Polyester Fibres Indtroduction: Polyester are polymers made by a condensation reaction taking place between small molecules, in which the linkage of the molecules occurs through the formation of estes groups. Polyesters are commonly made by interaction of a dibasic acid with a dihydric alcohol: HOOC-X-COOH+HO-Y-OH OC-X-COO-Y-OCO-X-COO-Y-OCO The formation of polyester was studied by Wallace H. Carothers of du Point during the investigation of polyesters which lead eventually to the discovery of nylon. Development of the polyesters was overshadowed, however, by the polyamide research, and it was not until 1941 that a valuable polyester fibre was discovered. in that year, J. T. Dickson and J. R. Winfield of the Calico Printers'
Both processes first produce the intermediate bis-(2-hydroxyethyl)-terephthalate (BHET) monomer and either methanol in DMT process or water in TPA process. The BHET monomer is then polymerized under reduced pressure with heat and catalyst to produce PET resins. The primary reaction for the DMT process is: Figure 11: Primary reaction of DMT process The primary reaction for the TPA process
Other disaccharides are broken down by other carbohydrase enzymes. Carbohydrates (starch)are broken down in the oral cavity by saliva amylose. They are made up of 3 elements, carbon (C), hydrogen(H) and oxygen(O) and can be found together in three different forms. Either as a monosaccharide, disaccharide or a polysaccharide they are differentiated by the number of rings in their chemical compound. There chemical formation is C6,H12,O6 and due to their bond angles between the carbons, tend to form a pentose of hexoses, stable ring structure.
They can impart localised structural rigidity, confer cytotoxicity by alkylation, or be secondary metabolites . The chemistry of epoxides is dominated by the reactions that involve opening of the strained three-membered heterocyclic ring by nucleophiles. Such reactions yield valuable bifunctional compounds. In nature, epoxide ring opening is catalysed by the phenolic proton of a tyrosine moiety . But in laboratory, the cleavage usually occurs in non-aqueous media in presence of a Lewis acid catalyst like Al2O3, Li+, Mg2+ etc.
Formate also serves as a substrate for ruminal methanogenesis but most of the formate is converted to H2 and CO2 prior to methanogenesis. Methylamine and methanol produced in the rumen also be used for methane production by methylotrophic methanogens of the order methanosarcinales and methanosphaera sps. from the methanobacteriales. Methane is also produced from acetate via aceticlastic pathway by methanosarcinales. The anaerobic conversion of organic matter to methane in the rumen involves a consortium of rumen microorganism with final step lead by methanogens.
This produces harmful carbon emissions, and also uses a nonrenewable fuel source to make electricity. A car’s emission is the most direct contribution to pollution. Engines that burn gasoline emit harmful gases. These gases include carbon dioxide, which builds up in the air and adds to global warming. Also, cars may leak fluids which can enter water systems.
Used solvents contain contaminants that can be removed by fractional distillation. The recycled solvents have purities suitable for re-use. Fractional distillation is used to separate the crude oil into its various components such as gasoline, kerosene oil, diesel oil, paraffin wax, liberating oil. Fractional distillation is also used for the purification of water. Water contains many dissolved impurities; these can be removed by this process.
The chemical and physical properties of a variety of chemicals work together to form a desired end product that is used commercially. Three chemicals that are used to form a bouncy ball in this experiment were; Polyvinyl Alcohol, Polyvinyl Acetate, and Borate. Polyvinyl Alcohol is a water-soluble polymer that is commercially used for paper and textiles products (Polyvinyl Alcohol PVA chemical Compound). Polyvinyl Alcohol is unique polymer, for it is only created with the dissolving of another polymer such as Polyvinyl Acetate, through hydrolysis (Polyvinyl Alcohol PVA chemical Compound).Polyvinyl Alcohol is an adhesive element. With the application of polyvinyl acetate that is formed from polyvinyl alcohol; is used as an adhesive in Elmer’s
Figure 5. Hexamethylenediamne (top) and Adipic acid (bottom), monomers used for polycondensation of Nylon 66. As a result, nylon 6,6 is formed. It can then either be extruded and granulated or it can be directly spun into fibres by extrusion through a spinneret and cooling to form filaments. Currently, nylon 6,6 costs $1.38 to $1.46 (figure 6.
1.3. An Overview for the Synthesis of Tetrahydropyrans, Piperidines and Dihydro-γ-pyrone Derivatives To build this class of heterocycles, many strategies have been developed over the years. The most widely used methods are the Prins cyclization, hetero-Diels–Alder (HDA) cyclization, oxonium-ene cyclization, the intramolecular Michael additions and ring-closing metathesis. Other strategies include electrophile-induced cyclizations of non-activated alkenes and Lewis acid promoted cyclizations of epoxy alcohols/amines. Reported methods used for six membered oxygen and nitrogen ring synthesis have their own advantages and disadvantages.