Posts

Showing posts from 2022

Classification of Natural Dyes

Image
Classification of Natural Dyes Dyes which are obtained from natural resources like plants, animals, and minerals are known as natural dyes .  So, natural dyes can be further classified into three types. 1. Natural Dyes obtained from Plants Dyes that are obtained from plant sources like roots, berries, bark, leaves, and wood are known as plant-based natural dyes .  For example, Logwood, Indigo, Henna, etc. They are also known as vegetable dyes and can be applied directly or with different mordants. 2. Natural dyes obtained from Animals Dyes that are obtained from animal sources like insects and invertebrates are known as animal-based dyes. Various shades of red and purple colors can be obtained from animal origin.  Cochineal, Tyrian Purple, and Lac are some common examples of animal dyes. 3. Natural dyes obtained from minerals Dyes that are obtained from mineral sources are called mineral dyes. They are produced by the metallic ions in the mordant salts.  Shades of the dye depend upon

Edible Dyes: Definition, Types, Properties and Applications

Image
Definition of Edible Dyes Dyes that impart color when it is added to food or drink and can be consumed, are known as edible dyes . They come in many forms like powders, gels, and pastes and can be used in drinks, cookies, candies, etc. Types of Edible Dyes Based on the source, edible dyes are further classified into two types is Natural edible dyes and Synthetic edibles dyes. 1. Natural Edible Dyes Dyes that are obtained from natural sources like plants, leaves, flowers, seeds, roots, and animals are called natural dyes. Since they are obtained from natural sources, so there will be no harm to use natural edible dyes in preparing attractive food. Natural edible dyes also contain vitamins that are very essential for the body. Adding these ayes in food does not affect the taste of food and makes the food look more attractive. Examples of natural edible dyes are Annatto, Turmeric, Carmine, Paprika, etc. 2. Synthetic Edible Dyes Dyes that are obtained from petroleum-derived substances a

Vulcanization of Rubber: Definition, Properties and Applications

Image
What is Vulcanization of rubber ? As we know that, natural rubber is soft and sticky and becomes even more so at high temperatures and brittle at low temperatures. Also, it is not resistant to the action of organic solvents and can be easily attacked by oxidizing agents.  So, to solve this problem, Charles Goodyear in 1839, found a process called Vulcanization , which can improve the physical and chemical properties of rubber. Vulcanization is a process that consists of heating raw rubber with sulfur at 373-415 K temperature. Since this process is slow, therefore additives like zinc oxide are used to accelerate the rate of vulcanization. During vulcanization, sulfur bridges or cross-links between polymer chains are introduced either at their reactive allylic positions or at the sites of the double bonds.  These cross-links make rubber hard and stronger and remove the stickiness of natural rubber because the individual chains can no longer lip over but are instead locked together in

Types of Rubber, their Properties and Applications

Image
1. Natural Rubber Natural rubber is a natural polymer that is manufactured from latex which is a colloidal solution of rubber particles in water. Latex is obtained by making cuts in the bark of rubber trees like Hevea brasiliensis, found in tropical and semi-tropical countries such as southern. India, Indonesia, Malaysia, Sri Lanka, South America, etc. The natural rubber has remarkable elasticity and undergoes long-range reversible extension even under a relatively small applied force. Preparation of natural rubber Natural rubber is a linear 1,4-addition polymer of isoprene. Since each repeating unit in polyisoprene contains a double bond having cis-stereochemistry. That's why natural rubber is cis-polyisoprene. Properties of Natural rubber Natural rubber has no polar groups and hence intermolecular forces of attraction are only weak van der Waals interactions. Cis-polyisoprene does not have a straight-chain but has a coiled structure. As a result, it can be stretched like a spri

Malachite Green: Definition, Synthesis, Properties and Applications

Image
What is Malachite Green? Malachite green is a type of Triphenyl methane dye that is used as a dyestuff for materials like silk, leather, and paper. It is bright green and can be used as an antimicrobial agent in aquaculture. Synthesis of Malachite Green Malachite green can be prepared by reaction of Benzaldehyde with N, N-dimethyl aniline in the presence of H₂SO₄ to form a triphenylmethane derivative. The subsequent oxidation with PbO₂ followed by treatment with an excess of concentrated HCl yields a green dye known as malachite green. Properties of Malachite Green Malachite green is green, crystalline, and water-soluble. Leuco form of malachite green is electrically neutral and undergoes a photoionization reaction that yields the cationic form of malachite green. It is toxic, thus not advisable to consume. Applications of Malachite Green It is used as a dye to color materials like silk, leather, and paper. It is used as an antiseptic for bacterial infection. It is used to catch thi

Conducting Polymers: Definition, Examples, Properties and Applications

Image
What are Conducting Polymers? As the name suggests organic polymers that conduct electricity are known as conducting polymers. They are also known as intrinsically conducting polymers (ICPs) and they have alternating single and double bonds along the polymer backbone (conjugated bonds) or that are composed of aromatic rings such as Phenylene, naphthalene, anthracene, pyrrole, and thiophene which are connected through carbon-carbon single bonds. Examples: Polyacetylene, Polypyrrole, Polyaniline, etc What is the reason behind conducting nature of these polymers? Conducting polymers comes in two forms that are doped conducting polymers and non-doped conducting polymers. The conductivity of non-doped conjugated polymers is due to the existence of a conductivity band similar to a metal. In a conjugated polymer, three of the four valence electrons form strong sigma bonds through sp² hybridization where electrons are strongly localized. The remaining unpaired electron of each carbon atom re

