Rubber & latexes

Question 1

What plant family is know for producing latex?

Answer 1

The “spurge” family, Euphorbiaceae.

Question 2

What kinds of cells are responsible for producing latex? What kind of plant molecule is latex?

Answer 2

Lactifiers produce the latex, which is a secondary metabolite.

Question 3

In which category of plants are lactifiers mostly found?

Answer 3

Flowering plants (dicots).

Question 4

What parts of the plant can contain lactifiers for latex production? What is the purpose of latex for the plant?

Answer 4

Can be produced in many structures (bark, seeds, stem, fruit, etc.) and has a defensive function (acts as an irritant).

Question 5

What molecular structure gives rubber its flexibility? How many isoprene units can this be composed of?

Answer 5

The long, unbranched terpene polymer chain made from up to 6000 isoprene units.

Question 6

How many species of plants contain rubber? Where are they mostly distributed?

Answer 6

> 2000 species of tropical plants.

Question 7

Where was rubber likely first used by humans? When did the Europeans discover it?

Answer 7

In tropical America, with the early Aztec and Mayan civilizations. Spanish conquistadors first observed its use in the 1500s.

Question 8

What is an example of a use for rubber by the ancient Aztecs? How did they modify the rubber to make it usable?

Answer 8

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.

Question 9

How did the Amazonians use rubber? How did they mix it with other compounds? At what ratio? What else was required for this process?

Answer 9

Amazonians made custom rubber shoes by mixing rubber with morning glory juice at a 1:3 juice:latex ratio (required heating).

Question 10

What was the purpose of coagulating rubber by heat?

Answer 10

Made the rubber coating waterproof.

Question 11

Who was the first to dissolve rubber in solvent? When? What was this product used for?

Answer 11

Charles Macintosh (1823) used it to make a waterproof coating that could be applied to fabrics, etc.

Question 12

What was a significant disadvantage of using solvent-dissolved rubber as a waterproof coating?

Answer 12

It cracked in the cold and became sticky in heat.

Question 13

Who solved the problem of rubber coating not withstanding temperature fluctuations? When? By what process?

Answer 13

Charles Goodyear (1839) developed vulcanization, which involves adding sulfur while heating, causing many isoprene cross-links to form.

Question 14

What mechanism does vulcanization of rubber enable that was employed unknowingly by the Aztecs?

Answer 14

The Aztecs added morning glory juice which contains sulfur, a critical step in the vulcanization of rubber.

Question 15

What are some examples of products which make use of the waterproof and elastic characteristics of rubber?

Answer 15

Boots, gloves, electric wire coating, hose, drive belts, tires, etc.

Question 16

What is the most common use for rubber today? How much of the world’s rubber consumption does this industry account for?

Answer 16

2/3 of the world’s rubber use to make tires.

Question 17

When did rubber stop getting harvested from the wild? What species was the main producer of wild rubber?

Answer 17

Harvested wild until 1880, 89% came from Hevea brasiliensis in Amazonian basin (spurge family).

Question 18

How was latex harvested from Hevea brasiliensis in the wild?

Answer 18

Tapped from spiral cuts in the bark to take advantage of the abundant lactifiers in the inner bark.

Question 19

Who first smuggled rubber seeds out of Brazil, breaking the monopoly? When? Whose payroll was he on?

Answer 19

The Royal Botanical Gardens paid for Sir Henry Wickam to smuggle the seeds out of Brazil in 1876.

Question 20

Where was rubber production introduced to once the Amazonian monopoly had been broken?

Answer 20

British, French, and Dutch colonies in SE Asia.

Question 21

How many rubber trees were there in SE Asia by 1910? Where is the majority of natural rubber production today?

Answer 21

50 million trees by 1910. Today, most of the world’s natural rubber production is in SE Asia and SW China

Question 22

Regarding rubber production, what did Henry Ford attempt in the 1930s? How did it turn out?

Answer 22

“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

Question 23

What was the motivation for creating synthetic rubber? When did this occur? Why is it inferior to natural rubber?

Answer 23

During WWII US rubber supply was cut off, needed a synthetic replacement. Synthetic rubber not as strong or flexible.

Question 24

In what applications is natural rubber required, rather than just using synthetic rubber?

Answer 24

‘High performance’ uses (racecar tires, aircraft tires, etc).

Question 25

What percentage of rubber used today is natural rubber from trees?

Answer 25

~40%.

Question 26

How many rubber trees are required to produce one tire if they produce latex for a month?

Answer 26

The latex drip from 4 trees over the course of a month will result in enough rubber for a single tire.

Question 27

Where did US import sanctions cause the spread of rubber production in the 1950s?

Answer 27

During Korean war (1950-1953), China expanded production in response to import ban, especially the hill region in the South.

Question 28

Besides China, what 7 Asian countries also underwent extensive forest clearing to enable rubber production?

Answer 28

1. Laos
2. Myanmar
3. Cambodia
4. Vietnam
5. Thailand
6. Malaysia
7. Indonesia

Question 29

Why can cultivation of latex for rubber cause an ecological problem?

Answer 29

Involves clearing large ecologically valuable areas for cultivation, and requires a large amount of water for irrigation.

Question 30

Which plant was presented in lecture as a possible alternate source of rubber?

Answer 30

Guyule, from the sunflower family

Question 31

Where does guyule grow? What makes extraction of latex from this plant different from others?

Answer 31

Grows in arid environment. Latex not present in lactifiers but rather in stem, extracted by crushing the plant and isolating latex using solvent.

Question 32

What is a health advantage inherent to latex produced by guyule that isn’t present in the latex produced by other species?

Answer 32

It is hypoallergenic.

Question 33

What chemical components make up gums?

Answer 33

polysaccharide salts, of sugar units other than glucose.

Question 34

What occurs when the salts present in gums interact with water?

Answer 34

The make gels.

Question 35

When are gums produced by a plant? Why?

Answer 35

In response to a wound, used for physical protection and to prevent infection.

Question 36

How are gums used by people?

Answer 36

As fillers, emulsifiers, texturizers (even in food). Also for stickiness in glues, cosmetics, etc.

Question 37

How are gums obtained by humans for use in products? What plant family is the main producer?

Answer 37

Some are tapped from trees while others are extracted from seeds. Mostly from plants in the legume family.

Question 38

What are some common uses for gum arabic? What plant family does this belong to?

Answer 38

From fabaceae, the legume family. Present in dairy products, as well as cosmetics, and even candy.

Question 39

What are some common uses for guar gum? What plant family does this belong to?

Answer 39

From fabaceae, the legume family. Traditionally used as animal feed, but now used to make high viscosity water for fracking.

Question 40

Why is guar gum used to make high viscosity water for fracking?

Answer 40

Gel allows the sand grains to be suspended in the water, keeping rock fractures open and allowing oil and gas to flow out.

Question 41

How much did the price of guar gum increase in 2011? What caused this? Why is it not still high?

Answer 41

Increased by 10x because of the application in fracking, but dropped off quickly because synthetic alternatives were found.

Question 42

Why do some forested mountain ranges seem to have a blue tinge when observed at a distance?

Answer 42

Because trees and shrubs emit isoprene into the air, which scatters short wavelength light.

Question 43

Why do plants emit isoprene? How much is emitted per year?

Answer 43

May protect plant photosynthesis from heat. Plants emit ~500 million tons per year.