Polymers may exist naturally or be synthesised in the laboratory, considering their structural arrangement, type of monomers, arrangement of molecules and attachment of functional groups with leading backbone chains of polymers.
While plastic is a distinct class of polymers offering specialised properties. These distinct properties of plastics play an essential role in considering them for particular end-use applications.
Polymers and plastics are considered distinct research and study fields in Material Sciences, but these materials are generally considered the same. The use of polymers and plastics is increasing day by day in our daily life; even these materials have made us habitual of their utilisation regularly.
What Are Polymers
Polymers comprise small repeating units of similar properties, forming a long compound chain. Polymers are classified into two types concerning their sources: natural and synthetic. Both of these polymer types are being utilised around us in many activities. Due to their organic sources, natural polymers are also known as biopolymers.
Natural polymers include protein, DNA, wool, cotton, etc. While examples of polymers are epoxy, Teflon, polyester, polyethylene etc.
Considering the vast range of their applications and industrialisation, synthetic polymers are classified into four sub-classes:-
- Synthetic Fibres
The types of polymers are specified considering the district features that help them generalise for a particular application. There are thousands of polymers being identified and discovered. So, it is challenging to remember and learn the properties of every single polymer.
In this way, the polymers are judged and utilised considering their functional group, applications and characteristics of their backbone chain.
Thermoplastics are the most utilised type of polymer and have a distinct characteristic of remelting and reshaping. Thermoplastics do not show degradation on heating above the melting point. This property of thermoplastics allows them to be remoulded repeatedly, however, with minor compromises on quality or required properties.
Thermosets are also termed thermosetting polymers. They can’t be remoulded or reshaped upon heating repeatedly. When these materials are heated, their leading backbone chains start nucleation and arrange themselves for cross-linking.
A slight increase in heat initiates crosslinking action followed by curing on lowering of temperature or cooling. With crosslinking, all chemical and physical characteristics of polymers are bounded and fixed.
Due to this reason, further heat application does not affect their properties as this crosslinking makes them highly stable towards heat and temperature.
Elastomers are immensely flexible polymeric materials. The structure of elastomers is highly amorphous. They also possess a lighter level of cross-linking, because of which they have very low glass transition temperature, even lower than the ambient temperature.
The most commonly used elastomers are acrylic, acrylic ethylene rubbers and silicon. The adaptability of elastomers is very impressive, which is why they are considered a suitable material for several applications.
Synthetic fibres are synthetically developed materials made from petrochemical resources. These synthetic fibres are long chains composed of polymers formed by combining identical repetitive units of monomers. The applications of synthetic fibres are in every sector, especially the Textile industry.
Textile and Apparel goods are only possible with synthetic fibre, i.e. nylon, cotton, rayon, and polyester fibre.
Morphology of Polymers
Molecular bonds, characteristics of the backbone chain, configuration of bonds and polymerization highly define the morphology of polymers. Characterizing polymers to finalize the final product’s or end-use application’s characteristics is considered significant.
The synchronization and optimization of the abovementioned factors should be considered for selecting suitable material for the application. Furthermore, the micro-level structural arrangements of polymers determine the behaviour of various material phases under various conditions.
- The molecular bonds of the polymer’s structure define the final product characteristics. The strength of monomer linkages, cross-linking and secondary forces is crucial for polymer classification, making them able to be used for particular applications.
- For better classification of polymeric material, monomer characteristics are essential to consider. The elements involved in monomer composition and bonds formed by these monomers play an essential role in developing high-quality products and finalising the required characteristics. However, the arrangement of monomers in a linear, branched or crossly linked chain is essential.
- The molecular weight of the polymer is significant for the structural arrangement of the polymer. The length of the chain is also associated with molecular weight. An increase in chain length means more monomers and more monomers indicate an increase in molecular weight.
The characteristics of polymers are identified by studying the physical and chemical changes occurring in the morphology of polymer upon variation of circumstances or processing parameters. However, the physical and chemical changes determine the final properties of polymers.
