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Lecture # 2

Lecture # 2. What is the meaning of polymers? This word stems from Greek: Poly = many, mers particles. So this term describes a molecule composed of many identical parts, called mers .

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Lecture # 2

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  1. Lecture # 2 What is the meaning of polymers? This word stems from Greek: Poly = many, mers particles. So this term describes a molecule composed of many identical parts, called mers. However, there are no mechanical properties below about 30 mers, while the useful average reaches 200-2,000 mers. molecular weights broad range between 5,000 up to 2 x IO6 may be representative, while in some cases it may reach 107

  2. Plastics (Synthetic polymers) ( plastomers) refer to the major group of polymers that in combination with various additives leads to materials of construction • natural polymers since the beginning of mankind: in food [protein, starch and others); in clothing (wool, cotton, silk); and in various other uses (cellulose for writing and natural resins for ornaments). polymers are also used as elastomers (rubber like), textiles, coatings and adhesives.

  3. By decomposition of coal at high temperature (an anaerobic process called cracking) products llke acetylene, methanol, or phenol are derived. • These chemicals serve as the primary source for an extended array of polymers. • Acetylene is derived from carbide, the latter obtained by a reaction between lime and coke (the major solid fraction obtained from coal pyrolysis). • The basic chemical reactions are as follows: THE PETROCHEMICAL INDUSTRY:

  4. A whole family of polymers is derived from formaldehyde: polyacetal (polymethylene oxide), phenol-formaldehyde, urea-formaldehyde and melamine- formaldehyde. • Note that the other components (phenol, urea and melamine) are also products of coal pyrolysis.

  5. Let us describe the routes to some selected monomers, produced by the petrochemical industry. • 1-Monomers Derived from Ethylene:

  6. Styrene can be synthesized by reacting ethylene with benzene (the latter present in the aromatic fraction of the oil cracking process- benzene, toluene and xylene):

  7. Another important monomer, methylmethacrylate (acrylic), is obtained by reacting propylene with carbon monoxide, oxygen and methanol:

  8. 3-Phenol and Other Aromatics: • This first man-made polymer, phenol-formaldehyde, bears the trademark Bakelite: • By reacting phenol with acetone, bis-phenol A is obtained. This serves as the basis for the manufacture of epoxy and polycarbonate.

  9. As stated previously, condensation between urea and formaldehyde leads to the formation of the polymer urea-formaldehyde.

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