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Plastics - Important Notes, Functions, Properties, Structure, FAQs

Plastics - Important Notes, Functions, Properties, Structure, FAQs

Edited By Team Careers360 | Updated on Jul 02, 2025 04:55 PM IST

In this article we will discuss what is plastic, what is plastic material, what does we mean by plastic in English, some important notes on plastic, about functions of plastic, how many types of plastics are there, classification of plastics, examples of plastic materials, who invented polythene, what is plastic made of, plastic material properties, plastic material list, about the structure of plastic, define acrylic glass, about recycling of plastic, uses of plastics, about plastic material.

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What is plastic?

Here we are talking about plastics. Plastics are basically the type of polymer that means it is made by repeating a single unit multiple times in order to make a long chain which further can be moulded according to the properties of the material used in to make it and then it is converted or shaped into numerous articles or more precisely objects. It is also produced not naturally but synthetically.

Now we will discuss that what is the plastic material? So the plastic material as the name suggests are the material those are made up of plastics. Talking about plastics they are many types and depending upon the type of plastic used the properties of the plastic material vary. There are many plastic materials that we use in our day to day life. Some of them include: switches, fans, chairs, tables, plates etc. Now we will discuss some important notes or points about plastics.

Firstly we will discuss the classification of plastics. As we have discussed that plastics are made up of polymers and these polymers are then further divided into two categories namely thermoplastics and thermosetting plastics. Now we will explain each of these category in detail.

Talking about the thermoplastics we come to know they are the plastics which can moulded and demoulded easily also there shape can easily be changed. They type plastics are said to have straight chains and not cross linked to each other therefore they are melted on heating and then reshaped. For example: polythene is one of the most popular example of this.

Then talking about the thermosetting plastics we can say that they cannot be changed into another shape on heating. Moreover from this it is concluded that these plastics once set into the shape then it cannot be reshaped or melted. They will be discarded only when not in use. As they cannot be changed further therefore we can say here that they are not the single long chains instead they are the chains which are cross linked making it tightly bonded to all the alternate monomers. For examples: Bakelite is one of the popular example.

plastic

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So these are the main classification of plastics but the of these two main categories forms different types of plastics which have specific names and uses that we usually come across. So we will discuss different types of plastics in short:

  • High density polyethylene: this is quite a stronger type of plastic and is used to store grocery items. It is really hard and thicker also.
  • Polyethylene tetraphthalate: it is basically lighter plastic that is used to make use and throw items.
  • Polyvinyl chloride: it is one of the mostly used plastic in everyday life. It is used make bottles, toys etc. we have also heard in the news that this plastic is really hazardous to the environment.
  • Low density plastics: this low density plastics as the name suggests that it is of low quality. It is the polythene bags which we usually use. It is also a threat to the environment.
  • Polypropylene: it does not melt easily on heating and it resistable to high temperature food items.
  • Polystyrene: it is very dangerous to human health. It is basically used for packaging purposes.

Here we have discussed about the different types of plastics found in nature.

Now we will discuss the composition and the structure of plastic.

As we have talked here a lot about the plastic the first question which comes to our mind is “what is plastic made up of?” or how is plastic formed?

When we talk of plastics we can say that they are usually made up of carbon, chlorine, oxygen, sulphur, nitrogen and hydrogen. Now we will see that how these molecules of organic chemistry are bound in order to form plastics. It is simple process while expressing here but practically it undergoes lot of work in industries in order to obtain the required form of it.

These different organic compounds ass mentioned above bound together with the help of different additives to obtain the property of plasticity. Elaborating about the property of elasticity we can say that it is property that the substance when it is folded and reshaped it should do so without breaking. These plastics are not naturally obtained from the given organic materials but they are obtained from the coal, natural gas and such compounds where the basic units are these organic compounds.

plastics

Also, students can refer,

Uses of plastics or functions of plastic

  • It has a wide application in the automobile industry. It is used to make different parts of the cars, bikes, trucks etc.
  • It is used to make polybags which are widely used all over to carry different items.
  • It also make the process of packaging easier nowadays because it can easily pack the products and also do not make it heavier.
  • It is used to make safety products like helmets.
  • There are also special type of plastics made in order to be used in the microwave ovens.

Some of the plastics are very difficult to dispose of and are now posing threat to the environment. We have discussed plastic notes here.

Also check-

NCERT Chemistry Notes:

Frequently Asked Questions (FAQs)

1. Define acrylic glass.

While defining the acrylic glass we can say that it is a glass with the composition of plastic in it which makes it lighter in weight and highly resistible to various damages.

