MSE2001H_6_1

MSE2001H_6_1 - 1 Chapter 6 Noncrystalline and...

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1 Chapter 6 Noncrystalline and Semicrystalline Materials Introduction Glass Transition Temperature Viscous Deformation Structure and Properties of Amorphous and Semi-crystalline Polymers Structure and Properties of Glasses Structure and Properties of Rubbers and Elastomers
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2 Introduction The emphasis thus far has been on crystalline materials. There are numerous engineering materials that lack the long range translational periodicity of a crystalline material. These non-crystalline materials are referred to as either- amorphous, glassy, or super-cooled liquids . Theoretically, any material can form an amorphous structure if the cooling rate from the melt is sufficiently rapid to suppress crystal formation . This chapter will emphasize the structural considerations that facilitate the development of an amorphous structure.
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3 N-th Order Phase Transition The usual definition of the order of a transition is in terms of the behavior of derivatives of the Gibbs free energy. An n-th order transition is one in which discontinuities appear only in the n- th and higher derivatives of G with respect to T and p. The ordinary first-order transition have discontinuities in T p G V = p T G S = The ordinary second-order transition have discontinuities in p T p p G T V T V V = = 1 1 α T T T p G V p V V = = 2 2 1 1 κ V p V V T G T T T S T C = = p p p T G T T S T C = = 2 2
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4 Glass Transition Temperature Glassy State A state of material in the absence of long-range order below the glass transition temperature Æ large scale mobility is frozen Æ atomic movement requires time. Rubbery State A state of material in the absence of long-range order above the glass transition temperature Æ atomic movement takes shorter time. Window glass vs. Rubber band What if you give them a good blow using a hammer? Glass transition temperature : the temperature below which the physical properties of amorphous materials vary in a manner similar to those of a solid phase (glassy state) , and above which amorphous materials behave like liquids (rubbery state) .
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5 Specific Volume for a Variety of Materials Liquid to glass solid transformation in a pure substance. The glass transition temperature, T g , is not an equilibrium transformation temperature.
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MSE2001H_6_1 - 1 Chapter 6 Noncrystalline and...

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