How can chlorine be used to make plastic

Because polyolefins are much more permeable than other types of plastics, these antioxidants are able to leach out of the plastic piping into the water flowing through it. So even when aggressive oxidizers like chlorine are not present in the water, polyolefins are slowly losing their protective additives.

When aggressive oxidizers like chlorine are added to the system, the protective antioxidants are destroyed even faster. Once the antioxidants are used up, chlorine or naturally occurring free radicals proceed directly to the polymer chain, breaking the molecule into smaller and smaller pieces until it loses strength and fails. CPVC, on the other hand, inherently has lots of chlorine atoms attached to and surrounding its chain structure. Chlorine atoms are huge in comparison to hydrogen, and they actually physically block the oxidants and radicals from reaching the CPVC chain structure.

CPVC also has no branching in its structure, so there are no easily oxidized tertiary carbons that require special protection. This is why the first PVC manufacturing plants were located close to natural sources of salt. The electrolysis of salt water produces chlorine. The chlorine is then combined with ethylene that has been obtained from oil. The resulting element is ethylene dichloride, which is converted at very high temperatures to vinyl chloride monomer.

These monomer molecules are polymerized forming polyvinyl chloride resin. On the other hand flexible PVC is achieved by adding plasticizers such as phthalates. Furthermore, pure poly-chloroethene is unstable when exposed to visible light or UV. In order to modify this disadvantage and make it suitable for different applications antioxidants are added. Some other additives comprise:. This is due to its chlorine compound. This makes it an ideal construction and cable material. This makes it ideal to be use in cables.

Manufacture of PVC The manufacturing plastics often creates large quantities of toxic chemical pollutants such as dioxin, hydrochloric acid, and vinyl chloride.

This poses a severe health risks to humans during the PVC life cycle. These toxins can produce sever illness like cancer, diabetes, neurological damage, reproductive and birth defects. Dioxin is a persistent Organic Pollutants POPs , this are chemical substances that persist in the environment, bio-accumulate through the food chain, and pose a risk of causing adverse effects to human health and the environment.

In addition, the chloro-ethene monomer is also a carcinogen released during PVC manufacture. This un-reacted monomer can also be present in the final PVC and released during its life cycle. Extrusion or a different moulding process then transforms these pellets into a finished or semi-finished product. Compounding often occurs on a twin-screw extruder where the pellets are then processed into plastic objects of unique design, various size, shape, colour with accurate properties according to the predetermined conditions set in the processing machine.

This literally means a polymer is made from many monomer-repeating units. Polymers are larger molecules formed by covalently joining many monomer-units together in the form of chains like pearls on a string of pearls. When we say plastics, we are referring to organic polymers synthetic or natural of high molecular weight which are mixed with other substances.

Plastics are high molecular weight organic polymers composed of various elements such as carbon, hydrogen, oxygen, nitrogen, sulphur and chlorine.

They can also be produced from silicon atom known as silicone along with carbon; a common example is silicone breast implants or silicone hydrogel for optical lenses. Plastics are made up of polymeric resin often mixed with other substances called additives. Plasticity describes whether a polymer would survive the temperature and pressure during the moulding process.

Chemistry allows us to vary different parameters to tune the properties of polymers. This allows plastics to be designed to have right properties for a specific application.

Most plastic in use today comes from hydrocarbons derived from crude oil, natural gas and coal — fossil fuels. Hydrocarbons are organic compounds can be aliphatic or aromatic made up of carbon and hydrogen. Aliphatic hydrocarbons have no cyclic benzene rings while the aromatics have benzene rings. It is able to pair up with four other electrons from any element of the periodic table to make up chemical bonds for hydrocarbon, it will pair up with hydrogen. CH 4 molecule is called methane, which is the simplest hydrocarbon and the first member of the Alkane family.

Similarly, if two C-atoms would bond together they can link with up to six H-atoms with three being on each C-atom to give a chemical formula of CH 3 -CH 3 or C 2 H 6 known as ethane and the series goes on as follows. Note that the 1-butylene and 2-butylene are isomers of butylene. Fossil fuels are mainly crude oil, natural gas and coal that are made up of carbon, hydrogen, nitrogen, sulphur, oxygen elements and other minerals Figure 1, ref.

