Neoprene rubber - CR rubber - definition, types, properties, applications

What is neoprene rubber?

Neoprene rubber is a specific type of rubber that consists of polymers of carbon, hydrogen and chlorine. These polymers crosslink during the vulcanization process, giving the rubber resistance to temperature, oil, water and solvents, as well as chemical stability. Neoprene rubber is also known as polychloroprene.

Neoprene is sold as solid rubber or latex. It is used in a variety of commercial industries (you will read more about this later in this article).

Is neoprene the same as rubber?

We could say that neoprene is the same as rubber. However, we should point out that natural rubber is made from the sap of the rubber tree, whereas neoprene is the fruit of chemical processes. Therefore, we are talking about synthetic rubber here.

Is neoprene a synthetic rubber?

Yes, neoprene is a synthetic rubber.

What does CR stand for?

CR stands for "chloroprene rubber".

How is neoprene rubber produced?

Neoprene rubber is produced by the free-radical polymerization of chloroprene.

In commercial production, the polymer is prepared by free-radical emulsion polymerization. The polymerization is initiated using potassium persulfate. Bifunctional nucleophiles, metal oxides (e.g., zinc oxide) and thioureas are used to crosslink individual strands of the polymer.

What are the types of neoprene rubber?

There are two main types of neoprene rubber:

• sponge,
• solid.

They are also divided into several sub-categories which you will read more about below.

Neoprene sponge

Neoprene sponge is an overarching name used to describe two different products. This type of rubber can be both open and closed cell foam.

While the former variety is softer, the latter is characterised by greater stiffness and strength.

Open-cell neoprene sponge

In the open-cell variant, air bubbles burst during the whipping or foaming process. This creates a solid network of particles that are interconnected, giving the product a softer texture.

Open-cell neoprene sponge has a higher degree of compression. This means that if significant pressure is exerted on a sheet of material, the rubber will return to its original shape more quickly than other elastomers (and especially their closed-cell counterparts).

Closed-cell neoprene sponge

In contrast to the open-cell variety, in this case the air bubbles do not burst during the formation of the neoprene sponge. The result is a material with fewer internal pores, i.e. a much more flexible and stronger rubber.

Solid neoprene rubber

Neoprene sponge is extremely popular and very useful, but it is not as durable as solid neoprene rubber. This is because the other material is designed to withstand much harsher physical conditions.

Over time, the physical structure of neoprene sponge degrades and weakens, causing it to lose its flexibility. Solid neoprene rubber, on the other hand, is characterised by its exceptional resistance to ageing. As with most other types of neoprene, solid rubber can be divided into two categories:

• hard,
• soft.

It is interesting to note that both have similar properties, such as excellent performance in outdoor weather and chemical environments.

The differentiating factor between hard and soft neoprene rubber is durability.

The hard will withstand much more physical abuse than the softer form. In addition, hard neoprene sheets weigh more and are denser. Soft sheets, on the other hand, have better resistance to fatigue from bending and are more flexible.

What are the properties of neoprene rubber?

The main properties of neoprene rubber are chemical resistance and excellent physical strength.

The material has high resistance to ozone, sunlight, oxidation, atmospheric conditions, oils, petrol, lubricants, solvents, petroleum oils, animal and vegetable oils, silicone oil, refrigerants, ammonia and carbon dioxide, water and steam.

Furthermore, unlike many polymers, neoprene resists swelling when exposed to hydrocarbon oils due to the presence of chlorine in its molecular structure. And its strong water resistance makes CR rubber popular for many water-related applications.

Neoprene also has very good flame resistance and is one of the few self-extinguishing rubbers. In addition, it has good physical properties, including a tensile range of 500 to 3,000 PSI and a maximum elongation of up to 600%.

Unfortunately, neoprene is relatively expensive. Several other materials have similar properties at a lower price. However, most do not offer such a large range of capabilities.

The biggest disadvantage of CR rubber is its poor resistance to strong oxidising acids, esters, ketones and some hydrocarbons. In addition, other rubbers offer better resistance to oils. Finally, it is worth adding that Neoprene can absorb water over time, making it not recommended as an electrical insulator.

