Dhristi JEE 2022-24

What is Polystyrene?

Styrene is a naturally occurring liquid material utilized to manufacture various powerful, flexible, and lightweight items. As the name suggests the monomer for polystyrene is styrene, which is also known as ethylbenzene, vinylbenzene, or phenylethane, which is the precursor of polystyrene and other well-known copolymers. The manufacture of styrene and its various applications is a significant element of the world economy. It helps to enhance people's lives by offering more energy-, cost-, and performance-efficient products.


Polystyrene is a rigid, strong resin that is stunningly transparent. It is the most extensively used plastic and is made from the polymerization of styrene. The thermoplastic polymer is a solid at ambient temperature, but it flows when heated above 100 °C. Polystyrene is water-insoluble. With a few exceptions, polystyrene is a non-biodegradable material. Many aromatic hydrocarbon solvents and chlorinated solvents dissolve it quickly. It's commonly utilized in the foodservice business as rigid trays, containers, disposable eating plates, and bowls, among other things.


Polystyrene is a polymer of styrene. It is a synthetic aromatic hydrocarbon. It is hydrophobic in nature. Its IUPAC name is poly(1-phenylethane-1,2-diyl). Its general formula is (C8H8)n.

 

Expanded polystyrene (EPS) or extruded polystyrene (XPS) is a foam material derived from polystyrene that is appreciated for its insulating and cushioning characteristics.

Structure of Polystyrene


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Properties of Polystyrene

  • Polystyrene exists in an amorphous state because of the presence of bulky phenyl groups, packing of polystyrene chains is not efficient. 

  • Polystyrene is non-polar in nature.

  • The polystyrene melting point is 240 degrees Celsius.

  • Polystyrene density is 1.05 g/cm3

  • The polystyrene boiling point is 430 degrees Celsius.

  • Polystyrene thermal conductivity is 0.003 W/m.K.

  • Polystyrene-specific gravity is 1.054.

  • Polystyrene has a good optical property like it is a transparent polymer allowing high transmission of all wavelengths. Moreover, its high refractive index gives it a particularly high brilliance.

  • Due to the chain stiffening effect of the benzene ring, polystyrene is hard but brittle. It emits a characteristic metallic sound when dropped.

  • Being a non-polar amorphous polymer, its softening temperature is low. It cannot withstand the temperature of boiling water.

  • Polystyrene has a low tendency for moisture absorption. Moreover, it has good electrical insulation characteristics. Therefore, it is used in making polystyrene insulation products.

  • Polystyrene has reasonable chemical resistance but mediocre oil resistance.

Preparation of Polystyrene

Polystyrene is prepared by free radical addition polymerization of styrene in the presence of benzoyl peroxide as a catalyst.

 

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Use of Polystyrene

  • It is used for making polystyrene products like polystyrene sheets, polystyrene foam, brush handles, and combs.

  • It is used for making talcum powder. 

  • It is used for making polystyrene plastic like small jars, bottle caps, polystyrene cups, and storage containers.

  • It is used for making audio cassettes.

  • The demand for styrene in liquid form is estimated to be more than 15 million metric tonnes, and the need for its many applications mainly determines it. Western and Eastern Europe and North America have the highest yearly capacity for styrene manufacturing.

Food Packaging and the Polystyrene Safety

  • Polystyrene has been declared safe for use in food contact by the Food and Drug Administration for decades. The European Commission/European Food Safety Authority and other regulatory bodies have reached similar conclusions.

  • Food-borne illness can be reduced by using polystyrene foodservice packaging, according to research and studies conducted by various research institutes.

  • Polystyrene is popular in the foodservice industry because it has been shown to outperform other commercially available alternatives. From organic salads to fiery chili, polystyrene packaging provides more convenience and dining satisfaction for those on the go.

  • Foodservice packaging made of polystyrene is frequently less expensive than paper-based or reusable alternatives.

  • When purchased from a wholesale market, it can be up to five times less expensive than reusable containers, which frequently necessitate the purchase of additional equipment, labor, water, electricity, detergent, and other items.

  • Foam polystyrene cups, plates, and sandwich containers require substantially less energy and water than comparable paper-based or corn-based alternatives, owing to foam polystyrene's significantly lower weight.

Did You Know?

  • Polystyrene is very light in weight, as it is composed of 95% air.

  • It exists in two forms: expanded polystyrene and extruded polystyrene.

  • It can be reused and recycled.

  •  It is environmentally friendly.

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FAQs (Frequently Asked Questions)

1. Why is Polystyrene brittle in Nature?

Due to the chain stiffening effect of the benzene ring, polystyrene is hard but brittle in nature. It emits a characteristic metallic sound when dropped.

2. Why does Polystyrene exist in Amorphous State?

Because of the presence of bulky phenyl groups, packing of polystyrene chains is not efficient and hence it is an amorphous polymer.

3. Explain the five properties of Polystyrene.

Five properties of polystyrene are given below:

  • Polystyrene has a good optical property like it is a transparent polymer allowing high transmission of all wavelengths. Moreover, its high refractive index gives it a particularly high brilliance.

  • Due to the chain stiffening effect of the benzene ring, polystyrene is hard but brittle. It emits a characteristic metallic sound when dropped.

  • Being a non-polar amorphous polymer, its softening temperature is low. It cannot withstand the temperature of boiling water.

  • Polystyrene has a low tendency for moisture absorption. Moreover, it has good electrical insulation characteristics. Therefore, it is used in making polystyrene insulation products.

  • Polystyrene has reasonable chemical resistance but mediocre oil resistance.

4. What are the opinions of scientists on the safety of polystyrene foodservice packaging?

A 12-member worldwide expert panel assembled by the Harvard Center for Risk Analysis undertook a comprehensive study of potential health concerns linked with styrene exposure in the workplace and the environment from 1999 to 2002.  The researchers determined that exposure to styrene from food or polystyrene in food contact applications such as packaging and foodservice containers poses no risk.

5. Is it typical for packaging materials to contaminate food?

Glass, aluminum, paper, and polymers like polystyrene all include chemicals that can "migrate" or sip into the foods or beverages at minimal levels. According to the test results provided to the FDA, the migration of styrene from polystyrene foodservice goods is small and is projected to be far below the safety standards set by the agency itself - 10,000 times less than the FDA's recommended daily consumption level.

6. Is it possible to develop eco-friendly styrene?

Several research organizations have been working on various modernization techniques to lower production costs and environmental implications throughout the last few decades. Some of these procedures include using new catalysts such as toluene or methanol to reduce the amount of styrene compound required, using fewer natural resources such as water or electricity, and improving the market for product delivery through weight reductions and packing efficiencies. Long-term testing and development of various modernization procedures are expected to be seen in the near future.

7. Is polystyrene harmful to people?

Polystyrene contains carcinogens and neurotoxins, Styrene and Benzene, potentially dangerous to people. In reality, hot foods and drinks cause the Styrofoam to partially degrade, letting certain pollutants enter our bloodstream and tissues.


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8. What exactly is meant by the term extruded polystyrene?

Extruded polystyrene is a form of plastic used to manufacture various items, including building materials and storage containers. After this material's prominent brand name variant, this product is also known as XPS and Styrofoam. Depending on the use, extruded polystyrene might be a dense foam or a more solid, plastic-like material.


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