When you look at a specification sheet for neoprene, hardness, density, and other properties of neoprene rubber matter a lot. Every application that utilizes neoprene rubber is unique in its own way; thus, every application involving neoprene, or polychloroprene rubber, demands a certain set of neoprene properties which you should be aware of when you buy neoprene for your project. First off, a product’s critical tolerance is the range of measurements that are acceptable for the product to remain operable. Products with narrow critical tolerances, like seals and gaskets, require a precise combination of compressibility, temperature range, and chemical resistance. On the other hand, applications with wider critical tolerances, like laptop sleeves, just need a tough and elastic neoprene fabric material. Though, please note that we at Rubber-Cal do not offer neoprene fabric: when it comes to neoprene, we specialize in solid neoprene and neoprene foam rubber. In this article, we will answer some important questions about neoprene. These guiding questions serve as signposts on our way toward a deeper understanding of the material. Product highlights such as neoprene hardness, neoprene density, and neoprene heat-resistance can seem more obfuscating than clarifying when left unexplained. The questions we answer in this article include the following:

• Does neoprene harden over time?
• How is neoprene rubber prepared?
• What is calendering process in neoprene rubber?
• How is neoprene foam rubber made?
• What is so special about neoprene?

Does Neoprene Harden Over Time?

In a stable environment, neoprene does not harden over time. (But, note that in extremely cold temperatures, neoprene does tend to crystallize, thereby becoming harder.) Neoprene hardness, or neoprene durometer, is established during its production phase. When neoprene manufacturers produce neoprene products, they determine the neoprene material’s blend, durometer, elasticity, and structure before these products are made. Once it is made, neoprene properties are set. Similarly, once you purchase neoprene, expect that its characteristics are—for the most part—unalterable. Thus, choosing the right neoprene product for your project is vital. You certainly do not want to find out after having bought, say, an open-cell neoprene sponge rubber sheet that you actually needed a closed-cell neoprene foam rubber sheet. These subtle distinctions become obvious differences with a small amount of background knowledge. Thus, with a little bit of research, you can avoid these nightmare situations in which some buyers find themselves after having made their purchases. To help you make the right choice, let us explore how the characteristics of neoprene—including the durometer, structure, elasticity, and density of neoprene rubber—are determined in the process of manufacturing neoprene. Both forms of neoprene, dense neoprene and sponge-like cell-neoprene, share the same initial processes, but they each undergo their unique finishing methods to assume their respective forms.

How Is Neoprene Rubber Prepared?

Neoprene rubber is prepared through chemical process wherein molecules of chloroprene (CR) are polymerized. Essentially, polymerization is the chemical bonding of multiple, relatively small molecules; these molecules are also known as monomers. Mono- is a term of Greek origin that denotes ‘singular or one’, and poly- is a prefix that means ‘many’ in Greek. Hence, polymers are composed of multiple monomers. When manufacturers (neoprene) polymerize chloroprene, they produce polymers of chloroprene, and the polymer of chloroprene is known as polychloroprene (‘many-chloroprenes’). Processing the dense sheet neoprene begins when the ingredients are mixed in an industrial-sized mixer. Polychloroprene, the basic constituent of neoprene, is mixed with bulking, pigmenting, and adhesive agents. This step is mainly what shapes neoprene hardness. Although the mixture is primarily composed of polychloroprene, the mixture’s quantity of other substances, such as sulfur, determine the final product’s level of neoprene hardness. When the batch is fully mixed, the neoprene solution is dried. When the mixture dries, it solidifies into crumbs. These pieces of neoprene are then pressed together into bales. By this point, the unfinished neoprene is ready for calendering.

What Is Calendering Process in Neoprene Rubber?

In the production of neoprene sheeting, calendering is the process in which pressed bales of neoprene bits are entered through a series of paired, heated rollers. When sequenced, a group of these rollers is known as calenders. Through the intense heat and pressure generated by the calenders, the bits of neoprene within the bales further amalgamate, cohering into a seamless sheet of smooth neoprene. This stage of the neoprene production process determines certain characteristics, such as neoprene thickness sizes. The further apart the pairs of heated rollers are from each other, the thicker the neoprene roll will be. Calendering is also integral to the production of paper. Similar to how a mixture of neoprene bits is pressed into sheets, motleys of bleached wood fibers are pressed into sheets of paper through calendering. For our purposes, the manufacturing process essentially stops here, and we are left with a thick neoprene sheet or a thin neoprene sheet, depending on the design of the calenders. While neoprene manufacturers employ further steps to produce their final products, most of the object’s qualities, such as neoprene rubber hardness, neoprene density, and neoprene temperature rating, are established by now.

How Is Neoprene Foam Rubber Made?

Nonetheless, you may wonder: how is neoprene foam rubber made? The spongy yet elastic neoprene form—like the other form of neoprene—begins in a large vat. As the polychloroprene rubber mixture is formed, manufacturers add a foaming agent to the mixture. The addition of this agent is not a step present in the creation of a dense sheet of neoprene. But it is crucial to the creation of neoprene sponge. After the foaming agent is added to the neoprene solution, the mixture is then heated in an oven. Catalyzed by heat, the foaming agent and the polychloroprene polymer react to produce nitrogen gas. Nitrogen is slightly lighter than oxygen, and its chemical inertness and wide temperature-range make it the ideal material for foaming neoprene. Much like how neoprene hardness is manipulable during the mixing phase of neoprene production, the density of neoprene rubber foam can vary depending on which substances are added to its mixture, as well as their quantities.

What Is So Special About Neoprene?

Considering everything that has been said, you might question: What is so special about neoprene? In short, neoprene is special because of its unparalleled versatility. Neoprene is a wondrous material. The list of neoprene applications is incredibly long—so much so that it could fill a book! And the rubber industry continues to find new ways to augment, enhance, and apply this neoprene material. Neoprene is known for its ability to perform most functions well. While it does excel in some applications—such as in the production of a neoprene seal material, a neoprene rubber lining, neoprene pads for construction, and a neoprene rubber edge trim—it is, for the most part, a general-purpose rubber.