Polymerization, Mechanical Engineering


Whether similar molecules join in long chain is termed as polymerization and resulting outcome is a polymer in a chemical reaction. Each plastic are polymers. This was stated that a molecule of ethylene can polymerise while several of these molecules connect in a chain structure as demonstrated in figure of Polyethylene Polymer. Ethylene or C2H4 is an unsaturated molecule since it has a twice bond among two atoms of carbon. This dual bond is again demonstrated in following figure (a). In the presence of a catalyst, pressure or heat the carbon-carbon dual bond is obtained and opens up for bonding along with another activated molecule of ethylene as following figure (b). This procedure of joining may continue until a few hundred to a few thousand molecules have connected in chain. The number of units or mers that join within polymerisation is termed as degree of polymerisation or DP. The polymerisation chain of ethylene is demonstrated in following figure (c) that is same as shown in previous figure of Polyethylene Polymer. This polymer is called as polyethylene and has average DP of 3500 to 25000. The polymer's molecular mass is the product of degree of polymerisation and molecular mass of one unit of the polymer. For illustration, the molecular mass of C2H4 is 2 × 12 + 4 × 1= 28 units. The molecular mass therefore, of polyethylene of DP of 5000 is 28 × 5000 = 140000 units.



Following figure demonstrates an ethylene monomer along with four hydrogen atoms replaced by radicals R1, R2, R3 and R4. Different polymers are acquired by placing such radicals as H, Cl, CH3, COOH3, C6H5, and so on in place of R1, R2, R3 and R4.

While R1 = R2 = R3 = R4 = H, polyethylene is obtained, polyethylene has been demonstrated in figure of Polyethylene Polymer and figure of A Monomer. It is generally utilized for household, tubes and sheets containers.

                                                                           2432_Polymerization 1.png

                                                                                  Figure: A Monomer

While R1 = R2 = R3 and R4 = Cl as shown in figure of Polyvinyl Chloride or PVC, the vinyl polymer, termed as polyvinyl chloride or PVC, is acquired. Polyvinyl Chloride is largely employed for conduit pipes and electrical insulation.


                                                               106_Polymerization 2.png

                                                                     Figure: Polyvinyl Chloride or PVC

If R1 = R2 = H, R3 = CH3 and R4 = COOH3 a polymer termed as polymethyl-methacrylate is acquired. This polymer, often referred to as PMMA, is demonstrated in following figure.

                                                          1766_Polymerization 3.png

                                                         Figure: Poly-methyl-meth-acrylate or PMMA

Poly-methyl-meth-acrylate is commercially called as perspecs, lucite or plexiglass. This is strong and hard but is generally used for its glass as like transparency.

Styrofoam, largely termed as for its porous structure and thermal insulation is acquired when R1 = R2 = H and R3 = R4 = C6H5. It is employed as insulator in buildings and refrigerators and as sound absorbent.

PTFE or polytetrafluoroethylene, commercially called as Teflon, is chemically resistant to each chemical except hydrofluoric acid. This polymer is acquired by replacing each R via fluorine radical, F. Teflon can retain its hardness upto relatively high temperature and thus employed as coating on razor blades, frying pans and for biomedical applications. This is also employed as bearing and vacuum ring.

Posted Date: 2/27/2013 4:35:39 AM | Location : United States

Related Discussions:- Polymerization, Assignment Help, Ask Question on Polymerization, Get Answer, Expert's Help, Polymerization Discussions

Write discussion on Polymerization
Your posts are moderated
Related Questions
EQUIPMENT FOR RESISTANCE WELDING-Stored energy equipments   Energy can be stored and further utilised for welding. One method of storing energy is in capacitors electrostat

What are the types of Boundary Layer and what do you understand by separation of Boundary layer. Can you Derive Hagen Poiseulle formula. Aslo illustrate Reynold's No.

Q. Corrosion resistance of Zirconium? Zirconium offers excellent corrosion resistance to most oxidizing and reducing acids and virtually all alkalis. However, it is not resist

Explain the concept of time dilation. Describe experimental verification of time dilation. Explain: (i) Length contraction (ii) Time Dilation in STR What are proper length an

1. Plot the functions x1 and x as functions of voltage 2. Assume that you hold the membrane potential V at -120 mV until the system reaches equilibrium (i.e. until dx=dt = 0, w

You are required to investigate the dynamic movement of a mass m sliding along a rod as shown in the diagram below. The rod is rotating at a constant angular velocity θ. The mass


Types of couple: Explain about different types of couple?  Sol.: There are mainly two types of couples: 1 . Clockwise Couple   A couple whose tendency

calculate the vertical reaction at A in Newtons

Stroke: The nominal distance through which a working piston moves between two successive reversals of its direction of motion is called the stroke and is designated by the letter