Dynamic Mechanical Analysis sump4动态力学分析sump4.pptVIP

mechanical testing dynamic mechanical analysis relationships test configurations typical behaviour polycaprolactone impact resistance in nylon material specification thermoset cure determination of Tg effect of plasticiser stress relief PET effect of frequency frequency domain frequency master curve effect of molecular weight gellation of polymer solution thermoset curing Gillham-Enns or TTT diagram recommended reading If, as in the case of DMA, a sinusoidal oscillating stress is applied to a specimen, a corresponding oscillating strain will be produced. Unless the material is perfectly elastic, the measured strain will lag behind the applied stress by a phase difference (δ) shown in here. The ratio of peak stress to peak strain gives the complex modulus (E*) which comprises an in?phase component or storage modulus (E’) and a 90° out?of?phase (quadrature) component or loss modulus (E”). An example of a frequency scan showing the change in a material’s behaviour as the frequency varies. Low frequencies allow the material time to relax and respond, hence flow dominates. High frequencies do not allow relaxation and elastic behaviour dominates. An example of a frequency scan showing the change in a material’s behaviour as the frequency varies. Low frequencies allow the material time to relax and respond, hence flow dominates. High frequencies do not allow relaxation and elastic behaviour dominates. The crossover point between either E and E or between E and h* for a material corresponds to the relative molecular weight and molecular weight distribution. * Dynamic Mechanical AnalysisDuncan PriceIPTME, Loughborough University? Copyright: D.M.Price@lboro.ac.uk (2006) Rubbery plateau is related to Me between cross-links or entanglements Tll in some amorphous polymers Tm = melting (1) For thermosets, no Tm occurs Rubbery plateau (2) In semicrystalline polymers, a crystal-crystal slip, Ta* occurs For purely crystalline materials, Tg occurs Tg is related to molecul