The generally accepted theory is that these hydrocarbons are formed from the remains of living-organisms called planktons tiny plants and animals that existed during the Jurassic era. Dead organisms decomposed without oxygen, which transformed them into tiny pockets of oil and gas. Crude oil and gas then penetrate in the rocks that ultimately accumulate in reservoirs. The oil and natural gas wells are found at the bottom of our oceans and beneath. Coal mainly originated from dead plants ref.

Figure 2. Elemental composition of fossil fuels ref. Scientists have also questioned this theory. A recent study in Nature Geoscience from Carnegie Institution in collaboration with Russian and Swedish colleagues revealed that the organic matter may not be the source of heavy hydrocarbon and that they could be existing already deep down in the Earth. Experts discovered that ethane and other heavy hydrocarbons could be made if the pressure-temperature conditions can be mimicked with those present deep inside the Earths core.

This is to say that hydrocarbons can be made in the upper mantle that is the layer of Earth between the crust and the core. They demonstrate it by subjecting methane to laser heat-treatment in the upper layer of the Earth that then transformed into hydrogen molecule, ethane, propane, petroleum ether and graphite. The scientists then exposed ethane to the same conditions which reversibility produced methane. Above findings indicate that these hydrocarbons might be created naturally without the remains of plants and animals ref.

How is synthetic plastic created from crude oil? Synthetic plastic comes from petrochemicals. When the source of oil beneath the surface of the Earth is identified, holes are drilled through the rocks in the ground to extract oil. Extraction of oil - Oil is pumped from underground to the surface where tankers are used to transport the oil to the shore. Oil drilling can also take place under the ocean using support from platforms.

Different size pumps can produce between 5 - 40 litres of oil per stroke Figure 1. Refining of oil - Oil is pumped through a pipeline that can be thousands of miles long and transported to an oil refiner Figure 1. Spillage of oil from the pipeline during transfer can have both immediate and long-term environmental consequences but safety measures are in place to prevent and minimise this risk. Distillation of crude oil and production of petrochemicals - Crude oil is a mixture of hundreds of hydrocarbons that also contains some solids and some gaseous hydrocarbons dissolved in it from the alkane family mainly it is CH 4 and C 2 H 6 , but it can be C 3 H 8 or C 4 H Crude oil is first heated into a furnace then the resultant mixture is fed as a vapour to the fractional distillation tower.

The fractional distillation column separates the mixture into different compartments called fractions. No significant change is observed in relation to Tm, Tc, or to the shape of melting and crystallization peaks. In the case of PPR, the polymer itself has a lower crystalline content than PERT and a wide melting peak, due to the presence of ethylene units randomly distributed along the macromolecular chain deriving from propylene.

With PPR, crystalline content increases over time but analyses of the surface are influenced by the presence of a powder formed during aging, which have lower melting and crystallization temperatures than PPR see Supplementary file, Figures S13 and S As it was mechanically removed, analyses of the surface of the pipe after its removal might anyway be influenced by the presence of residues.

The increase in crystallinity observed is in good agreement with microscope observations: higher crystallinity implies that materials become stiffer and more fragile, leading to the formation of cracks. C dl values for the different tested samples: new pipe and aged for 8 weeks. As PERT has been studied only with the IS technique due to the high electrical resistance of the material , the equivalent circuit that better fits the experimental data is an RC dl series, whose only C dl variations are predictive of the degradation of the material Table 3.

Chlorine dioxide probably reacts with polymer and antioxidant compounds, which damages and removes part of the material, increasing inner surface roughness. Before investigating the Cu pipe inner surface, Cyclic Voltammetry CVs have been used to identify the potential at which it is possible to highlight the surface degradation process that, for our purpose, is directly connected with the modification, both, of the surface area, affecting C dl , and the electron transfer process for Cu oxidation, acting on R ct.

Figure 8 shows CVs for two different samples: new pipe black continuous curve and aged 8 weeks dotted curve Cu tubes. It emerges that aged Cu shows higher values of current density, both for oxidation and reduction processes, probably connected with a more electro-active metallic surface after the contact with ClO 2. In particular, at the start potential of 0 V, the current is almost zero for both samples; then, during the anodic scan, current increases much more for aged than pristine samples, due to the corrosion process occurring at the Cu surface; during the backward scan, it is possible to see a cathodic bump at about 0 V, probably due to the reduction of Cu ions formed during the anodic scan.

