How Silicone, Isoprene, and Natural Rubber Differ

Synthetic rubber

Silicone rubber

Chemical structure

Silicone rubber is a lasting and highly enduring elastomer (rubber-like material) consisting of silicone (polymer) and another molecule of carbon, hydrogen, and oxygen. Primarily, it consists of a siloxane backbone (silicon-oxygen chain) and an organic moiety bound to the silicon.

Capable of having a varying composition, silicone rubber will also have varying properties. They change with the type of organic group attached to it, methyl, vinyl, phenyl, or another group.

Silicone rubber molecular structure

Properties

In contrast to the organic type, silicone rubber has the so-called Si-O bond in its structure. Thus, it has more resistance to heat, abrasion, and ozone. In addition, it has more excellent chemical stability and electrical insulation. It can withstand temperatures ranging from 500C to 3500C, depending on the duration of exposure.

Gadgets made of silicone rubber could tolerate exposure to wind, rain, and ultraviolet rays for long periods without affecting their physical properties. Specifically, silicone rubber could very well withstand ozone, unlike other organic rubbers, which could not. 

The most significant advantage of silicone rubber is its considerable resistance power. It resists acids, bases, solvents, chemicals, oils, and water.

Types

Classification of silicone rubber has two factors: (1) molecular structure and (2) viscosity and processing method.

In terms of molecular structure, silicone rubber belongs to methyl, methyl, and phenyl; methyl and vinyl; methyl, phenyl, and vinyl; fluoro, vinyl, and methyl groups. The viscosity and processing method classify silicone rubber as solid silicone rubber or treated under high temperature, liquid silicone rubber, and room temperature vulcanized.

Uses of silicon rubber

The unique molecular structure of silicone rubber makes it capable of carrying both inorganic and organic properties. Hence, it has been used extensively in aerospace, automotive, construction, medical, food processing, and many more. It is used as elastomers, adhesives, and sealants, potting, encapsulating compounds, coatings, lubricants, and many more. In our area, silicone is used as an injection site for the needle-free connector.

Isoprene Rubber (IR)

Chemical structure

Very similar to the natural type, the isoprene rubber undergoes a synthetic process, and its chemical name is cis-polyisoprene. Its properties are mainly identical to natural rubber. However, they are weaker because it is not 100% cis-isomer.

Chemical structure of isoprene and natural rubber

Properties

The physical properties of isoprene rubber are generally similar to natural rubber. However, they are weaker and inferior compared to natural rubber. In terms of chemical structure, isoprene rubber, and natural rubber have almost the same. The big difference is that isoprene rubber does not contain proteins, fatty acids, and other natural rubber substances.

Isoprene rubber shows lower green strength, cure rates, hot tears, and aged properties than natural rubber. Isoprene rubber is superior to natural rubber in product consistency, cure rate, purity, and processing.

Isoprene rubber has more advantages than natural rubber when used in mixing, extrusion, molding, and calendaring.

Types

There are two types of isoprene rubber: (1) the solid and (2) the liquid.

Uses of the solid isoprene rubber 

1. Industries needing materials with low water swell, high gum tensile strength, good resilience, good tack, and high hot tensile make use of solid isoprene rubber.
2. Production of rubber bands, cut thread, baby bottle nipples, and extruded hose comes from gum compounds made from isoprene rubber. 
3. Tires, motor mounts, shock absorbers, bushings, pipe gaskets, and molded and mechanical goods make use of solid isoprene rubber.
4. Footwear, sponge, and sporting goods make use of isoprene rubber.
5. Products made from isoprene rubber serve as suitable replacements for natural rubber products causing allergies to users. Some of our IV sets are made of latex-free rubber.

Natural rubber 

Chemical structure

The elastic material taken from the latex sap of trees is called natural rubber. The trees from the Amazon, South East Asia, and Africa serve as sources of this latex sap. Once this is vulcanized, fabrication and production of several rubber products take place.

Natural rubber

The rubber molecules present in the latex sap consist of 5 carbon and eight hydrogen atoms. These rubber molecules are joined with each other producing a long, chain-like structure. This chain of rubber molecules is called the polymers that provide the elasticity of the rubber.

Properties

1. The natural rubber has a perfect combination of high strength (tensile and tear) and outstanding resistance to fatigue;
2. It possesses excellent green strength and tack, thus having the ability to stick to itself and other materials, making fabrication easier; 
3. It possesses moderate resistance to environmental damage by heat, light, and ozone; 
4. It has excellent adhesion to brass-plated steel cord, thus ideal for rubber tires;
5. It has low hysteresis causing low heat generation, extending and allowing retreading;
6. It has low rolling resistance, thus reducing fuel consumption; and
7. Resistance to cutting, chipping, and tearing is high.

Uses

1. Natural rubber serves as an excellent barrier to water.
2. It serves as the best barrier to disease-causing microorganisms, such as the AIDS virus. Thus, the production of condoms and surgical and medical examination gloves starts with the use of latex. 
3. It is an excellent spring material.
4. Catheters, balloons, medical tubes, elastic thread, and adhesives make use of latex. Our latex rubber bulb, the part of IV set, is made of natural rubber.
5. Rubberwood, used as charcoal for cooking, comes from natural rubber. 

Summary of differences