Rubber & latexes Flashcards
What plant family is know for producing latex?
The “spurge” family, Euphorbiaceae.
What kinds of cells are responsible for producing latex? What kind of plant molecule is latex?
Lactifiers produce the latex, which is a secondary metabolite.
In which category of plants are lactifiers mostly found?
Flowering plants (dicots).
What parts of the plant can contain lactifiers for latex production? What is the purpose of latex for the plant?
Can be produced in many structures (bark, seeds, stem, fruit, etc.) and has a defensive function (acts as an irritant).
What molecular structure gives rubber its flexibility? How many isoprene units can this be composed of?
The long, unbranched terpene polymer chain made from up to 6000 isoprene units.
How many species of plants contain rubber? Where are they mostly distributed?
> 2000 species of tropical plants.
Where was rubber likely first used by humans? When did the Europeans discover it?
In tropical America, with the early Aztec and Mayan civilizations. Spanish conquistadors first observed its use in the 1500s.
What is an example of a use for rubber by the ancient Aztecs? How did they modify the rubber to make it usable?
Aztecs used it as a ball for a high-stakes game. Added morning glory juice to maintain bounce and prevent the rubber from becoming brittle.
How did the Amazonians use rubber? How did they mix it with other compounds? At what ratio? What else was required for this process?
Amazonians made custom rubber shoes by mixing rubber with morning glory juice at a 1:3 juice:latex ratio (required heating).
What was the purpose of coagulating rubber by heat?
Made the rubber coating waterproof.
Who was the first to dissolve rubber in solvent? When? What was this product used for?
Charles Macintosh (1823) used it to make a waterproof coating that could be applied to fabrics, etc.
What was a significant disadvantage of using solvent-dissolved rubber as a waterproof coating?
It cracked in the cold and became sticky in heat.
Who solved the problem of rubber coating not withstanding temperature fluctuations? When? By what process?
Charles Goodyear (1839) developed vulcanization, which involves adding sulfur while heating, causing many isoprene cross-links to form.
What mechanism does vulcanization of rubber enable that was employed unknowingly by the Aztecs?
The Aztecs added morning glory juice which contains sulfur, a critical step in the vulcanization of rubber.
What are some examples of products which make use of the waterproof and elastic characteristics of rubber?
Boots, gloves, electric wire coating, hose, drive belts, tires, etc.
What is the most common use for rubber today? How much of the world’s rubber consumption does this industry account for?
2/3 of the world’s rubber use to make tires.
When did rubber stop getting harvested from the wild? What species was the main producer of wild rubber?
Harvested wild until 1880, 89% came from Hevea brasiliensis in Amazonian basin (spurge family).
How was latex harvested from Hevea brasiliensis in the wild?
Tapped from spiral cuts in the bark to take advantage of the abundant lactifiers in the inner bark.
Who first smuggled rubber seeds out of Brazil, breaking the monopoly? When? Whose payroll was he on?
The Royal Botanical Gardens paid for Sir Henry Wickam to smuggle the seeds out of Brazil in 1876.
Where was rubber production introduced to once the Amazonian monopoly had been broken?
British, French, and Dutch colonies in SE Asia.
How many rubber trees were there in SE Asia by 1910? Where is the majority of natural rubber production today?
50 million trees by 1910. Today, most of the world’s natural rubber production is in SE Asia and SW China
Regarding rubber production, what did Henry Ford attempt in the 1930s? How did it turn out?
“Fordlandia”, a plantation in the Amazon with a town built around it and workers imported to operate it. A colossal failure because Henry Ford sux
What was the motivation for creating synthetic rubber? When did this occur? Why is it inferior to natural rubber?
During WWII US rubber supply was cut off, needed a synthetic replacement. Synthetic rubber not as strong or flexible.
In what applications is natural rubber required, rather than just using synthetic rubber?
‘High performance’ uses (racecar tires, aircraft tires, etc).
What percentage of rubber used today is natural rubber from trees?
~40%.
How many rubber trees are required to produce one tire if they produce latex for a month?
The latex drip from 4 trees over the course of a month will result in enough rubber for a single tire.
Where did US import sanctions cause the spread of rubber production in the 1950s?
During Korean war (1950-1953), China expanded production in response to import ban, especially the hill region in the South.
Besides China, what 7 Asian countries also underwent extensive forest clearing to enable rubber production?
- Laos
- Myanmar
- Cambodia
- Vietnam
- Thailand
- Malaysia
- Indonesia
Why can cultivation of latex for rubber cause an ecological problem?
Involves clearing large ecologically valuable areas for cultivation, and requires a large amount of water for irrigation.
Which plant was presented in lecture as a possible alternate source of rubber?
Guyule, from the sunflower family
Where does guyule grow? What makes extraction of latex from this plant different from others?
Grows in arid environment. Latex not present in lactifiers but rather in stem, extracted by crushing the plant and isolating latex using solvent.
What is a health advantage inherent to latex produced by guyule that isn’t present in the latex produced by other species?
It is hypoallergenic.
What chemical components make up gums?
polysaccharide salts, of sugar units other than glucose.
What occurs when the salts present in gums interact with water?
The make gels.
When are gums produced by a plant? Why?
In response to a wound, used for physical protection and to prevent infection.
How are gums used by people?
As fillers, emulsifiers, texturizers (even in food). Also for stickiness in glues, cosmetics, etc.
How are gums obtained by humans for use in products? What plant family is the main producer?
Some are tapped from trees while others are extracted from seeds. Mostly from plants in the legume family.
What are some common uses for gum arabic? What plant family does this belong to?
From fabaceae, the legume family. Present in dairy products, as well as cosmetics, and even candy.
What are some common uses for guar gum? What plant family does this belong to?
From fabaceae, the legume family. Traditionally used as animal feed, but now used to make high viscosity water for fracking.
Why is guar gum used to make high viscosity water for fracking?
Gel allows the sand grains to be suspended in the water, keeping rock fractures open and allowing oil and gas to flow out.
How much did the price of guar gum increase in 2011? What caused this? Why is it not still high?
Increased by 10x because of the application in fracking, but dropped off quickly because synthetic alternatives were found.
Why do some forested mountain ranges seem to have a blue tinge when observed at a distance?
Because trees and shrubs emit isoprene into the air, which scatters short wavelength light.
Why do plants emit isoprene? How much is emitted per year?
May protect plant photosynthesis from heat. Plants emit ~500 million tons per year.
