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Classification of Crystalline Solids

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What are Crystalline Solids ? We know that solids that have their constituent particles arranged in a definite pattern are called crystalline solids. So, depending upon the nature of these constituent particles, crystalline solids are further classified into four types: 1. Ionic solids 2. Molecular solids 3. Covalent or network solids 4. Metallic solids We will discuss all the above crystalline solids one by one. Classification of Crystalline Solids Following are the classification of crystalline solids: 1. Ionic Solids As the name suggests, crystalline solids that are made up of ions i.e cations and anions are called ionic solids. For example; NaCl is an ionic solid which contains Na⁺ and Cl⁻. These ions are held together by strong electrostatic attraction forces.  Properties of ionic solids Following are some properties of ionic solids: 1. They have high boiling and melting points due to the presence of strong electrostatic forces of attraction. 2. They are bad conductors of

Polystyrene: Definition, Preparation, Properties and Applications

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What is Polystyrene ? Polystyrene, also known as Polyvinyl benzene is hard, brilliantly transparent, stiff resin which is produced by the free radical addition polymerization of styrene in the presence of benzoyl peroxide. Polystyrene is non-biodegradable and widely used in the food-service industry as rigid trays, containers, disposable eating plates, bowls, etc. Preparation of Polystyrene Polystyrene is prepared by free radical addition polymerization of styrene in the presence of benzoyl peroxide as a catalyst. Properties of Polystyrene 1. Polystyrene exists in an amorphous state due to the presence of bulky phenyl groups which makes packing of Polystyrene inefficient. 2. Polystyrene is non-polar having a melting point of 240 ℃. 3. Polystyrene is a transparent polymer having a good optical property that allows high transmission of all wavelengths. 4. Polystyrene is hard but brittle due to the chain-shifting effect of the benzene ring. 5. Polystyrene has good insulation properti

Bakelite and Novolac- Phenol Formaldehyde Resins

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What are Phenol formaldehyde resins? Phenol formaldehyde resins (PF) or Phenolic resins are the oldest synthetic polymers. These are obtained by condensation of phenol with formaldehyde in the presence of either an acid or a base catalyst. Phenol formaldehyde resin possesses excellent adhesive properties and is usually used as bonding glue. They can withstand very high temperatures and are resistant to non-oxidizing acids, salts, and many organic solvents. Examples of Phenol formaldehyde resins Following are the most common examples of Phenol formaldehyde resins: 1. Bakelite Bakelite is a thermosetting phenol-formaldehyde resin that was developed by Belgian-American chemist Leo Baekeland in 1907. Bakelite is a cross-linked condensation copolymer that is prepared by a condensation reaction of phenol with formaldehyde in the presence of either acid or base catalyst. Preparation of Bakelite The reaction begins with the formation of o- and p-hydroxymethyl phenol derivatives which f

Poly (methyl methacrylate) (PMMA): An Acrylic Polymer

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What are Acrylic Polymers ? Acrylic Polymers, commonly known as acrylics are strong, stiff, and transparent plastic materials. They are prepared by free-radical polymerization of monomers that belong to ester acrylate (R=H) and methacrylate (R=CH₃) families. Acrylic Polymers are found in the market under the trade names perspex, Acrylite, Europlex, Optix, Duraplex, and Plexiglass. They are used for lighting, electronics screen, automotive components, and outdoor glazing in architecture and construction. Most common Acrylic Polymer: Poly (methyl methacrylate) (PMMA) Poly (methyl methacrylate) (PMMA) is a transparent thermoplastic that is used in sheet form as a lightweight or shatter-resistant alternative to glass. It is a synthetic polymer of methyl methacrylate which is prepared by free radical polymerization of this monomer. Preparation of Poly (methyl methacrylate) (PMMA) Poly (methyl methacrylate) (PMMA) is a vinyl polymer that is prepared by free radical polymerization of

Biodegradable Polymers: Definition, Examples, Properties and Applications

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What are Biodegradable Polymers? Polymers such as polysaccharides (starch, cellulose, etc), proteins, and nucleic acid that can disintegrate themselves in biological systems during a certain period by enzymatic hydrolysis and by oxidation, are called biodegradable polymers. These polymers do not have a disposable problem and they do not cause pollution like their other counterpart polymers. Moreover, their availability is good and they are non-toxic. The most important class of biodegradable polymers are aliphatic polyesters are polyamides. Examples of Biodegradable Polymers Some common examples of biodegradable polymers are given below: (i) Poly-b-hydroxybutyrate-co-b-hydroxyvalerate (PHBV) It is a thermoplastic copolymer of 3-hydroxybutyric acid and 3-hydroxypentanoic acid in which two monomer units are connected by ester linkages. It is used in specialty packaging, orthopedic devices, and controlled drug release.  For example, when a drug is enclosed in a capsule of PHBV, it is