Alizarin Dye: Definition, Synthesis, Properties and Application

Image
What is Alizarin Dye? Alizarin is a red dye having chemical formula C₁₄H₈O₄ which is generally used to dye cotton, wool, and silk.  Alizarin was originally obtained from the root of a common madder plant called Rubia tinctorum. It is also known as Turkey Red as it was best dyed in Turkey and in 1869, it becomes the first natural dye to be duplicated synthetically. Synthesis of Alizarin Following are some methods for the synthesis of alizarin: 1. From anthraquinone The starting material for the synthesis of alizarin is an anthraquinone. It can be easily obtained by Friedel-crafts acylation of benzene with phthalic anhydride. Anthraquinone is then sulfonated with concentrated sulphuric acid at a high temperature to give anthraquinone-b-sulphonic acid. Alizarin is obtained by fusion of anthraquinone-b-sulphonic acid with caustic soda. 2. By bromination of anthraquinone Another synthesis is given by Graeve (in 1869). In this method, anthraquinone is brominated to yield dibromo anthraqui

Crime Scene: Definition, Types and Characteristics

Image
What is a Crime Scene ? A place where the crime is committed or where the maximum physical evidence related to crime is found is known as a crime scene. A crime scene is a starting point of the investigation which provides information about the suspect and the victim. This helps to reconstruct the crime and fast resolution of the case. It is noted that the crime scene is not limited to a single place but may extend to a wider area depending upon the nature of the crime committed. For example, In a murder case where murder is done at one place and the body is disposed on another place. In this case, we have two crime scenes that give information about the crime. Types of Crime Scene Based on evidence found on the crime scene: 1. Primary Crime Scene The crime scene where the actual crime occurred or where more usable pieces of evidence were found is known as the primary crime scene. For example, A murder scene, theft, assault, etc. 2. Secondary Crime Scene The crime scene which is some

Degree of Crystallinity: Definition, Factors Affecting and Determination Methods

Image
What is Degree of Crystallinity? The degree of crystallinity of the polymer is defined as the fraction of the sample which is crystalline. It can be either expressed in terms of the mass fraction or the volume fraction. The degree of crystallinity by a volume fraction is given by Where,  Xₘ = Degree of crystallinity by mass V = Specific volume of the sample Vₐ = Specific volume of fully amorphous polymer Vc = Specific volume of fully crystalline polymer Factors affecting the degree of crystallinity 1. Molecular weight With the increase in molecular weight of the polymer, the degree of crystallinity increases due to a large number of entanglement of the chain which restricts the growth of a crystallite. 2. Symmetry of repeating unit A symmetrical repeating unit structure like CH₂ makes it easier for the formation of crystallites. Thus, increasing the degree of crystallinity. That's why random copolymers do not crystallize because there is no regularity of the repeating unit. 3. Chai

Silicone Polymers: Definition, Preparation, Properties and Applications

Image
What are Silicone Polymers? Silicones are polymeric organosilicon compounds containing (Si-O-Si) linkages and have the general formula (R₂SiO) . They are typically colorless, oils, or rubber-like substances that may be linear, cyclic, or crosslinked.  Silicone polymers have very high thermal stability and are also called high-temperature polymers. They are widely used in sealants, adhesives, lubricants, medicine, and cooking utensils. Preparation of Silicone Polymer When methyl chloride reacts with silicon in the presence of copper as a catalyst at a temperature of 570 K , various types of methyl-substituted chlorosilanes are formed. Hydrolysis of dimethyldichlorosilane that is (CH₃)₂SiCl₂  followed by condensation polymerization forms straight-chain polymers called silicone polymers. Properties of Silicone polymer 1. It has low thermal conductivity, chemical reactivity, and toxicity. 2. They have low surface tensions and are capable of wetting most surfaces. 3. It does not support mi

Styrene Copolymers: Types, Preparation, Properties and Applications

Image
1. Butadiene-styrene Copolymer (SBR or Buna-S) Buna-S or SBR is a copolymer of 1,3-butadiene and styrene which is prepared by copolymerization of 1,3-butadiene and styrene along with sodium. In Buna-S, Bu stands for butadiene, Na for sodium which is the polymerizing agent and S stands for styrene. It is tough and is a good substitute for natural rubber. It possesses high abrasion resistance, high load-bearing capacity and is used for the manufacture of automobile tires. Preparation of Buna-S Styrene-butadiene rubber (SBR) or Buna-S can be prepared by copolymerization of a mixture of 1,3-butadiene and styrene in the ratio of 3:1 in the presence of sodium. Properties of Buna-S 1. Buna-S has high abrasion resistance, high bearing capacity, and resilience. 2. Buna-S is very tough and is a good substitute for natural rubber 3. Buna-S swells in organic solvents up to a limited extent. 4. Buna-S gets oxidized in the presence of traces of ozone. Applications of Buna-S 1. Buna-S is used for

Polyolefins: Types, Properties and Applications

Image
What are Polyolefins? A polymer that is produced from a simple olefin monomer (also called alkene having general formula CₙH₂ₙ) is called Polyolefin . For example (a) Polyethene is a polyolefin produced by polymerization of olefin ethylene (b) Polypropylene is a polyolefin produced by polymerization of olefin propylene. The IUPAC nomenclature of polyolefins is poly (alkene) . Polyolefins are produced by different common forming techniques like injection molding, blow molding, extrusion, and thermoforming using standard thermoplastic equipment. Due to low prices and easy processability, polyolefins have a variety of applications in the plastic industry. Application of Polyolefins 1. Polyolefins are used for making blow-molded components in toys. They are also used to make heat-shrink tubing which protects connections in electronic items. 2. Polyolefins are used in the pharmaceutical and medical industry for HEPA filter certification. 3. Polyolefins sheets have packaging applications of