How many kinds of popular science | plastics are there? What are the common plastics? Where did you go last?

Before reading this article, first look around you, as well as your hands, I believe you can find a few kinds of plastic products. At least, the mobile phone in your hand has many parts made of plastic. If the clothes on your body are made of chemical fiber, it is also plastic. Plastic has penetrated into all aspects of our lives, without plastic, our modern civilization will not exist. However, more and more plastics have not been properly disposed of, causing many environmental problems. But in addition to practitioners, the vast majority of the public know little about plastic. Today, I will introduce you to some basic knowledge about plastics.

01 How many kinds of plastic?

There is no precise number of types of plastics, and there are theoretically thousands of them. And scientists and the R & D departments of chemical companies are constantly inventing new varieties of plastics. The national standard "GB/T 16288-2008 Mark of Plastic Products" lists 140 kinds of plastics, covering most of the plastics currently used on a large scale. However, the following are common in our daily life: PET, PE (including HDPE and LDPE), PP, PS, PVC, PC, ABS, EVA, EPS, etc., as well as chemical fibers (nylon, polyester) commonly used in clothing industry.

Most beverage bottles are made of PET. Plastic bags are mostly PE; Express lunch boxes are mostly PP, and some are PVC. Both PET and HDPE bottles for toiletries are available. The CD is made of PC.

Where did all the plastic go?

After plastic is used, there are four places to go-incineration, landfill, recycling, and abandoned wilderness lakes and seas. About 9% of this is recycled, 12% is incinerated, and 79% is in landfills or the natural environment. (This data comes from UNEP United Nations Environment Program) If the temperature control of plastics is not good, they will produce carcinogenic dioxins. This is one of the reasons to separate the wet waste as much as possible, because the presence of wet waste can make temperature control very difficult. Even if the temperature can be strictly controlled, the fly ash from the incineration plant should be collected and finally solidified for landfill. Landfilling does not make plastic disappear. Because traditional plastics are not degradable, it will take at least 500 years to disappear in the case of landfill.

The most ideal way of disposal is recycling. The most ideal is the same level of regeneration, such as beverage bottles recycled into new food grade PET particles, still used to make beverage bottles. This cycle back and forth, forming a closed loop. However, in most cases, it is degraded and recycled. For example, the particles recycled from beverage bottles are used to make chemical fiber and clothing, while chemical fiber clothing is recycled and used to make greenhouse sheds. Recycling extends the life cycle of plastics and reduces the total amount of plastic waste. But it will eventually become waste.

Source of land-based plastic waste entering the sea in 2010: Jambeck et al.Science,2015

The worst is random discard, a phenomenon that is particularly common in rural and poorly managed scenic spots. Most of the plastic waste that has not been properly collected and disposed of will enter the water body and eventually flow into the sea.

The shade of color represents the proportion of plastic waste that is not adequately managed; the size of the circle represents the weight of plastic waste flowing into the ocean. The picture comes from UNEP's official website. The data comes from Jambeck et al.Science. 2015 scientists collected and analyzed samples from 57 rivers. It is estimated that more than 90% of the plastic waste brought into the ocean by rivers is through 10 rivers -8 in Asia, 2 in Africa, and 4 of the 8 rivers in Asia are located in China.

Image from UNEP official website Data from The Helmholtz Centre for Environmental Research in Leipzig,Germany, the study was published in the Environmental Journal of Science & Technolog

After the plastic enters the ocean, part of it quickly sinks to the bottom of the sea and part floats on the surface. Some are accidentally eaten by marine life, resulting in death. There's more to break down into microplastics, as ocean currents walk to every corner of the world. Microplastics have been detected in the North and South Poles, in marine life, and in our drinking water.