can however lead to problems with poor flow, poor joins and particularly backrinding.

Polymers made up of two types of monomer are known as copolymers or dipolymers, while those made from three are called terpolymers.

Figure 1: Single Monomer units polymerized to form a polymer

Figure 2: Two different monomers from a copolymer( or dipolymer)

Figure 3: Three different monomers form a terpolymer.

IV. Polymers AdditivesPolymer additives are similar and controlled by the molecular structure. The entired type of polymers additives are the fillers, plasticizers, stabilizers, colorants, and flame retardant. Each of the type of polymers additives have their own purposes to enhance and modify many properties.

FillersFillers are added primarily to provide reinforcement and secondly to reduce cost. They fall into two basic categories: reinforcing or semi-reinforcing, and diluent.

The most popular reinforcing and semi reinforcing fillers are carbon blacks, which are categorized primarily by means of particle size. Carbon blacks and nonblack fillers become more reinforcing as particle size decreases. Highly reinforcing fillers can make a compound tough, which can result in poor flow. Carbon blacks are alkaline in nature and tend to accelerate cure.

Diluent, or non-reinforcing, fillers have a large particle size and do not 'bond' to the polymer in the same way as reinforcing fillers. They are mainly added to reduce cost. Examples include soft clay, calcium carbonate, and talc.

PlasticizersPlasticizers need to be compatible with the polymer. They reduce hardness with a given level of filler, and can help with filler incorporation and dispersion. Special types of plasticizer can improve the low temperature flexibility of some rubber types like, nitrile and neoprene. Process aids can also assist with filler dispersion, although they are normally added to improve processability downstream. High levels of plasticizer/process aid can bloom to the surface of make-up and give knitting problems (flow marks and poor joins) in the manufactured product. They can also create difficulties when bonding to metal. Excessive softening of the compound can lead to air trapping in the mould.

Plasticizers can also cause problems when a product is subjected to thermal cycling or certain solvents, as they can leach out at high temperatures and adversely affect the low temperature properties.

Colorants

Colorants may play a major role is a coloring agent for polymer. This colorant is similar as to a dyes but this colorant is dissolves in the polymer. Pigments are filler materials that do not dissolve, but remain as a separate phrase, normally they have a small particles size and a refractive index near to that parent polymer.

Flame Retardants

Most elastomers support combustion, and the resulting by-products can be extremely hazardous. To improve their flame resistance a number of products may be added to the compound, either inorganic or organic. They include antimony trioxide, zinc borate, aluminium hydroxide and chlorinated paraffins.

Flame retardants are added to different materials or applied as a treatment to materials to prevent fires from starting, limit the spread of fire and minimize fire damage. Some flame retardants work effectively on their own; others act as synergists to increase the fire protective benefits of other flame retardants. A variety of flame retardants is necessary because materials that need to be made fire-resistant are very different in their physical nature and chemical composition, so they behave differently during combustion. The elements in flame retardants also react differently with fire. As a result, flame retardants have to be matched appropriately to each type of material. Flame retardants work to stop or delay fire, but, depending on their chemical makeup, they interact at different stages of the fire cycle. To better understand how flame retardants work, its helpful tounderstand the fire cycle:

Initial ignition source can be any energy source (e.g., heat, incandescent material, a small flame). Ignition source causes the material to burn and decompose (pyrolysis), releasing flammable gases. If solid materials do not break down into gases, they remain in a condensed phase. During this phase, they will slowly smolder and, often, self-extinguish, especially if they char, meaning the material creates a carbonated barrier between the flame and the underlying material. In the gas phase, flammable gases released from the material are mixed with oxygen from the air.In the combustion zone, or the burning phase, fuel, oxygen and free radicals combine to create chemical reactions that cause visible flames to appear. The fire then becomes self-sustaining because, as it continues to burn the material, more flammable gases are released, feeding the combustion process.

When flame retardants are present in the material, they can act in three key ways to stop the burning process. They may work to: Disrupt the combustion stage of afire cycle, including avoiding or delaying flashover, or the burst of flames that engulfs a room and makes it much more difficult to escape. Limit the process of decomposition by physically insulating the available fuel sources from the material source with a fire-resisting char layer.

Dilute the flammable gases and oxygen concentrations in the flame formation zone by emitting water, nitrogen or other inert gases.

V. Machine used in the Manufacturing Rubber Products:

Roll MillRubber is a material that shares some of the properties of both solid and liquid. Tough raw natural rubber will be loaded into a mill, where counter-rotating steel rollers grind it into a softened, semi-fluid mass. This action, in the presence of oxygen in the air, tears the long, chain-like rubber molecules into shorter lengths. The rubber becomes softer and easier to process, and it readily accepts any other ingredients that may be needed to create a "compound". A compound is the total combination of the rubber polymer and modifiers, such as reinforcing fillers, oils, pigments, antioxidants, vulcanization chemicals, and any other polymer additives.

