General properties of neoprene rubber Part 2

by Dongrubber on December 16, 2010 · 0 comments

Formula and conditions of the polymerization (molecular weight regulator, polymerization initiator, and the varieties and dosage of emulsifier, conversion rate, the purity of chloroprene and polymerization temperature) as well as the separation process and the post-processing of polymer all have a great influence on molecular structure and properties of neoprene rubber, including molecular weight and molecular weight distribution.

Raw rubber molecular weight and its distribution is the important structure characteristics. Molecular weight distribution curve of neoprene rubber is generally similar to natural rubber. Sulfur adjusted neoprene rubber has similar molecular weight distribution curve to that of natural rubber after plastication, but the difference is the polymer has more different points. However, polymer molecular weight distribution is one of the most easily changing structure characteristics. Therefore, even if a raw rubber can have different molecular weight distribution curves and it reflect on the performance which brings obvious differences. Gel content also has very big effect.

The crystallization ability of raw rubber plays a important role on its storage and processing characters. Trans polychloroprene is an elastomer with quite fast crystallization rate. As a result, some manufacturers reflect that on the raw rubber goods brand.

Because the large chlorine atom on 1, 2 structural molecular side chains, it is easy to generate hydrogen chloride under the action of light, heat, and then makes the chain to become structured, make the storage stability of neoprene rubber not good. Type CR1211 neoprene rubber molecular chain contains a small amount of double sulfur and multi sulfur links, easily broken, and make the molecules produce cross links and metamorphism, neoprene rubber storage stability also change.

Neoprene rubber molecular structure is neat and easy to crystallization elongation, so pure neoprene vulcanized rubber has very high strength, same as natural rubber and far better than that of styrene butadiene rubber. Reinforcing carbon black is no help on the max strength of neoprene rubber, but can increase stretch stress, improve abrasion, tear strength and other performances.

Because of the chlorine atoms in the neoprene molecule chain, protects the double bond, decreases activity, therefore, neoprene rubber has good aging resistance, weather resistance and ozone resistance in particular. Due to the presence of chlorine atom, neoprene rubber also has good flameproof property. Polarity chlorine atoms make neoprene rubber good oil resistance and solvent resistance. Except strong oxidizing acid, it is almost not affected by corrosion, and therefore it has good resistance to chemicals.

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