Abstract
Mechanical properties of semicrystalline polymeric materials are strongly influenced by the morphology into which these materials crystallize. In addition the morphology can be altered by changes in crystallization temperature and regime, crystallization pressure, melt treatment conditions, shear history, and probably other processing conditions. The mechanical properties reflect the changes in morphology not only in the initial moduli values but also the overall stress-strain relationships, including the fracture mechanism. A strong influence is noted, at least in the polymers cited, even when slight changes occur in average spherulite size, spherulitic fine structure, and in the nature of interlamellar ties. Smaller, finer textured spherulites with higher interconnections arc apparently more susceptible to yielding by neck formation and elongation to high values than are the larger, coarser textured spherulites than tend to fail by random brittle failure mechanisms at low elongations. In addition, if the chlorinated polyether (Penton) is typical of slowly crystallizing polymers, the change from spherulitic morphology obtained during crystallization from the melt to the small platelet morphology obtained during slow crystallization from quenched glassy state has a complex effect on mechanical properties. The specimens slowly crystallized from the glass exhibit initial shear and tensile moduli values higher than those exhibited for rapid crystallization from the melt and rapid crystallization from the glass, but lower than the corresponding values for slow crystallization from the melt. In addition, the only specimens of this chlorinated polyether that exhibited the ability to draw to high degrees of elongation (as a result of yielding by a necking phenomenon) were those crystallized slowly from the quenched glassy state.