Natural rubber latex state

A test which is claimed to be a more reliable guide to the condition of a natural rubber latex than the KOH number. The test is performed by steam distillation of the latex and titration of the distillate with standard alkali solution. The VFA number is a measure of the state of degradation of the latex. 

The effect of particle size and spinning of the NMR tube were studied for the latex state 13C-NMR of natural rubber latex fractionated by particle size [134], High-resolution spectrum was obtained by measurement without sample spinning. The diffusion constant of Brownian motion was found to be a dominant factor governing the intensity and halfwidth of the signals. As the particle size decreased and temperature of measurement was raised, the intensity of signals increased and was comparable to the theoretical value, which was observed by the addition of triethylene glycol as an internal standard. 

The earliest of these applications was natural rubber latex bonded paper. This was patented in En and in 1926 and commercially developed in the United States before 1930 to produce products which eSectively replaced leather in applications such as shoe insoles and roidsoles. Latex was... 

Allergy to natural rubber latex, first reported in 1989 in the United States, is a common cause of occupational allergy for health care workers. Natural rubber is a processed plant product from the commercial rubber tree, Hevea brasiliensis. Latex allergens are proteins found in both raw latex and the extracts used in finished rubber products. Latex gloves are the largest single source of exposure to the protein allergens. ... 

In some cases bonding is carried out with the adhesive in a part dried condition, as natural rubber latex films combine very easily in this state. Further reduction in water content at the combination stage may be allowed if small quantities of a tackifying resin are added. 

It seems probable that when governmental subsidies are relaxed in the United States and certain other countries where synthetics are produced on emergency funds, natural rubber will be in a fairer position relative to synthetics, and latex rubber may increase its popular lead. In 1952 the world consumed 1,860,000 long tons of latex rubber, and in 1953 about 80,000 more than this. The Far East still produces over 90% of the natural rubber of the world, and nearly half of that percentage comes from Malaya. Africa ships about 3%, and Latin America about 2%. 

Until 1920, the only flexible foam available was the natural sponge, but chemically foamed rubber and mechanically foamed rubber latex were introduced before World War II. These foams may consist of discrete unit cells (unicellular, closed cell), or they may be composed of interconnecting cells (multicellular, open cells) depending on the viscosity of the system at the time the blowing agent is introduced. Over 1.5 million tons of foamed plastic is produced annually in the United States. 

We will now apply to natural rubber, i.e., NR, biosynthesis what we have learned so far. As mentioned before, in 2005 approximately 10 million tons of NR was produced worldwide for commercial use, from which about 15% was consumed in the United States. While the United States is self-sufficient in S5mthetic mbber production, with substantial export activities, no NR is produced domestically. The development of a U.S.-based supply of NR is recognized in the Critical Agricultural Materials Act of 1984 (Laws 95-592 and 98-284). The Act recognizes that NR latex is a commodity of vital importance to the economy and the defense of the nation. It is important to emphasize that synthetic polyisoprene does not match the performance of imported Hevea NR in several applications, so NR remains irreplaceable. 

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