Neoprene elastomers

This paper considers Neoprene elastomers and their use as barriers to water penetration. Long time effects on permeability and composition will be discussed as will the effects on permeability of temperature and high-frequency mechanical (acoustic) agitation. 

Contact adhesive n. A liquid adhesive that dries to a film that is not sticky to other materials but very sticky to itself. A typical contact adhesive is a neoprene elastomer mixed with either an organic-solvent vehicle or an aqueous dispersion medium. The adhesive is applied to both surfaces to be joined and dried at least partly. When pressed together with light to moderate pressure a bond of high initial strength results. Some definitions of contact adhesive stipulate that, for satisfactory bonding, the surfaces to be joined shall be no further apart than about 0.1 mm. Skeist I (ed) (1990) Handbook of adhesives. Van Nostrand Reinhold, New York. 

Parel elastomer, natural rubber, and neoprene, compounded with standard recommended formulas for each, were heat aged in a 125 C. forced draft oven. Figure 3 is a plot of the change in tensile strength and hardness of the vulcanized Parel and neoprene elastomers. Neoprene maintained its properties for 3 days, but after a week at 125 C., it was quite hard and brittle. Results with natural rubber are not included in the figure because it failed so quickly at 125 C. It was seriously deteriorated in about 3 days at 100 C. 

Figure 3. Physical properties of Parel arid neoprene elastomers aged at 125 C...

Figures 5 and 6 compare the compression set of vulcanized Parel, natural rubber, and neoprene elastomers at 100 and 150 C., respectively. At 100 C., the compression set of Parel elastomer is within experimental error of that of natural rubber neoprene is clearly superior. When the compression set test was run for a long time at 150 C. (Figure 7), Parel elastomer was the best of these three rubbers. Natural rubber had 100% compression set...

G-type Neoprene elastomers that are made from the copolymerization of the chloroprene monomer with sulfur and usually stabilized with a thiuram disulfide. 

W-type Neoprene elastomers that contain no sulfur or thiuram disulfide and possess a narrower molecular weight distribution. 

T-type Neoprene elastomers that are very similar to the W-types except they also contain highly crosslinked gel, which functions as a processing aid. 

Neoprene elastomer was first synthesized in the 1930s and became the first synthetic elastomer to provide significant advantages over natural mbber. The monomer for neoprene is 2-chloro-l,3-butadiene and the polymer is prepared by emulsion polymerization. Being inherently a latex polymer may have been thought to provide commercial advantage over the solvent-based versions, but it was found that the tack properties and the ability of the adhesive to form a quick bond with itself... 

---