War Fears Step Up Search For Plantation Rubber Substitutes
pp. 53-54 · Read in the full issue
Plantation Rubber Substitutes
Alternatives to plantation rubber, which was bringing less than 12 pence per pound about 18 months ago, but now has spiralled to over 6/ per pound, are already being sought in unorthodox places.
It has been reported from America re cently that a successful process for extracting natural rubber from the goldenrod plant, apparently indigenous to North America, has been developed. Ex periments were first made during World War 11, but more recent efforts by the US Department of Agriculture have im proved on former processes until it is now on the possible list —but for emer gencies only.
It is stated that tests of goldenrod rub ber made in pilot-plant operations revealed that it gave good performance in manufactured articles, such as hot water bottles, rubber heels for shoes, bicycle tyres, and power-transmission belts. Bicycle tyres made of goldenrod rubber gave three times as much mileage as did standard wartime bicycle tyres and nearly twice as much mileage as natural rubber tyres of pre-war make.
Goldenrod rubber also proved satis factory for blending with or substituting for either synthetic or other natural rubbers, including Hevea (plantation) rubber.
The first step in the process developed by the Department of Agriculture is to extract the unwanted resinous material from ground goldenrod leaves with the solvent acetone. The leaves are treated with another solvent, benzol, to dissolve the rubber, which is then precipitated
from the benzol-rubber mixture with acetone.
A simple treatment of the goldenrod leaves before solvent extraction—using an active bacterial culture from sewage sludge—permits more complete extraction of better quality rubber in about one third to one-fourth less time than is re quired for untreated leaves, When the rubber has been obtained it is given a unique pre-curing step—the key to successful goldenrod rubber nro duction. In this step, called “solution compounding,” the rubber is redissolved in benzol, and certain benzol-soluble chemicals are added. The resulting mix ture is heated to boiling point, stirred in a steam-heated mixer until the benzol is completely distilled, then heated again before cooling.
This “pre-curing” step is essential to producing a tough rubber from goldenrod suitable for use in manufactured products If not pre-cured, the rubber is sticky and soft, almost fluid when heated, and is satisfactory only as a blending agent, Although developed specifically for goldenrod, this process is showing possi bilities for use with other rubber-bearing plants grown in the United States, the Department of Agriculture reports. Some of its features have already proved useful in the extraction of guayule rubber.
Washington also reports “slow but significant progress” being made towards profitable production of natural rubber in the United States, and the time is fore seen when rubber will be produced on the dry mesas of south-west United States at a cost below the current market price.
The Department of Agriculture dis closed that new high-yielding strains have been obtained from the rubber plant guayule, a shrub that grows on the dry tablelands of Mexico and Texas. These new strains will produce about 1,200 pounds of rubber per acre in five grow ing seasons. (Continued Next Page.)
The guayule is one of the methods used by the US Government to produce rubber during World War 11. After the war, the project was abandoned because it was too costly, except for emergency use.