Polytetrafluoroethyene (Teflon): A Fluoropolymer

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What is a Fluoropolymer?  A fluoropolymer is a fluorocarbon-based polymer with multiple carbon-fluorine bonds which is produced from alkenes in which one or more hydrogen atoms is replaced by fluorine. Fluoro polymers have high resistance to solvents, acids, and bases that's why it is used in making kitchenware and industry wares. Following is the common example of Fluoropolymers: Polytetrafluoroethyene (PTFE) or Teflon Polytetrafluoroethylene (PTFE) or Teflon is a synthetic fluoropolymer that is made by polymerizing tetrafluoroethylene. It is chiefly used to coat non-stick cooking utensils and to make seals and bearings. Preparation of Teflon Teflon is prepared by heating tetrafluoroethylene in the presence of peroxides or ammonium persulphate catalyst at high pressures. Properties of Teflon 1. Teflon is flexible and inert to solvents and boiling acids even to aqua regia and is stable up to 598K temperature. 2. It has a low coefficient of friction and low dielectric constan

Polyvinyl Chloride (PVC): Definition, Preparation, Properties and Applications

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What is Polyvinyl Chloride (PVC)?  Polyvinyl Chloride (PVC) is the third most widely used thermoplastic polymer after polyethylene and polypropylene. It is prepared by radical polymerization of vinyl chloride to produce material composed of an average of 10,000 to 24,000 monomer units. It is atactic and therefore amorphous, but it has a relatively high glass transition temperature (Tg) because of the large size of its molecules and its polar carbon-chlorine bond. Preparation of Polyvinyl Chloride (PVC) The monomer vinyl chloride is treated with peracid under pressure to obtain Polyvinyl Chloride (PVC) Properties of Polyvinyl Chloride (PVC) 1. It is a linear polymer and thermoplastic in nature. 2. It is a white brittle solid, hard, rigid material which tends to stick to the metallic surface. 3. It is insoluble in all hydrocarbon solvents. 4. It has a melting point of 212℃ and glass transition temperature (Tg) is 80℃ . Applications of Polyvinyl Chloride (PVC) 1. When PVC is plastici

Polymer Additives and It's Types

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What are polymer additives? The chemicals which are added to base polymers to improve their processability, life span, color, and other physical and chemical properties, are called polymer additives. They provide excellent properties like heat resistance, U.V resistance, anti-oxidant, high tensile strength, etc to the polymers. These polymers are widely used in flame retardants, agrochemicals, pharmaceuticals, paints, and coating and for inkjet printing inks. Types of polymer additives Following are the common types of polymers additives: 1. Plasticizers Plasticizers are a type of polymer additive that is used in base polymer to make it more flexible. Plasticizers decrease the attraction between the polymer chains, thereby allowing them to slide past one another. For example , Di-2-Ethylhexyl phthalate is the most common plasticizer which is added to PVC to make it more flexible. Thus, PVC can be used to make products like vinyl raincoats, shower curtains, and garden hoses. A plasticiz

Polymer Chemistry: 5 Types of Classification of Polymers

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What is a Polymer? Polymers are defined as macromolecules having high molecular mass (10^3-10^7 u) substances in which each molecule consists of a very large number of the simple repeating structural unit (monomers) joined together through covalent bonds in a regular fashion. The simple and reactive molecules from which the repeating structural units are derived are called monomers and the process by which these simple molecules (monomers) are converted into the polymer is called polymerization. For Example: Classification of Polymers Polymers are classified in many ways: 1. Classification based upon the source of availability Depending upon the source from which they are obtained, polymers are broadly divided into the following three classes: 1. Natural Polymers Polymers that are directly found in nature that is in animals and plants are called natural polymers. For example:   (a) Proteins which make up our body. (b) Nucleic acids which control heredity at the molecular level. (c) Ce

Henry's Law: Definition, Formula, Applications and Limitations

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What is Henry's Law? Henry's law deals with the solubility of the gas in a liquid at a particular temperature. This law was given by Henry in 1803 which states that The mass of a gas dissolved in a given volume of the liquid at constant temperature is directly proportional to the pressure of the gas present in equilibrium with the liquid. We can understand Henry's law by a simple experiment. Let us consider a dynamic equilibrium system shown in the given figure. The lower part of the system is liquid and its upper part is filled with a gas having pressure P and temperature T. Now, slowly increase the pressure over the system as shown in the figure. You will notice that the concentration of particles of gas in the liquid increases i.e gas is getting dissolved in the liquid. The more you increase the pressure, the more gas will dissolve in the liquid till a saturation point is attained. This is nothing but Henry's law. Mathematical Derivation of Henry's Law Mathema