2. Explain recycling of plastics.

As it is known that the plastics cannot be decomposed easily therefore they need to be recycled and for that ones the particular item is fully used and cannot be further used then changed into the other products and this way it does not pose threat to the environment.

3. Give a short note on “Say no to plastics.”

As it is known that the plastics are a great threat to the environment. It is nowadays posing deadly for the animals because they are feeding on the waste which is generally mixed with the plastic which chocks their body functions. It is difficult to dispose them of also and as we know that the thermosetting plastics once used cannot be further changed into the other useful items so it becomes very difficult to store it. In keeping all these points in view our government has launched a program of say no to plastic under which efforts are made to decrease the use of plastics in our lives.

4. From where are the plastics obtained?

Plastics are basically obtained from crude oil, cellulose, petroleum, and natural gas which are processed in the industries in order to form the required plastics with the required properties.

5. List some of plastic items one uses in day to day life.

Some of the items which we use everyday are: toothbrushes, switches, cookwares, furniture including table and chair, bottles, cans, tanks, pipes, bags etc.

6. Who invented polythene?

Polythene is invented by Hans von Pechmann.

7. Give the list of properties of plastics.

Properties of plastics are:

  • They are easier to carry as the materials of other items.

  • Some of the plastics can be moulded also.

  • They have a good resistant property.

  • They are not much costly.

