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Chap._300036 - linearly proportional to the pressure 3 In...

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Homework 3: 1. There are three types of commercial polyethylene polymers, including HDPE, LDPE, and LLDPE, Brief explain their differences in chemical structure, synthesis, thermal and mechanical properties, and commercial application. 2. In the commercial production of polyethylene by Ziegler-Natta catalyst (TiCl 4 and Et 3 Al), hydrogen is used to control polymer molecular weight. The following Table shows polymer molecular weight vs. hydrogen pressure in the polymerization that is carried out at 50 o C with hexane solvent, 100 psi (5 M) ethylene pressure, and catalyst concentration 2 x 10 -6 M. H 2 (psi) 0 5 (0.2 M) Mw (g/mole) 2.8 x 10 6 5.6 x 10 5 If you would like to reduce PE molecular weight to 5.6 x 10 4 g/mole, what has be done in hydrogen pressure to achieve the objective. Assuring the hydrogen concentration in hexane is
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Unformatted text preview: linearly proportional to the pressure. 3. In the preparation of polyethylene copolymers, such as poly(ethylene-co-1-octene), metallocene homogeneous catalyst is preferred over Ziegler-Natta heterogeneous catalyst. Explain why? 4. Compare the differences in the reaction mechanism and reaction conditions to prepare isotactic and syndiotactic polypropylene during Transition metal coordination (Zieger-Natta) polymerization. 5. Polyethylene and polypropylene are two most important commercial plastics. They are semi-crystalline polymers. Explain why their copolymers – poly(ethylene-co-propylene) – are rubbery material used in every tires....
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