What is so special about neoprene?

Neoprene is so special because of its unique combination of properties It features degradation and weather resistance, chemical resistance, a wide range of operating temperatures, physical strength, fire resistance, water resistance and insulating properties, as well as flexibility and suppleness.

How durable is neoprene rubber?

Neoprene rubber is very durable. By this we mean tensile, elongation, compression and abrasion resistance, as well as resilience or rebound properties. However, take into account that the exact properties of neoprene rubber may vary depending on the grade or quality of the material.

Does neoprene absorb water?

In general, neoprene does not absorb water and is classified as a waterproof material. The amount of air in the rubber structure determines how much water can penetrate it. Open-cell neoprene is breathable but less waterproof than closed-cell neoprene. Sheets of solid neoprene rubber are more resistant to water and do not absorb moisture. However, prolonged exposure to water can cause it to begin to penetrate the material.

What is the temperature range of neoprene rubber?

The temperature range of neoprene rubber ranges from -40°C to 110°C (briefly even 130°C).

However, its worth noting here that neoprene rubber crystallises when stored at temperatures below 0°C, which irreversibly increases its stiffness.

What are the applications of neoprene rubber?

Applications for neoprene rubber include many demanding use cases such as seals, rubber hoses and corrosion-resistant coatings. It can also be used as a glue base, acoustic insulation in power transformer installations and as a liner in external metal enclosures to protect the contents while allowing an accurate fit.

As neoprene is more resistant to combustion than purely hydrocarbon-based rubbers, it appears in fire door seals and in combat clothing such as gloves and face masks.

However, these are not all the applications for neoprene rubber. It also finds use cases in:

• Civil engineering (e.g. as a component of elastomeric bridge bearings); 
• Water sports (e.g. divers' wetsuits are made from neoprene);
• Home accessories (e.g. laptop sleeves, tablet holders, remote controls);
• Music (e.g. in speaker membranes or piano hammers);
• Hydroponic gardening (e.g. neoprene plant liners); 
• Other (e.g. clothing, board game mats, roof membranes, etc.).

What is neoprene rubber used for?

Neoprene rubber is used for a wide range of applications, such as gaskets, O-rings, seals, tubing, automotive parts, water sports and diving suits, medical orthoses, personal protective equipment, exercise equipment, construction applications.

What are the trade names of neoprene rubber?

The most common trade names for neoprene rubber are:

• Baypren, 
• Neoprene,
• Chloroprene bottoms, 
• Skyprene, 
• Butachlor.

Many manufacturers also use the terms CR rubber or chloroprene rubber.

Who invented neoprene rubber?

Neoprene rubber was invented by Julius Arthur Nieuwland. Nieuwland was a professor at the University of Notre Dame and a priest of the Congregation of Holy Cross. He was born to Flemish parents in Hansbeke, Belgium, and later emigrated with his family to South Bend, Indiana.

He graduated from Notre Dame in 1899, studied for the priesthood and was ordained in 1903, and received his doctorate from the Catholic University in 1904.

He taught botany at Notre Dame and became a professor of organic chemistry in 1918. His discovery of the reaction between acetylene and arsenic trichloride led to the development of the poisonous gas lewisite.

His work with acetylene also led him to work with scientists at DuPont. He discovered that if monovinyleacetylene was treated with hydrogen chloride and the resulting chloroprene polymerised, neoprene would be formed.

Eventually, neoprene was first introduced to the market in 1932 by DuPont under the name Duprene.

What are the disadvantages of neoprene?

Disadvantages of neoprene include its cost, environmental impact, poor resistance to some chemicals, and inferior resistance to oil (compared to other rubbers).

Why is neoprene so expensive?

Neoprene is so expensive because it offers increased durability, temperature resistance and material resistance. The manufacturing process and high strength add to the cost of any project in which it is used. However, in return you get a rubber that can easily handle extreme conditions.