8. Why are plastics so widely used in everyday life?
Plastics are widely used due to their versatility, durability, and low cost. They can be easily molded into various shapes, are lightweight, resistant to corrosion, and have good insulating properties. These characteristics make them suitable for a wide range of applications, from packaging to construction materials.
9. How do additives modify the properties of plastics?
Additives are substances incorporated into plastics to modify their properties. They can improve durability (stabilizers), change color (pigments), enhance fire resistance (flame retardants), increase flexibility (plasticizers), or provide other specific characteristics. The type and amount of additives used can significantly alter the behavior and performance of the plastic.
10. How do plasticizers work and why are they used in some plastics?
Plasticizers are additives that increase the plasticity or fluidity of a material. They work by embedding themselves between the polymer chains, increasing their mobility and making the plastic more flexible. Plasticizers are often used in PVC to make it softer and more pliable for applications like vinyl flooring or wire insulation.
11. What is the glass transition temperature and why is it important for plastics?
The glass transition temperature (Tg) is the temperature at which an amorphous polymer transitions from a hard, glassy state to a soft, rubbery state. It's important because it determines the temperature range in which a plastic can be used effectively. Below Tg, plastics are rigid and potentially brittle; above Tg, they become more flexible and easier to shape.
12. How do plastics conduct electricity and heat?
Most plastics are poor conductors of electricity and heat, making them good insulators. This is due to the lack of free electrons in their molecular structure. However, some plastics can be made conductive by adding conductive fillers like carbon black or through special processing techniques. The thermal conductivity of plastics is generally low, which makes them useful for insulation applications.
13. What are plastics and how are they related to polymers?
Plastics are synthetic materials made from polymers. Polymers are large molecules composed of repeating subunits called monomers. Plastics are a specific type of polymer that can be molded or shaped when soft and then set into a rigid or slightly elastic form.
14. What is the difference between thermoplastics and thermosets?
Thermoplastics can be repeatedly softened by heating and hardened by cooling, allowing them to be reshaped multiple times. Thermosets, on the other hand, undergo a chemical change when heated, forming a three-dimensional network that cannot be reshaped once set. This makes thermosets more durable but less recyclable than thermoplastics.
15. What is the structure of a typical plastic polymer?
A typical plastic polymer consists of long chains of repeating units (monomers) bonded together. These chains can be linear, branched, or cross-linked, depending on the type of plastic. The specific arrangement of these chains and the types of monomers used determine the properties of the plastic.
16. What are some common monomers used in plastic production?
Common monomers used in plastic production include ethylene (for polyethylene), propylene (for polypropylene), styrene (for polystyrene), vinyl chloride (for PVC), and terephthalic acid and ethylene glycol (for PET). The choice of monomer determines the specific properties of the resulting plastic.
17. How does the molecular structure of plastics affect their properties?
The molecular structure of plastics directly influences their properties. For example, linear polymers tend to be flexible and easily molded, while highly cross-linked polymers are more rigid and heat-resistant. The length of the polymer chains affects the material's strength and melting point, with longer chains generally resulting in stronger and higher-melting plastics.
18. How do plastics impact the environment?
Plastics can have significant environmental impacts. They are not biodegradable and can persist in the environment for hundreds of years. Plastic waste often ends up in oceans, harming marine life. Additionally, the production of plastics from fossil fuels contributes to greenhouse gas emissions. However, efforts are being made to develop more sustainable and biodegradable plastics.
19. How does plastic recycling work?
Plastic recycling involves collecting, sorting, cleaning, and reprocessing plastic waste into new products. Different types of plastics are separated based on their resin codes. Thermoplastics can be melted and remolded, while thermosets are typically ground into powder for use as fillers. However, not all plastics can be easily recycled, and the quality of recycled plastic is often lower than virgin plastic.
20. What is the role of interfacial adhesion in plastic composites?
Interfacial adhesion refers to the bonding between the plastic matrix and reinforcing materials in composites. Strong interfacial adhesion is crucial for effective stress transfer from the matrix to the reinforcement, which determines the overall strength and performance of the composite. Poor adhesion can lead to delamination or failure under stress. Various treatments and coupling agents are used to improve interfacial adhesion in plastic composites.
21. What is the difference between addition and condensation polymerization?
Addition polymerization involves monomers joining together without the loss of any atoms, typically through the opening of double bonds. Condensation polymerization, on the other hand, involves the joining of monomers with the elimination of small molecules like water. Addition polymers include polyethylene and PVC, while condensation polymers include nylon and polyester.
22. What are bioplastics and how do they differ from conventional plastics?
Bioplastics are plastics derived from renewable biomass sources, such as vegetable fats, corn starch, or microbiota, rather than fossil fuels. They can be biodegradable or non-biodegradable. The main difference is their source material and potentially their end-of-life behavior, as some bioplastics can decompose more readily in the environment.
23. How does the crystallinity of a polymer affect its properties?
The crystallinity of a polymer refers to the degree of structural order in the material. Highly crystalline polymers tend to be stronger, more rigid, and have higher melting points, but they can also be more brittle. Amorphous (non-crystalline) polymers are generally more flexible and transparent. Many plastics have both crystalline and amorphous regions, with their ratio affecting the overall properties.
24. What are microplastics and why are they a concern?
Microplastics are tiny plastic particles less than 5mm in size. They can come from larger plastic items breaking down or be intentionally manufactured (like microbeads in cosmetics). They're a concern because they can easily enter the environment, particularly water systems, and be ingested by marine life. There are also concerns about their potential impact on human health as they enter the food chain.
25. How does cross-linking affect the properties of plastics?
Cross-linking is the formation of chemical bonds between polymer chains. It increases the rigidity, strength, and heat resistance of the plastic but decreases its flexibility. Highly cross-linked plastics, like thermosets, cannot be melted and reshaped once formed. The degree of cross-linking can be controlled to achieve desired properties for specific applications.
26. What is the role of catalysts in polymer production?
Catalysts in polymer production help to initiate and control the polymerization reaction. They can increase the rate of reaction, allow polymerization to occur at lower temperatures or pressures, and influence the structure and properties of the resulting polymer. Different catalysts can lead to polymers with varying molecular weights, distributions, and stereochemistries.
27. How do the properties of plastics change with temperature?
The properties of plastics are highly temperature-dependent. As temperature increases, plastics generally become softer and more flexible. Thermoplastics will eventually melt, while thermosets will decompose at high temperatures. At low temperatures, plastics tend to become harder and more brittle. The specific behavior depends on the type of plastic and its glass transition and melting temperatures.
28. What is polymer degradation and how can it be prevented?
Polymer degradation is the deterioration of plastic properties due to environmental factors like heat, light, oxygen, or chemicals. It can lead to discoloration, brittleness, or loss of strength. Prevention methods include adding stabilizers to the plastic formulation, using protective coatings, or controlling the environmental conditions during use and storage.
29. What is the difference between thermoplastic and thermosetting elastomers?
Thermoplastic elastomers (TPEs) are polymers that have the elastic properties of rubber but can be processed like thermoplastics. They can be melted and reshaped multiple times. Thermosetting elastomers, like vulcanized rubber, form cross-links when heated and cannot be remelted or reshaped once formed. TPEs offer easier processing and recyclability, while thermosetting elastomers often have superior elastic properties and chemical resistance.
