I. Natural rubber plants
Hevea brasiliensis is a tall tree growing in tropical areas. Its trunk can reach tens of centimeters, up to 10~20m, and its leaves are in groups of three, as shown in figure 1-3, so it is called a three-leaf rubber tree. Rubber trees can begin to produce rubber in 6~7 years after cultivation, and the rubber yield is rich in 10~20 years. The trunk, roots, leaves and fruits of this tree have laticifers, most of which are in the cortex of the trunk, so the tapping is cut from the trunk. On the trunk about 1250px above the ground, the cortex was cut with a sharp rubber cutter at a certain inclination angle, and the latex tube was broken. Due to the expansion pressure in the tube, the latex flows out of the tube. After discharging glue 1 ~ 2 hours, due to the evaporation of water and the action of coagulase, the latex automatically solidified on the incision to form a glue layer to close the incision. Rubber tapping is usually done at sunrise, every other day or every other day. This tree originated in the Amazon River valley and was successfully transplanted to Southeast Asia by the British in 1876. 1904, China began to introduce plants, which were planted in Guangdong, Guangxi, Hainan and Yunnan after liberation. According to 1992 statistics, the annual output of natural rubber in China is 280kt, ranking fourth in the world.
Chrysanthemum is a perennial shrub, which mainly grows in desert areas of Mexico. Chrysanthemum gum exists in the form of latex in the stem bark and roots of plants, and is extracted by grinding and separation.
Rubber produced by Eucommia rubber tree. If it is trans-polyisoprene, it becomes Eucommia ulmoides Oliv. It belongs to the same category as gutta percha and balata gum abroad, and it is also a wild resource.
Question 2: What is natural rubber? What is its origin? Early rubber was made of latex of rubber tree, rubber grass and other plants, and was made into elastic, insulating, water-tight and air-tight materials after processing. High elastic polymer compound. Natural rubber is made from rubber tree, rubber grass and other plants after extracting gum; Synthetic rubber is polymerized from various monomers.
The word rubber comes from the Indian cau-uchihu, which means "weeping tree". Natural rubber is formed by condensation and drying of latex of rubber tree with three leaves. 1770, British chemist J. priestley discovered that rubber can be used to erase pencil handwriting. At that time, the material used for this purpose was called rubber, which has been used ever since. The molecular chain of rubber can be crosslinked, and the crosslinked rubber has the ability of rapid recovery when deformed by external force, and has good physical and mechanical properties and chemical stability. Rubber is the basic raw material of rubber industry, which is widely used to manufacture rubber products such as tires, hoses, tapes and cables.
Hevea brasiliensis provides the most commercialized rubber. When it is injured (such as the bark of the stem is cut), it will secrete a lot of juice containing rubber emulsion.
In addition, fig trees and some Euphorbiaceae plants can provide rubber. Germany tried to obtain rubber from these plants because the supply of rubber was cut off during World War II, but later it changed to produce artificial rubber.
The original rubber trees grew in South America, but after artificial transplantation, a large number of rubber trees were also planted in Southeast Asia. In fact, Asia has become the most important source of rubber.
Rubber made of chrysanthemum gum can reduce sensitivity.
Question 3: What is compound glue? What's the difference with natural rubber? 10 natural rubber is a natural compound obtained by dehydration of latex in rubber trees. It is the most widely used universal rubber.
Composite rubber refers to rubber with natural rubber content of 95%-99.5%, and a small amount of stearic acid, styrene-butadiene rubber, cis-butadiene rubber, isoprene rubber, zinc oxide, carbon black or peptizer is added and mixed.
Natural rubber has many properties that are not suitable for industrial applications, such as low strength, difficulty in molding and aging. Adding additives can improve and improve the functional requirements of industrial application of natural rubber.
Question 4: What are 4:Jp Rubber Company and Hutian Rubber respectively? What is the difference? JP Rubber Company is the continuous trend of natural rubber futures in Japan. Hutian rubber refers to Shanghai natural rubber futures.
