What chemicals make plastic brittle?

Chemical properties of plastic

A recent study has identified an organism capable of disposing of PET, one of the most abundant plastics. Bacteria that eat plastic could mean a before and after in bioremediation. Hidden among plastic bottles, a team from Kyoto University has found a bacterium capable of feeding on this material. And for the first time it has been possible to cultivate, study and measure the capacity of these organisms. These plastic-eating bacteria open an incredible door to a future where this material could be easily treated and would no longer be the environmental problem it is today. And, although this discovery is new, the truth is that we have known for some time about the existence of certain beings capable of biodegrading plastic. But never so effectively. And we had never managed to “work” with them. Now, all that has changed.

However, Ideonella sakaiensis, the bacteria that eat plastic, are able to feed on this polymer. To do so, they have a set of enzymes never before seen in nature.  Enzymes are proteins responsible for degrading a product. The first of these is responsible for converting the plastic into a product called mono(2-hydroxyethyl) terephthalate, or MHET. Once it has been “digested”, the MHET is captured by Ideonella and “digested” again by another enzyme, but this time inside the bacteria. Thus, this organism converts PET into its main source of carbon.

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Physical properties of plastic

One of these is Bisphenol A, present in some plastic bottles (BPA). Salinas explains that these compounds are quite harmful, as they were created to make products more resistant and durable, without considering the environmental consequences this would have. “Plastics were very revolutionary in their time. They were made with an intention that later could not foresee what was going to happen in environmental issues,” says the researcher. “The loss of biodiversity for me is the maximum expression of environmental deterioration, and that is what could happen here.”

For González, this research can help to take into account the seriousness of plastic pollution on a planetary level. “Antarctica can be a place to become aware and measure how pollution can be affecting such a pristine environment. Just as it happened with the Montreal Protocol in the face of the hole in the ozone layer,” he reflects.

Salinas, in the same line, highlights the importance of caring for the sea, even if we are far from it or from territories such as Antarctica. “It is not unreasonable to think that although I am on the continent, this has nothing to do with what happens in other places. It’s all interconnected, Antarctica regulates the climate on a planetary level and it’s important to be aware of it. To understand it as something dynamic, alive and interrelated”, concludes the researcher.

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Types of polymer degradation

Plastic is a material made up of organic or synthetic compounds that have the property of being malleable and can therefore be molded into solid objects of various shapes. This property gives plastics a wide variety of applications.[1] Its name derives from plasticity, a property of materials, which refers to the ability to deform without breaking.

In 1839 Goodyear in the United States and Hancock in England developed in parallel the vulcanization of rubber, i.e. the hardening of rubber and its increased resistance to cold. This was the beginning of the commercial success of thermosetting polymers.[8] The plastics industry began with the development of plastics.

The plastics industry begins with the development of the first thermoset plastics by Baekeland in 1909. Baekeland produced the first synthetic polymer and also developed the plastic molding process, which enabled him to produce various articles of commerce. These early plastics were named Bakelite in honor of their discoverer. Bakelite is formed by a condensation reaction of phenol with formaldehyde.[9] Baekeland’s first synthetic polymer is called bakelite.

All plastics have the same properties

Any analysis of a plastic begins with preliminary tests. In addition to observing characteristics such as solubility, density, softening and melting behavior, heating in a combustion tube (pyrolysis test) and in a flame (flame test) is very important.

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Due to the high molecular weight of the polymers it is necessary to chop the sample as finely as possible. If the sample is difficult to cut, it can be frozen with carbonic snow or liquid nitrogen, which will make it glassy, more brittle and easier to cut.

Among the numerous plastic solvents, the most widely used are benzene, tetrahydrofuran, dimethylformamide, diethylether, acetone and formic acid. In certain cases, chloroethylene, ethyl acetate, ethanol, methanol, toluene, hydrocarbons and even acids or bases are often used.

Nylon has a high breaking strength, high elasticity and low density. It melts at temperatures of around 260 ºC and softens at 180 ºC. By condensation polymerization, a filamentous, whitish paste is obtained, which becomes elastic and resistant when cooled. It burns smoothly and melts. It is quite stable against chemical agents.