Polymers: A good analogy for understanding polymers is a paper clip chain. Each paper clip represents a monomer, a single molecule in the polymer chain. Hundreds of thousands of monomers, chemically bonded together forms a polymer. If the bonds between the monomers break, which happens when gelatin is heated or acids are added, the polymer loses viscosity and strength. If several paper clip chains are joined with cross linking monomer paper clips the properties of the polymer are changed. Usually, polymers become more rigid, and less viscous. Adding borax to gelatin caused cross-linking with borate ions linking the gelatin chains, making the product more rigid than pure gelatin.
Gelatin. {jel'-uh-tin} Gelatin is a protein obtained from the skin, tendons, and bones of animals. It is used in food products and pharmaceuticals, in many industrial processes, and for cooking. Derived from COLLAGEN, a constituent of animal skin and bone, it is extracted by treating hides and bone with lime or acid; boiling, filtering, and concentrating the material; and then drying and grinding it to produce commercial gelatin, in the form of transparent, odorless, and tasteless granules. Gelatin dissolves in hot water and congeals to form a gel as the solution cools. Gelatin is an incomplete protein lacking the essential amino acid tryptophan, but as a food supplement it supplies several amino acids lacking in the protein of wheat, barley, and oats. Free of antigens, it does not cause allergic reactions. In foods, gelatin is used in gelatin desserts, candy, meat products, and jellied canned soups; as an emulsifier in such foods as ice cream, marshmallows, and chiffon pie fillings; and as a stabilizer in cake fillings, icing mixers, and gum. Gelatin's most important industrial uses are in photography, where it provides a basic ingredient in the manufacture of photographic film and paper, and in lithography and photocopying. It is used in the plastics industry to improve blending characteristics; in metallurgy to achieve greater purity in refining, as a corrosion inhibitor, and to produce bright finishes in electroplating; in drilling as a protective colloid; in agriculture as an ingredient of fertilizers, animal feeds, and sprays; and in pharmaceuticals for capsules, pill coatings, suppositories, and emulsions. Sheets of dyed gelatin are used in stagelighting as an inexpensive substitute for glass. Isinglass is a form of gelatin produced from the bladders of fish, and AGAR is a gelatinous seaweed extract used as a laboratory culturing medium and as a gelling agent in foods.
Plastics. Plastics are made from oil and natural gas. The first petroleum plastics were synthesized from the smaller molecules created in the refining of crude oils and were called synthetic plastics. The first true synthetic plastic was made by American chemist Leo Bakeland in 1907. Created by heating phenol, a disinfectant, with formaldehyde, embalming fluid, a very hard moldable material was produced. Molecules of plastics contain hydrogen and carbon atoms, along with oxygen, nitrogen sulfur, chlorine, fluorine and silicon atoms. The basic molecules are called monomers. The monomers are chemically joined together in repeating units to form gigantic molecules first called polymers. The type of molecules making up the polymer and how the molecules are joined together determine the properties of the polymer. The properties of polymers are as diverse as the products they form.