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Dolphin Rubber is specializes in the design and manufacture of custom molded rubber and plastic products for our OEM customers worldwide. From concept to finished molded component, our team of knowledgeable professionals works to ensure excellence in the product we deliver to our customers

Contact Information
17, Baliyadev Colony
 N.H.NO - 8, At & Post POR
Dist. - Vadodara - 390023


PhoneMobile : +91 99989 83158
Fax Phone : 0265-2831299
WWW Link Website : www.dolphinrubber.com
Email Email : info@dolphinrubber.com



Our Services
Introduction To Rubber

Rubber comes in two basic types, Natural and Synthetic. Both are thermoplastics originally but as special chemicals added during mixing and heat is applied they cure and become tough and rubbery. After curing heat will not re shape them, they are thermo set.

Natural is taken as latex sap from a rubber tree. It is obtained by wounding the tree by cutting out a thin strip of bark. The latex exudes from the cut & is collected, as shown below.

Latex Being Collected From A Rubber Tree

Synthetics are made from oil & show the same process characteristics as natural. Synthetic materials each have their own set of special properties, to make them suitable for certain applications. Synthetics are all your common types of rubber i.e. Nitrile, Neoprene, etc.
To achieve a strong rubber product that we use everyday, there are a number of processes to complete in order to make the final product.

Long chain polymer

Rubber molecules are made to be very long, which helps to strengthen the material. However, rubbers are still relatively weak & will flow under load. This is very useful to mould rubber into a particular shape, but not if rubber will not retain its shape in use. To overcome this problem need to “fix” the polymer chains to allow them to slip over each other, but without letting them slip so far as to separate out of chain. This is done by joining polymer chains together at a limited number of points. This process is called cross-linking.

Cross-linking

In most rubbers cross-linking is done using heat and chemicals known as curatives. The process of cross-linking is normally known as ‘curing’ or in sulphur-based compounds it is called vulcanisation. This is where double bonds become very useful. Sulphur will react with these bonds and form polysulphide (s-s-s-s-s-s-s-s-s) links between the polymer chains.

There are lots of double bonds in most rubbers but you don’t want to cross-link too many of them. Limiting the amount of sulphur controls the amount of cross-linking. Normally about 2 parts weight of sulphur is used per 100 parts of rubber.

Not all rubbers contain double bonds so other chemical methods have to be used, nevertheless the effect is always the same, to produce the right level of cross-linking to hold the rubber together, but not make it too hard to lose its rubbery properties. Once cross-linking is achieved you can make rubber parts, which will stay in shape and not distort. However, they will still not be strong enough for say a tyre, so the next step is to increase the strength of the rubber by including a "reinforcing filler” in the mix. For most applications Carbon Black is the most effective filler.

Carbon Black

Carbon black has a remarkable effect on the properties of rubber. It improves its strength, abrasion resistance and weathering properties. So to achieve a strong rubber product we use every day we need a long chain polymer, cross-linking and carbon black. Although that is not the end of the story.

Mixtures

Many other materials may be added to achieve special properties. A rubber compound is more like a recipe than a simple material. Formulating the right mix is one of the key areas of rubber technology. As stated before, carbon black is effective at strengthening the rubber, but process oils must also be added to allow the carbon black to mix in without significant heat build up. This makes it easier to mix in and reduces the power consumption during mixing. Most compounds contain a significant amount of both black and oil in a controlled balance to achieve the properties for the particular use. To speed up the process of cross-linking chemicals such as zinc oxide, stearic acid and other accelerators speed up the reaction. With accelerators aiding the speed of the curing it may be necessary to delay the start of the cross-linking until the rubber is nearly at curing temperature, this is done by adding retarders. These are needed, as we do not want the rubber to start cross-linking until it is in its final shape.

