Rubber crops

In the original scenario, potential rubber crops were considered. Since then, it was decided to develop guayule (Parthenium argentatum) as a domestic source for natural rubber (1. The U.S. rubber market can potentially be supplied by guayule grown in the southwest. Thus, barring discovery of an... 

Uses Emulsifier, thickener, wetting agent, pigment dispersant, lubricant, solubilizer for cosmetic and industrial emulsions, emulsion polymerization, metal cleaning, monomer systems, floor waxes, paper finishes, rubber, crop protection applies. textile scouring agent emollient for pharmaceuticals Properties Liq. HLB 9.7 cloud pt. 0-5 pH 6.5 (1%) 100% act. 

Current production of NR is about 5.2 X 10 tonnes. For some years it has enjoyed a premium price over SBR because of its desirable characteristics described above and, compared with other large tonnage polymers, a somewhat restricted supply. Clearly it is difficult to substantially increase the production of such a material in a short period of time and indeed the attractions of other crops such as palm oil as well as the desire to move away from a monoculture economy mitigate against this. The indications are that, unless there is undue intervention of political factors, the future of natural rubber as a major elastomer remains secure. 

In the Far East, on the whole, the most troublesome hevea rubber diseases are root decays. It is commonly realized (4, 11, 35, 36, 40, 42, 43, 45) that, left unchecked, rubber root rots would have very soon destroyed commercial production of plantation rubber in the Orient. There is no tree crop that has had its many root rot diseases given such thorough study as has rubber. E. W. Brandes, R. D. Rands. Theodore J. Grant, E. P. Imle, and John B. Carpenter agreed that these troubles have been of practically no concern in tropical America. Langford (19) found little root rot trouble in his considerable observations specifically on rubber in the Western Hemisphere. 

Hevea rubber is undoubtedly one of the unique crops of history and of all agriculture, and one of the most interesting. It is not easy to produce rubber. Research is the tool by which it is possible to grow vast acreages of the tree as a profitable crop. This could never have been done without the past /and present intensive investigations of careful scientists over more than 30 years. Repeated reference in the literature indicates that diseases are the limiting factors in natural rubber production, and that planters owe a debt to disease-control workers. 

Bureau of Plant Industry, U. S. Department of Agriculture, and its successors. Special mention should be made of Theodore J. Grant and E. P. Imle, who, as directors of the regional rubber research station in Turrialba, have had much to do with the success of re-establishing rubber as a crop in the Western Hemisphere, and J. B. Carpenter, recently rubber pathologist at that station. Library facilities and reports of experimental work of the station were freely opened at all times. 

In the past 10 years, chemical weed killers have replaced the machete and the hoe to a large extent in the tropics, especially in sugar cane fields. More than any other chemical, 2,4-D and its derivatives are used. Herbicides could also be used profitably to a greater extent in crops such as pineapple, rubber, rice, coffee, pastures, and lawns. Methods and chemicals used in Puerto Rico are described and results are compared with other areas. 

The most economically important materials with respect to ozone damage are paint, elastomers (rubbers), and textile fiber-dye systems. Damage to polyethylene by ozone is considered to be negligible. The 1970 ozone damage to materials has been estimated as follows paint, 540 million elastomers, 569 million and textile fibers and dyes, 84 million—for a total of over 1 billion. Thus, the total combined material and crop damage falls between 1.5 and 2 billion per year. Estimates of damage to natural ecosystems are not available. 

Today both natural mbber, an agricultural crop, and synthetic elastomers are multi-billion dollar businesses. Looking back at Fig. 16.1, we see that Synthetic Rubber (NAICS 325212) totals 5.7 billion. It is a large area of polymer use and is 1% of Chemical Manufacturing. But in the related industry covering final end products called Plastics and Rubber Products... 

Hexachlorobutadiene is used as a chemical intermediate in the manufacture of rubber compounds (ERA 1982d). Lesser quantities of hexachlorobutadiene are used as a solvent, a fluid for gyroscopes, a heat transfer liquid, hydraulic fluid, and as a chemical intermediate in the production of chlorofluorocarbons and lubricants (ERA 1980 lARC 1979 Verschueren 1983). Small quantities are also used as a laboratory reagent (ERA 1982d). In the international market, Russia is reported to be one of the major users of hexachlorobutadiene, where it is used as a fumigant on grape crops. 

Ot and photo-oxidants Pulmonary oedema, emphysema, asthma, eye. nose, and throat irritation, reduced lung capacity. Vegetation damage, necrosis of leaves and pines, stunting of growth, photosynthesis inhibitor, probable cause of forest die-back, suspected cause of crop loss. Attack and destruction of natural rubber and polymers, textiles and materials. 

B) dl-Leucine.—To 1500 cc. of technical ammonium hydroxide (sp. gr. 0.90) in a 3-I. round-bottomed flask is added 300 g. (1.56 moles) of a-bromoisocaproic acid. A rubber stopper is wired in, and the flask is allowed to stand for a week at room temperature. The crude leucine from four such flasks is collected on a filter and washed with 400 cc. of alcohol. This crop amounts to about 300 g. The ammonia is removed from the filtrate by heating the solution in a 12-I. flask on a steam cone overnight. The solution is concentrated under reduced pressure until vigorous bumping occurs (about 2.5 1.). The mixture is then cooled to about 150 and filtered. The precipitate is washed with 250 cc. of cold water and 250 cc. of 95 per cent alcohol. The total yield of crude leucine in the two fractions is 440-460 g. 

This large family is cosmopolitan except for arctic areas, with centers of distribution in tropical America and Africa. It is of major economic importance as the source of rubber, tung and castor oils, a basic food crop (manihot, native to South America and introduced into Africa and southeast Asia), and familiar ornamentals (croton, poinsellia). 

NOTE Chlorine is widely used in the protection of drinking water, the manufacture of pharmaceuticals, crop pesticides, paper, rubbers, resins and plastics, and thousands of other products. Nevertheless, since the early 1990s, there has been a groundswell of opinion to either ban or severely limit the use of chlorine in all manners of processes. This is based on observations associated with the probable adverse effect to the environment from certain chlorinated organic chemicals, such as polychlorinated biphenyl (PCB) and the insecticide DDT. There is also concern in a number of other areas, for example, that free chlorine may contribute to effluent toxicity due to the formation of chloramines and trihalomethanes (THMs). In the United States in 1993 to 1994, this opinion was fueled by the possibility that the Environmental Protection Agency (EPA) would... 

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