30. How does the molecular weight of a polymer affect its properties?
The molecular weight of a polymer significantly influences its properties. Higher molecular weight generally results in increased strength, toughness, and melt viscosity. It also tends to increase the melting point and glass transition temperature. However, very high molecular weights can make processing more difficult. The distribution of molecular weights in a polymer sample also affects its properties and processability.
31. What are composite materials and how do they relate to plastics?
Composite materials are made by combining two or more materials with different properties to create a new material with unique characteristics. Many composites use plastics as the matrix material, reinforced with fibers (like glass or carbon) or particles. This combination can result in materials that are stronger, lighter, or have other enhanced properties compared to the plastic alone.
32. How do plastics respond to mechanical stress?
The response of plastics to mechanical stress depends on their molecular structure and the nature of the stress. Some plastics deform elastically and return to their original shape when the stress is removed. Others may undergo plastic deformation, permanently changing shape. Under high stress, plastics can fracture. The behavior also depends on factors like temperature, rate of stress application, and the presence of defects or additives.
33. What is the role of polymer blending in plastic production?
Polymer blending involves mixing two or more polymers to create a material with properties that are a combination of its constituents. This technique allows for the creation of plastics with tailored properties without the need to synthesize entirely new polymers. Blends can improve impact resistance, processability, or other specific characteristics. However, not all polymers are compatible for blending, and the resulting properties can be complex to predict.
34. How do plastics interact with solvents?
The interaction between plastics and solvents depends on their chemical compatibility. Some plastics can dissolve in certain solvents, while others may swell or become brittle. This interaction is based on the principle of "like dissolves like" - plastics tend to dissolve in solvents with similar chemical structures. Understanding these interactions is crucial for selecting appropriate plastics for specific applications, especially those involving exposure to chemicals.
35. What is the significance of tacticity in polymer structure?
Tacticity refers to the stereochemical arrangement of side groups along the polymer chain. It can be isotactic (all on one side), syndiotactic (alternating sides), or atactic (random). Tacticity significantly affects the physical properties of the polymer. For example, isotactic polypropylene is crystalline and has a higher melting point, while atactic polypropylene is amorphous and has different mechanical properties.
36. How do plastics behave under UV light exposure?
Many plastics are susceptible to degradation when exposed to UV light. UV radiation can break chemical bonds in the polymer chains, leading to discoloration, brittleness, and loss of mechanical properties. This process is called photodegradation. To prevent this, UV stabilizers are often added to plastics used in outdoor applications. Some plastics, like those containing aromatic rings, have better inherent UV resistance.
37. What is the role of chain entanglement in polymer properties?
Chain entanglement refers to the intertwining of polymer chains in a material. It plays a crucial role in determining the mechanical properties of plastics, particularly in amorphous regions. Higher degrees of entanglement generally lead to increased strength, toughness, and viscosity. The extent of entanglement depends on factors like molecular weight, chain flexibility, and processing conditions.
38. How do plastics contribute to thermal insulation?
Plastics are effective thermal insulators due to their low thermal conductivity. This property arises from their molecular structure, which lacks free electrons to conduct heat efficiently. Many plastics contain tiny air pockets that further reduce heat transfer. Foamed plastics, like expanded polystyrene, are particularly good insulators and are widely used in construction and packaging for their thermal insulation properties.
39. What is the difference between linear and branched polymers?
Linear polymers consist of long, straight chains of monomers, while branched polymers have side chains attached to the main backbone. Linear polymers tend to pack more closely, resulting in higher density, strength, and melting points. Branched polymers often have lower melting points, are easier to process, and have different flow characteristics. The degree and type of branching can significantly affect the properties of the plastic.
40. How do plasticizers affect the glass transition temperature of polymers?
Plasticizers lower the glass transition temperature (Tg) of polymers by increasing the free volume between polymer chains. This increased mobility of the chains makes the plastic more flexible at lower temperatures. The effect is to shift the Tg to a lower temperature, effectively making the plastic softer and more pliable at room temperature. The amount and type of plasticizer can be adjusted to achieve the desired flexibility.
41. What is the importance of molecular orientation in plastic properties?
Molecular orientation refers to the alignment of polymer chains in a specific direction. It can significantly enhance certain properties of the plastic, such as tensile strength and stiffness in the direction of orientation. Orientation can be induced during processing methods like extrusion or fiber spinning. However, it can also lead to anisotropic properties, where the material behaves differently depending on the direction of applied force.
42. How do plastics behave in response to cyclic loading?
Under cyclic loading (repeated stress application), plastics can exhibit fatigue, where their properties degrade over time even if the individual stress events are below the material's yield strength. This can lead to crack formation and eventual failure. The response depends on factors like the polymer type, stress amplitude, frequency, and environmental conditions. Some plastics show good fatigue resistance, while others may fail after relatively few cycles.
43. What is the role of crystallization kinetics in plastic processing?
Crystallization kinetics describes how quickly and to what extent a polymer forms crystalline regions as it cools from a melt. This process significantly affects the final properties of semi-crystalline plastics. Faster cooling generally results in smaller, less perfect crystals and more amorphous regions, while slower cooling allows for larger, more organized crystalline structures. Understanding and controlling crystallization kinetics is crucial for achieving desired properties in plastic products.
44. How do plastics respond to different types of radiation?
Different types of radiation can affect plastics in various ways. UV radiation, as mentioned earlier, can cause photodegradation. Ionizing radiation (like gamma rays) can cause chain scission or cross-linking, depending on the polymer type and radiation dose. Some plastics are more resistant to radiation than others. Radiation effects can be used beneficially in some cases, such as in the cross-linking of certain polymers to improve their properties.
45. What is the significance of polymer chain conformation?
Polymer chain conformation refers to the three-dimensional shape that a polymer chain adopts. It can range from tightly coiled to extended, and affects properties like solubility, viscosity, and the ability to crystallize. The conformation is influenced by factors such as the chemical structure of the monomer, temperature, and the presence of solvents. Understanding chain conformation is crucial for predicting and controlling polymer behavior in various applications.
46. How do plastics behave at cryogenic temperatures?
At cryogenic temperatures (extremely low temperatures), most plastics become very brittle and lose their flexibility. This is because the polymer chains have very little thermal energy for movement. However, some specially designed plastics maintain some flexibility and toughness at these temperatures. The glass transition temperature and the presence of plasticizers play important roles in determining low-temperature behavior.
47. How do plastics respond to high strain rates?
The response of plastics to high strain rates (rapid deformation) can be quite different from their behavior under slow deformation. Many plastics become more brittle and show increased strength but decreased elongation at high strain rates. This behavior is important in applications involving impact or rapid loading. Some plastics, however, can exhibit strain rate hardening, where they become tougher under rapid deformation.
48. What is the importance of melt viscosity in plastic processing?
Melt viscosity is a measure of a plastic's resistance to flow when melted. It's crucial in processing techniques like injection molding, extrusion, and blow molding. Lower melt viscosity allows for easier filling of molds and better surface detail, but may lea

