Showing posts from February, 2022

Crime Scene: Definition, Types and Characteristics

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

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

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