CHEM 4214 Lecture Notes - Lecture 40: Scattering, Cross-Link, Polycarbonate
Document Summary
Final exam: friday may 13, 1:30-3:30 pm, smith hall 100. Mechanical properties of polymers how materials deform and their uniaxial extension. Do taylor expansion for epsilon << 1 this is consistent with our previous definition. Toughness: energy absorbed prior to failure brittle materials are not that tough . rubbery materials are. Macroscopic behavior: ductile fracture (polycarbonate) (applies to metals ductile b/c of defects in metal if were perfect crystal, would be brittle) Reorganization and extension of chains neck width is constant as we go along to right. F ~ constant strain hardening before breaking: brittle fracture (e. g. ps, pmma for t << tg) Stress whitening bubbles scatter light and that"s why it looks a bit white void spacing at [leum?] creates strong light scattering. Temperature strongly influences the stress vs strain curve (b/c might be in glassy or rubbery region) T << tg polymer doesn"t relax either breaks or doesn"t move at all.
