Polymers

Phenolic resins Phenol formaldehyde resins or phenolic resins were the first commercial synthetic resins. Phenolic resins (phenoplasts) are produced by Leo Baekeland. This material is often called Bakelite. Phenyl formaldehyde resins or phenolic resins are important class of polymers which are formed by condensation polymerisation of phenol and formaldehyde in acidic or alkaline medium. Initially the monomers combine to form methylol phenol derivative depending upon phenol to formaldehyde ratio. Synthesis of Phenolic resins step 1. The phenol formaldehyde derivatives react among themselves or with phenol to give a linear polymer (novolac) or a high cross-linked polymer Bakelite. Synthesis of Phenolic resins step 2. The phenolic resins are widely used in plywood manufacture. Other applications of phenolic resins include lacquers and varnishes, cutlery handles and toilet seats. They have been widely used for production of molded products including billiard balls, as...

Thermosetting resins Thermosetting resins are the materials that undergoes irreversible changes under the influence of heat from a fusible and soluble materials into infusible and insoluble materials through the formation of covalently cross-linked, thermally stable networks. The main characteristic of thermosets is that they require curing. Thermosets are generally used in liquid state and solidify and harden on curing. Some resins can be part cure and hold on to what is called B stage for completely curing at latter time. Some examples of thermosets include epoxies, polyesters and formaldehyde based resins. The formaldehyde based resins is classified into two classes, the condensation products obtained on reacting formaldehyde with phenol (or resorcinol) called phenolic resins or phenoplasts and the products obtained on reacting formaldehyde with urea (or melamine) called amino resins or amino plastics. Thermosetting resins have excellent resistance to solvents and corros...

Molded plastics. The molded plastics are formed by injection molding. Here the molded plastics are formed by injecting molten liquid plastic into the mold, which is then allowed to stand sometime in order to cool after which it gets solidifies and take the shape of the mold. Plastic injection molding is extremely versatile method of producing parts and products. Not only is plastic injection molding simpler and more reliable, it is also extremely efficient. Many of the plastic parts that we use in everyday life are injection molded. These plastics are used as different shaped containers like shampoo bottles, water bottles and food containers etc. Molded plastics. They are also used as computer parts, car parts etc. Molded plastics. They are also used in medical application. Home decoration products and lawn decoration are constructed to large extend from molded plastics. Molded plastics   NEXT

Plastic Pipes. Plastic pipes are tubular sections or hollow pipes/cylinders made of plastics. They are usually but not necessarily of circular cross-section. The plastic pipes are used to convey substances that can flow such as liquids and gases (fluids), slurries, powder and small mass of solids. Slurries. They are used as hollow pipes. Hollow pipes are stiffer than solid pipes. A common example of plastic pipe is polyvinyl chloride (PVC) pipes made from combination of plastic and vinyl chloride. Polyvinyl chloride pipes. PVC pipes are durable, hard to damage and long-lasting. They do not rust, rot or wear overtime. Thus, these pipes are used in water system, underground wiring and sewer lines. The monomer used in production of PVC is vinyl chloride. Polyvinyl chloride formation. The polyvinyl chloride is produce by heating a water-emulsion of vinyl chloride in the presence of benzoyl peroxide or hydrogen peroxide in an autoclave under pressure. Next Auto...

Polyelectrolytes. Polyelectrolytes are polymers that have dissociating groups in their repeating unit. They contain ionizable group along the chain, normally exhibit this property in solution that makes it different from non ionizable structures. Examples of polyelectrolytes. Like ordinary electrolytes are divided into acids, bases and salts, the polyelectrolytes are classified into polyanions, polycations and polysalts. Polysalts are made from reacting polyacids (polyanions) with monomeric base and vice versa. The polyelectrolytes behaves as both electrolytes and polymers. Like regular salts their solution are electrically conductive and like polymers their viscosity depends on molecular weight and polymer concentration. In non ionizing solvent -for example poly(acrylic acid) in dioxane- polyelectrolytes behave in completely normal fashion, but in aqueous solution they are ionised. Polyelectrolytes are used in water treatment as flocculation agents. Water treatment....

Cellular Polymers. Cellular materials widely occur in nature such as wood, cork, corals, sponge, human bones etc. These natural materials with cellular structure have been used for centuries. The idea of developing and manufacturing the broad range of cellular polymers arose when these natural cellular structures exhibited excellent properties such as high strength of wood, cushioning properties of cork and straw and good insulating properties of cork and balsa. Example of cellular polymers. The multifunctional cellular materials are widely used structurally for cushioning, thermal insulation, energy absorption from impacts, sound absorption and vibration dampening. The cellular polymers consist of two phase i.e solid and gas. Cellular rubbers are cellular polymer consisting rubber matrix containing a mass of cells. Some properties of cellular rubbers are;      1) Limited water absorption.      2) Weather resistant.     ...