- Polymers don’t melt. However, they change their structure from crystalline to amorphous. The increase in amorphous structure softens the polymer decreasing its glass transition temperature, improving its flexible properties.
- The tensile properties of the polymer are highly dependent on the type of bonding. The length of the bond and degree of the crystalline structure determines the strength of the bond, ultimately improving the tensile characteristics of the polymer.
- Polymers are found primarily enable or do hydrogen bonding. The presence of hydrogen bonding improves the strength of polymeric chains. The hydrogen bonding mainly results in cross-linking, which makes it thermally stable even at very high temperatures.
- The ionic bonds formed by polymers are also considered very important for the greater strength of polymers. The bond formed due to the attraction of opposite charges in polymer makes the polymer chains closer to each other forming secondary forces that may lead towards the formation of crosslinking upon given specified circumstance. This crosslinking ultimately improves the mechanical properties of a polymer.
- While dealing with polymers below their softening temperature, fragile Van der Waals forces are found in their structure. These weak secondary interactions determine the linkages of polymer chains with the same or other polymers forming a blend or copolymer for a particular application exhibiting a specialized set of properties. Furthermore, these Van der Waals forces increase the amorphous region in a polymeric material stricture, lowering the polymer’s glass transition temperature. This lowering in transition temperature improves the flexibility of the polymer; however, the brittleness is observed in the absence of these Van der Waals secondary forces among chains of the polymer.
The polymers are synthesized by addition or condensation reactions of monomers forming long chains of hydrocarbons and sometimes of their derivatives.
Polymer offers excellent properties, so it is utilized in several applications, including:-
- Textile Fibers
- Moulded Products
- Formed Products
- Paints & Coatings
- Films & Sheets
- Inks & Pigments
The use of polymer is everywhere in our daily life. We can witness thousands of polymer examples around us. Some of the daily or commodity applications of polymer are polyethene cups, plastic bags, small plastic parts, PET bottles, PP ducts etc.
Due to their very adaptable nature and properties, polymers have been chosen for study by numerous researchers and used in various applications. The blends of polymers with other materials like ceramics, fibres or metals forming composites are now becoming adaptable everywhere. Polymer composites are considered the strongest materials with limited weight values.
This class of materials having a high strength-to-weight ratio have made this material a tremendous, breath-taking and the most suitable material for lightweight applications with greater strength.
What Are Plastics
Plastic is considered a synthetic material derived from polymers, which are larger molecules made up of smaller molecules called monomers that are repeated. Polymers are composed of small units that may be natural or synthetic.
The difference between polymers and plastics originates from the stability of these materials upon temperature or heat. Polymers can be synthetic or natural, but plastic is strictly synthetic.
Furthermore, plastics typically can be strong, light, and easy to shape, making them useful for various purposes like construction, packing and consumer goods.
All polymers are not plastics; however, they may have similar properties but some dissimilarities. They can also be used for many things, such as in adhesives, textiles and biomedical materials.
Plastics are used because they last for an extended period and don’t break down quickly. This is one of the main reasons why they are so popular. Plastics are made of long chain branches of polymers that can withstand many stresses in the environment that would cause other materials to break down.
The fact that plastics last for such a long time is both a strength and a weakness. On the one hand, this makes them perfect for things like building materials or car parts that must last for a long time. On the other hand, plastics can stay in the environment for long because they are so durable.
This can pollute the environment and hurt wildlife. Plastics can also be made to have certain qualities, like being flexible, transparent, rigid or resistant to chemicals or heat. This makes them useful for various materials, from flexible and soft ones like plastic bags and food wraps to hard and strong ones like electronic devices and water bottles.
Plastics have changed many businesses and made it possible to make many things that weren’t possible or practical before. For example, plastic is commonly used in many places where glass, wood and metal are used. Plastic is often used to make commercial products like electronics, toys, and tools because it is light, durable, and cheap.
