Producing millions of tons of plastic products every year, Photo source: Bert Kaufmann / Wikimedia, CC BY
From the second world war and early on, the polymer commercial industry - long-chain synthetic molecules - 'plastic' is a common misnomer - has grown rapidly. In 2015, more than 320 million tons of polymers were produced worldwide, excluding fiber..
In the past five years, designers of polymer products have initially not considered what happens after the end of their useful life. But this situation is beginning to change and will receive more attention in the next few years.
Plastic industry
'Plastic' has become a misleading way of describing polymers. They usually come from long-chain molecules of oil or natural gas, with hundreds or thousands of links in each chain. Long chains convey that short molecules simply cannot match. Important physical properties such as strength and toughness.
'Plastic' is actually an abbreviation of 'thermoplastic', a term describing a polymer material that can be shaped and reshaped using heat.
The modern polymer industry is actually Founded by Wallace Karos in the 1930s His arduous study of polyamides led to the commercialization of nylon, as wartime silk shortages forced women to look for other materials to make stockings.
When other materials became scarce during the Second World War, researchers looked for synthetic polymers to fill the gap. For example, Japan's conquest of Southeast Asia cut off the supply of natural rubber for automotive tires, leading to a synthetic polymer. A substitute appears.
CC-BY-ND Source: Plastics Europe
Breakthroughs in chemistry have driven the further development of synthetic polymers, including polypropylene and high-density polyethylene, which are now widely used. Some polymers have been discovered by chance, such as Teflon.
finally, The combination of demand, scientific advancement and accidental discovery forms a complete set of polymer products that you can now easily identify as 'plastic' These polymers are quickly commercialized as they seek to reduce the weight of their products and provide inexpensive alternatives to natural materials such as cellulose or cotton.
Plastic type
The globally produced synthetic polymers are mainly Polyolefin - Polyethylene and Polypropylene.
There are two types of polyethylene: 'high density' and 'low density' On a molecular scale, HDPE looks like a comb with regularly spaced short teeth. In contrast, the low-density version looks like a long-toothed comb with irregular spacing; When viewed from a height, it is a bit like a river and its tributaries. Although they are all polyethylene, the difference in shape makes these materials behave differently when they are molded into films or other products.
CC-BY-ND Source: Scientific Progress (2017)
There are several reasons for the advantages of polyolefins. First, they can be produced using relatively inexpensive natural gas. Second, they are the lightest synthetic polymers produced on a large scale; their density is so low that they can float. Third, polyolefins can withstand water, air, Grease, detergent damage - all problems that these polymers may encounter when using them. Finally, they are easily molded into products, yet strong enough that the crates made of them are not deformed in transport trucks that are exposed to the sun all day.
However, these materials have serious drawbacks. Their degradation rate is very slow, which means that polyolefins exist in the natural environment for decades to centuries. At the same time, waves and wind erosion mechanically wear them, resulting in Microparticles that can be swallowed by fish and animals. These particles move toward us along the food chain.
Due to collection and cleaning problems, recycling polyolefins is not as simple as one would expect. During reprocessing, oxygen and heat can cause long-chain damage, while food and other substances can contaminate polyolefins. Continued progress in chemistry has created new Grades of polyolefins enhance strength and durability, but they cannot always be mixed with other grades during recycling. More importantly, polyolefins are often combined with other materials in multi-layer packaging; Although these multilayer structures work well, they are not recyclable.
Due to the growing shortage of oil and natural gas, the production of polymers has been criticized. However, the proportion of natural gas or petroleum used to produce polymers is very low; less than 5% of the oil or natural gas produced each year is used to produce plastics. Ethylene can be extracted from sugar cane ethanol, just as Brazil's Braskem is doing commercially.
CC-BY-ND Source: British Plastics Federation
How to use plastic
Depending on the function, the package The total amount of polymer consumed is 35% to 45% of the total amount of synthetic polymer. 2. Polyethylene terephthalate dominates the market for beverage bottles and textile fibers.
Houses and civil buildings consume 20% of the total polymer produced, with PVC pipes predominating PVC pipes are lightweight, can be glued without soldering or brazing, and are extremely resistant to the damaging effects of chlorine in water. But unfortunately, the chlorine atoms that give this advantage to PVC make recycling very difficult—large Most are discarded at the end of their useful life.
Polyurethane is a complete group of related polymers, widely used in foam insulation materials and architectural coatings for household and electrical appliances.
The automotive industry uses more and more thermoplastics, mainly to reduce weight and thus achieve higher fuel efficiency standards. The EU estimates that 16% of the weight of ordinary cars is plastic parts, and most importantly, interior parts and components.
CC-BY-ND Source: Scientific Progress (2017)
More than 70 million tons of thermoplastics are used annually for textiles, mainly clothing and carpets. More than 90% of synthetic fibers (mainly polyterephthalate) are produced in Asia. The growth of synthetic fibers in clothing is at the expense of natural fibers such as cotton and wool, which require a large amount of farmland to be produced. Due to special performance requirements such as stretching, moisture wicking and breathability, the synthetic fabric industry's clothing and carpets have seen significant growth.
As with packaging, textiles are usually not recycled. Ordinary US citizens produce more than 90 pounds of textile waste per year. According to Greenpeace, In 2016, the average person buys clothes 60% more per year than ordinary people 15 years ago, and the clothes are kept for a shorter period of time..