Technology helps plastic waste “transform” to serve food, clothing, housing and transportation

Repurpose waste to serve food, clothing, housing and transportation

The “Double Eleven” shopping festival has just passed, and the pleasure of “buying, buying, buying” has not completely dissipated, and the mountains of express packaging already need to be “thrown away”.

In recent years, with the surge in online shopping orders, the waste generated by express packaging has also increased. In order to protect the environment and save resources, many companies have adopted recyclable packaging or set up waste packaging recycling points to reduce the generation of garbage and waste in various ways.

In addition to the common waste cartons, there are many things, such as waste plastics, old tires, waste glass, etc., that can be recycled. Nowadays, with the help of technology, many wastes have been “reformed” and returned to us in another way, making daily life more green and sustainable.

Plastic bottles can also be made into clothes

According to statistics, the average use time of a plastic bottle is only 15 minutes, but it takes hundreds of years to completely degrade it. But now, in addition to being buried and burned as garbage, plastic bottles have a new destination – becoming raw materials for clothing.

Plastic bottles are usually made from polyethylene terephthalate, which is primarily derived from petroleum. The raw material polyester fiber for the polyester fabrics that people often wear in daily life also comes from petroleum. The two are actually “relatives” with the same origin, which also determines that they can achieve mutual transformation with the help of scientific and technological means.

However, the process of turning waste plastic bottles into wearable clothes is not simple.

After plastic bottles are recycled to the factory, staff will first sort and clean them. The cleaned plastic bottles are dried and crushed into fine plastic particles, which are the raw materials for subsequent processing. These tiny plastic particles are fed into a furnace where they are melted at high temperatures and turned into a viscous polyester solution. Then comes the critical step. The solution will turn into filaments five times thinner than hair. These filaments are polyester fibers. Workers then weave the polyester fibers into polyester “noodles” that can be used as raw materials for clothing.

This kind of fiber made from recycled waste plastic is called recycled polyester fiber. It has the same physical and chemical properties as virgin polyester fiber, and clothes made from it also have the advantages of wrinkle resistance, resistance to fading, resistance to deformation, durability, and quick-drying after washing. In terms of the wearing feel of the clothes, there is no significant difference between this type of clothes and clothes made of virgin polyester fiber, and they are even better than the latter in terms of elasticity.

In addition to waste plastics, waste clothing itself and a large amount of leftover materials generated in the clothing production process can also be recycled.

Spandex and polyester, which are commonly found in waste textiles, have similar chemical structures. In traditional recycling methods, the catalyst can only degrade the two at the same time and cannot effectively separate them, making it difficult to recycle related materials and reducing the recovery rate. The emergence of biomimetic enzyme targeted catalysis technology has solved this problem. This technology can depolymerize polyester materials into monomers under mild conditions and completely separate the spandex components. After further purification, the decomposed spandex can be polymerized into polyester fiber for textile use.

Mao Debin, CEO of Qingdao Amino Material Technology Co., Ltd., the technology research and development unit mentioned above, said that the production cost of spandex is high, and a large amount of highly toxic isocyanate is used in the production process, which has a great impact on the ecological environment. This recycling technology can replace some of the spandex production, thereby reducing the use of toxic chemicals. In addition, traditional spandex production consumes a lot of water, but this recycling technology uses a waterless process, which greatly saves water resources.

Old tires mixed with asphalt paving

Just as difficult to degrade as plastic are waste tires. Due to its strong heat resistance, friction resistance and corrosion resistance, the traditional disposal methods of waste tires are mostly burying and incineration. No matter which method is used, it will have varying degrees of negative impact on the environment. However, with the help of technology, even troublesome scrap tires can now become a usable resource.

The main components of waste tires are natural rubber and synthetic rubber, and additives also include carbon black, iron oxide, calcium oxide and other ingredients.

For the harmless treatment of waste tires, the current international common practice is to make them into rubber powder and then further utilize them.

However, in recent years, there has been a new method, which is to mix asphalt into processed waste tires and use them as raw materials to pave roads after processing.

To pave roads with waste tires, the waste tires must first be turned into rubber powder. Rubber powder produced using the normal temperature crushing method (breaking by pulling external force) will form some “tentacles” on the broken surface. These “tentacles” subsequently expand after absorbing the light components in the bitumen. When the amount of asphalt is incorporated to a certain level, these expanded “tentacles” can be connected together. The interconnection between the “tentacles” will form a stable three-dimensional spatial network structure, which can improve many properties of asphalt.

For example, adding rubber powder can greatly increase the viscosity of asphalt, thereby significantly improving its resistance to high temperature deformation.shape ability. In addition, the addition of rubber powder can also reduce the low-temperature brittleness of asphalt, making its low-temperature fracture deformation capacity nearly 7 times higher than that of ordinary asphalt.

Therefore, adding treated waste tires into asphalt can not only effectively solve the problem of waste tire disposal, but also significantly improve the performance of asphalt pavement materials and reduce the cost of modified asphalt, which has strong economic and social benefits.

According to Wang Jiaqing, associate professor at the School of Civil Engineering at Nanjing Forestry University, a member of the team said that the team’s tests on the simulated section of the Lianxu Expressway (G30) showed that mixing waste tire rubber powder into asphalt and paving 200 kilometers of road can reduce carbon emissions by nearly 3,000 tons.

Building houses with waste glass instead of sand

Glass is a common material in life, ranging from glass bottles to glass curtain walls. While the ubiquitous glass material adds convenience to life, it also creates a large amount of glass waste that is difficult to dispose of. Rational use of these waste glass can not only obtain economic benefits, but also solve the environmental problems caused by waste glass.

In recent years, waste glass grinding powder has been increasingly used in the field of concrete due to its low cost and good mechanical properties.

As a frequently used building material, concrete is mixed with particulate matter of different sizes. Previously these particulate materials were usually sand, but now they can also be ground waste glass.

The main component of glass is silica, and sand is also composed of silica, which makes glass a possible substitute for sand. The researchers crushed the glass waste into fragments of five different sizes: coarse, medium, fine, ultrafine and dusty, to replace the sand typically used as concrete aggregate.

Experimental results show that adding glass powder can improve the working performance of concrete and increase the slump (plasticizing performance and pumpability of concrete). The compressive strength of concrete after adding glass powder is improved to varying degrees compared with the ordinary group of concrete without glass powder. The researchers also loaded concrete containing ground waste glass into the 3D printer and successfully printed a 40-centimetre-high concrete object. During the entire printing process, the concrete flowed easily through the printer nozzle without clogging, and the concrete did not deform or collapse before curing.

There is another benefit to mixing glass powder into concrete instead of sand. Since glass is much less absorbent than sand, concrete incorporating glass powder also requires less water during production. Using glass powder instead of sand to make concrete not only puts a large amount of discarded glass to use, but also saves increasingly scarce sand resources, bringing significant economic and social benefits.