Sciencedoze: Science, Education and Technology

What are Polycarbonates? Polycarbonate (PC) are high-performance tough thermoplastic polymers that have organic functional groups linked together by carbonate groups (-O-(C=O)-O-).   Polycarbonates have high impact resistance and are obtained by condensation of diethyl carbonate or carbonyl chloride and bisphenol-A. It is widely used for bullet-proof windows and safety or crash helmets. Lexan is the most common example of Polycarbonates. Structure of Polycarbonate Preparation of Polycarbonate Polycarbonate is produced by condensation polymerization between bisphenol A and either Carbonyl chloride or diphenyl carbonate. (a) Preparation of Polycarbonate by condensation polymerization between bisphenol-A and Carbonyl Chloride The polymer is usually formed by the reaction of bisphenol-A and carbonyl chloride in a basic solution where polymerization takes place at the interface between the aqueous and organic layer with the help of a catalyst can amine. (b) Preparation of Polycarbonat...

What are Polyamides?  Polymers that have amide linkages are called polyamides. These are prepared by condensation polymerization of dibasic acids with diamines or their equivalents. Polyamides occur both naturally and artificially like proteins, such as wool and silk are naturally occurring polyamides whereas nylons, aramids and sodium poly(aspartate) is artificially manufactured polyamides. Following are some famous polyamides: 1. Nylon 6,6 Nylon 6,6 is a type of polyamide that is made of two monomers that is hexamethylenediamine and adipic acid each containing 6 carbon atoms. That's why it is called nylon 6,6. Nylon 6,6 has high mechanical strength, rigidity, and stability under heat and chemical attack. That's why it is used for making machine parts, airbags, ropes, conveyor belts, etc. Preparation of Nylon 6,6  It is prepared by the condensation polymerization of adipic acid and hexamethylenediamine. The acid and the amine first react to form a salt which when heated...

What is Poly (vinyl acetate)? Poly (vinyl acetate) (PVA) was discovered in Germany in 1912 by Fritz Klatte. It is an aliphatic rubbery synthetic polymer with chemical formula (C₄H₆O₂)n which belongs to the polyvinyl ester family. It is also known as wood glue or Elmers's glue due to its adhesive properties for which it is used as adhesive for porous materials like wood, paper, and cloth. Structure of Poly (vinyl acetate) (PVA) Preparation of Poly (vinyl acetate) (PVA) Poly (vinyl acetate) (PVA) is a vinyl polymer that is prepared by free radical vinyl polymerization of the monomer vinyl acetate. Properties of Poly (vinyl acetate) (PVA) 1. PVA is an amorphous polymer having a glass transition temperature (T𝘨) between 30-45 ℃ . 2. PVA offers good adhesion to most of the surfaces. 3. Degree of polymerization of PVA is between 100 to 5000 and it can be treated with alkali, which gradually results in polyvinyl alcohol and the alkali acetate. 4. PVA does not cross-link and it ca...

What is Polyurethane? Polyurethane (PU) is a polymer having organic units joined by urethane (also known as carbamate). Urethane is a compound that has an O-R group and an NH-R group bonded to the same carbonyl carbon. Polyurethanes are thermosetting polymers but their thermoplastic variants are also available in the market. Polyurethanes are prepared by the polymerization of toluene-2,6-di-isocyanate and ethylene glycol. If the reaction is carried out in the presence of a blowing agent, the product is polyurethane foam. Preparation of Polyurethanes Polyurethanes are formed by reacting a polyol (an alcohol with more than two reactive hydroxyl groups per molecule like ethylene glycol) and di-isocyanate or a polymeric isocyanate in the presence of suitable catalyst and additives. Properties of Polyurethanes 1. Polyurethane has high load capacity in both tension and compression that may change shape under heavy load but will return to its original shape once the load is removed ...