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Questions related to

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Question : On a cold day when the room temperature is 15o C, the metallic cap of a pen becomes much colder than its plastic body, though both are the same temperature of 15o C, because:

Option 1: metals have higher thermal capacity than plastics

Option 2: plastics have a lower density than metals

Option 3: metals are good conductors of heat

Option 4: plastic have a higher thermal conductivity than metals

Correct Answer: metals are good conductors of heat


Solution : The correct option is metals are good conductors of heat.

On a cold day, the metal cap of a pen gets significantly colder than its plastic body since metals are good conductors of heat. This implies they can transport heat more efficiently than other materials. On a chilly day, the outside air is substantially colder than the inside air. When the pen's metal cap is exposed to cold air, it swiftly transfers heat away from the pen and into the air. This causes the cap to seem cooler than the plastic body, which is a poor heat conductor. On a hot day, the reverse is true. The metal cap will conduct heat away from the pen faster than the plastic body, making it seem colder to the touch.

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Team Careers360 20 January,2024

Question : Select the most appropriate option that can substitute the underlined segment in the given sentence.

Polyethylene terephthalate, one of the most often recycled plastics and the material used in the majority of water and soda bottles, can be transformed into everything from polyester fabric to automotive parts.

Option 1: might be placed

Option 2: might be evolved

Option 3: may be converted

Option 4: may be devaluated

Correct Answer: may be converted


Solution : The correct choice is the third option.

"Convert" means to change the form or function of something and is a synonym for "transform," which makes it the appropriate choice for the substitution. It does not change the context of the sentence.

The meanings of the other options are as follows:

  • "Might be placed" is not the correct choice here as it does not fit in the sentence contextually.
  • "Might be evolved" should not be used in this sentence, as evolve means something that changes gradually and does not help convey the intended meaning of the sentence.
  • "May be devaluated" is also not the correct choice, as devaluate means something that loses its value, which is not the intended message.
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Team Careers360 21 January,2024
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