Plastics are useful because of several additional characteristics about them as well. For instance, plastics can be made clear and useful for things like windows and glasses.
Plastics can also be made to resist heat, which means they can be used in places with high temperatures, like car engines or kitchen machines. So, you can use plastic in many ways, which also benefits your everyday life.
Plastic has many advantages, making it a popular choice among customers and manufacturers.
Some of the main advantages of plastics are:
- Durability: Plastics are resistant to wear and tear and can handle exposure to water, chemicals and harsh environmental conditions. This makes them perfect for various uses, from consumer goods to materials used in industry.
- Plastics are versatile because they can be made in many shapes and sizes. This makes them perfect for making goods with detailed designs or unique forms. Plastics can also be made in various colors and shapes for multiple purposes.
- Lightweight: Plastic is much lighter than metal or glass, making it easier to move and handle. This can help cut shipping costs and make goods easier for customers to get their hands on.
- Cheap: Plastics are often more economical to manufacture than other materials, which makes them a good choice for manufacturers. This can also help bring down the price of goods for customers.
What is the Difference Between Polymers and Plastics? Let’s Understand With Examples
All plastics are polymers but of specialized type and properties. Generally, all polymers are named plastics because of some common properties of plastics and polymers. This is a well-adopted misconception in the consumer market.
Typically, these substances are referred to as “non-polymeric materials or “non-polymeric plastics”. Cellulose acetate, used to create products like toothbrushes, buttons, and eyewear frames, illustrates a non-polymeric plastic.
Cellulose acetate is synthesized using modification in the structure of natural cellulose. Although cellulose acetate is not a typical polymer, it has many characteristics in common with plastics, such as the capacity to be molded into different shapes and colors.
Polyvinylidene chloride (PVDC), utilized as a barrier material in food packaging applications, is another example of a non-polymeric plastic.
Despite not being an actual polymer, PVDC is frequently referred to as a plastic due to its similarities in characteristics and uses.
It’s important to remember that the word “plastic” is often used in a more general meaning to describe any substance that may be shaped or molded into an intended form. In this sense, materials like metals and ceramics may also be called “plastics” under certain conditions.
However, plastic is a general term well adopted in fields, industries or marketplaces to understand the physical characteristics of polymers or their derivatives.
Moldability of Plastics & Polymers
Polymers and plastics are processed through injection moulding in the same way. Most of this plastic is obtained in pallet form. It is added to the injection moulding extruder, filling the mould with a suitable temperature per the required characteristics. The procedure is a simple and continuous-batch process.
However, the considerable parameters for injection moulding are injection pressure, extruder temperature, mould temperature, melt temperature, extruder speed, gearbox and polymer properties. The injection moulding of plastics and polymers is very common and is utilised for many daily use, commodity and high-quality products.
The selection of plastics or polymers is crucial for finalising end-use applications. However, the polymers are mainly selected when higher thermal stability, mechanical brittleness, strength and hardness are required. While on the other hand, plastics are mostly preferred where flexibility, recyclability, toughness, ductility and softening on temperature are required.
So, if you select the best-suited material for your application with the required properties of toughness, flexibility, ductility and glass transition temperature, then thermoplastics or simply plastics will be the most feasible for you.
While on the other hand, if you need to select the material for applications having properties of thermal stability, stiffness, elastic strength, resistance and a sharp melting point, then polymers are the best solutions.
Apart from these mechanical and physical properties, optical, electrical, chemical resistance, viscous behaviour, degree of crystallinity, service temperature, durability, viscoelasticity, density, and polymerization are kept under consideration specific to the application and required properties.
Furthermore, these properties are studied thoroughly before selecting material for better results and final product properties.
So, if you are going to select the material from plastics or polymers, in that case, you must first consider the subject materials’ physical, mechanical and thermal properties, followed by the study and analysis of properties you want in your material for a particular application.
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