Neoprene was first invented in the 1930s by Dupont Chemicals, USA, as a synthetic rubber made by the polymerization of chloroprene. The original process involved oil which was used along with other petroleum based chemicals to produce the chlororprene rubber chips for the first stage of neoprene production.
The 1960s saw a new type of neoprene pioneered by Japan's Yamamoto Corporation. Instead of traditional oil-based neoprene, Yamamoto developed special technology to convert the calcium carbonate from limestone into chloroprene rubber chips, producing limestone neoprene.
Limestone, the good stuff
Limestone makes up about 10% of the total volume of all sedimentary rocks. It has numerous uses: as a building material, as aggregate for the base of roads, as white pigment or filler in products such as toothpaste or paints and as a chemical feedstock.
As a key part of construction, limestone and lime has been used for thousands of years. Archeological discoveries in Turkey indicate lime was used as a mortar as far back as 7,000 years ago. Ancient Egyptian civilization used lime to make plaster and mortar. In the United States, lime use has changed dramatically. In 1900, more than 80% of the lime used in the U.S. was for construction uses. Today, nearly 90% is used for chemical and industrial uses.
It was Yamamoto Corporation from Osaka, Japan that first developed neoprene from limestone—and with no oil at all—thanks to an abundance of pure limestone close by in the mountains of Japan (their reserve of limestone is estimated to be sufficient for the next 3,000 years). Yamamoto has set the standard for quality and innovation in the neoprene industry with their advanced manufacturing techniques, leading to the creation of a limestone neoprene that has a completely independent cell structure and multi-directional stretch capacity.
The calcium carbonate, found in the limestone, is used as the base with chloroprene by a process of polymerization to produce limestone based-chloroprene rubber chips. This is the first of four stages that form the basic process of converting limestone to neoprene [read the next chapter on how this is done].
What are the advantages of limestone neoprene?
Limestone neoprene has a high micro-cell structure. These are independent closed cells (bubbles basically) within the neoprene that are packed together at an extremely high density. Oil-based neoprene has a cell penetration of 60-70%, whereas limestone neoprene has a 94% cell penetration. What this means in simple terms is that limestone neoprene has a lot more air bubbles inside the rubber than other brands (over 30% to be exact), and is way less dense than oil-based neoprene.
Because of this micro-cell structure, limestone neoprene provides several serious distinct advantages to the functionality of wetsuits compared to the traditional oil-based neoprene:
It is impermeable
It is lighter in weight
It is warmer
- It is more durable
- It is stretchy
The more air neoprene has inside it, the less water can soak into it. Each individual closed-cell in limestone neoprene is filled with nitrogen gas. Because these cells do not absorb water, the neoprene itself has low water penetration. Less water absorption also means limestone neoprene dries very quickly.
Because of it's lower cell penetration and its liquid base, traditional oil-based rubber has less air and more rubber in the neoprene, making it easier for water to penetrate into it (to soak up water). In short, wetsuits made from limestone neoprene don't absorb as much water as other wetsuits.
Because the nitrogen closed-cells prevent water absorption, limestone neoprene is considerably lighter than oil-based neoprene. The weight of the limestone neoprene remains almost the same wet or dry—it does not soak up water during use, unlike oil-based wetsuits that come out of the surf weighing heavier than when you changed into it.
It is warmer
The nitrogen gas enclosed in all the individual closed-cells makes limestone neoprene super warm, thanks to its excellent thermal insulation. The nitrogen closed-cells are a better insulator than air, which allows for exceptional heat retention and efficiency.
The best thing about the nitrogen cells in limestone neoprene is that you can wear a thinner wetsuit than you normally would without sacrificing warmth. As so much of our Feedback confirms, limestone 2mm is just as warm as 3mm of traditional rubber.
It is more durable
The uniform micro-cell structure in limestone neoprene means if any part of the neoprene's surface is defaced or scarred, new independent concave micro-cells are exposed insuring continuous functionality.
In plain English, limestone neoprene tears less because of the structure of its independent cells. In traditional, oil-based wetsuits cells are more connected with each other, so a tear is likely to cause more damage that limestone neoprene with lots of stand-alone cells.
Limestone neoprene is also designed to disperse stretch, elongation, pressure and compression, ensuring a lightweight material with great strength and longevity [there's more on this in the next chapter]
It is stretchy
While oil-based rubber can be made to feel super soft, it often stretches after a few seasons and ends up being a size or two larger than when you purchased it. Limestone neoprene has what is called 'cell memory'—meaning it molds to your body shape and doesn't get loose over time.
Limestone neoprene also has an elongation of 480-580%. Compare that to the elongation of the human skin under the arm, which is 60-70%. This gives limestone neoprene amazing elasticity, memory, and multi-directional stretch capacity.
What are the problems associated with inferior-quality neoprene?
The advantages of limestone neoprene are many, but it's worth quickly noting the problems associated with inferior-quality neoprene:
- Delamination: blisters between the nylon and rubber which deteriorates quickly
- Compression: neoprene 'cave-ins', especially around the knee/elbow areas
- No memory: does not return memory (hold its shape) and the fit gives out over time
- Splits: neoprene splits unnecessarily within the nylon layers
These are just some of the reasons why Seventhwave only uses Yamamoto neoprene in all of its products.