JP Rubber Company is the trend of Japanese rubber, and Hutian rubber is the price trend of natural rubber in Shanghai Futures Exchange.
As the opening time of Japanese rubber is 1 hour earlier than that of China, the trend of Japanese rubber seems to be ahead of that of Shanghai rubber.
Question 5: What is the use of natural rubber? 50% natural rubber has excellent resilience, insulation, water repellency and plasticity. After proper treatment, it also has valuable properties such as oil resistance, acid resistance, alkali resistance, heat resistance, cold resistance, pressure resistance and wear resistance, so it is widely used. For example, rain boots, warm water bags and elastic bands used in daily life; Surgical gloves, blood vessels and condoms used in the medical and health industry; All kinds of tires for transportation; Industrial conveyor belts, conveyor belts and acid alkali resistant gloves; Irrigation and drainage hoses and ammonia bags for agriculture; Sounding balloons for meteorological measurement; Sealed shockproof equipment for scientific experiments; Aircraft, tanks, cannons and gas masks for national defense; Even high-tech products such as rockets, artificial earth satellites and spaceships are inseparable from natural rubber.
Question 6: What is natural rubber? What are the advantages and disadvantages of natural rubber? Natural rubber refers to the natural latex collected from rubber trees in Brazil, which is an elastic solid made by solidification, drying and other processing procedures. Natural rubber is a kind of natural polymer compound with cis-1, 4- polyisoprene as the main component. Its rubber hydrocarbon (cis-1, 4- polyisoprene) content is above 90%, and it also contains a small amount of protein, fatty acids, sugar and ash.
Main uses Natural rubber has the above-mentioned series of physical and chemical characteristics, especially its excellent resilience, insulation, water repellency and plasticity. After proper treatment, it also has valuable properties such as oil resistance, acid resistance, alkali resistance, heat resistance, cold resistance, pressure resistance and wear resistance, so it is widely used. For example, rain boots, warm water bags and elastic bands used in daily life; Surgical gloves, blood vessels and condoms used in the medical and health industry; All kinds of tires for transportation; Industrial conveyor belts, conveyor belts and acid alkali resistant gloves; Irrigation and drainage hoses and ammonia bags for agriculture; Sounding balloons for meteorological measurement; Sealed shockproof equipment for scientific experiments; Aircraft, tanks, cannons and gas masks for national defense; Even high-tech products such as rockets, artificial earth satellites and spaceships are inseparable from natural rubber. The advantages and disadvantages of natural rubber are not fixed. If different characteristics are applied in different occasions and the application occasions are wrong, some advantages will become disadvantages.
Characteristics of natural rubber:
1, high elasticity, depending on the formula, the highest elasticity can reach 80%.
2, the elongation is high, and the highest elongation can reach more than 1000%.
3. The elastic modulus and shear modulus are lower than those of some rigid materials such as steel.
Because natural rubber is crystalline rubber, its strength is very high in rubber. The tensile strength of unreinforced natural rubber is 25~30MPa, and it can reach 32MPa after reinforcement. But far below steel.
5, good cold resistance, glass transition temperature of minus 72℃.
6. The density is low, and the density of raw rubber is less than 1g/cm 3.
7. There is a methyl side group in the main chain, which is easy to rearrange and has poor heat resistance. Long-term use temperature does not exceed 70℃
8. The main chain contains double bonds, which is easy to be attacked and not aging-resistant. At the same time, double bonds can be modified, such as chlorination and epoxidation, to improve heat resistance and oil resistance.
9. The oil resistance and chemical resistance (except alkali) are not good. In concentrated hydrochloric acid, the double bond will produce a protective film on the surface with the addition of HCl to prevent further reaction.
Question 7: What are the raw materials of synthetic natural rubber? 2- methyl -2.3- butadiene.