Abstract
To summarize the principal results of the present investigation, it was found that whereas natural rubber is a poor raw material for the manufacture of semiebonite, butadiene-styrene and butadiene-acrylonitrile rubbers are suitable raw materials, especially in combination with unsaturated hydrocarbon extenders of the Naftolen type. The superiority of GR-S to natural rubber in the form of semiebonite should be an interesting piece of information for every compounder conscientious about the importance of keeping up the use and the manufacture of GR-S. With natural rubber becoming more and more available, there exists, as we all know, the definite danger that GR-S will be pushed into the background. As a matter of fact, we are approaching the situation where the supply of rubber hydrocarbons, natural and synthetic, will exceed the demand by multiples if new uses for rubber in large volume are not found. The increased use of rubber products in the building and construction industry and in road surfacing might provide such an outlet for rubber. Semiebonite with good aging qualities might find many uses along these lines. It might lend itself to the manufacture of floor coverings, of waterproof wall insulation, etc. The possibilities of using semiebonites from GR-S for tire beads has been suggested in a previously published article, but no detailed study comparing various rubbers has been reported. The primary purpose of this report is to present these basic data, which can be used as starting points for compound development and to point out that we have in the semiebonite range a possibility of using GR-S to advantage. As to butadiene-acrylonitrile rubbers, with which, in distinction to GR-S, very useful semihard rubber products can be made with phenolic resins, the medium sulfur range opens the possibility of making semiebonites which are easier to process and cheaper than resin combinations. The use of plastics in the rubber industry was recently discussed and summarized by Winkelmann. The compounding of semiebonites with Naftolen-type products offers a means of regulating the plasticity of the uncured stock as well as the elongation of the vulcanizate. Aging and prevention of sulfur bloom appear also improved. In other words, it was found that the combined use of 15 to 20 parts of sulfur with 15 to 50 parts of a Naftolen-type hydrocarbon gives a satisfactory semiebonite with GR-S, as well as with Hycar, and both these rubbers appear superior to natural rubber in semiebonites.
Biomass Production and Nutrient Accumulation by Natural Rubber (Hevea brasiliensis Wild. Ex A. Juss.) Müell. Arg. Clones in a Humid Tropical Area in South India
