BME 314 TEST 2 REVIEW - BME 314 TEST 2 REVIEW...

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BME 314 TEST 2 REVIEW Crystallinity: polymers with strong IMF; polymers cooled from melt state; compact structures; As crystallinity increases, polymer becomes more opaque due to scattering of light Crystallinity increases stiffness * higher young’s modulus * Less flexibility; diffusion rates are less permeable to molecules * necessary for drug delivery sometimes * Low penetration of h2o; slow hydrolysis Ex. PLGA, Polyethylene Teraflate Bone implants, bad for optics Amorphousness: called glassy polymers; brittle; when heated become soft; rubbery Lack crystalline domains that scatter light * transparent * Ex. Poly(methyl methacrylate) Optics, PMMA, PDMS, poly Syrene T m : crystalline melting point; temperature at which all crystalline regions melt; as crystallinity inc., so does Tm T g : glass transition temperature; temp at which a polymer changes from a solid glassy state to a rubbery state
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Heat capacity, density, permeability, dielectric constant, etc. change at Tg Silicones have low Tg and Tm, always fluid at relative temps (breast implants);
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BME 314 TEST 2 REVIEW - BME 314 TEST 2 REVIEW...

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