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.
FAQs on Polystyrene
1. What is polystyrene and how is it formed?
Polystyrene is a versatile synthetic polymer made from the monomer styrene. It is created through a process called addition polymerization, where many styrene molecules link together to form long chains. This process is typically initiated by free radicals.
2. Can you explain the chemical structure of polystyrene?
The structure of polystyrene consists of a long hydrocarbon chain with a phenyl group (a C₆H₅ benzene ring) attached to every other carbon atom. This bulky side group is a key feature that significantly influences the polymer's properties, such as its rigidity and transparency.
3. Why is polystyrene a brittle and hard plastic?
Polystyrene is hard but brittle due to the chain-stiffening effect of the large, planar benzene rings in its structure. These rings restrict the movement and rotation of the polymer chains, preventing them from easily sliding past one another. This makes the material rigid and hard, but also prone to fracturing under stress instead of bending.
4. What makes polystyrene an amorphous polymer instead of a crystalline one?
The bulky and irregularly placed phenyl groups along the polymer chain prevent the chains from packing together in a neat, orderly fashion. This lack of long-range order results in an amorphous (non-crystalline) structure, which is responsible for its transparency.
5. What are the key properties and common uses of polystyrene?
Polystyrene is known for several key properties:
- Transparency and Brilliance: It has excellent optical clarity.
- Hardness and Rigidity: It is a stiff material.
- Good Electrical Insulation: It does not conduct electricity well.
- Low Moisture Absorption: It resists water.
Because of these properties, it is commonly used to make disposable cups, plastic cutlery, CD jewel cases, and laboratory ware. When expanded into a foam, it is used for packaging and insulation.
6. What is the difference between solid polystyrene and polystyrene foam like Thermocol?
Solid polystyrene is a dense, transparent, and brittle plastic. Polystyrene foam, commonly known by the brand name Styrofoam or as Thermocol, is the same polymer but with a blowing agent added during manufacturing. This creates a lightweight material that is about 95% air, making it an excellent thermal insulator and protective packaging material.
7. Is polystyrene considered safe for use with food and drinks?
Polystyrene is generally considered safe for food contact at cold or room temperatures. However, there are concerns that when heated, small amounts of styrene, its monomer, can migrate into food or beverages. For this reason, it is often recommended to avoid using polystyrene containers for hot liquids or for reheating food in a microwave.
8. Why does polystyrene have a relatively low softening temperature?
As an amorphous polymer, polystyrene lacks a sharp melting point and instead softens over a range of temperatures. The forces between the polymer chains (van der Waals forces) are relatively weak. This means it doesn't take much heat energy to allow the chains to start moving, causing the material to soften at a low temperature (around 100°C), making it unsuitable for holding boiling water.
9. What are the main types of polystyrene available?
The two main types of polystyrene are:
- General-Purpose Polystyrene (GPPS): This is the transparent, brittle, and inexpensive form used for items like petri dishes and plastic cups.
- High-Impact Polystyrene (HIPS): This is a tougher, opaque version created by adding polybutadiene rubber. The rubber particles absorb impact energy, making HIPS much less brittle and suitable for products that need more durability, like refrigerator liners and toys.
10. How does polystyrene impact the environment?
Polystyrene has a significant environmental impact primarily because it is non-biodegradable. It persists in the environment for hundreds of years, breaking down into smaller pieces called microplastics that can harm wildlife and ecosystems. While it is technically recyclable, the process is often not economically viable, leading to low recycling rates and contributing to plastic pollution in landfills and oceans.
