In recent years, scientists have taken petroleum, natural gas, and refinery gas as their main raw materials, and have chemically synthesized a polymer with better properties than natural resins, the "synthetic resins" with which we have become increasingly familiar. The main principle of synthesis is to crack the hydrocarbons in the petroleum "extended family" to obtain olefins, and under certain conditions, many ethylene molecules are connected together to obtain polyethylene polymer. The so-called "polyvinyl chloride" is a chain polymer formed by the aggregation of about 2,000 to 2,500 vinyl chloride molecules (Figure 59). Many of these polymers come together to form the white powdery polyvinyl chloride resin that is commonly seen. They are the basic raw material for making plastics.
Polyvinyl chloride is a thermoplastic that softens when heated, and is the most widely produced, cheapest, most versatile and most promising plastic in the world.
Polyvinyl chloride plastic hard, soft points, the former is not afraid of acid, alkali, corrosion-resistant, can replace the steel material manufacturing equipment. Many of China's fertilizer plant nitric acid absorption tower is manufactured with it, both to extend the life of the equipment, but also inexpensive. In addition, it can also manufacture corrosion-resistant pipelines, centrifugal pumps and ventilators. After adding color, soft PVC plastic can be made into a variety of wires and cables, artificial leather, raincoats and plastic cloth. Transparent soft PVC film is an indispensable material for greenhouses in agricultural production, and it is superior to glass in that it is cheaper, but also has the advantages of good light transmission, strong heat preservation ability, and does not take up space when collecting.
Petroleum products in the milky white translucent non-toxic polyethylene can be made into a variety of daily necessities, but also, because of its electrical insulation and water absorption rate is very small, can be used to manufacture a variety of high-frequency cables and submarine cable insulation and protective layer.
Figure 58 Temperature resistance of plastics
Figure 59 Schematic diagram of the production of polyvinyl chloride in thermoplastics, there is also a very familiar species - Plexiglas, which is chemically known as "methyl methacrylate". The figure of plexiglass has appeared more and more in people's daily life and high-tech, defense industry in the field. From photographic equipment to medical appliances, fighter cabin glass, instrumentation, tank periscopes, and so on, are plexiglass products.
In the second generation of petroleum products, there is a famous "plastic king" - PTFE. In the ability to dissolve gold, platinum, "aqua regia" (three parts of concentrated hydrochloric acid plus a concentrated nitric acid solution made of strong acid), it will be as solid as ever. This plastic has a strong heat resistance, cold resistance, high temperature resistance and electrical insulation and other characteristics. Widely used in chemical, electrical, refrigeration, pharmaceutical and other industries, there is a "universal plastic" said.
People use petroleum as raw material, through the chemical polymerization method, more than a thousand acrylonitrile molecules are regularly connected together into a very long polyacrylonitrile polymer, and then pumped into the fiber, and become a dazzling synthetic fiber products.
Among the many synthetic fiber products, there is nylon, which is made from phenol or benzene in petrochemical industry. Its abrasion resistance and strength is great, a finger-thick nylon rope can lift a nearly 10-ton truck. To petrochemicals in the xylene as the main raw material made of polyester fiber, we are very familiar with the "indeed", its most important feature is not wrinkled, free of ironing and free of pulp, shrinkage rate is small, not easy to go, but also has the defects of moisture absorption and poor air permeability.
In addition, there are petrochemical raw materials in the propylene and ammonia made of "synthetic wool" polyacrylonitrile fibers, polyvinyl chloride fibers (polyvinyl chloride), acetylene and acetic acid as the raw material for the production of polyvinyl chloride - polyvinyl alcohol fiber. Vinylon's moisture absorption and breathability are excellent, and resistant to insects, chemical corrosion, mildew, sunlight, can be made into sheets, quilt lining, canvas, rope, fishing nets and so on.
Petroleum in the cracking process can produce a large number of propylene, it is a sufficient source of low production costs, so it is the most inexpensive varieties of synthetic fiber products. This product is strong, good abrasion resistance, does not go out of shape, does not shrink, with it made of mosquito nets weighing only 50 to 100 grams, the weight is about half of cotton.
Rubber products have become civil, industry and agriculture, national defense, high-tech development of essential materials, but 3,000 rubber trees in a year to produce a ton of rubber, far from meeting the needs. As early as 1914, people have successfully synthesized methyl rubber, later, scientists found that a large number of raw materials such as ethylene, propylene, butene and aromatic hydrocarbons needed to synthesize rubber can come from petrochemical products. People first obtain the monomers from petroleum to produce synthetic rubber, and then through polymerization, like the polymer molecules in plastics, the synthetic rubber monomers are polymerized into elastic macromolecular solids.
Particularly valuable is that people can be based on the needs of the economy, life and national defense, the synthesis of general-purpose rubber and special rubber, such as cold-resistant potassium butyl rubber and high-temperature, chemical-resistant fluorine-containing rubber.
The petroleum as raw materials can also be made into fertilizers, pesticides, pharmaceuticals, detergents, explosives, dyes, synthetic proteins and so on. According to incomplete statistics, people use modern petrochemical technology, has been from the oil "black gold" in the nearly 6000 kinds of products, widely used in daily life, industry, agriculture, transportation, national defense and high-tech fields.