Neoprene latex

Neoprenes. Of the synthetic latices, a type that can be processed similarly to natural mbber latex and is adaptable to dipped product manufacture, is neoprene (polychloroprene). Neoprene latices exhibit poor initial wet gel strength, particularly in coagulant dipped work, but the end products can be made with high gum tensile strength, oil and aUphatic solvent resistance, good aging properties, and flame resistance. There are several types of neoprene latex, available at moderately high (ca 50 wt %) and medium soHds content. Differences in composition between the types include the polymer s microstmcture, eg, gel or sol, the type of stablizer, and the total soHds content (Table 22). 

Neoprene latex type Comonomer Emulsifiers Chlorine content, wt % pH at 25° C Standard soHds, wt % Distinguishing features Primary appHcations... 

Because the viscosity of neoprene latex at a given soHds content is less than that of natural mbber latex, thickeners are generally needed with the former. MethylceUulose and the water-soluble salts of poly(acryhc acid) are the two most commonly used thickeners. Natural and synthetic gums are also used. 

For natural or neoprene latex dipping, suitable coagulants are as foUow ... 

Neoprene latexes contain 0.5 to 0.02% residual chloroprene depending on the specific latex type. The amount of free alkaH in the water phase of latexes varies from 0.1 to 0.08% depending on type and age of the material. Eye protection and appropriate skin protection have been recommended for use in situations where splashes or spills are possible. Toxicity and safe handling practices have been recommended for Du Pont types (171). Since compositions may vary with other manufacturers, specific information should be obtained for other products. 

There is only one non-ionic latex Neoprene latex 115) all other polychloroprene latices are anionic and are emulsified with rosin soaps. 

Neoprene latex 115 contains a copolymer of chloroprene and methacrylic acid, stabilized with polyvinyl alcohol [15], With respect to other polychloroprene latices, this latex has two major advantages (1) excellent colloidal stability, which gives high resistance to shear and a broad tolerance to several materials ... 

Fig. 38. Effect of resin type in Neoprene latex 750 adhesives on canvas-to-canvas peel strength. Bonds aged 7 days at room temperature [14].

Because of their widespread use in the American workplace, butyl rubber, nitrile latex, neoprene latex, poly(vinyl alcohol), surgical rubber latex, and Viton elastomer were chosen for the present studies. The composite/bonded substances of this study were not in all cases presently available as commercial material for protective garments, but rather were chosen to determine their potential for resistance to solvent permeation. Likewise, Teflon gloves were included in these studies simply because they are commercially available. 

For the homogeneous, nonbonded materials evaluated in these studies (butyl rubber, neoprene latex, nitrile latex, polyethylene, polyvinyl alcohol), surgical rubber latex, and Viton elastomer), only the perlyVinyl alcohol) did not correlate well in this relationship. As has been shown in Fig. 6, most likely the polyethylene... 

Cotton, viscose, nylon, polypropylene, acrylic, polyester, or wool are generally used in carpets as the face or pile fabric over Neoprene latex. Carpets are usually flame retarded by back-coating with antimony-halogen system. The primary U.K. tests for carpet are BS 6307 198237 and BS 4790 1987,38... 

Neoprene, or polychloroprene, is a synthetic rubber discovered by the Du Pont Company in 1931. It is an organic polymer composed of carbon, hydrogen, and chlorine in the ratio of 55 5 40. Its relatively high chlorine content was responsible for the early recognized resistance of the polymer to burning. Practical use of this property was not developed until procedures for making foam structures from neoprene latex were developed in the 1940 s. The U.S. Navy adapted the material to make neoprene foam mattresses that reduced the fire hazards in the crews quarters of naval vessels. For many years neoprene has been the only material to meet Navy specifications for this application. 

Figure V-3 8 shows the attenuation measured (normalized by frequency, ra= 15 MHz) as a function of weight and volume fractions for suspensions of rutile (Ti02) (a), and neoprene latex (b) particles. As one can see, the linear relationship between a/at and the volume fraction,, for rutile dispersion holds up to only 10 %, and for latex particles up...