A disadvantage to double bonds is that they will react with the oxygen in the air, especially with heat and break the chains. So special materials known as antioxidant and antiozonants which slow down these processes, are often added to the rubber mixtures. Some other materials that can be added include fillers, fire retardants, deodorants and reodorants to change the smell and in the case of non-black products white fillers and pigments.

Common Rubbers

Going back and looking at all the different processes and materials added, it takes a special kind of polymer to make a rubber, but that does not mean we don’t have a wide range of rubbers to chose from and a wide range is necessary as rubber products have to perform many different functions under a wide range of conditions. Below is a list of common rubbers used within the industry; more details are available in our materials matrix page, which may also be of interest.
Natural rubber came first and has a high level of “bounce” and a low level of heat generation which makes it useful in products such as engine mountings and truck tyres where other rubbers might get over heated and begin to break down. Natural has poor ozone resistance with tendency to perish in open air.
EPDM is the most water resistant compound and has very high resistance to most water based chemicals. EPDM will not resist oil or oil based products.
Neoprene was one of the first synthetic rubbers developed. It is easy to process and cost effective. Neoprene is unsuitable for applications requiring contact with fuels.

Hypalon is extreme resistant to ozone & weathering. It withstand harsh outdoor conditions.
Silicone is a synthetic rubber with a wide temperature range and excellent resistance to weathering. It is also easily coloured. Silicone is not a very strong & is relatively expensive.
Viton is the best material for resistance to hostile chemical and oil environments. It is strong and has good resistance to water.
Viton is a more expensive rubber. Nitrile is the most suitable rubber for applications requiring resistance to petroleum-based fluids. Nitrile has poor resistance to outdoor weathering; it is flammable and burns with toxic fumes.


Services For Rubber Moulding Process

Dolphin Rubber provides full spectrum of custom rubber moulding services. Developing innovative solutions has given us a reputation for quality & value which is envy of our peers, often delivering most challenging applications, even where previous attempts have failed.

You may feel sceptical about such claims? Others feel the same way, but having tried Dolphin Rubber, found our engineering solutions to be “second to none”.

As a result Dolphin Rubber Mouldings have a loyal customer base world-wide.

Dolphin Rubber - Range of Services

• Injection Moulding • Transfer Moulding • Fabrication Assembly • Silicone RTV Moulding • Rubber to PTFE Bonding • Rubber to Fabric Moulding • Compression Moulding • Prototype Moulding • Twin Shot Moulding • Rubber to Metal Bonding • Rubber to Plastic Moulding
• Custom applications

tudies prove Dolphin Rubber solutions more cost effective, than “cheaper” quotes. These frequently prove technically inferior, with erratic quality and deliveries, long lead times and poor engineering support, negating any potential savings on paper.

COMPRESSION MOLDING

• Least complex of thermal set moulding processes • Wide variety of size, shape and complexity of parts available • Performs is placed directly in cavity o Rubber is compressed, under heat, between top and bottom plates o Compound flows to fill cavities, spilling into overflow grooves o When cure cycle is complete, plates open, and formed parts are removed • Typically, deflating or trimming is required as a secondary operation • Typically requires the least expensive tooling. • Typically works best for all-rubber parts (no inserts) .

TRANSFER MOLDING

• Most versatile molding method • Uncured rubber is placed in transfer pot o Under heat, ram pushes fluid rubber into cavities o Under continued heat and pressure, rubber vulcanizes to cavity shape o When cure cycle is complete, parts are removed; “transfer pad” must also be removed • Secondary operations may be required; flashless/trimless available • Tooling costs vary based on design complexity • Designed for complex part geometry • Allows for over-molding of inserts .

INJECTION MOLDING

• Most automated process • Uncured rubber is injected into cavities via a runner system and gates into closed mould o Under continued heat and pressure, rubber vulcanizes to cavity shape o When cure cycle is complete, parts are removed; runner system must also be removed • Secondary operations may be required; fleshless/trim less available • Tooling costs typically higher than for other processes • Designed for high volume/ high speed
• Allows for over-moulding of inserts .

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