Chloroprene vs. Natural Rubber

Natural rubber (NR), extracted from the latex of rubber trees, is a naturally occurring polymer. Its molecular composition is cis-1,4-polyisoprene, with numerous carbon-carbon double bonds and no other substituents. This naturally occurring structure provides excellent elasticity due to the double bonds, while the long linear chains ensure its flexibility.

Chloroprene (CR), on the other hand, is a synthetic rubber formed by the polymerization of chloroprene monomers. Its molecular composition is polychloroprene, which not only retains the carbon-carbon double bonds but also incorporates chlorine atoms as substituents. The strong electronegativity of chlorine atoms alters the polarity and chemical stability of the molecule, which is the key difference between CR and natural rubber.

In terms of aging resistance, natural rubber, due to the numerous carbon-carbon double bonds in its molecular chain, is easily oxidized by oxygen, ozone, and ultraviolet light, leading to aging, manifested by hardening, cracking, and a loss of elasticity. For example, natural rubber tubing exposed to sunlight can develop cracks within a few months.

Because chloroprene rubber contains chlorine atoms, the electron-withdrawing effect of chlorine reduces the electron cloud density of its double bonds, making it less susceptible to oxidation. Chlorine atoms also inhibit the reaction of ozone molecules with double bonds, resulting in far superior ozone, UV, and atmospheric aging resistance compared to natural rubber. For example, automotive weather strips made of chloroprene rubber can maintain their elasticity after 5-10 years of outdoor exposure, while natural rubber products may fail within three years.

In terms of oil and chemical resistance, according to the principle of "like dissolves like," natural rubber is a non-polar polymer with good compatibility with non-polar solvents such as mineral oil and gasoline. However, upon contact, it rapidly swells, softens, and loses its properties.

For example, a natural rubber oil seal may fail within a week after contact with motor oil. Because chloroprene rubber contains polar chlorine atoms, its molecules are highly polar, resulting in poor compatibility with non-polar oils (mineral oil and diesel). While it exhibits excellent resistance to non-polar oils, it exhibits poor tolerance to highly polar solvents such as acetone and esters.

Furthermore, the chlorine atoms in chloroprene rubber make it more stable against acids and alkalis, while the double bonds in natural rubber are easily corroded by acids and alkalis. Therefore, chloroprene rubber is more suitable for applications such as chemical pipe linings and acid- and alkali-resistant gloves.

In terms of elasticity and mechanical properties, the polyisoprene segments in natural rubber are extremely flexible, allowing the molecular chains to rotate freely. This results in excellent elasticity and resilience, with rebound reaching 80%-90% and elongation at break reaching 500%-800%.

This makes it suitable for applications requiring high elasticity, such as tire treads and sports equipment cushioning. Due to the steric hindrance of chlorine atoms, chloroprene rubber exhibits slightly less flexibility, resulting in slightly lower elasticity and resilience, with a rebound of approximately 60%-70%. However, the polarity of chlorine atoms enhances intermolecular forces, resulting in superior tensile strength, tear strength, and abrasion resistance.

The tensile strength can reach 25-35 MPa, compared to approximately 20-30 MPa for natural rubber, making it suitable for applications requiring high strength, such as conveyor belts and seals.

In terms of temperature resistance and environmental adaptability, natural rubber has a narrow operating temperature range, typically -60°C to 80°C. At low temperatures, its molecular chains become rigid and its elasticity decreases.

Above 80°C, it tends to soften, become sticky, and even decompose. Chloroprene, thanks to the stabilizing effect of chlorine atoms, has a wider temperature range of -40°C to 120°C (and can withstand 150°C for short periods), and its performance fluctuates less under alternating high and low temperature environments.

For example, engine compartment seals made of chloroprene rubber can withstand the high temperatures of engine operation, whereas natural rubber is susceptible to aging and failure in these environments.

In terms of processing and cost, natural rubber has mature processing technology, good fluidity during mixing, and easy-to-control vulcanization speed (sulfur vulcanization is commonly used). However, raw material costs fluctuate significantly, ranging from approximately $15,000 to $20,000 per ton, depending on production locations such as Southeast Asia.

Chloroprene processing requires temperature control to prevent the high-temperature decomposition of chlorine atoms to produce hydrogen chloride. Vulcanization typically uses metal oxides (zinc oxide + magnesium oxide), which is a somewhat complex process. As a synthetic rubber, its cost is influenced by oil prices, hovering around $25,000-35,000 per ton, consistently higher than natural rubber.

In terms of applications, natural rubber, thanks to its high elasticity and low cost, is primarily used in tire treads (accounting for over 70% of natural rubber consumption), tapes, hoses, balls, and more. Neoprene, relying on its aging, oil, and temperature resistance, is used in wire and cable sheathing (ozone resistance and leakage prevention), automotive sealing strips (weather resistance), diving suits (water and aging resistance), adhesives (chloroprene adhesives are strong and aging-resistant), and fire hoses (flame retardant, containing chlorine to inhibit combustion).