Vulcanization, natural rubber

Fig. 85.—Force-temperature curves at constant length obtained by Anthony, Gaston, and Guth for natural rubber vulcanized with sulfur for elongations from 3 percent to 38 percent (at 20°C), as indicated.

These conclusions have been confirmed by Wood and Roth, who carried out measurements at both constant lengths and at constant elongations using natural rubber vulcanized with sulfur and an accelerator. Their results at constant elongation, to be considered later in connection with the thermodynamics of rubber elasticity at higher elongations, are summarized in Fig. 89. 

Similar results have been obtained for natural rubber vulcanized in like manner. Here also the observed equilibrium stress tends... 

Price,C., Allen,G., de Candia,F., Kirkham,M.C., Subramaniam,A. Stress-strain behavior of natural rubber vulcanized in the swollen state. Polymer (London) 11, 486-491 (1970). 

M 4. Meltzer, T. H., W. J. Dermody, and A. V. Tobolsky The fraction of effective sulfur crosslinking in high sulfur-natural rubber vulcanizers. J. Appl. Polymer Sci. 7, 1493 (1963). 

Polymer forming began with the chemical modification of natural polymers such as natural rubber vulcanization and cellulose acetylation. The first efforts to shape natural polymers and early synthetic ones into useful products such as textile fibers and films for packaging date from the middle of the 19 century. 

Figure 22. Proposed cross-linked structure of natural rubber vulcanized with dlcumyl peroxide.

FIGURE 3.1 Magnified portion of NMR spectrum of natural rubber vulcanized to half its maximum torque. The peak at 16 ppm arises due to cis-to-trans isomerization (Mori and Koenig, 1998). 

S/Ac in a natural rubber-like fashion. A difference here is that evidence for model monosulfidic crosslinks was lacking while model disulfldic crosslinks were more apparent than in the case of natural rubber vulcanization. 

FIG. 18-14. Dynamic bulk storage and loss compliances of natural rubber vulcanized by sulfur, reduced to 0°C and 1 atm pressure by equation 6 and plotted against logarithm of reduced frequency, var.p (McKinney, Belcher, and Marvin. )... 

Poly (vinyl acetate) Natural rubber vulcanized with 50° 1.59 0.41 0.30 0.19 38... 

If the quantity Afi can be interpreted as the compressibility of the free volume, it should be the same (after applying a correction to isothermal conditions) as /3/ = aj dT/dP)r, the free volume compressibility appearing in equation 59 of Chapter 11. In the investigations of Marvin and collaborators, this was found to be the case for natural rubber vulcanized with sulfur but not for poly(vinyl acetate), where (8/ was smaller than the isothermally corrected AB by nearly a factor of 2. The difference may be associated with the presence of side groups which are considerably bigger than the methyl group of natural rubber. 

Natural Rubber Vulcanized with DUT-Polyisocyanate Direct Bonding to Polyisocyanate-Treated Polyester Fabric. 

E. Southern Yes, we used natural rubber vulcanized in the usual way with sulphur but this does not make the natural rubber as polar as polychloroprene. The more polar nature of polychloroprene is easily demonstrated by its lower equilibrium swelling in non-polar hydrocarbons such as decane. 

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