Fig. V-38. The experimentally measured attenuation to frequency ratio, a/o) (to= 15 MHz), as a function of weight and volume fractions of (a) - Ti02 (rutile), and (b) - neoprene latex suspensions in water. The frequency was kept constant at 15 MHz. Volume fractions, cf>, are shown by numbers over the data points. (From ref. [26], with permission)...

Neoprene is also available in a variety of forms. In addition to a neoprene latex that is similar to natural rubber latex, neoprene is produced in a "fluid" form as either a compounded latex dispersion or a solvent solution. Once these materials have solidified or cured, they have the same physical and chemical properties as the solid or cellular forms. 

A surprising absence of particle-particle interaction was observed wifli neoprene latex (15). This experiment showed that attenuation is a linear function of volume fractions up to 30% for fliis particular system (Fig. 1). This linearity is an indication diat each particle finction contributes to the total attenuation independently of other finctions, and is a superposition of individual contributions. Superposition works only when particle-particle interaction is insignificant. 

Figure 1 Dependence of attenuation in the neoprene latex at a frequency of 15 MHz) on the dispersed system weight fraction. Corresponding volume fractions in % are shown as the data points labels.

The ratio of the critical volume fractions depends on the frequency. For instance, for neoprene latex, the critical thermal volume fraction is 10 times higher than the critical viscous volume fraction for 1 Mhz and only three times higher for 100 Mhz. 

There have been many successful experiments that have characterized latex systems by using both acoustics and electroacoustics. For instance, Allegra and Hawley (10) measurd polystyrene latex. We measured Standard Dow latex which is also polystyrene in nature (see above). There is another successful application, this time with neoprene latex, which is described in Ref. 15. 

This low-density latex dispersion (Neoprene Latex 735A) is designed by DuPont as a wet-end additive to fibrous slurries. The fraction of the latex in the initial dispersion is 42.8% by weight (37.3% by volume). The pH value at 25°C is 11.5. The physical properties of the neoprene (slow crystallizing polychloroprene homopolymer) have been measured in die DuPont laboratories many years ago. 

A dilution test was performed on this latex by using distilled water with a pH adjusted to 11.5 with 1 N potassium hydroxide. The samples were prepared with various dispersed concentrations (1.4, 4, 6.6,13, 19.4, 25.6, 31.6, and 37.5 % by weight) by adding diluting solution to the initial neoprene latex. 

The experimental data collected by the acoustic method with the neoprene latex provided an opportunity to check the validity of the ECAH theory when thermal losses were the dominant mechanism of the sound attenuation (see Fig. 18). In order to calculate the theoretical attenuation spectra, information is required about the particle size, thermodynamic properties of the dispersed phase, and dispersion medium materials as well as partial intrinsic attenuations. Fortunately, all of the required parameters are available in this case. The approximate thermodynamic properties of the neoprene are known from the independent investigation performed by DuPont. 

Figure 19 Experimental and theoretical attenuation spectra for neoprene latex for the weight fractions indicated in the legends.

Uses Polychloroprene for mfg. of cellulose and asbestos paper, blending with other Neoprene latexes to improve wet-gel strength used for adhesives, bonded batts, coatings, saturants Properties Vise. 5 cps pH 11.5 45% solids 38.5% chlorine Neoprene Liq. Disp. 750 [DuPont DuPont Canada]... 

Chem. Descrip. Pentaerythritol ester of tall oil rosin CAS 8050-26-8 EINECS/ELINCS 232-479-9 Uses Tackifier for NR, SBR, IR, SBS, hot-melt adhesives, mastic adhesives, contact cements, and pressure-sensitive adhesives in emulsion form used in SBR, natural rubber, and neoprene latex adhesives food pkg, adhesives, coatings, paper, closures with sealing gaskets for food containers defoamer in food-contact paper/paperboard Features High-melting... 

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