Strip Cutting MachineThis invention relates to a machine for cutting sheets of material into any desired predetermined lengths, and is particularly to a rubber strip cutting machine. Objects of this invention are to provide a machine which will cut rubber strips into any desired length at a point in the process immediately following the operation of the calender or tubing machine, so that the continuous strip or sheet of rubber is fed directly from the calender or tubing machine to the cutting machine, and means are provided for carrying the severed strips from the cutting machine at a higher rate of speed than the travel of the sheet of stock material so that such cut strips may be delivered in an orderly manner into the press room or other suitable part of the factory.When it is considered that the material which this machine is adapted to handle and cut is of an easily deformed type, it is to be appreciated that the usual modes of controlling sheet material by means of stops against which the material strikes, or by passing the material between contact actuating members, is unserviceable and inoperative where the material as described above.This invention, however, is designed to overcome the defects noted above which result from the distortion of the strip and its failure to operate the devices, and objects of such invention are to provide a novel form of strip cutting machine which is adapted to operate upon easily deformed flexible and yielding stock, and which is so constructed that the exact width or length of the strips may be maintained throughout the operation of the machine.

Mandrel MachineAn object used to shape machine works, tool components that grips or clamps materials to be machined and a tool component that can be used to grip other moving tool components. Also used in industrial composite fabrication such as infilament winding. During the manufacturing process, resin-impregnated filaments are wound around a mandrel to create acomposite materialstructure or part. The structure is cured and the mandrel is removed. One problem with this type of process is that the mandrel can be very difficult to remove once the part has been cured. As a result, engineers have created a new type of mandrel that has the ability to change shape and be easily extracted. When heated above a certain temperature, the mandrel becomes elastic and can be manipulated into the desired shape and then cooled to become rigid again in the new shape. It can then be used in the filament winding process.

AutoclaveAnautoclaveis a device used forsterilizationthat supplies by subjecting them to high pressure saturated steam at 121C for around 1520 minutes depending on the size of the load and the contents.Most buffers and other solutions used in any lab are sterilized before use to prevent bacterial and fungal growth during storage. There are two basic techniques for sterilizing solutions: autoclaving and sterile filtration. Most buffers and other salt solutions are autoclaved, because filtration of large volumes is time-consuming and disposable sterile filters are expensive. However, before autoclaving any solution you should always check whether it contains any heat labile ingredients. If it does, the heat-labile substance will usually have to be prepared separately, filter-sterilized, and added to the remainder of the solution after autoclaving.

VI. What is Vulcanization?The word vulcanization may we connect about rubber but what means is just putting air to expand and can be used as a finished product but totally this word has a broad section of terms and meaning. Vulcanization is an irreversible process during which a rubber compound, through a change in its chemical structure cross-linking, becomes less plastic and more resistant to swelling by organic liquids. The result is that elastic properties are conferred, improved, or extended over a wide range of temperature. The term vulcanization was originally employed to denote the process of heating rubber with sulfur, but has been extended to include any process with any combination of materials which produces this effect. Vulcanization can be carried out under numerous conditions.

VII. Rubber Hose Manufacturing Flow Chart

RubberMilling ProcessCutting Process

Final Layering ProcessVerificationInitial Layering Process

Trimming ProcessVulcanization ProcessMicrowave Curing Process

ShipmentPackaging

VIII. Rubber Hoses Manufacturing Process

Factory makes a low pressure and medium pressure rubber hoses. The intended use is what determines the rubber composition. Function also determines the color because the industrial hoses are now often color coded.

The rubber arrives with a factory from the supplier in roll strip. The first step is to run a through a mill. The roller heat the rubber softening and smoothening it to an even texture.

The next machine cuts the rubber in strips to the precise width and thickness required for the size of hose they're going to construct.

Workers lubricate a steel mandrel that see exact size of the hoses bore. As the mandrel spins, they wrap a rubber strip around it, measuring and layering if necessary to build the thickness thereafter.

Next, they add one or more reinforcement layers. This strip is made of high strength synthetic fabric that's been coated in rubber. It design to withstand the pressure to which the holes to be subjected.

The last layer of rubber forms the hoses outside covering. After verifying that the final diameter is correct, they wrap the entire hose construction tightly in wet nylon tape. The tape would later shrink and compress all the materials together.

This factory also makes hoses with a bilt in attachment on the end. They position on the mandrel, glue the first layer of rubber through it then they reinforced the bond with special textile strips and tightly round high strength carbon steel wire. They continue the wire more loosely down the body of the hose as the specific angle design to withstand vacuum pressure.

Carbon steel wire

Bilt in Attachment

Then they wrap the hose in soft stretchy rubber strips that fills the gaps between the wires.

Next comes the layer of high strength rubber coated fabric then finally the exterior covering. Light blue rubber for the model.

They pressure wrap again with wet nylon tape then to make the hose more flexible, they create corrugations by wrapping it tightly in rope. Whats under the ropes compact creating a dip.

They add another layer of nylon tape to hold the rope in place. When construction is finished, the hoses on their respective mandrills go in to an "auto clave" a cylindrical chamber into which they feed hot steam at high pressure.

This vulcanization process has it called, triggered a chemical reaction that cures the rubber to make it elastic. As the hoses come out and cool, the worker remove the shrunk tape. The layers are solidly compress. They wash the nylon tape and then rewind and reuse it.

Now workers begin the process of removing the hose from the mandrels. They tight one end with a rope to create a pressure

then gently pump water between the mandrill and rubber. The lubricant they applied earlier has prevented the rubber from sticking to the steel so the hoses separate easily.

They simply slide it off from the mandrel. Workers will now trim the ends, cut the hose to length for customer ordered then coiled and package the hose.

IX. References:

http://www.wisegeek.com/what-is-synthetic-rubber.htm

http://www.google.com/patents/US1684158

http://www.most.gov.mm/techuni/media/PR_02034_13.pdf

Elastomer Engineering Guide 7; James Walker

8