What is Neoprene?

Neoprene, also known as chloroprene, is a synthetic rubber that is produced under the DuPont trade name CR. To create neoprene rubber, chloroprene molecules undergo polymerization, which involves linking single molecules together to form multiple-unit molecules. The resulting polychloroprene chips are then melted and combined with foaming agents and carbon pigments.

Polychloroprene rubber exhibits excellent mechanical properties and fatigue resistance, ranking second only to natural rubber. In addition, Neoprene rubber boasts superior resistance to oil, chemicals, and heat. Due to these characteristics, both Polychloroprene rubber is commonly utilized in various general engineering applications.

Neoprene Rubber Properties

• Polychloroprene rubber has good mechanical strength.
• It is high ozone and weather resistance.
• Neoprene also has good aging resistance.
• It has low flammability as one of its properties.
• It has good chemicals resistance.
• Polychloroprene rubber is moderately oil and fuel resistant.
• Neoprene rubber properties include its capability of adhesion to many substrates.
• Polychloroprene or neoprene rubber can be vulcanized by using various accelerator systems over a varied temperature range.
• It is less resistant than natural rubber to low temperature stiffening. This helps in giving improved low temperature resistance.
• Polychloroprene rubber can also be used easily with mineral oils, greases, dilute acids and alkalis.

Crystallization

One important characteristic of stereoregular polymers is their ability to form crystals. Polymers such as natural rubber or chloroprene rubber become rigid because of the creation of tiny crystal formations. The rate of crystallization is affected by the regularity of the polymer chain, with more regular chains leading to a higher inclination for macromolecule orientation and faster crystallization rates.

The hardness that results from crystallization is completely reversible, and applying heat or dynamic stress can eliminate it. The hardening that occurs due to crystallization is not linked to the hardening that takes place when a product transitions to a glassy state. At temperatures below the glass transition point, all polymers exhibit significantly increased moduli.

The tendency of polymers to crystallize can be altered by controlling the production process. Therefore, rubber products made from Baypren®, which have a low tendency to crystallize, remain nearly unchanged in hardness due to crystallization, even after prolonged exposure to low temperatures. In contrast, polymers with a strong inclination to crystallize will exhibit increased hardness after only a brief period.

Modified Neoprene Rubber

The properties of Neoprene rubber are influenced by the type of modification of the raw polymer.

Effect of pre-crosslinking:

• Decrease in the elastic rebound (bounciness) of the raw rubber and uncured compound
• Reduction in die swell
• Enhancement in calendering performance
• Improvement in the surface smoothness of injection-molded and extruded products
• Improvement in the dimensional stability of uncured profiles.

Effect of sulfur modification:

• Eases rubber mastication, allowing for soft compounds with good bonding ability
• Only requires magnesium oxide and zinc oxide for vulcanization
• Better tear resistance than regular grades
• Improved adhesion to fabrics compared to standard grades
• Enhanced dynamic properties.

Effect of xanthogen disulfide (XD) modification:

• Lower elasticity (less rigidity) which results in easier processing (calendering or extrusion)
• Better mechanical properties compared to standard grades with the same formulation
• Possible to use higher filler loadings.

Neoprene Rubber Characteristics