After this analysis, the selected investigating potentials for EIS measurements have been 0, 0. CV in 0. Figure 9 a,b shows the Nyquist diagram for new continuous curve and aged dotted curve samples at different polarization potentials for the frequency range selected to highlight the behavior of electron transfer resistance, R ct , and double layer capacitance, C dl.

The use of a constant phase element CPE is necessary due to the presence of rough metallic surfaces and pores, and in the case of the aged sample, due to the corrosion product film on the metallic surface, thus evidencing a diffusion step in the same frequency domain.

Cu new pipe continuous curve and after 8 weeks aging dotted curve at 0. The reduction in the R ct values from the semicircle amplitude is evident, increasing the polarization potential from 0 to 0.

Figure 9 b , due to the increase of the Cu corrosion process rate. At a lower potential, this phenomenon is much more evident for the aged Cu see R ct in Table 4 , as its surface is already modified and damaged by ClO 2 action, and at 0. SCE, the anodic polarization accelerates the corrosion process. This is most likely due to the modification of pore sizes and the shape present in the corrosion film on the Cu surface; a phenomena that can deeply affect the diffusion of ions back and forth towards the underlying metallic surface, thus reducing the electron transfer rate evidenced by the increase of R ct.

In any case, this behavior is strictly connected with the film layer on the Cu surface produced during the aging process in the presence of ClO 2.

No such behavior has been detected for the pristine Cu. Lastly, the C dl values for the pristine sample are smaller, of about one order of magnitude, than the aged values Table 4 , thus indicating a more corrugated metallic surface due to the damaging action of ClO 2.

The physical degradation is accompanied by changes in the chemical structure of plastics PERT and PPR and in the chemical composition of the surface of metal pipes copper and galvanized steel. Metals are also visible on the surface of plastic pipes, due to transportation in the water flux. DSC analyses on plastic pipes show an increase in crystallinity, leading to increased brittleness, whereas impedance measurements particularly evidenced by the increased values of C dl , are directly connected with an increase of inner surface roughness.

In the case of aged metal tubes, the electron transfer rate for the oxidation process is accelerated, due to the embrittlement and damaging of metal surfaces treated with ClO 2 disinfectant agent.

The results obtained suggest that issues related to progressive deterioration of pipes caused by ClO 2 should be seriously taken into account, especially considering that the products of degradation, both in terms of microplastics and of metallic species, are likely to reach common drinking water in houses. Conceptualization, M.

Alessandro Minguzzi ; impedance analyses—Cu sample: L. Alessandro Miani ; writing—original draft preparation, M. Alessandro Miani and A. Alessandro Minguzzi ; supervision, M. National Center for Biotechnology Information , U. Published online Nov Find articles by Alberto Vertova. Find articles by Sandra Rondinini. Find articles by Alessandro Minguzzi. Author information Article notes Copyright and License information Disclaimer. Received Oct 31; Accepted Nov This article has been cited by other articles in PMC.

Associated Data Supplementary Materials ijerphs Abstract Chlorine dioxide ClO 2 has been widely used as a disinfectant in drinking water in the past but its effects on water pipes have not been investigated deeply, mainly due to the difficult experimental set-up required to simulate real-life water pipe conditions.

Keywords: chlorine dioxide, water disinfection, plastic pipes, metal pipes, microplastics, water treatment, degradation by-products. Introduction In the last decades, there has been a growing interest in the use of chlorine dioxide ClO 2 as an efficient drinking water disinfectant [ 1 , 2 , 3 , 4 , 5 ] versus other disinfectants, such as chlorine-free typically deriving from either sodium hypochlorite, calcium hypochlorite or Cl 2 or monochloramine because its strong oxidizing power is capable of eliminating viruses and chlorine-resistant pathogens for example in Legionella surveillance [ 6 ] , as well as preventing biofilm formation.

Materials and Methods 2. Open in a separate window. Figure 1. Characterization 2. Electrochemical Impedance Spectroscopy Electrochemical impedance measurements EIS or IS were conducted on a multilayer pipe and a metal, namely PERT pipes and copper to characterize the samples in terms of double-layer capacitance C dl for both samples, and also electron transfer resistance R CT in the case of the metal sample.

Results and Discussion 3. Figure 2.