MSE2001H_6_2

MSE2001H_6_2 - 1 Chapter 6 Noncrystalline and...

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1 Chapter 6 Noncrystalline and Semicrystalline Materials •I n troduction t oduct o Glass Transition Temperature Viscous Deformation tructure and Properties of Amorphous and Semi- rystalline Structure and Properties of Amorphous and Semi crystalline Polymers tructure and Properties of Rubbers and Elastomers Structure and Properties of Rubbers and Elastomers
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2 Factors Affecting Crystallinity in Polymers actors influencing the efficiency of packing polymer chains The size of the side groups Factors influencing the efficiency of packing polymer chains The extent of chain branching Tacticity The complexity of the repeat unit The degree of secondary bonding
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3 The size of the side groups Bulky side group? H H H H C H C H n C H C H n CH 3 CH 2 CH n The extent of chain branching HDPE is defined by a density of greater or equal to 0.941 g/cm 3 . HDPE has a low degree of ranching and thus tronger intermolecular forces and tensile strength HDPE can be branching and thus stronger intermolecular forces and tensile strength . HDPE can be produced by chromium/silica catalysts, Ziegler-Natta catalysts or metallocene catalysts . The lack of branching is ensured by an appropriate choice of catalyst (e.g. chromium catalysts or Ziegler-Natta catalysts) and reaction conditions. Æ high crystallinity LDPE is defined by a density range of 0.910 - 0.940 g/cm 3 . LDPE has a high degree of short and long chain branching, which means that the chains do not pack into the crystal structure as well.
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MSE2001H_6_2 - 1 Chapter 6 Noncrystalline and...

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